WO2014083156A2 - Hydrocarbon markers - Google Patents

Abstract

Specific naphthalene derivatives are used to mark hydrocarbon liquids such as mineral oil and kerosene. The marker group includes the 2-methoxy and 2-ethoxy and 2-isobutoxy naphthalene derivatives along with deuterated isomers/analogs. The combination of deuterated isomers into a given non-deuterated marker to give a marker with a unique isotopic composition can be used as a means of coding a liquid for identification and for tracking and tracing purposes. The distinctive fragrant properties of the alkoxynaphthalene markers can be employed as a screening method for the detection of marked fuel in the field using the olfactory senses of humans or specially trained animals.

Description

HYDROCARBON MARKERS

Introduction

The present invention relates to compounds which may be used as hydrocarbon markers and to a method of marking and identifying hydrocarbons. In particular the invention relates to a method of marking and identifying mineral oils, hydrocarbon fuel, diesel, petrol (gasoline), paraffin oil (kerosene), gas oil (fuel oil), petroleum and the like.

In most industrialised countries, fuels are charged at different amounts of taxation depending on their usage and on the individual or organisation using the fuel. Off-road fuels, e.g. for industrial and/or agricultural use, are commonly at a lower rate of tax than other fuels and are sometimes referred to as "rebated fuel". For example, in order to promote agricultural activity fuels for machinery employed in farming are rebated compared to the equivalent tax levied for private cars.

Hydrocarbon markers based on a number of different chemistries are widely employed to identify rebated fuel so that the authorities can determine whether the fuel is being used lawfully or not. Examples of such markers are visual dye compounds and compositions. Solvent Yellow 124 ("Euromarker") is a yellow azo dye which has been used since August 2002 as a fuel marker to distinguish rebated diesel fuel intended for heating from motor diesel fuel. According to European Union (EU) law, this marker must be used across the EU territories. However, as this dye is easily removed (laundered) or interfered with (masked), many jurisdictions require the addition of further markers. For example, in the United Kingdom a composition containing a red dye and a quinizarin antioxidant is used to mark rebated diesel.

A particular problem with many of the current chemicals that are used for marking is that these are either easily removed from the marked fuel by way of extraction with inexpensive absorbents, acids or bases or made undetectable by masking with another agent. Although some conventional markers are more resistant to removal than others, it is of course important to keep one step ahead of fuel launderers to reduce and preferably prohibit the illegal trade in the removal of markers. Such tax evasion represents a major problem in many territories. While some of the markers and methods described in the prior art have some applicability they do not provide a marker method to address the more complex problems of the criminal misuse of fuel in the current market. Many thousands of markers and methods for marking hydrocarbons have been described over many years but address only a small portion of the need and none possess all the elements required to satisfy the current need. The current widespread and preferred use of readily available adsorbent materials such as Fullers earth, bleaching earth, activated carbons, various silicas and zeolites which are capable of removing all dyes as well as those markers susceptible to acid or base extraction and also solvent extractible markers undermine the effectiveness of even the best of present day marker systems.

WO2012153132A1 describes the use of aromatic compounds containing halide atoms. The presence of halides can allow the detection of the markers to extremely low levels in hydrocarbons using analytical technologies such as ECD (electron capture detection). The addition of halide species to fuel is not generally acceptable as they do not burn well and are converted to corrosive acids and salts on combustion resulting in damage to engines with prolonged use. The enormous quantities of marker required to satisfy the market for even one year would involve many tonnes of halide compounds released into the environment.

WO2011032857A2 describes the use of aromatic compounds as markers for hydrocarbon fuels. In this patent the aromatic compounds must have at least two substituents of general formula COOR. The COOR group confers a property on the aromatic compounds whereby they can be detected readily by analytical technology such as Infrared spectroscopy. This technology may be used in the laboratory or as a portable device in the field. The COOR groups are acid esters and readily hydrolysed by acids or bases. They are also readily susceptible to chemical alteration. Aromatic esters are generally polar and may be absorbed onto common adsorption media such as activated carbons etc. For these reasons this method of marking does not satisfy the current need.

It is known to use a combination of markers in specific ratios to confer an identity on a marked liquid that can be revealed on measurement of the marker ratio in the marked substance. However, the use of laundering tools such as absorbing solids make this approach unreliable as the absorbing earths absorb materials with even the most subtle physical or chemical differences to different degrees and the relative absorption is also dependent on the matrix for example diesel or kerosene. The absorption of a particular substance from a hydrocarbon mixture onto a solid is in competition with the other chemicals present in the matrix thus the removal of a particular substance with a particular solid will vary with the matrix composition.

A need still exists for alternative or supplementary fuel marking methods which prohibit laundering techniques. These methods should involve markers which are capable of thwarting 21st century fuel launderers, i.e. markers which are more robust than conventional markers. Both traditional laundering techniques as well as new laundering techniques that would be economically viable to support illegal activity should be prohibited by such methods.

Statements of Invention

Viewed from a first aspect the invention provides a method of marking hydrocarbons comprising the addition or mixing of at least one compound of general formula (I) or an enantiomer, diastereomer or rotamer thereof to a h drocarbon so that it dissolves therein:

wherein R¹ represents an optionally substituted alkoxy or deutero alkoxy group, or an optionally substituted aryloxy or deutero aryloxy group; and R² represents a hydrogen atom, a deuterium atom, an optionally substituted alkyl or deutero alkyl group, an optionally substituted aryl or deutero aryl group or an optionally substituted acyl group.

It is preferred that, in the above structure, R¹ is situated at the 2 or 6 position of the naphthalene core. Further, it is also preferred that R² is situated at the 2 or 6 position of the naphthalene core.

By "optionally substituted alkyl or deutero alkyl group" is meant a substituted or unsubstituted straight-chained, branched or cyclic alkyl or deutero alkyl group. The substituted groups may be mono or poly-substituted. Suitable substituents may be selected from low chemically active and low polarity groups such as alkyl groups containing up to 10, preferably up to 8, particularly preferably up to 6, especially preferably up to 4, e.g. up to 2 carbon atoms. By an "aryl" group is meant a group which is aromatic. As used herein, the term "deutero aryl group" means that at least one of the hydrogens in an aryl group is replaced by a deuterium. Preferred aryl and deutero aryl groups comprise up to 20 carbon atoms, more preferably up to 12 carbon atoms, for example, 10 or 6 carbon atoms.

Aryl groups which may be present in the compounds of the invention may be heteroaromatic (e.g. 5-7 membered heteroaromatics) but are preferably non- heteroaromatic.

Aryl groups which may be present in the compounds of the invention may optionally be substituted by one or more (e.g. 1 to 5), more preferably one or two, groups (e.g. one group). Preferably the aryl group is substituted at the meta or para position, most preferably the para position. Suitable substituent groups may include alkoxy (preferably Ci_₆ alkoxy) and Ci_₆ alkyl. Preferred Ci_₆ alkyl groups include methyl, isopropyl and t-butyl, particularly methyl. Particularly preferred substituent groups include methoxy and ethoxy. Still more preferably the aryl group is unsubstituted.

As used herein, the term "alkoxy", unless stated otherwise, includes any long or short chain, cyclic, straight-chained or branched aliphatic saturated hydrocarbon group singularly bonded to an oxygen atom. Unless stated otherwise, such groups may contain up to 20 atoms. However, alkoxy groups containing up to 10, preferably up to 8, particularly preferably up to 6, especially preferably up to 4, e.g. up to 2 carbon atoms are preferred.

By "optionally substituted alkoxy group" is meant a substituted or unsubstituted straight- chained, branched or cyclic alkoxy group. The substituted alkoxy groups may be mono or poly- substituted. Suitable substituents may be selected from low chemically active and low polarity groups such as alkyl groups containing up to 10, preferably up to 8, particularly preferably up to 6, especially preferably up to 4, e.g. up to 2 carbon atoms.

By an "aryloxy" group is meant a group containing an oxygen atom connected to an aryl group as defined above. A preferred aryloxy group is naphthyloxy.

