EP1393053A1 - Electrodes sensibles aux ions se basant sur des oxa-azamacrocycles en tant que ionophores pour determiner la presence d'anions nitrate, salicylate ou periodate - Google Patents

Electrodes sensibles aux ions se basant sur des oxa-azamacrocycles en tant que ionophores pour determiner la presence d'anions nitrate, salicylate ou periodate

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Publication number
EP1393053A1
EP1393053A1 EP02730426A EP02730426A EP1393053A1 EP 1393053 A1 EP1393053 A1 EP 1393053A1 EP 02730426 A EP02730426 A EP 02730426A EP 02730426 A EP02730426 A EP 02730426A EP 1393053 A1 EP1393053 A1 EP 1393053A1
Authority
EP
European Patent Office
Prior art keywords
ions
macrocyclic compound
nitrate
electrode
concentration
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02730426A
Other languages
German (de)
English (en)
Inventor
Paul Kong Thoo Lin
Albert N. Araujo
Maria Da Conceicao Branco S. Mendonga Montenegro
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Gordon University
Original Assignee
Robert Gordon University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB0113634A external-priority patent/GB0113634D0/en
Priority claimed from GB0114453A external-priority patent/GB0114453D0/en
Application filed by Robert Gordon University filed Critical Robert Gordon University
Publication of EP1393053A1 publication Critical patent/EP1393053A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/333—Ion-selective electrodes or membranes
    • G01N27/3335—Ion-selective electrodes or membranes the membrane containing at least one organic component

