WO2013060829A2

WO2013060829A2 - On-line system and method for nicotine analysis of a smoking article

Info

Publication number: WO2013060829A2
Application number: PCT/EP2012/071236
Authority: WO
Inventors: Karl-Heinz Schaefer; Peter Schnell
Original assignee: Philip Morris Products S.A.
Priority date: 2011-10-28
Filing date: 2012-10-26
Publication date: 2013-05-02
Also published as: WO2013060829A3

Abstract

A method for performing a puff by puff analysis of the nicotine delivery of a smoking article during smoking comprises the steps of: mounting the smoking article in a smoking machine (12); operating the smoking machine (12) to perform a smoking test during which air is drawn through the smoking article; directing the smoke emitted from the smoking article during the smoking test into a smoke analysis device (14) connected to the smoking machine (12), wherein the smoke analysis device comprises an alkali flame ionisation detector (26); and measuring the nicotine concentration of the smoke directed into the smoke analysis device using the alkali flame ionisation detector (16).

Description

ON-LINE SYSTEM AND METHOD FOR NICOTINE ANALYSIS OF A SMOKING ARTICLE

The present invention relates to a system and method for performing an analysis of the nicotine delivery of a smoking article during smoking. The invention finds particular application in the puff-by-puff analysis of the smoke generated by a smoking article during smoking.

Smoking tests are commonly carried out on combustible smoking articles in order to analyse the constituents of the smoke generated during combustion of the tobacco material in the smoking article. For example, it is often necessary to establish the tar and nicotine delivery of a particular type of smoking article. Such tests are typically carried out using an automatic smoking machine, such as a Borgwaldt® smoking machine, which automatically smokes a lit smoking article in a standardised sequence of puffs. In conventional methods, the cumulative smoke generated during the sequence of puffs is collected, for example in a suitable solvent or trap, and then subsequently analysed using suitable apparatus.

During smoking tests carried out on combustible smoking articles, the carbon monoxide level in the collected smoke may be measured to provide a direct indicator of the total gas phase concentration of aerosol within the smoke. However, this methodology is unsuitable for monitoring the aerosol generated by smoking articles in which an aerosol generating substrate is heated rather than combusted. During smoking tests carried out on such heated smoking articles, there will be significantly less, and even no, carbon monoxide generated since there is little if any burning of the tobacco material.

It would be desirable to provide a system and method for reliably measuring the aerosol content of smoke generated by a smoking article. It would also be desirable if the system and method provided reproducible measurements. It would further be desirable to provide a system and method that could be used for heated smoking articles as well as combustible smoking articles. It would be particularly desirable to provide such a system and method that can be used on-line with a smoking machine to provide real-time chemical analysis of the smoke emitted from a smoking article during a smoking test.

According to the present invention there is provided a method for performing a puff-by- puff analysis of the nicotine delivery of a smoking article comprising mounting the smoking article in a smoking machine and operating the smoking machine to perform a smoking test during which air is drawn through the smoking article, wherein during a smoking test the air is drawn through the smoking article in a sequence of puffs, wherein the smoke emitted from the smoking article during each puff is directed into a smoke analysis device connected to the smoking machine, wherein the smoke analysis device comprises an alkali flame ionisation detector and wherein the nicotine concentration of the smoke from each puff is independently measured using the alkali flame ionisation detector. According to the present invention there is further provided a system for performing a puff-by-puff analysis of the nicotine delivery of a smoking article during smoking, the system comprising a smoking machine for performing a smoking test during which air is drawn through the smoking article in a sequence of puffs, a smoke analysis device comprising an alkali flame ionisation detector, and a conduit for directing smoke emitted from the smoking machine during the sequence of puffs from an outlet of the smoking machine to an inlet of the smoke analysis device.

The present invention further provides a method of monitoring the nicotine concentration of the smoke generated by a smoking article during a smoking test carried out using the system of the invention as defined above. The method of monitoring comprises the steps of inserting a smoking article into the smoking machine, operating the smoking machine to smoke the smoking article in a smoking test, directing the smoke generated by the smoking article during each puff into the smoke analysis device, and measuring the nicotine concentration of the smoke using an alkali flame ionisation detector.

