Steve Purkis and Michael Intorp
Since 1999, the CORESTA Special Analytes Sub Group (SPA SG) has been working on the development of CORESTA Recommended Methods (CRMs) for the analysis of cigarette smoke components. All CRMs have been posted on the CORESTA website and several associated papers published. In this study, 21 laboratories shared data and in-house methodologies for 28 additional smoke components of regulatory interest to prioritise the development of further CRMs. Laboratories provided data, where available, from CORESTA monitor test pieces (CM6 and CM7) and Kentucky Reference Cigarettes (1R5F / 3R4F) covering the period 2010-2012 obtained under both the ISO 3308 and Health Canada Intense regimes. Scant data were available on the CORESTA monitor test pieces and the Kentucky 1R5F reference. The greatest amount of data was obtained on the Kentucky 3R4F and this was used in the analyses described in this paper. SPA SG discussions provided invaluable insight into identifying causes and ways of reducing inter-laboratory variability which will be investigated in joint experiments before embarking on final collaborative studies using draft CRMs to obtain mean yields, repeatability and reproducibility values. Phenolic compounds (phenol, 3 cresol isomers, hydroquinone, catechol and resorcinol) gave consistent results by liquid chromatography (LC) separation and fluorescence detection after extracting collected “tar” on a Cambridge filter pad (CFP). Yields were similar to those obtained by a derivatisation method followed by gas chromatography - mass spectrometry (GC-MS) analysis. Similar ratios of phenols were also obtained from each method. Of the 28 studied analytes, the between-laboratory variability was lowest for the phenols. Hydrogen cyanide was derivatised using various reagents and the colour development measured after continuous flow analysis (CFA) by ultra-violet absorbance. Although, methodologies gave reasonably consistent results, investigations on the trapping system and on differences in the application of the various colour complexes used for quantification with UV absorbance is required. Ammonia analysis was carried out by ion chromatography (IC) followed by conductivity measurement and gave very similar results between laboratories. Yields were similar to those obtained by a derivatisation method followed by LC/MS-MS methodology. Optimal conditions for the separation of ammonium from interfering ions and minimizing artefactual ammonia formation from other smoke components need to be addressed during standardisation. Aromatic amine methods involved either LC/MS-MS separation and detection or derivatisation by one of two main reagents followed by GC-MS analysis. Yields were at similar but variable levels using these different techniques. It is currently unclear which method will be taken to a CRM. In general, four compounds were measured (1-amino naphthalene; 2-amino naphthalene; 3-amino biphenyl and 4-amino biphenyl) although two others were incorporated in methodologies used by 3 laboratories (o-anisidine and o-toluidine). Semi-volatiles (pyridine, quinoline and styrene) were often integrated with the selected volatiles method by measurement of the combination of CFP extracts and the contents of the impinger trapping system. Less data, obtained mainly by inductively-coupled plasma - mass spectrometry (ICP-MS), were available on metals (cadmium, lead, arsenic, beryllium, cobalt, chromium, nickel, selenium and mercury) in smoke. Trace metals were the most variable of the studied smoke analytes. Optimisation of the digestion step to remove the organic matrix needs to be addressed. As a consequence of this study and subsequent discussions within the Sub Group, it was decided to prioritise the development of CRMs for selected phenols followed by hydrogen cyanide and ammonia.
M Intorp, S Purkis, M Whittaker and W Wright
Regulatory authorities are currently discussing the measurement of and imposition of ceilings on certain smoke analytes, the so called ‘Hoffmann analytes’. However, as a pre-requisite, the measurement methods and the tolerances around the measurements first need to be established.
In 1999, the Cooperation Centre for Scientific Research Relative to Tobacco (CORESTA) set up a Task Force ‘Special Analytes’ to deal with analytical methodology for measuring ‘Hoffmann analytes’ under International Standard (ISO) smoking and to work towards the standardisation of methods. This paper describes the output and conclusions from a 2005-2006 joint experiment made within the Task Force representing laboratories currently able to analyse these compounds. Data were obtained on most ‘Hoffmann analytes’ from reference cigarettes (2R4F and 1R5F), collecting data according to the existing methods used by the nineteen participating laboratories, in order to describe the within and among laboratory variability and to see which methods could most benefit from more rigorous standardisation work.
In some cases, the applied statistical analysis found that methods could not well differentiate the 1R5F and 2R4F cigarettes of differing ‘tar’ yield. This was explained, in part, by the broad range of methods used by the participating laboratories but also indicated that there were significant inadequacies in the choice of some methods or weaknesses in their application.
Results indicate that ‘Hoffmann analyte’ data are generally more variable both within and among laboratories than nicotine free dry particulate matter (NFDPM); nicotine and carbon monoxide due to their lower smoke yields. Accordingly, tolerances around methods adopted for regulatory purposes will need to be proportionately higher.
Methods for benzo[a]pyrene (B[a]P) and tobacco-specific nitrosamines (TSNAs), already taken to CORESTA recommended methods or ISO standardised methods through the efforts of this Task Force, give some of the most reproducible results, showing the value of this process. However, these data strongly suggest that even these analytes have much higher among-laboratory variability than for NFDPM, nicotine and CO and, based on the only two available one point in time studies, may need tolerances in the range of 35-45% for B[a]P and 26-55% for TSNAs, if they are to be measured for regulatory purposes.
The collected data is useful to participating laboratories for internal method validation and laboratory accreditation, and data comparisons with others allow laboratories to identify strengths and weaknesses in their current methods.
However, much work still needs to be carried out to take most of the methods towards standardisation. Although some fundamental differences or areas of concern around the methodology are discussed herein, they are not comprehensive and there may be others that need to be addressed before methods can be considered ready to take to a Recommended Method and/or to an ISO Standard. These methodological issues are being addressed in further CORESTA work within this Task Force. Smoke analytes with the highest variability found in this study and those analytes that are currently of highest regulatory interest are being prioritised and after further joint experiments, the results are intended to be published.