Volume 25 (2012): Issue 2 (June 2012)

A recommended method has been developed and published by CORESTA, applicable to the quantification of selected carbonyl compounds (acetaldehyde, formaldehyde, acetone, acrolein, methyl ethyl ketone, crotonaldehyde, propionaldehyde and butyraldehyde) in cigarette mainstream smoke. The method involved smoke collection in impinger traps, derivatisation of carbonyls with 2,4-dinitrophenylhydrazine (DNPH), separation of carbonyl hydrazones by reversed phase high performance liquid chromatography and detection by ultra violet or diode array.

At the start of the process it was determined that most laboratories participating in the CORESTA Special Analytes Sub-Group (SASG) used a similar method involving such derivatisation and so this was chosen as the basis of the recommended method. Initial joint experiments, specific experiments by single laboratories and ongoing discussions addressed some methodological aspects that needed to be considered before moving to a recommended method.

As a first step, a joint experiment by 17 laboratories was carried out in 2009-2010 that investigated three features of the methodology on two reference cigarettes (3R4F and CM6) considered most important by SASG members. These were the volume of the impinger solution (25 or 35 mL); the type of mineral acid (perchloric or phosphoric) used to initiate the derivatisation and the time of derivatisation (5 or 30 min) before terminating the reaction with Trizma^TM base. Overall, it was concluded that these studied parameters in the methodology seemed to have little effect on the overall yield data, compared to the underlying variability among laboratories. The 25 mL impinger solutions appeared to give somewhat higher yields, although not with statistically significant differences, than those obtained when using 35 mL solutions.

Some laboratories volunteered to carry out other investigations, for example, to confirm the identity of both the Eand Z-isomeric acetaldehyde hydrazone peaks within the chromatogram of smoke carbonyls and to investigate methodology factors influencing the hydrazoneisomerisation.

The CORESTA recommended method (CRM) was produced through a final collaborative experiment involving 15 laboratories from 11 countries using 7 linear and 8 rotary smoking machines. Some notes are included in the CRM to inform other laboratories that might wish to adopt the method, concerning the main features that need to be well controlled to provide data as robust as possible and to provide similar repeatability and reproducibility data.

Statistical evaluations were made according to ISO 5725 recommendations and are included. As expected from previous work on other smoke components, the levels of reproducibility of carbonyl yields among laboratories are much greater than the levels found for “tar”, nicotine and carbon monoxide and given in the equivalent ISO standards. When expressing the reproducibility (R) value as a percentage of the mean yield among-laboratories and across all of the studied products, values ranged from 67-125% for formaldehyde; from 24-55% for acetaldehyde; from 41-108% for acetone; from 45-73% for acrolein; 31-75% for propionaldehyde; from 63-140% for crotonaldehyde; from 62-90% for 2-butanone and from 42-58% for butyraldehyde. The lowest “tar” yielding product gave the most variable data. These levels are generally in line with those determined for selected volatiles.

Arsenic is one of the metals found in cured tobacco and mainstream cigarette smoke. Levels of arsenic in modern filtered cigarette smoke range from sub-ppm to a few tens of ppms. To enable accurate smoke toxicity assessment on arsenic in cigarette smoke, it is desirable to establish its chemical forms in addition to total quantities because different arsenic compounds possess different toxicological potentials.

Progress has been made on measuring the arsenic speciation in tobacco and mainstream cigarette smoke by using a combination of synchrotron-based X-ray absorption spectroscopy and high-performance liquid chromatography- inductively coupled plasma mass spectrometry (HPLC-ICP-MS). In this paper, we describe the experimental procedures developed together with the main findings. A transient redox transformation between As(V) and As(III) was confirmed in freshly generated mainstream smoke. Potential areas for future research are highlighted in order to further our understanding of the speciation mechanism for arsenic in tobacco products.

The relationship between cigarette blend sugar and acetaldehyde formed in its smoke is a matter of current regulatory interest. This paper provides a re-analysis of data from 83 European commercial cigarettes studied in the 1970s and more modern data on sugar levels and acetaldehyde yields from a series of 97 European commercial cigarettes containing both inherent sugar and in other cases inherent and added sugar. It also provides data from 65 experimental cigarette products made from single curing grades of tobacco, having a wide range of inherent sugar levels but no added sugar.

This study has shown that there is no relationship between acetaldehyde yields and blend sugar content even if a multivariate analysis is carried out taking into account Nicotine Free Dry Particulate Matter (NFDPM) as a co-factor. Such analyses should take into consideration each of the known contributory factors in order to avoid misleading conclusions.

No distinction was found between the mainstream acetaldehyde yields from dark air-cured, flue-cured or US blended style cigarettes irrespective of their sugar content after taking account of differences in NFDPM yields. Similarly, no distinction was found between mainstream acetaldehyde yields of cigarettes made from single grades of either flue-cured, sun-cured or air-cured tobaccos with no sugar added.

This work supports the conclusion that structural material in the tobacco plant is the main source of acetaldehyde in mainstream smoke after combustion during cigarette smoking.

Catechol and alkylcatechols are known co-carcinogens present in cigarette smoke. Hydroquinone, although nongenotoxic, can form a metabolite with nephrotoxic properties and is a potential human carcinogen. The formation of dihydroxybenzenes during smoking originates with the pyrolysis of several precursors from tobacco. These include cellulose, chlorogenic acid, rutin, etc. The present study attempts to quantitate the contribution of chlorogenic acid and rutin to the formation of dihydroxybenzenes and of some alkyldihydroxybenzenes. Also it estimates the contribution to the formation of dihydroxybenzenes from other potential precursors including glucose, fructose, sucrose, cellulose, pectin, starch, and lignin. The study was done in three parts: 1. pyrolytic evaluation of the amount of dihydroxybenzenes in smoke generated from isolated potential precursors; 2. analysis of smoke from cigarettes made from a variety of tobaccos (14 single grades) and two blended cigarettes, followed by correlations of dihydroxybenzenes yield with the tobacco content of various suspected precursors; 3. addition of chlorogenic acid or rutin to several tobaccos followed by the smoking of the spiked cigarettes and measurement of dihydroxybenzenes yield increase. The study shows that for a variety of singlegrade cigarettes and for two blended cigarettes (one being the 2R4F Kentucky reference), the contribution of chlorogenic acid and of rutin to the formation of catechol and hydroquinone in smoke depends on the blend. For the 2R4F cigarette, the contribution from chlorogenic acid is 8.7% for catechol, and 7.7% for hydroquinone (for ISO smoking protocol). For the same cigarette, the contribution from rutin is 3.7% for catechol and 5.1% for hydroquinone. The results of the study are in agreement with a previously reported finding indicating that chlorogenic acid contributes about 13% to the catechol formation in smoke for the 1R1 Kentucky reference cigarette. The study results suggest that other components in tobacco, besides chlorogenic acid, rutin, glucose, fructose, sucrose, cellulose, pectin, starch, and lignin are major contributors to the formation of catechol and hydroquinone in cigarette smoke.