The present invention further provides a use of the system of the invention, as defined above, to perform on-line monitoring of the nicotine concentration of the smoke emitted by a smoking article during a smoking test in the smoking machine. In particular, the present invention provides the use of the system of the invention to perform on-line monitoring of the nicotine concentration of the aerosol emitted by a heated smoking article in which tobacco material is heated without combustion or pyrolysis.

The present invention provides an integrated system and method in which the smoke generated during a smoking test on a smoking machine is directed to an on-line smoke analysis device. The system and method use an alkali flame ionisation detector to measure the nicotine concentration of the smoke. This arrangement enables the smoke to be channelled directly to the smoke analysis device, rather than being first collected or trapped before being analysed in a subsequent process.

The term "on-line" is used to refer to a device that is incorporated within a system or apparatus and in connection with other components of the system. This is also sometimes referred to as incorporating a device "in-line". In the system and method of the present invention, the smoke analysis device is referred to as "on-line", meaning that it forms part of the overall system for analysing the smoke and is connected to the smoking machine so that the smoke passes directly to the smoke analysis device. This advantageously enables real time analysis of the smoke generated from the smoking article. Furthermore, since the smoke is channelled directly to the smoke analysis device from the smoking machine, the steps of extracting or collecting the smoke or smoke compounds can be eliminated. This provides a more efficient analysis process and also saves the time and cost of subsequent chemical analysis.

The system and method of the present invention can selectively monitor the nicotine concentration in the smoke generated by a smoking article and provide a reliable method for the analysis of both combustible smoking articles and heated smoking articles. A heated smoking article is one in which tobacco material is heated with minimal, or in some cases no, combustion or pyrolysis. Unlike carbon monoxide, which is only released upon the combustion of tobacco material, nicotine will be released from a tobacco material upon combustion or upon heating of the material to generate an aerosol. The system and method of the present invention can therefore be successfully applied in the testing of a wide variety of combustible and non- combustible smoking articles.

The system and method of the present invention may be used to analyse the nicotine delivery of filter cigarettes and other smoking articles in which an aerosol forming substrate, such as tobacco material, is combusted to form smoke. The system and method of the present invention may also advantageously be used in smoking articles in which an aerosol generating substrate, such as tobacco material, is heated to form an aerosol, rather than combusted. The system and method of the present invention may also used in smoking articles in which a nicotine-containing aerosol is generated from a tobacco material, tobacco extract, or other nicotine source, without combustion or heating.

As used herein, the term "smoke" is used to describe smoke produced by combustible smoking articles, such as filter cigarettes, and aerosols produced by non-combustible smoking articles, such as heated or non-heated smoking articles of the types described above in which tobacco flavours are generated without combustion or pyrolysis of a tobacco material.

The smoke analysis device used in the system and method of the present invention comprises gas chromatographic apparatus including an alkali flame ionisation detector (AFID), which is preferably provided downstream of a chromatographic column. Preferably, the smoke analysis device comprises a chromatographic column, most preferably a heated spiral chromatographic column upstream of the AFID. Preferably, the chromatographic column is formed of fused silica or glass. During the analysis method of the invention, the smoke from the smoking machine is preferably mixed with an inert carrier gas prior to injection into the chromatographic column.

The alkali flame ionisation device (AFID) is used to measure the concentration of nicotine in the smoke. Alkali flame ionisation devices are also known as nitrogen selective detectors and nitrogen phosphorus detectors (NPD) and are commercially available, for example, from Linde. An AFID is a type of thermionic detector used in gas chromatography for the detection of nitrogen containing compounds in a gas sample. Such detectors are extremely sensitive to nitrogen containing compounds and are used in the system and method of the present invention to provide a reliable and accurate measurement of the amount of nicotine in a smoke sample. Nicotine (or 3-(1 -Methyl-2-pyrrolidinyl)pyridine) is a nitrogen containing compound of the formula Ο₁₀Η₁₄Ν₂ and can therefore be readily detected with the AFID.