By the term "acyl" group is meant a group of the formula RCO-, where R represents an alkyl or aryl group that is attached to the CO group with a single bond. Preferred acyl groups comprise up to 20 carbon atoms, preferably up to 10, particularly preferably up to 8, especially preferably up to 6, e.g. up to 4 carbon atoms are preferred. Preferred acyl groups include formyl, acetyl, propionyl, benzoyl and naphthoyl especially acetyl.

In a preferred embodiment according to the invention, R¹ is OR³ and R² is a naphthoyl group substituted by an OR³ group, i.e. the compound of general formula (I) may be depicted as compound of sub formula (la):

(la) wherein each R independently represents or may contain deuterium, an optionally substituted alkyl or deutero alkyl group, an optionally substituted aryl or deutero aryl group.

In a preferred embodiment according to the invention, R¹ is OR³ and R² is an OR³-substituted naphthyl group, i.e. the compound of general formula (I) may be depicted as compound of sub formula (lb):

(lb) wherein each R³ independently represents an optionally substituted alkyl or deutero alkyl group, an optionally substituted aryl or deutero aryl group.

Any reference to compounds of general formula (I) naturally includes compounds of sub formulae (la) and (lb). It is also noted, that although the OR³ substituents in sub formulae (la) and (lb) are depicted to be in the 2 and 6 position on the naphthalene core, other positions on the naphthalene core are of course contemplated within the scope of the invention. The compounds defined herein have a chemical activity and polarity similar to that of diesel. The physical and chemical nature of the compounds used in the invention ensures that they are are very soluble and perfectly stable in oil and fuel, that they are compatible with combustion, environmentally acceptable, safe and will resist chemical laundering.

Particularly preferred for use in the invention are those compounds of formula (I) in which R¹ represents an unsubstituted alkoxy group, preferably a Ci_s alkoxy group, particularly preferably a Ci_4 alkoxy group, e.g. a methoxy, ethoxy, propoxy or isopropoxy group, butoxy, especially a methoxy group.

Also preferred for use in the invention are those compounds of formula (I) in which R² represents an unsubstituted acyl group, preferably a Ci_₆ acyl group, particularly preferably an acetyl group.

In especially preferred compounds R¹ represents a methoxy group and R² represents a hydrogen atom or an acetyl group.

(8) (9) (12)

Compound (1) is 2-methoxynaphthalene (nerolin, yara yara), compound (2) is 2- ethoxynaphthalene (nerolin, bromelia) and compound (3) is 2-(2-methylpropoxy)naphthalene (nerolin, fragarol). These compounds are known in the fragrance industry and are used as fragrances in the perfume and soap industries.

Compound (4) is 2-acetyl-6-methoxynaphthalene (acetyl, yara yara or acetynerolin) and is known as a precursor for pharmaceutical drugs such as Naproxen and Nabumetone and is also a fragrance. Compound (4) is a known impurity in Naproxen

The compound is most preferably selected from one or more of:-

These alkoxynaphthalene derivatives are ideally suited to be used as markers for hydrocarbon liquids and in particular for marking petroleum hydrocarbon fuels. The physicochemical properties and attributes of these alkoxynaphthalenes make them ideal markers to meet the current marker need.

All mineral oil based fuels contain significant quantities of naphthalene species and in particular the methylated derivatives of naphthalene. The alkoxynaphtalenes of this invention are very similar to the mineral oil methylnaphthalenes but differ sufficiently in both their physical and chemical properties to allow their specific detection and measurement in even the most complex matrices by a variety of technologies. Analytical measurements from % to ppb are possible. The similarity in physicochemical properties prevents the removal of the markers from the fuel by any reasonable physical or chemical means. The markers may be prepared on the very large scale by current industrial procedures. The markers of this invention are currently used in the fragrance and pharmaceutical markets and are produced in very large (1000 tonne) quantities.

The fixed position of substitution on the naphthalene ring confers a predictable variation in the basic physical and chemical properties of each compound within the overall marker family leading to a selection of markers with a range of properties including resistance to laundering techniques such as absorption on solid phase media and solvent extraction, consistency in analytical detection and measurement, and measurement to extremely low limits of detection. A number of members of this marker family also have additional physical and chemical properties that make them the preferred markers of this invention. The invention particularly concerns the use of 2-methoxynaphthalene (1), 2-ethoxynaphthalene (2), 2-isobutoxynaphthalene (3) and 2-acetyl-6-methoxynaphthalene (4) and l-acetyl-6-methoxynaphthalene (5), and the deuterated analogues (6, 7, 8, 9, 10, 11) to mark hydrocarbon liquids such as mineral oil and kerosene and bio-fuels.

The position of an alkoxy group on the naphthalene ring is known to alter the chemical properties of the naphthalene ring by selectively activating or deactivating other positions on the rings toward chemical reaction. For example, the methoxy group in 2-methoxynaphthalene is known to selectively activate the 1 and 6 positions toward bromination as described in US4628123A. This selective activation is associated with the electron density distribution of the naphthalene ring system. Surprisingly, the modulation of the electron distribution in an alkoxynaphthalene by the 2-alkoxy groups also affects the physical properties of the alkoxynaphthalene in such a way that is advantageous to their use as markers in complex hydrocarbon matrices.

The UV absorbance spectrum of 2-methoxynaphthalene for example is very different to that of a similarly methylated species in that it has a substantial extra absorbance maximum at 328 nm while the corresponding methylated species has none in this region. Measurement of 2- methoxynaphthalene by HPLC with UV detection at 328nm is therefore possible and measurements to extremely low levels are achieved without interference from the naphthalene and phenyl UV absorbing species of the matrix. Alkoxy substitution on other positions of the naphthalene ring do not result in a significant absorbance band at around 328nm.

The activation of specific carbons in the ring, especially the 6 position, by the 2-alkoxy group makes possible the preparation of single ring position isotope derivatives such as but not limited to the mono deuterated compounds 6, and 7. To those skilled in the art they may be prepared readily, economically and in high purity from the reaction of magnesium metal and the appropriate brominated 2-alkoxynaphthalene (2-bromo-6-alkoxynaphthalene) to form the corresponding Grignard reagent and then by reaction of the Grignard reagent with deuterium oxide or other suitable deuterium source such as D₂SO₄. "Twenty Years of Naproxen Technology". Organic Process Research & Development 1997, 1 , 7276 ( Harrington and Ludovic)

Compounds 4 and 5 are commonly prepared by the Freidel-Crafts acetylation of the 2- alkoxynaphthalene. A re-examination of the Friedel-Crafts acetylation of 2-methoxynaphthalene

R. B. Girdler, P. H. Gore and J. A. Hoskins

J. Chem. Soc. C, 1966, 181-185

The 2-alkoxynaphthalenes are usually prepared on the small scale by alkylation of β-naphthol with alkylating reagents such as dimethylsulphate. Industrial scale production may use high temperature gas phase continuous methylation technologies among others.

While 2-alkoxynaphthalenes are relatively unreactive they do undergo some chemical reactions such as those described above, however, the reagents, solvents and conditions that are required to complete such reactions are not generally compatible with most hydrocarbon liquids and especially not compatible with mineral oil based fuels which contain many compounds that would also react and therefore adversely affect the fuel.

2-alkoxynaphthalenes of the favoured embodiment of the invention also have other physical properties that are advantageous for chemical markers:

1. They sublime at low temperatures They are low melting

They are widely used in the pharmaceutical industry as precursors to drugs such as Naproxen and Nabumetone and are readily available in extremely large quantities.

The 2-methoxynaphthalene, 2-ethoxynaphthalene and 2- butoxynaphthalenes (nerolins) have a very distinctive and intense orange blossom fragrance (neroli) with a substantivity factor of 400 and are widely used in the fragrance and flavours industry.

They 2-alkoxynaphthalenes can be detected and quantified using a wide range of analytical technologies

a. Gas Chromatography with the usual detection systems such as FID,TCD, MS and MS/MS

b. HPLC Chromatography with the usual detection systems of UV/DAD detection, fluorescence, Mass Spectrometry with ESI, APCI and also APPI Photoionization. (without the need for dopant addition).

c. The compounds fragrance can be detected at ppm levels by the human olfactory system in complex matrices such as diesel and kerosene after the smelly volatile hydrocarbon fractions have evaporated. Animal olfactory systems (canine for example) can detect to much lower levels with greater specificity in the same complex matrices.