Definitions

  • the present invention relates to a method and apparatus for determining ion presence and, preferably, concentration.
  • the present invention is particularly applicable to determine the presence and/or concentration of nitrate, periodate or salicylate ions.
  • Nitrates are found in many environmental sources. The most important sources of contamination by nitrates are from the excretions of farm animals, artificial fertilisers, and industrial and domestic waste. Foodstuffs and beverages can thereby accumulate great quantities of nitrates depending on the fertilisation procedures.
  • Nitrate has also traditionally been used as an additive conferring positive benefits in the food industry, for example, to prevent the botulism produced by the bacteria Bacillus Clostridium Botulinum, to slow lipid oxidation and the production of unpleasant smells, and to prevent the swelling of cheese.
  • Nitrates have been previously measured by spectrophotometry . This is typically based on the measurement of the absorption of the end products after the nitration of phenolic compounds such as those used in the xylenol orange method, the chromotopic acid and phenolsulphonic acid methods. Such nitrate determinations are indirectly performed since they actually measure the presence of ammonia or nitrite, the reduced form of nitrate, and are generally time consuming.
  • Ion chromatography is another instrumental technique commonly used.
  • a mixture is injected into a column and the retention times of the various constituents of the mixture are measured and compared with retention times for known ions/constituents.
  • IC Ion chromatography
  • the success of conventional analytical techniques for the determination of nitrates depends on high reproducibility of the results or on the simultaneous determination of nitrate in the presence of other anions such as nitrites, chlorides, fluorides, sulphates, etc.
  • nitrate ion-selective electrodes belonging to the liquid membrane group an organic ion- exchanger is dissolved in an appropriate solvent, which is then placed inside a glass or plastic tube. At the bottom of it there is a porous thin membrane (e.g. cellulose ester, glass etc.) that separates nitrate sensor from the sample solution to be analysed. In contact with the membrane a second electrode (e.g. AgCl/Ag) is immersed in a reference solution containing nitrate ion which acts as an inner reference electrode.
  • a second electrode e.g. AgCl/Ag
  • Polymeric membranes were introduced to improve the mechanical robustness of the liquid membrane electrodes, and polymeric supports such as polyacrylates, silicon rubber, polyurethane foams and PVC .
  • a common characteristic found in every electrode described before is related to the use of an inner reference solution and the corresponding reference electrode. Attempts to eliminate the use of this solution and electrode include coating a conductive wire with a polymeric membrane .
  • Periodate ions have been measured before by techniques such as spectrophotometric, polarographic, potentiometric and more recently by capillary electrophoresis .
  • Salicylate ions had been measured by ion chromatography and GC/ S (gas chromatography and mass spectrometry.
  • apparatus for the determination of at least one of the presence and concentration of ions in a sample having an electrode comprising a macrocyclic compound.
  • the invention also provides a method of determining at least one of the presence and concentration of ions in a sample, the method comprising the steps of exposing the sample to a macrocyclic compound and determining potentiometric changes in the macrocyclic compound.
  • the apparatus and method can determine the amount of ions present .
  • the ions are typically nitrate ions. However the invention can also be used to determine the presence of periodate or salicylate ions.
  • the macrocyclic compound is a macrocyclic base.
  • the macrocyclic base is typically supported on a conductive substrate, typically a conductive metal such as copper, although other metals are also useful for this purpose.
  • a conductive substrate typically a conductive metal such as copper, although other metals are also useful for this purpose.
  • Good substrates also include non-metallic substances such as graphite.
  • the macrocyclic base comprises a solid, more preferably a solid membrane.
  • the base is typically layered onto the conductive support. There may be a single layer or alternatively a plurality of layers.
  • the base is typically dissolved in a solvent such as dibutylphthalate and mixed with an immobilising agent such as PVC, so that when the base-solvent- immobiliser is layered onto the substrate the solvent can evaporate and leave a thin layer or "membrane" of immobilised base on the surface of the conductive substrate.
  • the macrocyclic base is dissolved in an appropriate mediator solvent such as dibutylphthalate with a lipophilic additive such as tetraoctylammoniumchloride .
  • an appropriate mediator solvent such as dibutylphthalate
  • a lipophilic additive such as tetraoctylammoniumchloride .
  • the resulting mixture can be immobilised on an inert polymeric matrix such as PVC dissolved in anhydrous THF.
  • the solution can then be applied dropwise on a conductive support (e.g. graphite glued on with Araldite or silver epoxy resin) if an electrode without an inner reference solution is required.
  • the substrate is typically housed in a plastic housing along with the necessary electrical connectors to facilitate determination by either conventional means i.e. manually measuring conductivity, or by flow procedures i.e. measuring conductivity while solution is flowing.
  • the base is typically a heteromacrocyclic base.
  • the heteromacrocyclic base includes a nitrogen heteroatom, more preferably two nitrogen heteroatoms .
  • the heteromacrocyclic base includes an oxygen heteroatom, more preferably two oxygen heteroatoms.
  • heteroatoms may be used, e.g. P and S.
  • the heteromacrocyclic base is an oxa-aza cyclic alkane.
  • the base may be of a general formul : -
  • n and m are independently, 2, 3, 4, 5 or 6 , In preferred embodiments n is 3 and m is 2 or 3.
  • the base is of the formula :-
  • Heteromacrocyclic bases show very good working characteristics with low detection limit of 10 "7 M.
  • the selectivity of such electrodes to nitrate ions is very good since interference from other ions such as chloride, bromide, sulphate and nitrite does not affect measurement of nitrate concentration in solution.