The AFI D is a modified type of flame ionisation device (FID). In their unmodified form, FI Ds are used to detect hydrocarbon compounds in a gas sample. An FID typically comprises a hydrogen flame and a collector plate or electrode assembly. A gas sample from a chromatographic column is fed into the FID and undergoes combustion in a hydrogen/synthetic air flame. Ions and free electrons are formed within the flame, which produce a measurable current in the collector plate or electrodes.

For the detection of nitrogen compounds, the FID configuration is adapted so that the gas sample passes over a source of an alkali salt which is provided in the region of the flame. The collector plate or electrode assembly detects electrons released from the alkali salt and the resultant current is measured. The electron emission increases in the presence of nitrogen (or phosphorus) compounds.

The method of the present invention preferably further comprises the step of mixing the smoke emitted from the smoking article during the smoking test with a combustible carrier gas, such as hydrogen, prior to directing the smoke into the AFID. Preferably, the effluent from the chromatographic column is mixed with a carrier gas, upstream of the AFI D.

The source of alkali salt is preferably in the form of a ring, bead or pellet, which is heated by a heating element and placed close to the hydrogen flame. The alkali salt is formed of a salt of an alkali (Group 1 ) metal which is typically combined with a ceramic material. Preferably, the alkali salt comprises a rubidium (Ru⁺¹) or caesium (Ca⁺¹) salt or a silicate. A particularly preferred example of an alkali salt for use in the AFID of the system and method of the present invention is rubidium chloride (RuCI).

The current measured by the AFID is directly proportional to the nicotine content in the smoke sample. The nicotine concentration of the smoke can therefore be readily and directly arrived at from the measured current value, without the need for complex computation. An AFID typically exhibits substantially no signal drift and has substantially no sensitivity to pure hydrocarbons. It can therefore be used to provide an extremely accurate measurement of the nicotine concentration in the smoke. AFIDs are generally relatively low cost devices compared to other types of apparatus commonly used for smoke analysis, such as for example mass spectrometers. In addition, AFI Ds are simple to operate and can be conveniently and readily incorporated on-line into a system including a smoking machine. It has also advantageously been found that AFIDs provide robustness to the particulate matter in smoke generated from a combustible smoking article. Preferably, the method of the present invention comprises the step of calibrating the AFID prior to the analysis of the smoke generated from the smoking article. The calibration step preferably comprises directing nicotine solutions of a known concentration into the smoke analysis device and measuring the output of the AFI D. The calibration step may further comprise checking the base line or zero point of the AFID, for example, using a system which cuts down the flow of gas through the AFID very quickly. Preferably, the calibration step is computer controlled so that a calibration can be activated at any time during the analysis process, for example, at regular intervals during the process.

Preferably, the method of the present invention comprises the step of generating an output signal from the smoke analysis device based on the measured nicotine concentration, and transmitting the output signal to a controller. The controller preferably calculates and records the nicotine content based on the signal height from the AFID and any parameters obtained from a calibration step. From the nicotine content of the smoke, it is possible to determine the aerosol concentration of the smoke, which will be in direct proportion to the nicotine content.

The smoke analysis device may further comprise one or more additional detectors for measuring the amount of other constituents of the smoke generated from the smoking article during the smoking test. In this way, the method of the present invention can be adapted to measure one or more additional components of the smoke. The selection of additional detectors may depend upon the nature of the smoking article being tested. Suitable detectors for incorporation into the smoke analysis device in addition to an AFID include, for example, flame ionisation detectors adapted to selectively monitor other compounds, such as carbon compounds. Output signals from the one or more additional detectors may be transmitted to a controller, which may advantageously be the same controller as that receiving the output signal from the AFID.

The smoke analysis device of the system of the present invention is connected to the smoking machine by means of a suitable conduit, which provides a flow path for the smoke. The smoke generated from the smoking article during the smoking test is preferably transferred directly from an outlet of the smoking machine, through the conduit to the inlet of the smoke analysis device. The smoke may be transferred through the conduit with or without a carrier gas, such as air. Where a carrier gas is used, the conduit preferably comprises an inlet for the introduction of the carrier gas into the conduit, to mix with the smoke stream.