A preferred embodiment of the invention is the addition of a fragrant marker to the hydrocarbon fuel. The neroli smell will persist long after the hydrocarbon smells have diminished when the fuel is exposed to evaporation deliberately or through accidental spillage. Importantly, the concentration of marker in the fuel cannot be measured using the smell intensity. The fragrant marker will thus serve both as a semi-overt and a covert marker depending on the circumstances but will not provide information on the concentration of the marker to the criminal as the visible dyes that obey the Beer-Lambert law certainly do. The substitution of the 2-alkoxy group with specific alkanes described above generates a homologous series of 2-alkoxy derivatives with predictable GC and HPLC relative retention times while still maintaining the fundamental physical and chemical attributes of the marker. Thus a suitable specific marker can be chosen "off the shelf and the choice based on the characteristics of the marker and the requirements of the substance to be marked. The acetyl alkoxy derivatives also can be prepared in a homologous series as described above. The position of the acetyl group on the naphthalene ring relative to the alkoxy group confers different properties on the individual positional isomers. The presence of the methoxy group on the 6 position and its effect on the electronically conjugated carbonyl bond in the 2 position is primarily responsible for the favourable marker related properties of the 2-acetyl-6-methoxynaphthalene. In contrast to other naphthalene derivatives such as acetonaphthone. For example, the extremely high (at about 10 times) extinction coefficient of absorption at around 254nm in the UV compared to other naphthalene derivatives such as acetonaphthone derivatives and the like allows detection of the 2-acetyl-6-methoxynaphthalene to extremely low levels of detection by HPLC/UV. Also, and for the same reasons, the enhanced fluorescence observed for 2-acetyl-6- methoxynaphthalene compared to other naphthalene derivatives such as acetylnaphthalenes lacking an alkoxy group in the 6 position makes the measurement of the 2-acetyl-6-methoxynaphthalene to ppb levels readily achievable with simple HPLC/fluorescence technology. Reference: R. Gatti, V. Cavrini, P. Roveri, Chromatographia, Vol 33, No. ½, January 1992

Interestingly the 2-acetyl-6-methoxynaphthalene (4) and the l-acetyl-6- methoxynaphthalene (5) also differ in a number of key marker attributes.

a. The 1 -acetyl is extremely resistant to all laundering techniques including absorption on solids

b. The 2-acetyl is less resistant than the 1 -acetyl to absorption on solids but equally resistant to all other laundering technologies

c. The 2-acetyl fluoresces very strongly while the 1 -acetyl fluoresces very weakly

d. The 2-acetyl is readily measurable by simple kit analysis in the field e. The 1 -acetyl is extremely resistant to methanol /water extraction f. The 1 -acetyl alkoxynaphthalene is the kinetically stable form and the 2- acetyl is the thermodynamically stable form. The 1 -acetyl can be transformed (at the analytical scale) to the 2-acetyl by known technology. Selective synthesis of 2-acetyl-6-methoxynaphthalene over HBEA zeolite, Fromentin, E; Coustard, J-M.; Guisnet, M.; Royal Society of Chemistry special publication; 266, 145-151, 2001 g. An embodiment of the invention involves the marking of the hydrocarbon with the highly laundering resistant 1 -acetyl isomer. The 1 -acetyl may then be transformed into the 2-acetyl in an analytical sample preparation. The 2-acetyl is then readily extracted and analysed by a simple field test.

The 1 -acetyl and 2-acetyl compounds may be used individually or together to allow the analysis of either marker where appropriate, for example, where adulteration or smuggling or theft is involved. Both the 1-acety and the 2-acetyl methoxynaphthalenes elute individually from the HPLC and elute before any other significant components of fuel.

The presence of the alkoxy group on the 2 position (or 6 position) of the naphthalene ring is also associated with the excellent safety record of this group of compounds in humans. As described already they are used globally in many substances for fragrance and flavour purposes. The overall safety properties of the alkoxynaphthalenes are in stark contrast to that of naphthalene itself which has been banned in moth balls in Europe since 2008. Simple acetyl derivatives of naphthalene such as 1-acetynaphthalene are also considered hazardous especially orally and as irritants and skin sensitizers.

The substitution of an atom such as hydrogen with deuterium or a carbon- 12 with carbon- 13 in a marker does not alter the physical or chemical properties sufficiently to change their response to laundering. Deuterium and carbon- 13 isotopes are present in nature and deuterium and carbon- 13 analogues of all hydrocarbons are ubiquitous.

The invention provides a set of markers that can be used in a method of marking hydrocarbon fuels that deliver the following key advantages:

1. entirely foreign to the liquid to be marked

2. can be supplied as concentrated solutions in compatible solvents

3. may be detected in the field

4. are not obscured by unstable natural components of the liquids

5. are stable over the storage life of the marked liquid

6. can be detected and measured by many alternative laboratory methods

7. resistance to laundering

8. resistant to chemical change 9. compatible with the use of the marked liquid (combustion for example)

10. compliant with health and safety regulations

11. acceptable environmental impact

12. can be used in all petroleum derived fuels and biological derived fuels and mixtures thereof

13. cannot be observed visually when dissolved in a marked substance

14. may be measured over a wide range of concentrations in simple and complex matrices

15. Analytical methods for marker measurement are validated to international standards.

16. Markers may be measured to forensic standards to support legal proceedings

17. commercially acceptable (cost)

18. different markers for different jurisdictions to deter smuggling

19. markers may be identified and incorporated into legislation

20. testing methodology may be published and is generally available

21. Allow the detection of concealed marked fuel The markers can be used in combination with other markers from the defined marker set or individually to mark a wide variety of complex hydrocarbon liquids and fuels. A given marker or combination of markers with specific physicochemical properties may be matched with the hydrocarbon liquid physicochemical properties to satisfy the specific marking requirements such as the detection of adulteration, dilution, substitution or the prevention of laundering.

In accordance with the invention, the compounds may be added to and dissolved in fuel in a broad range of predetermined amounts, either individually or in combination. The compounds can also be used in combination with further markers and additives, such as dyes or pigments, which may be required by law.

Conventionally, hydrocarbon markers and additives are added during production, when fuel storage tanks or reservoirs are being filled. The compounds may be prepared in high concentrations in fuel or other suitable solvent directly as a concentrate. For example, a compound may be added as a solid to fuel and dissolved therein to give a specified concentration. This concentrate can then be added to the hydrocarbon to be marked.

Thus, a fuel concentrate comprising a compound of the invention or an enantiomer or diastereomer thereof forms a further aspect of the invention. The low melting nature of the markers also provides the opportunity of adding the markers as a neat liquid to the substance to be marked.

Large quantities of the compounds especially (1), (2), (3) and (4) are available at low cost thus making them suitable for addition in larger amounts to fuel as markers. Large amounts of marker make detection easier and removal more difficult. The actual amount of marker added to a given hydrocarbon will vary depending on such factors as the purpose of the marker and the level of detection required. Ppb to % levels are possible. The availability of large quantities of low cost marker is also important since billions litres of fuel require marking in the current market.

In a preferred embodiment of the invention, at least one compound is added to and dissolved in the hydrocarbon to be marked in an amount of at least 5ppm, preferably in an amount in the range of from 5 ppm to 200 ppm, particularly preferably in the range of from 50 ppm to 100 ppm.

The alkoxy nature of the marker compounds ensures unique mass spectral fragmentation patterns relative to the natural components of fuel and allows the specific detection and quantification of the markers in the incredibly complex fuel matrix to very low levels (e.g. sub ppm levels) by a variety of common analytical procedures. Gas chromatography-mass spectrometry (GC-MS) is ideal for this purpose and does not require any pre-sample treatment or preparation.

Preferably single quadrupole GC-MS or GC-tandem MS (GC-MS/MS) is used. As will be appreciated by those skilled in the art, MS/MS analysis may comprise product ion scan, precursor ion scan, multiple reaction monitoring (MRM).