  • Fig 1 is a schematic representation of a sequence of steps for construction of an electrode housing
  • Fig 2 is a schematic representation of a sequence of steps for construction of a conductive substrate for the fig 1 electrode
  • Fig 3 is a schematic representation of constructed electrode
  • Fig 4 is a schematic representation of an electrode showing the application of the base
  • Fig 5 is a graph showing typical calibration curves for two 3333 free base electrode units used to detect the presence and/or concentration of nitrate ions
  • Figs.6a-6d are graphs showing typical calibration curves for four 3232 free base electrode units used to detect the presence and/or concentration of nitrate ions
  • Figs. 7a-7d are repeat results of the calibration curves shown in Figs. 6a-6d
  • Figs. 8a-8d are a second set of repeat results of the calibration curves shown in Figs 6a-6d;
  • Fig. 9 is schematic representation of the synthesis of the 3232 free base;
  • Figs. lOa-lOd are graphs showing typical calibration curves for two 3333 free base electrode units used to detect the presence and/or concentration of salicylate ions;
  • Figs, lla-lld are graphs showing typical calibration curves for two 3333 free base electrode units used to detect the presence and/or concentration of periodate ions;
  • Fig 12 is a Reilley diagram showing the effect of pH on the response of a 3333 free base electrode; and,
  • Fig. 13 is a graph demonstrating the apparatus and method of determining nitrate concentration according to the present invention compared with a known technique.
  • an electrode housing 1 comprises a set of Perspex cylinders.
  • a middle 130mm long body Cm of outer diameter 10mm and inner diameter 7mm houses an inner plate support cylinder Ci of outer diameter 6.5mm and inner diameter 3.5mm, and is capped by an external 20mm long cap Ce with inner diameter 10mm and outer diameter 15mm as shown in fig Id.
  • a plate 5 is attached to the support with adhesive (e.g. Araldite TM) and a wire 6 is soldered to the plate 5, or is alternatively attached with a conductive adhesive such as a mixture of Araldite and graphite.
  • the plate is typically copper but can be any other conducting material e.g. graphite.
  • the wire 6 extends through the top of the cylinder Cm and the cap Ce and is secured to the cap Ce with Araldite.
  • a BNC terminal is connected onto the other end of the wire 6 which is shielded by a cable (not shown) outside the cylinder Cm.
  • the housing 1 including the plate 5 is inverted - as shown in Fig. 2d - and a macrocyclic, electroactive free base solution, described in more detail below, is then applied to the plate 5.
  • the solvent of the solution - in one embodiment being tetrahydrofuran (THF) - is allowed to evaporate leaving the free base layered on the plate 5 as shown in fig 4b.
  • THF tetrahydrofuran
  • the solution containing the electroactive free base is applied dropwise onto the plate 5 and the THF evaporates leaving a free base membrane layered on top of the plate 5.
  • the first (3333) electroactive free base to be applied to the plate 5 is typically made as described in (Kong Thoo Lin, P. et al . Synthesis, 6, 1034-1038, 1999) which is incorporated herein by reference, with modifications as follows/ STEP 1
  • N- hydroxyphthalimide 36g, 0.22M
  • DMF dimethyl formamide
  • 1 , 3 -Dibromopropane . 17.97g, 0.089M
  • triethylamine 0.225M, 22.5g, 31 cm 3
  • the solvent DMF was removed at the rotary evaporator (rfe) followed by the addition of water (300 cm 3 ) to form a thick precipitate, which was filtered using a large Buchner funnel .
  • the precipitate was sequentially washed thoroughly with water; saturated solution of sodium bicarbonate; dilute NaOH (1M) ; and water.
  • the diol (6.64g, 0.01133M) was dissolved in anhydrous THF (100 cm 3 , freshly distilled over calcium hydride) .
  • the following reagents are then added in the following order (I) triphenyl phosphine (6.09 g, 0.0226M) (ii) bismesitylene derivative (5.33 g, 0.01133M) (iii) DIAD, diisopropylazodicarboxylate (4.699g, 0.0226M).
  • the reaction was exothermic on addition of the DIAD and the solution was left stirring at room temperature for 2-3 hours after which a precipitate was formed. All the THF was removed at the rfe and ethanol (100 cm 3 ) was added to the residue. The suspension was warmed and then allowed to cool on ice. The precipitate formed was filtered off and washed with cold ethanol. After drying in a vacuum oven, 7.15g (62%) of the protected macrocycle was obtained.
  • the protected macrocycle (6.15g, 6.02mmol) was dissolved in freshly distilled dichloro ethane (128 ml) followed by the addition of 20% hydrobromic acid in glacial acetic acid (26g) .
  • the reaction mixture was left stirring overnight to form an orange precipitate.
  • the latter was filtered off using a Buchner sintered funnel .
  • the precipitate was washed with (i) dichloromethane (ii) ethyl acetate and (iii) ethanol to give finally a pale yellow solid (2.20g, 60%) .
  • a solution of methanolic KOH was prepared was adding KOH (13.5 mM, 0.8g) to methanol (11 cm 3 ).
  • the macrocycle salt (1.5g, 2.4 mM) was added while stirring.
  • the suspension was left stirring at room temperature for 2 hours. After that time, the suspension was filtered off and washed with chloroform. The filtrate was evaporated and resuspended with chloroform.
  • the solution was filtered again and after removal of the solvent at the rfe, the 3333 free base (0.77 g) was obtained as a thick yellow oil.
  • a second free base (hereinafter the 3232 free base) has also shown good response to detecting the presence and concentration of nitrate and other ions.
  • the 3232 base has the structure detailed below:-
  • the 3232 free base is marginally smaller than the 3333 free base.
  • the 3232 oxazane macrocycle system (shown above) was synthesised as shown in Fig. 9 and as detailed in the aforementioned document - Kong Thoo Lin, P. et al . Synthesis, 6, 1034-1038, 1999.
  • a sensor membrane incorporating the 3333 free base was prepared as follows. 0.0453 g of 3333 free base as ionophore was dissolved in 0.1517 g of dibuthylphtalate as solvent mediator. About 0.0020 g of tetraoctylammonium chloride as additive was added to the previously prepared solution.
  • the mixture referred above was immobilised in 0.15g of PVC previously dissolved in THF. This solution allows the coating of about 3-4 electrodes.
  • the solution above prepared was dropped on the conductive graphite or copper substrate plate 5 of the electrode. After THF evaporation a thin membrane was formed.