Preferably, the smoke is pumped through the conduit from the smoking machine to the smoke analysis device by means of a suitable pump connected to the conduit. Preferably, the smoke is introduced into the smoke analysis device at a flow rate of 1 to 6 millilitres per minute. Preferably, the conduit comprises at least one inlet for the introduction or injection of standard nicotine solutions into the apparatus, for the purposes of calibration, as described above.

The smoke may be continuously transferred from the smoking machine to the smoke analysis device, as it is generated. Alternatively, the conduit between the smoking machine and the smoke analysis device may include one or more valve arrangements to control the smoke flow through the conduit.

The smoking machine of the system of the present invention is an automatic smoking machine for smoking one or more smoking articles, which utilises a pump system to draw air through the smoking article after heating or combustion of the tobacco material has been initiated. Preferably, during the smoking test, air is drawn through the smoking article in a sequence of puffs. A suitable sequence of puffs may be carried out in order to simulate the typical pattern of puffs on the smoking article by a consumer.

For the purposes of the present invention, the smoking machine is operated to perform a 'smoking test' in which 1 0 consecutive 35 ml puffs, each lasting 2 seconds are carried out every 60 seconds. The smoking test is carried out in accordance with ISO 3308:2000.

The smoking machine may be a linear or rotary smoking machine. Preferably, the smoking machine is operated to smoke a plurality of smoking articles simultaneously such that the cumulative smoke from the plurality of smoking articles can be collected and analysed. Suitable smoking machines for use in the present invention would be well known to the skilled person. A range of suitable smoking machines are available, for example, from Borgwaldt KC.

The smoke emitted from the smoking article during each puff is directed to the smoke analysis device such that the nicotine concentration of the smoke from each puff is independently measured using the AFID. In this way, it is advantageously possible to perform a puff-by-puff analysis of the nicotine delivery of the smoking article. From this data it is then possible to readily derive the puff-by-puff aerosol delivery profile of the smoking article.

The system and method of the present invention is used to perform an analysis of the mainstream smoke generated by a smoking article during the smoking test. The 'mainstream smoke' refers to the smoke that is drawn through the smoking article and which would be inhaled by the consumer during use.

The invention will be further described, by way of example only, with reference to the accompanying drawing in which:

Figure 1 shows a schematic diagram of a system according to the present invention for performing a puff-by-puff analysis of the nicotine concentration of the smoke generated by a smoking article during a smoking test. The system 10 illustrated in Figure 1 comprises a smoking machine 12 for carrying out a smoking test on one or more smoking articles. The smoking machine 12 is connected to a smoke analysis device 14 by means of a conduit 16 extending between an outlet 18 of the smoking machine 12 and an inlet 20 of the smoke analysis device 14. A pump 22 is connected to the conduit 16 in order to pump the smoke from the smoking machine 12 to the smoke analysis device 14. The conduit 16 additionally comprises an injection port 24 for injecting standard nicotine solutions into the conduit 16 during a calibration.

The smoke analysis device 14 comprises a fused silica chromatographic column 26 and a downstream alkali flame ionisation device (AFID) 28 which receives the effluent from the chromatographic column 26. A source of air is connected to the conduit at an inlet 30 adjacent to the inlet 20 of the smoke analysis device 14, so that air can be mixed with the smoke before the smoke enters the fused silica column 26. Sources of air hydrogen are connected to the smoke analysis device at respective inlets 32a, b between the chromatographic column 26 and the AFID 28. During operation, the smoke is mixed with the hydrogen and air before passing into the AFID 28.

The AFID 28 comprises a hydrogen flame 34, an alkali salt ring 36 formed of RuCI positioned around the flame 34 and a collector plate (not shown) which can be positioned at a variable distance from the hydrogen flame 34.

To perform an analysis of a smoking article using the apparatus shown in Figure 1 , a smoking article is placed within a port of the smoking machine 12 and automatically smoked in a smoking test by puffing air through the smoking article in 35 ml puffs for 2 seconds, every 60 seconds. Prior to the smoking test, the tobacco material is lit (in the case of a combustible smoking article) or heating of the tobacco material is initiated in order to produce smoke from the smoking article.