A wide range of other analytical technologies and combinations of these technologies with each other and with GC-MS may be employed in the analysis of the markers. Exemplary techniques include HPLC, UV/Vis spectrometry, fluorescence spectrometry, olfactory measurement, thin layer chromatography (TLC), FID and AED. Each of these techniques can be automated.

GC-MS combines the features of gas-liquid chromatography (separation of components) and mass spectrometry (detection of the compounds of interest based on their mass fragmentation pattern) to identify different substances within a test sample. The physical and chemical attributes of the compounds used in the invention allow their accurate and specific quantification to very low ppm levels with GC-MS. Single quadrupole GC-MS is common in modern analytical laboratories and is ideal for the separation of volatile organics in a complex mixture. Markers according to the invention are detectable and quantifiable in all common fuel types, including rebated fuel, at prescribed dosage levels (e.g. at least 20 ppm) using low cost GC-MS. Ultra low levels of marker (e.g. at least 200 ppb) can be detected in rebated fuel using GC- MS/MS. Thus, in a further aspect the invention provides a method of identifying fuel marked with a compound as defined herein comprising the use of GC-MS.

Another unique feature of the invention is related to the fragrant properties of certain compounds. The distinctive fragrance of these compounds has the feature that it lingers where other fragrances evaporate and disappear. For example, compounds (1) and (2) have an intense and distinct fragrance of orange blossom (neroli) at parts per billion levels. The intensity of the fragrance and the fragrance itself is directly linked to the presence of the alkoxy group at the 2 or 6 position on the naphthalene ring. The linger or persistence of fragrances is well defined and measurable. The persistence factor for compound (1, 2 and 3) is very high at about 400 hours.

The persistence of the fragrance of the markers is enhanced further due to another special property of this group of compounds, sublimation. Certain compounds of formula (I), e.g. compounds (1) and (2), sublime at room temperature. Some compounds of formula (I) with increased molecular weight and/or polarity sublime to a lesser degree than compounds (1) and (2). The ability of these markers to enter the gas phase and then to condense directly as a solid on surfaces where it can stick then re-enter the gas phase in a prolonged equilibrium gas/solid cycle enhances the property of a lingering smell. This sublimation equilibrium cycle has the effect that prolonged unprotected contact with large quantities of fuel containing ppm levels of the marker compounds will result in ppb levels of compound condensing on clothing and equipment. Such levels are harmless but are easily detected and recognised by the human or animal olfactory system. This special attribute of the markers allows the detection of these markers by the human olfactory system when other interfering/masking smelly substances in the marked hydrocarbon have diminished. The fragrance can only be removed by very slow natural evaporation over time (months) or with exhaustive laundering with detergent. This phenomenon will mark those criminals actively involved in fuel laundering and their equipment used in fuel laundering and render them easily identifiable. The lingering smell from the markers will act as a deterrent to those who would operate laundering equipment that exposes large quantities of marked fuel to the environment without sufficient containment.

Olfactory (human or animal) detection and identification either directly or with the aid of technology is an acceptable analytical methodology for use in the invention. For example, the olfactory detection port for GC by Gerstel allows sensing of compounds by the human nose as they elute from the gas chromatograph. Canine smell sensitivity is commonly used for the detection of illicit drugs and other hidden substances by law enforcement agencies such as customs and revenue agencies. Roadside detection of the markers by smell is feasible. In accordance with the invention, fluorescence measurement may also be used as a method of detecting certain compounds of formula (I), i.e. compounds of formula (I) which have a carbonyl group next to the alkoxynaphthalene core, e.g. compounds wherein R² is an acyl group.

The presence of fluorescent marker compounds such as (4) can be verified by a simple and quick fluorescence test to allow in field revenue status determination of the hydrocarbon without the use of sophisticated technology or equipment. The precise amount of each marker in a fuel sample from the field can then be measured at a later date by an alternate validated laboratory method. In the fluorescent test mentioned above, a small sample of a solution containing a compound of general formula (I) in solution (e.g. methanol) is placed (spotted) onto a TLC plate coated with fluorescent dye, e.g. the green fluorescent dye F254. The plate is placed in a beam of UV light, e.g. at 254 nm. The F254 dye glows green everywhere except where the compound is applied. This is because the compound (I) absorbs the irradiating light and prevents fluorescence by the dye underneath it.

The compounds of general formula (I) also absorb the UV light and fluoresce giving the spot a distinct colour. For example, compound (4) fluoresces blue. The darkness of the applied spot and the intensity of the light emitted from the applied spot are directly proportional to the amount of compound (4) present in the spot. This visual effect allows detection of the compound of formula (I) at extremely low levels by the naked eye.

The intensity of the spot may be compared visually with a calibration card of spots for defined ppm levels. The level of compound of formula (I) in a solution may be determined in this way.

Thus, in a further aspect the invention provides a method of identifying a hydrocarbon (e.g. a fuel) marked with a compound of formula (I) in which R² is an acyl group comprising the use of fluorescence measurement.

The fluorescence of the compounds of formula (I) can be used in the road side detection of the marker in fuel using a simple test kit (e.g. using a portable TLC fluorescent technique).

For certain compounds for use in the invention, for example, compound (4), direct fluorescence measurement, e.g. observation of this fluorescence with the naked eye directly is possible once the compound has been partially separated from the marked hydrocarbon (e.g. rebated fuel) by an analytical scale solvent extraction. This is due to the fact that compounds of general formula (I) in which R² is an acyl group fluoresce when irradiated with UV light, e.g. compound (4) absorbs UV light at between 200-350 nm and emits intense visible blue light at about 440 nm. The most intense emission of blue light is achieved by irradiation with 313nm light. Lamps with this wavelength (UVB) are commonly used for dermato logical phototherapy treatments and are readily available.

Compound (4) has a slightly more polar nature than natural fuel components and has a distinctive UV spectrum with a very high UV extinction coefficient. The very slight increase in polarity relative to the majority of natural fuel components allows an analytical scale procedure involving the selective extraction/partition of analytical amounts of this compound from marked hydrocarbons with a polar matrix, for example in a solvent such as methanol or in silica gel solid, e.g. a methanol/water (80:20 v/v) extraction. It is noted that any combination of water to methanol may be used to extract the marker to a greater or lesser degree. There is greater extraction of fuel components at the higher methanol levels. The fluorescence resulting from the interaction with UV light may be observed directly by the eye as detailed above. When diesel containing the compound of general formula (I) is extracted with a set volume of a water/methanol mixture (20:80 for example) a percentage of the compound of formula (I) will partition into the extraction solution from the diesel. Preferred mixtures include 10-50 % water/methanol mixtures, especially 20%. The percentage of the partition is constant for a given extraction solution. In the example of a water/methanol mixture, the concentration of compound of formula (I) in the methanol is directly related to the concentration of compound of formula (I) in the diesel. The majority of marker remains in the fuel.

The very small amounts (sub ppm) of the compound in the aqueous methanol can be readily measured with an appropriate spectrometer (e.g. standard HPLC technology with diode array (DAD) and/or fluorescent (FLD) detection) or visualised using a simple new procedure involving a fluorescence viewer. 313 nm is the preferred wavelength preferred for HPLC and spectrofluorimetry detection. Suitable viewers are available. Thus, in a further aspect the invention provides a method of identifying fuel marked with a compound of general formula (I) or an enantiomer or diastereomer thereof comprising fluorescence observation by the naked eye.

In the methods of the invention, the hydrocarbon is preferably selected from among mineral oils, fuel, diesel, petrol (gasoline), paraffin oil (kerosene), gas oil (fuel oil) and petroleum and fuels from biological sources. Particularly preferably, the hydrocarbon is diesel.

Deuterium isotopes of each of the compounds of formula (I) are also suitable as hydrocarbon markers and such isotopic variants form a further aspect of the invention. As described already alkoxy substituents on the compounds of formula (I) interact with the electron density of the naphthalene ring. This allows for the preparation of physically and chemically identical compounds with a deuterium isotope in place of hydrogen. The deuterated versions of the compounds of formula (I) can only be distinguished from the normal hydrogen compounds by mass spectrometry.