  • Conventionally shaped electrodes were prepared as described for the 3333 free base by applying dropwise- the membrane on a support consisting of graphite powder- reated epoxy resin.
  • the constructed electrodes were conditionated by soaking in 10 '1 M potassium nitrate solution and when not in use were stored in a solution with a concentration of 10 "4 M.
  • the conventionally-shaped electrodes were typically prepared in accordance with a technique described elsewhere [J.L.F.C. Lima, M.C.B.S.M. Montenegro and A. M. Roque da Silva, J. Flow Injection Anal., 7, 19-33 (1990 )] by applying the base dropwise to the substrate to dry and form membranes over a graphite and epoxy resin support of the electrode.
  • An indicator electrode was used in conjunction with an Orion 90-02-00, silver chloride/silver double- junction electrode as the reference electrode.
  • the external compartment of the latter electrode contained an electrolyte with low interference such as 0.033 M potassium sulphate since the sulphate anion showed reduced interference, as determined by measurement of the potentiometric selectivity coefficients. pH measurements were carried out with a Philips GAH 110 glass electrode.
  • ELECTRODE BEHAVIOUR The working characteristics of the conventionally- shaped electrodes constructed were evaluated by repeated calibration curves in solutions without and with ionic strength adjusted to 0.1 M by using potassium sulphate. The calibration curves were made by adding known volumes of 0. IM of nickel nitrate or other nitrate salt to water or to the ionic strength adjuster.
  • An advantage of the electrodes shown above and certain other embodiments of the invention is that the response times for the electrodes shown above are smaller than the response times for other nitrate detectors.
  • Another advantage of certain embodiments of the invention is their detection of ions at a low concentration e.g. the lower detection limit for the electrodes shown in table 1 above are 10e-7M whereas known nitrate detection electrodes have a lower detection limit of around 10e-5M.
  • the electrodes showed an initial drift of potential, and the response stability appeared after the 3333 nitrate electrode had been conditioned for three days in 10 "1 molL "1 solution of the primary ion.
  • the all-solid-state PVC membrane electrodes without internal reference solution there is no well-defined internal reference potential system. In practice, however, these electrodes provide reproducible potentials.
  • the establishment of a constant electrode potential requires a period to stabilize the internal reference potential in the graphite conductive epoxy-PVC boundary, by means of the 0 2 -H 2 0 coupled as has been previously suggested.
  • a further advantage of certain embodiments of the present invention is that the concentration of nitrate, periodate or salicylate ions may be determined without the need for an inner reference solution in the measuring device. This reduces the cost of constructing the measuring device and allows it to be versatile, robust and smaller than known nitrate ion sensors.
  • a further advantage of certain embodiments is the low cost to manufacture the electrodes, due in part, to the small quantities of free base used for each electrode.
  • Figure 5 shows the calibration curve for 2 3333 free base electrodes in nitrate solution.
  • Calibration curves plot the conductivity of the free base membrane electrodes at various concentrations of nitrate ions. A linear relationship demonstrates that the free base membrane electrodes accurately measures the nitrate concentration. A good linear relationship is shown in the Fig. 5 curves.
  • Calibration curves using the 3333 free base electrodes for salicylate ions and periodate ions are shown in Figs lOa-lOd and lla-lld respectively. These results also show a good linear relationship and demonstrate that the 3333 free base electrode is also useful for determining the presence and/or concentration of such ions.
  • the calibration curves shown show that the ion selective electrode containing the 3232 free base also gave a linear relationship with good Nerstian gradients.
  • the lower limit of detection is 7.99x10 " S M of nitrate (N0 3 _) .
  • the Reilley diagram indicated a pH operational working range between pH 2.3 and 12.0. However for the lower concentrations the pH operational range diminishes. Hence the adjustment of the pH samples before analysis will be probably necessary in some applications at very low nitrate concentration. Nevertheless the range of pH over which certain embodiments of the electrode may be used without adjusting the pH of the samples is ideal for biological and environmental samples.
  • the potentiometric selectivity coefficients shown in table 3 were determined with three different concentrations of the primary ion together with the same concentration of an anion interferent (10 ⁇ 4 , 10 " 3 and 10 "2 mol L "1 ) , following the separated solution method detailed above.
  • Certain embodiments of the invention exhibit a better selectively coefficient towards chloride ions (the main interference of the nitrate selective electrodes) than other known nitrate sensor units.
  • An advantage of embodiments of the present invention is that the concentration of the nitrate ions may be determined in the presence of other ions, e.g. in food where natural salt and therefore chloride ions are present .
  • the variation in the working characteristics with time was used as criterion for evaluating the electrode's lifetime.
  • the electrodes when in regular use were stored in 10 ⁇ 4 mol L "1 potassium nitrate solution. All the 3333 electrodes analysed had a lifetime generally greater then 10 months, which is longer then the durability of known electrodes whose membranes are based on mobile carrier sensors but constructed using an internal reference solution. This is probably due to the presence of just a single contact surface between the membrane and solution, instead of two as in conventional electrodes; that is, the area through which leaching occurs is halved. Certain embodiments of the present invention benefit from the absence of an inner reference solution which provides a number of benefits including longer lifetime of the electrodes as described above.
  • sample Preparation To accomplish nitrate determinations in real samples, an accurately weighed sample - 1 g of previously homogenized and fully dried (65°C) vegetable was extracted in 100 mL of deionized water during 30 min at room temperature. The extract was filtered over a 100 ml volumetric flask and was made up to volume with deionized water.