The smoke generated during each puff is pumped from the outlet 18 of the smoking machine 12 through the conduit 16 to the smoke analysis device 14. Before entering the smoke analysis device 14 the smoke is mixed with air which is injected into the conduit 16 through the inlet 30.

The air and smoke mixture is injected through the chromatographic column 26 and the effluent from the column 26 is mixed with a mixture of hydrogen and air, which is provided through the inlets 32a, b before being directed into the AFID 28 to determine the nicotine concentration of the smoke. This process is repeated for the smoke generated during each puff so that a puff-by-puff analysis of the smoke can be performed. Based on the output from the AFID 28, the nicotine delivery during each puff can be measured, as well as the total nicotine delivery during the smoking test. Whilst the description above refers to a single smoking article, a plurality of smoking articles may be mounted in the smoking machine and smoke simultaneously. In this case, the cumulative smoke generated from the plurality of smoking articles during each puff is analysed and an average nicotine delivery can be calculated.

Claims

1 . A method for performing a puff-by-puff analysis of the nicotine delivery of a smoking article comprising;

mounting the smoking article in a smoking machine; and

operating the smoking machine to perform a smoking test during which air is drawn through the smoking article,

wherein during a smoking test the air is drawn through the smoking article in a sequence of puffs, wherein the smoke emitted from the smoking article during each puff is directed into a smoke analysis device connected to the smoking machine, wherein the smoke analysis device comprises an alkali flame ionisation detector and wherein the nicotine concentration of the smoke from each puff is independently measured using the alkali flame ionisation detector.

2. A method according to claim 1 wherein the smoke emitted from the smoking article is pumped through a conduit connecting an outlet of the smoking machine to an inlet of the smoke analysis device.

3. A method according to claim 1 or 2 further comprising mixing the smoke with a combustible carrier gas prior to directing the smoke into the alkali flame ionisation detector.

4. A method according to any preceding claim further comprising calibrating the alkali flame ionisation detector, wherein the calibrating comprises directing nicotine solutions of a known concentration into the smoke analysis device and measuring the output of the alkali flame ionisation detector.

5. A method according to any preceding claim further comprising generating an output signal from the smoke analysis device based on the measured nicotine concentration and transmitting the output signal to a controller.

6. A method according to any preceding claim further comprising measuring one or more additional components of the smoke emitted from the smoking article by providing one or more additional detectors within the smoke analysis device.

7. A method according to any preceding claim wherein the smoke directed from the smoking machine to the smoke analysis device is the mainstream smoke emitted from the smoking article during the smoking test.

8. A system for performing a puff-by-puff analysis of the nicotine delivery of a smoking article during smoking, the system comprising:

a smoking machine for performing a smoking test during which air is drawn through the smoking article in a sequence of puffs;

a smoke analysis device comprising an alkali flame ionisation detector; and

a conduit for directing smoke emitted from the smoking machine during the sequence of puffs from an outlet of the smoking machine to an inlet of the smoke analysis device.

9. A system according to claim 8 further comprising a pump connected to the conduit for pumping smoke from the outlet of the smoking machine to the inlet of the smoke analysis device during use.

10. A system according to claim 8 or 9 wherein the smoke analysis device comprises a heated spiral chromatographic column upstream of the flame of the alkali flame ionisation device.

1 1 . A system according to claim 8, 9 or 10 wherein the alkali flame ionisation device comprises an alkali salt ring formed of a rubidium salt.

12. A method of monitoring the nicotine concentration of the smoke generated by a smoking article during smoking using the system of any of claims 8 to 1 1 , the method comprising:

inserting a smoking article into the smoking machine;

operating the smoking machine to smoke the smoking article in a smoking test during which the smoking machine performs a sequence of puffs through the smoking article;

directing the smoke generated by the smoking article during each puff into the smoke analysis device; and

measuring the nicotine concentration of the smoke generated by the smoking article during each puff using the alkali flame ionisation detector.

13. Use of the system of any of claims 8 to 1 1 to perform on-line monitoring of the nicotine concentration of the smoke emitted by a smoking article during a smoking test in the smoking machine.

14. Use according to claim 13 for performing on-line monitoring of the nicotine concentration of the aerosol emitted by a heated smoking article.