Markers with different isotopic ratios may be made simply by preparing mixtures by weight. A particular isotopic ratio mixture in a marker may be used to mark a specific hydrocarbon. Analysis of the isotopic ratio of the marker in a hydrocarbon (e.g. by standard GC/MS methodology, or HPLC/MS) will therefore be useful in defining the exact source (refinery, distribution centre, retailer, country) and the revenue status of the original marked hydrocarbon. The identification of the source of fuel is of particular importance in combating criminal activities such as smuggling and environmental spillage and dumping of fuel. Surprisingly, the alkoxynaphthalene markers of this invention, unlike many other similar compounds, form exclusively the parent ion species M⁺ rather than a mixture of M⁺ and (M+H)⁺ in the HPLC using the Atmospheric Pressure Photoionization process for ionization (APPI). Also surprisingly the APPI process, in this case, does not require the addition of a dopant species as is usual to achieve the formation of the ions. Readily available HPLC/ APPI mass spectral analysis does therefore provide the means to measure the isotopic composition of the markers and using the same HPLC method as is used for detection with UV or Fluorescence. This feature of the markers allows for the automated comprehensive analysis of marker in the marked fuel using a single HPLC methodology and when used in tandem with a multitude of detection methodologies for a single injection of neat sample.

The combination of deuterated and non-deuterated compounds in a single marker composition forms a further embodiment of the invention. This embodiment adds an increased level of variation in the markers and will allow a greater number of possible marker combinations for marking the rebated fuel. The deuterated and non-deuterated analogs are indistinguishable from each other as hydrocarbon markers both chemically and physically and they also retain the same fragrance characteristics.

Thus viewed from a further aspect, the invention provides a fuel marker composition comprising (i) at least one compound of formula (I), or an enantiomer or diastereomer thereof and (ii) an additive.

Suitable additives for inclusion in such compositions are well known in the art and are not especially limited. These include dissolution aids, miscibility aids and stability aids. In accordance with the invention, the fuel marker composition may also include further markers, such as those required by law, e.g. solvent yellow 124, solvent green 33, solvent blue 79, solvent blue 35, sudan blue 79, sudan blue 35, solvent red 19, solvent red 24, solvent red 161, solvent red 164 and the like. The fuel marker composition may also comprise antioxidants, such as quinazarin and anti-theft dyes, e.g. sudan liquid blue, solvent blue 36, sudan liquid yellow, solvent yellow 12, solvent yellow 14, solvent yellow 18, solvent yellow 56, sudan liquid green, solvent green 3, solvent violet 13, solvent violet 14 and the like.

Thus, the invention provides a method of marking hydrocarbons comprising the addition to the h drocarbon or the mixing with the hydrocarbon of at least one compound of the formula:-

(8) (9)

Also provided is a method of marking hydrocarbons comprising the addition to the hydrocarbon or the mixing with the hydrocarbon of at least one compound of the formula:-

(1 ) (2)

Further provided is a method of marking hydrocarbons comprising the addition to the hydrocarbon or the mixing with the hydrocarbon of at least one deuterium isotope analog of at least one of the compounds (1), (2), (3), (4) or (5) as defined above. The invention also provides a method of marking hydrocarbons comprising the addition to the hydrocarbon or the mixing with the hydrocarbon of at least one compound of the formula:-

Also provided is a method of marking hydrocarbons comprising the addition to the hydrocarbon or the mixing with the hydrocarbon of at least one compound of the formula:-

The invention also provides a method of marking hydrocarbons comprising the addition to the hydrocarbon or the mixing with the hydrocarbon of a compound of the formula:-

In some embodiments the compounds are added to and dissolved in fuel either individually or in combination.

The compounds may be used in combination with further markers, such as dyes or pigments. At least one compound may be added to and dissolved in the hydrocarbon to be marked in an amount of at least 0.5ppm.

At least one compound may be added to and dissolved in the hydrocarbon to be marked in an amount of at least 5ppm.

The compound may be added in an amount in the range of from 5 ppm to 200 ppm. The compound may be added in an amount in the range of from 50 ppm to 100 ppm.

In some embodiments more than one marker compound is used and the marker compounds are added in different concentrations to each other.

In one case compound 5 is dissolved in the marked hydrocarbon liquid and is subsequently transformed into compound 4.

The marker may comprise a composite of or with deuterated isotopic isomers as defined in any of claims 1, 3 or 4. Also provided is a method of identifying fuel marked with a compound of the invention comprising detecting the presence of a compound of the invention in a sample.

The detection method may involve the use of gas chromatography-mass spectrometry. The detection method may involve olfactory (human or animal) detection and identification either directly or with the aid of technology.

In one case the marker compound has a carbonyl group next to the alkoxynaphthalene core and the detection method comprises use of fluorescence measurement. The fluorescence detection may be by the naked eye.

In some embodiments the detection involves chemically converting any one of compounds as defined into compound 4 or 5 for the purpose of detection or quantitative analysis. In some cases compound 4 is selectively extracted from the marked hydrocarbon using a solvent mixture for the purpose of detection and measurement. The detection may comprise detecting compound 4 in the extraction solution. The quantity of compound 4 in the extraction solution may be measured. The method may comprise analysing the extracted solution for marker 4 by a tic, uv, and/or fluorescence technique. The result of the tic test may be visually evaluated. In another case the method comprises visually comparing the result of the tic test with a pre- prepared standard chart. The pre-prepared standard chart may be in an electronic form. The electronic form may comprise a digital picture defined by pixels of different colours capable of being individually counted by electronic means and delivering total pixel numbers corresponding to the concentration of marker 4 in the marked liquid. In one case detecting compound 4 involves treating the extracted marker with Bailey solution to confirm the presence or absence of ketone species. In one case the extracted ketone species is passed through a cartridge comprising immobilised 2,4 dinitrophenylhydrazine to provide a coloured species. In some cases compound 4 is detected by analysing the extracted marker chromatographically or directly by fluorescence spectrometry.

In one embodiment the marker comprises a composite of deuterated isotopic isomers as defined and the method comprises measuring the isotopic mass composition. The method may involve comparing the measured isotopic mass composition of the fuel marker in the fuel to the isotopic mass composition of the fuel marker prior to addition to the fuel.

In some embodiments deuterated analogs of a marker are added to the non-deuterated analogs in a weight percent of between 0.1% to 99.9%.

In some embodiments the marker is detected and measured by HPLC. The marker may be detected and measured by HPLC without sample modification and the analysis may be performed automatically. The marker may be detected at a wavelength of between 250nm and 350 nm.

In some embodiments the marker is detected by APCI mass detection or ESI mass detection or fluorescence detection. In one case the marker is detected by APPI mass detection. The marker may be detected by APPI mass detection with or without the addition of a dopant.

In some cases the marker isotopic analog composition is measured by APPI or APCI mass detection.

In some embodiments the marker isotopic composition is compared to reference marker isotopic analog compositions. The isotopic analog composition of the marker may be used to define the origin of the marked substance.

In one embodiment the marker is detected and measured using a kit.

In one case the kit comprises a liquid transfer device, a liquid measuring device, adsorbent material, a UV irradiation device, a fluorescence viewer device, and marker reference material. The kit may also include an extraction solvent. The adsorbent material may be fixed on a solid support. In some cases the adsorbent material contains a fluorescent substance. In one case fluorescence due to the marker is detected by the naked eye. Additionally or alternatively fluorescence due to the marker is detected electronically. The measured fluorescence values due to marker may be compared with pre-determined reference values and the marker concentration in the marked substance calculated.

In one embodiment a sample is prepared for a smell test using a kit. The kit may comprise a liquid transfer device, a liquid measuring device and an adsorbent substance. In some cases a kit that uses sublimation is used to isolate marker from the marked hydrocarbon. The kit may comprise a device to heat the sample hydrocarbon to vaporization temperature. The kit may comprise a cold surface for contact with the vapour and on which the marker desublimes. The desublimed marker may be made available to analytical technology for measurement.