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Abstract

La présente invention concerne un dispositif et un procédé servant à déterminer la présence et/ou la concentration d'ions nitrate. Le dispositif comprend une électrode sélective aux ions revêtue d'une base libre macrocyclique telle que 1,7,11,17-tétraoxa-2,6,12,16-tétraazacyclolicosane (RN=235092-95-2) ou 1,6,10,15-tétraoxa-2,5,11,14-tétraazacyclooctodécane (RN=236104-63-5). Le dispositif peut servir à déterminer la présence de nitrate à des concentrations faibles, et a une bonne sélectivité aux ions nitrate en la présence de certains autres ions. Cette invention concerne également un procédé et un dispositif servant à déterminer la présence et/ou la concentration d'ions salicylate et périodate.
EP02730426A 2001-06-05 2002-06-05 Electrodes sensibles aux ions se basant sur des oxa-azamacrocycles en tant que ionophores pour determiner la presence d'anions nitrate, salicylate ou periodate Withdrawn EP1393053A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
GB0113634 2001-06-05
GB0113634A GB0113634D0 (en) 2001-06-05 2001-06-05 Method and apparatus
GB0114453A GB0114453D0 (en) 2001-06-14 2001-06-14 Method and apparatus
GB0114453 2001-06-14
PCT/GB2002/002292 WO2002099409A1 (fr) 2001-06-05 2002-06-05 Electrodes sensibles aux ions se basant sur des oxa-azamacrocycles en tant que ionophores pour determiner la presence d'anions nitrate, salicylate ou periodate

Publications (1)

Publication Number Publication Date
EP1393053A1 true EP1393053A1 (fr) 2004-03-03

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EP02730426A Withdrawn EP1393053A1 (fr) 2001-06-05 2002-06-05 Electrodes sensibles aux ions se basant sur des oxa-azamacrocycles en tant que ionophores pour determiner la presence d'anions nitrate, salicylate ou periodate

Country Status (2)

Country Link
EP (1) EP1393053A1 (fr)
WO (1) WO2002099409A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103616471A (zh) * 2013-11-22 2014-03-05 安徽华业香料股份有限公司 水杨酸己酯生产过程中酯化反应的检测方法

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JPS5539042A (en) * 1978-09-14 1980-03-18 Tokyo Daigaku Ion selecting field-effect sensor
JPS58154565A (ja) * 1982-03-09 1983-09-14 Ajinomoto Co Inc ジアザクラウンエ−テル類の製造法
DE4209376A1 (de) * 1992-03-23 1993-09-30 Siemens Ag Flächerstrahl-Computertomograph
JP3307687B2 (ja) * 1992-08-31 2002-07-24 鈴木 孝治 イオン選択性配位分子およびイオンセンサ
WO1994010557A1 (fr) * 1992-11-05 1994-05-11 Porton Diagnostics, Inc. Procede de production de membranes
DE29818621U1 (de) * 1998-10-20 1999-01-28 Kurt-Schwabe-Institut für Mess- und Sensortechnik e.V. Meinsberg, 04720 Ziegra-Knobelsdorf Ionenselektive Nitratelektrode
US6432296B1 (en) * 1999-09-24 2002-08-13 Daniel S. Daniel Polymeric compositions for ion-selective electrodes

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103616471A (zh) * 2013-11-22 2014-03-05 安徽华业香料股份有限公司 水杨酸己酯生产过程中酯化反应的检测方法

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