The hydrocarbon may be selected from among mineral oils, fuel, diesel, petrol (gasoline), paraffin oil (kerosene), gas oil (fuel oil), petroleum, petroleum products, biologically derived fuels, and hydrocarbon solvents. In one case the hydrocarbon is diesel. In another case the hydrocarbon is kerosene. In a further case the hydrocarbon is marine diesel. Also provided is the use of a compound as defined in any of claims 1 to 6 for marking a hydrocarbon fuel. The invention also provides use of a deuterium isotopic analog of compounds (1), (2), (3), (4) or (5) as hydrocarbon markers.

Also provided is the use of a combination of deuterated and non-deuterated compounds as defined as a single marker composition.

The invention also provides a fuel marker concentrate comprising a compound as defined in any of claims 1 to 6.

Further provided is a fuel marker composition comprising (i) at least one compound as defined and (ii) an additive. The composition may include a further marker. The composition may include an antioxidant.

The invention further provides the use of a compound as defined herein for marking a hydrocarbon fuel.

Brief Description of the Figures

In a number of the figures, the following notation is given: ml for compound (1), m2 for compound (2) and m3 for compound (4). Description of the figures: Figs, la and lb are graphs of fluorescence vs concentration of compound (4) in diesel

(HPLC/FLD);

Fig. 2 is a graph of fluorescence vs concentration of 20: 1 diluted extract of compound (4) in diesel (direct spectrometer measurement);

Figs. 3a to 3d show GC/MS (SIM) chromatographs for compounds (1), (2) and (4) in kerosene at 100 ppm;

Fig. 4a is a validated GC/MS graph of integrated peak area vs concentration of compound (1) in diesel. Figure 4b is a validated GC/MS graph of integrated peak area vs concentration of compound (2) in diesel. Figure 4c is a validated GC/MS graph of integrated peak area vs concentration of compound (4) in diesel;

Fig. 5a is a GC/MS-MS graph of integrated peak area vs concentration of compound (1) in diesel. Figure 5b is a GC/MS-MS graph of integrated peak area vs concentration of compound (2) in diesel. Figure 5c is a GC/MS-MS graph of integrated peak area vs concentration of compound (4) in diesel;

Figs. 6a to 6b show UV spectra of compounds (1) and (4);

Fig. 6c is the UV spectrum of methylnaphthalenes;

Fig. 7 shows HPLC with UV 328 nm detection of compound (1) and compound (4) at 150 ppm in diesel;

Fig. 8 is a graph showing the reduced presence of compound (4) in diesel after attempted laundering with large amounts of activated Fuller's earth;

Fig. 9 shows a road test TLC for compound (4) in diesel;

Fig. 10 shows a road test TLC for compound (4) in diesel after attempted laundering with large amounts of activated Fuller's earth;

Figs. 11a and l ib show validation data for compound (1) in fuel by HPLC/UV at 328 nm;

Figs. 12a to 12c show GC/MS validation data for compounds (1), (2) and (4), respectively, in kerosene; Figs. 13a to 13c show further validation data for compounds (1), (2) and (4), respectively, in kerosene; Fig. 14a shows the HPLC chromatogram of 50 ppm of a 50:50 (w/w%) of 2- methoxynaphthalene (1) and 2-methoxynaphthalene-D (6) in kerosene using DAD UV328nm and APPI detection; and Fig. 14b shows the HPLC chromatogram of 50 ppm of 2-methoxynaphthalene (1) in kerosene using APPI detection.

Detailed Description

The invention is illustrated by the following examples:

Example 1 - Identification of compounds of general formula (I) in fuel Fluorescence

Figures la and b show HPLC Fluorescence detection FLD of compound (4) at 50 ppm to 0 ppm and 5 ppm to 0 ppm, respectively. Figure 2 shows direct fluorescence measurement of a 20: 1 diluted water/methanol extract using a spectrophotometer (Excitation wavelength of 313 nm, Emission wavelength of 440 nm).

GC-MS

Figures 3a to 3d show GC/MS chromatographs for compounds (1), (2) and (4) in kerosene at 100 ppm. Peak 23.592 is compound (1), peak 25.421 is compound (2) and peak 33.544 is compound (4). The linear relationship of concentration (ppm) to integrated peak area in Figures 4a-4c validates this GC-MS detection method (0 to 250 ppm with LOD at 20 ppm). GC-MS/MS

Figure 5a shows quantitation to sub ppm levels of compound (1) in diesel by MRM GC-MS/MS (158, 1 15). Figure 5b shows quantitation to sub ppm levels of compound (2) in diesel by MRM GC-MS/MS (172,144). Figure 5c shows quantitation to sub ppm levels of compound (5) in diesel GC-MS/MS MRM (200,115).

UV

It is an important requirement of a marker test method that it does not generate false positive results. The UV spectra of the markers are very different from those spectra found in hydrocarbon fuels. The markers are sufficiently resolved from other fuel components in the HPLC for the UV spectra to be used to confirm the identification of a marker in the fuel simply by measurement of the UV spectrum in the HPLC and comparison to a standard spectrum of a given marker. The fine structure in the UV spectrum observed around 300nm in the alkoxynaphthalenes is especially useful in this respect.

The UV spectra of compounds (1) and (4) are presented in Figure 6a and Figure 6b respectively. The unique nature of the UV in both compounds is evident from these Figures. In Figure 6a, the absorbance in the 300 nm region and the fine structure of this absorbance is unique to the alkoxynaphthalenes when compared to the UV spectra of diesel and kerosene components. Compound (2) has an almost identical UV spectrum to compound (1).

The very high absorbance of compound (4) at about the 260 nm region is a result of the conjugated carbonyl at the 2 position on the naphthalene ring and the methoxy group at position 6. The absorbances at about 300 nm are again evident in the graph for compound (4) but are more intense than for compound (1).

The presence of an absorbance at 328 nm that is not present in similar diesel compounds such as the methylnaphthalenes allows the selective detection and accurate quantitation of both compound (1) and compound (4) in the complex diesel matrix easily and rapidly with simple and readily available HPLC instrumentation.

HPLC/UV

HPLC with UV 328 nm detection of compound (1) and compund (4) at 150 ppm in diesel is shown in Figure 7. In this Figure, compound (2) is overlapped by a diesel component. Straightforward modifications to the HPLC method remove this interference.

HPLC analysis of the markers may be suitable as a roadside detection method using a simple mobile HPLC unit. The method may be optimised further for speed and sensitivity using fast HPLC and rapid resolution columns. Interestingly the method works well with no sample preparation. Injection of neat diesel or kerosene for example gives excellent chromatography for the detection of the alkoxynaphthalenes with no deterioration in performance. This surprising feature of the HPLC analysis of the alkoxynaphthalenes in all fuel matrices allows for the automation of the HPLC analysis both in the laboratory and in the field. A further advantage of this feature is that the HPLC analysis uses a small aliquot of the sample only and does not change the nature of the remaining sample material in any way. This is important for law enforcement and prosecution purposes.

Figure 14a (page 43) shows the HPLC chromatogram of a mixture of the 2-methoxynaphthalene (1) and 2-methoxynaphthalene-D analog (6) using DAD UV328nm and APPI mass spectral detection. As expected (1) and (6) have identical retention times in the HPLC. The isotopic profiles measured here are the same as measured on the mixture of (1) and (6) independent of the sample matrix and using the same HPLC method. The isotopic results from the HPLC are also consistent with those obtained by GC/Mass Spectral analysis. Similar results were obtained for other mixtures of (1) and (6) and in different matrices (Fig 14b).

Example 2 - Resistance to laundering

Attempts at liquid and solid laundering were carried out with a broad selection of agents and the results are shown in Table 1 below.

Table 1. Results of laundering studies on compounds (1), (2) and (4)

Values measured by GCMS and HPLC/UV/Fluorescence

Before Launder Compound (1) (2) (4)

50 PPM STD ppm ppm ppm

50 50 50

Liquid laundering Volume to diesel Post Launder

4M H₂S0₄ 1 to 1 51.0 51.5 47.6

4M HC1 1 to 1 52.5 53.0 49.9

4M KOH 1 to 1 61.0 58.8 58.4

Solid laundering %Weight to diesel

Fuller's earth (cat litter) 20 50.6 50.6 39.5

Fuller's earth ( cat litter) 100 52.3 3.8

Fuller's earth (cat litter, pulverized) 75 52.9 1.4

activated carbon 20 37.8 11.3

activated fullers earth 10 43.1 7.5

(100-200 mesh) Sigma Aldrich 20 34.0 2.9

30 39.5 1.5 40 1.3

Decant half diesel and replace 20 51.1 7.1

Measured by HPLC/UV/FLD, compound (2) values taken to be the same as

for compound (1)

Compounds (1) and (2) were found to be extremely resistant to all laundering attempts and behaved identically in all the laundering tests. Compound (4) also proved extremely resistant to laundering with strong acids and bases.

Compound (4) was found to be somewhat reduced in diesel by treatment with Fuller's earth, activated Fuller's earth and activated carbon. However, excessive amounts of these solid laundering agents were required to reduce this compound to low levels. This is consistent with the slightly more polar nature of compound (4) relative to other diesel components.

Although it was found that reduction from 50 ppm to single figure ppm levels was possible using 100 % by weight of Fuller's earth, the presence of remaining compound (4) was readily detected by any of the following analytical methods: Extraction/TLC/FL440, Extraction/Spectrophotometer Ex313/Em440 or the extremely sensitive HPLC/FL440 (Ex313/Em440).

The extremely active Fuller's earth 100-200 mesh from Sigma Aldrich was found to be the most efficient material at reducing compound (4) in diesel. This material is an off-white very fine powder. At 40 % by weight with diesel the material absorbed almost all the diesel into itself. Even in this extreme case the supernatant diesel still had about 1.5 ppm of compound (4). This amount of compound (4) was more than sufficient to be easily detected by the analytical methodology described above.

Replacement of 50 % of the diesel with fresh marked material showed far less reduction of compound (4) in the supernatant. The ability of the activated Fuller's earth to remove compound (4) diminishes dramatically with reuse.

Figure 8 shows the exponential nature of the removal of compound (4) during the initial treatment with large amounts of activated Fuller's earth. The data indicates that even in the extreme case compound (4) will not be reduced to levels less than about lppm. Such levels are readily detected and quantified.

Example 3 - Fast and convenient method of determining the presence of compound (4) in fuel

Test kit contents: Calibrated test card

Silica Gel, F254 TLC plate, 4 cm x 6 cm

Plastic graduated Pasteur pipette

2 mL glass vial with screw cap

2 mL water/methanol mix (20%water in methanol)

Plastic capillary Method:

1 mL of the fuel to be tested (diesel) was placed into a 2 ml vial using a Pasteur pipette. 1 mL water/methanol mix was added. The mixture was shaken well until uniform cloudy white and then allowed to settle and separate. This took about 4 minutes. A capillary was dipped into the lower water layer allowing the lower liquid to enter the capillary. The capillary was subsequently taken out of the mixture and the liquid removed from the capillary (by touching the end of the capillary onto a tissue) until only 1 cm remained in the capillary. The tip of the capillary was placed onto a designated point on a silica gel TLC plate coated with F254 forming a spot of about 3 mm diameter (5μ1 spot). This was allowed to dry for 30 seconds and observed under a fluorescence viewer at 254 nm.

As shown in Figure 9, a dark blue ring toward the centre and fringes of the spot was seen confirming the presence of compound (4). The intensity of the blue ringed spot was compared to a calibration card and the level of marker in the diesel in ppm (0-30 ppm) was determined by comparing the sample spot with the spots for different ppm levels on the calibrated card.

Example 4 - Organoleptic test kit and method

Kit: A plastic bag with an adsorbent material (tissue for example) in it, pipette, wide necked bottle Method:

5 mL of the diesel sample is placed in wide necked bottle. A tissue is placed over the bottle mouth for five minutes to absorb diesel vapours. It should be ensured that the tissue is not wet with diesel liquid. The tissue is removed and placed to one side to dry for about 5 minutes.

The dry tissue is smelled. A distinct sweet orange blossom smell will be present on the tissue if there are markers such as compound (1) or (2) in the diesel sample.

Organoleptic detection of the compounds may be performed by human, animal or machine

Example 5 - Fast and convenient method of determining the presence of compound (4) in laundered diesel

A sample of 50 ppm diesel marked with a combination of compounds (1), (2) and (4) was treated with 20% Activated Fuller's earth as a slurry overnight. The supernatant diesel was decanted and analysed by HPLC UV/FLD.

The supernatant contained 2 ppm of compound (4) and 48 ppm of compounds (1) and (2). The supernatant was extracted with an equal volume of 80:20 methanol/water. 5uL of extract was applied to a TLCF254 plate as described in Example 3. A sample of unmarked diesel was also extracted and 5uL applied to the TLC plate. The plate was viewed under a TLC plate viewer at 254 nm. The test took about 5 minutes to perform. The result is shown in Figure 10. The spot on the left is from the laundered diesel and the spot on the right from the unmarked diesel. The marked increase in the blue fluorescence in the laundered diesel is clearly visible by eye. Quantitative data may be acquired using plate reader software.

Example 6 - HPLC/UV method and validation data for compound (1) in fuel

Method:

Column: Waters Novapak cl8

UV DAD at 328nm

Sample 1 :3 dilution of neat fuel with THF

Flow lmL per minute

Injection 3uL

Gradient mobile phase A Water

Table 2

Table 3

Area counts uv injection order ppm 328 nm

16 spike 1 90 54.71

22 55.83

25 56.13

9 spike2 120 71.48

14 71.78

19 71.67

10 lod 1 5 1.15

15 2.5

18 2

11 lod 2 10 5.27

13 5.27

24 5.53

8 cal 3 75 42.4

21 cal = c3 42.2

27 44.2

12 base 25 12.97

17 base = cl 14.3

23 14.1

7 blank 0 0

The results from Tables 2 and 3 are shown in Figures 11a and l ib, respectively. The linear relationship in Figures 11a and l ib validates the use of HPLC in detecting compounds of formula (I) in diesel.

Example 7 - GC-MS validation data for compounds (1), (2) and (4) in kerosene

(ppm of marker to Area counts)

Table 4

Table 5

injection sample ppm Compound (1) Compound (2) Compound (4)

7 Blank 0 63859 34029 739

20 0 68729 38359 1024

26 0 63060 36223 858

8 Cal 3 100 3246296 1872964 1298132

21 100 2979524 1731878 1261908

27 100 2984285 1745102 1263499

16 spike 1 120 3786997 2198976 1632511

22 120 3541747 2072477 1582979

25 120 3824313 2211879 1600788

9 spike 2 195 6211209 3664316 2822892

14 195 6250625 3685971 2796204

19 195 6114345 3583315 2686531

10 lod 1 20 772334 414225 242898

15 20 687667 381132 223691

18 20 687459 379951 210316

11 lod 2 30 1057412 632905 335021

13 30 970269 539818 330434

24 30 967328 542243 348112

12 base cl 50 1509336 856105 576802

17 50 1577479 898825 617152 23 50 1517127 870779 592417

The results from Tables 4 and 5 are shown in Figures 12a-c and Figures 13a-c, respectively. The linear relationship in these figures validates the use of GC-MS in detecting compounds of formula (I) in kerosene. Similar results were found for diesel.

The entire contents of all published patent documents and technical literature mentioned throughout this specification are hereby incorporated herein by reference in their entirety.

It will of course be understood that the invention is not limited to the specific details as herein described, which are given by way of example only, and that various alterations and modifications are possible without departing from the scope of the invention.

Claims

Claims

1. A method of marking hydrocarbons comprising the addition to the hydrocarbon mixin with the hydrocarbon of at least one compound of the formula:-

(8) (9)

A method of marking hydrocarbons comprising the addition to the hydrocarbon mixing with the hydrocarbon of at least one compound of the formula:-

(1 ) (2)

A method of marking hydrocarbons comprising the addition to the hydrocarbon or the mixing with the hydrocarbon of at least one deuterium isotope analog of at least one of the compounds (1), (2), (3), (4) or (5) as defined in claim 1.

A method of marking hydrocarbons comprising the addition to the hydrocarbon mixing with the hydrocarbon of at least one compound of the formula:-

A method of marking hydrocarbons comprising the addition to the hydrocarbon mixing with the hydrocarbon of at least one compound of the formula:-

A method of marking hydrocarbons comprising the addition to the hydrocarbon mixing with the hydrocarbon of a compound of the formula:-

A method as claimed in claim any of claims 1 to 6 wherein the compounds are added to and dissolved in fuel either individually or in combination.

8. A method as claimed in any of claims 1 to 6 wherein the compounds are used in combination with further markers, such as dyes or pigments.

9. A method as claimed in any of claims 1 to 6 wherein at least one compound is added to and dissolved in the hydrocarbon to be marked in an amount of at least 0.5ppm.

10. A method as claimed in any of claims 1 to 6 wherein at least one compound is added to and dissolved in the hydrocarbon to be marked in an amount of at least 5ppm.

11. A method as claimed in claim 10 wherein the compound is added in an amount in the range of from 5 ppm to 200 ppm.

12. A method as claimed in claim 11 wherein the compound is added in an amount in the range of from 50 ppm to 100 ppm.

13. A method as claimed in any of claims 1 to 12 wherein more than one marker compound is used and the marker compounds are added in different concentrations to each other.

14. A method as claimed in claim 1 wherein compound 5 is dissolved in the marked hydrocarbon liquid and is subsequently transformed into compound 4.

15. A method as claimed in any of claims 1 , 3 or 4 wherein the marker comprises a composite of or with deuterated isotopic isomers as defined in any of claims 1 , 3 or 4. 16. A method of identifying fuel marked with a compound as defined in any of claims 1 to 6 comprising detecting the presence of a compound as defined in any of claims 1 to 6 in a sample.

17. A method as claimed in claim 16 comprising the use of gas chromatography-mass spectrometry.

18. A method as claimed in claim 16 comprising olfactory (human or animal) detection and identification either directly or with the aid of technology.

19. A method as claimed in claim 16 wherein the compound has a carbonyl group next to the alkoxynaphthalene core and the method comprises use of fluorescence measurement.

20. A method as claimed in claim 16 comprising fluorescence detection by the naked eye.

21. A method as claimed in claim 16 comprising chemically converting any one of compounds 1 to 3 as defined in claim 1 into compound 4 or 5 as defined in claim 1 for the purpose of detection or quantitative analysis.

22. A method as claimed in claim 16 wherein compound 4 is selectively extracted from the marked hydrocarbon using a solvent mixture for the purpose of detection and measurement.

23. A method as claimed in claim 22 comprising detecting compound 4 in the extraction solution.

24. A method as claimed in claim 22 or 23 comprising measuring the quantity of compound 4 in the extraction solution.

25. A method as claimed in any of claims 22 to 24 comprising analysing the extracted solution for marker 4 by a tic, uv, and/or fluorescence technique.

26. A method as claimed in claim 25 comprising visually evaluating the result of the tic test.

27. A method as claimed in claim 26 comprising visually comparing the result of the tic test with a pre-prepared standard chart.

28. A method as claimed in claim 27 wherein the preprepared standard chart is in an electronic form

29. A method as claimed in claim 28 wherein the electronic form comprises a digital picture defined by pixels of different colours capable of being individually counted by electronic means and delivering total pixel numbers corresponding to the concentration of marker 4 in the marked liquid.

30. A method as claimed in claim 23 comprising detecting compound 4 by treating the extracted marker with Bailey solution to confirm the presence or absence of ketone species.

31. A method as claimed in claim 30 comprising passing the extracted ketone species through a cartridge comprising immobilised 2,4 dinitrophenylhydrazine to provide a coloured species. 32. A method as claimed in claim 23 comprising detecting compound 4 by analysing the extracted marker chromatographically or directly by fluorescence spectrometry.

A method as claimed in claim 15 wherein the marker comprises a composite of deuterated isotopic isomers as defined in any of claims 1, 3 or 4 and the method comprises measuring the isotopic mass composition.

34. A method as claimed in claim 33 comprising comparing the measured isotopic mass composition of the fuel marker in the fuel to the isotopic mass composition of the fuel marker prior to addition to the fuel.

35. A method as claimed in claims 1 to 11 wherein deuterated analogs of a marker are added to the non-deuterated analogs in a weight percent of between 0.1% to 99.9%.

36. A method as claimed in any of claims 1 to 11 wherein the marker is detected and measured by HPLC.

37. A method as claimed in claim 36 wherein the marker is detected and measured by HPLC without sample modification and the analysis is performed automatically. 38. A method as claimed in claim 36 or 37 wherein the marker is detected at a wavelength of between 250nm and 350 nm.

39. A method as claimed in any of claims 1 to 11 wherein the marker is detected by APCI mass detection or ESI mass detection or fluorescence detection.

40. A method as claimed in any of claims 1 to 11 wherein the marker is detected by APPI mass detection.

41. A method as claimed in claim 40 wherein the marker is detected by APPI mass detection with or without the addition of a dopant.

42. A method as claimed in claim 41 wherein the marker isotopic analog composition is measured by APPI or APCI mass detection. 43. A method as claimed in any of claims 1 to 11 wherein the marker isotopic composition is compared to reference marker isotopic analog compositions.

44. A method as claimed in claim 43 wherein the isotopic analog composition of the marker is used to define the origin of the marked substance.

45. A method as claimed in any of claims 16 to 44 wherein the marker is detected and measured using a kit.

46. A method as in claim 45 wherein the kit comprises a liquid transfer device, a liquid measuring device, adsorbent material, a UV irradiation device, a fluorescence viewer device, and marker reference material.

47. A method as claimed in claim 46 wherein the kit includes an extraction solvent. 48. A method as claimed in claim 46 or 47 wherein the adsorbent material is fixed on a solid support.

49. A method as claimed in any of claims 46 to 48 wherein the adsorbent material contains a fluorescent substance.

50. A method as claimed in any of claims 45 to 49 wherein fluorescence due to the marker is detected by the naked eye.

51. A method as claimed in any of claims 45 to 49 wherein fluorescence due to the marker is detected electronically

A method as claimed in claim 50 or 51 wherein the measured fluorescence values due to marker are compared with pre-determined reference values and the marker concentration in the marked substance is calculated.

53. A method as claimed in claim 45 wherein the sample is prepared for a smell test using a kit.

54. A method as claimed in claim 45 wherein the kit comprises a liquid transfer device, a liquid measuring device and an adsorbent substance.

55. A method as claimed in claim 45 wherein a kit that uses sublimation is used to isolate marker from the marked hydrocarbon.

56. A method as claimed in claim 55 wherein the kit comprises a device to heat the sample hydrocarbon to vaporization temperature.

A method as claimed in claim 56 wherein the kit comprises a cold surface for contact with the vapour and on which the marker desublimes.

58. A method as claimed in claim 57 wherein the desub limed marker is made available to analytical technology for measurement.

59. A method as claimed in any of claims 1 to 58 wherein the hydrocarbon is selected from among mineral oils, fuel, diesel, petrol (gasoline), paraffin oil (kerosene), gas oil (fuel oil), petroleum, petroleum products, biologically derived fuels, and hydrocarbon solvents. 60. A method as claimed in claim 59 wherein the hydrocarbon is diesel.

61. A method as claimed in claim 59 wherein the hydrocarbon is kerosene.

A method as claimed in claim 59 wherein the hydrocarbon is marine diesel.

63. Use of a compound as defined in any of claims 1 to 6 for marking a hydrocarbon fuel. 64. Use of a deuterium isotopic analog of compounds (1), (2), (3), (4) or (5) as defined in claim 1 as hydrocarbon markers.

65. Use of a combination of deuterated and non-deuterated compounds as defined in claim 1 or 20 as a single marker composition. 66. A fuel marker concentrate comprising a compound as defined in any of claims 1 to 6.

67. A fuel marker composition comprising (i) at least one compound as defined in any of claims 1 to 6 and (ii) an additive. 68. A composition according to claim 67 including a further marker.

69. A composition as claimed in claim 67 or 68 including an antioxidant.