Red light on toxic tobacco leads to class separation in China

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  • Published: Dec 1, 2016
  • Author: Ryan De Vooght-Johnson
  • Channels: Gas Chromatography
thumbnail image: Red light on toxic tobacco leads to class separation in China

The problem of analysing tobacco volatiles

Tobacco is a multi-billion pound industry that presents its own analytical challenges. The flavour, and hence the value, of tobacco samples depends on the thousands of volatile chemicals that are produced on heating tobacco.

Tobacco is a multi-billion pound industry that presents its own analytical challenges. The flavour, and hence the value, of tobacco samples depends on the thousands of volatile chemicals that are produced on heating tobacco. Chemometric methods, such as principal component analysis (PCA), are often used to simplify the data arising from the myriad of compounds.

Analysis of tobacco samples needs a quick and inexpensive way of producing the volatiles from the leaf. Traditional methods include heating leaf samples in a water bath, steam distillation and solvent extraction. These methods are inefficient and lengthy, give low sample throughput and also risk decomposing unstable volatiles due to the prolonged heating times. More modern, quicker methods involve the use of ultrasound and/or microwaves. However, expensive equipment is needed and great care has to be exercised to avoid potentially dangerous microwave leakage. There remains a need for a quick, cheap and efficient method of analysing volatile compounds from tobacco leaves.

Tobacco analysis using an infrared lamp, SPME and GC/MS

A group of Chinese researchers, writing in the Journal of Separation Science, report the development of a novel method of analysis that involves heating cut tobacco samples using an infrared lamp. The samples were placed in a vial above the lamp. Headspace analysis was carried out by placing an SPME fibre in the vial above the sample. After a set period of infrared heating, the SPME fibre was removed and placed in the injector port of a GC/MS instrument to detect the many volatile compounds present.

The conditions employed, such as the extraction time, the lamp power, the type of SPME fibre and the distance of the lamp from the sample, were all optimised. The new method, with an optimised extraction time of 20 minutes, compared favourably both with the more time-consuming technique of heating samples in a water bath and a non-heating method.

Ten samples from different regions were examined under the optimum conditions. The data from the GC/MS showed a mass of peaks from the many compounds present. To make some sense of the results, various chemometric methods were employed. Firstly, principal component analysis was used, from which two principal components were found; together these accounted for 90.7% of the variance. Putting the values for the samples from different regions onto a plot of these two components grouped them into three classes, corresponding to ‘fresh’, ‘moderate’ and ‘rich’ styles, which could be identified by tobacco flavour experts. Hierarchical cluster analysis (HCA) and similarity analysis gave similar results, again putting the ten different samples into three distinct classes.

New method improves tobacco analysis

The new analytical method allows for the fast analysis of many tobacco samples. It has environmental advantages, since no solvents are used, and the prolonged heating of water baths is avoided. The authors state that the new method is a ‘simple, time-saving, low-cost, highly efficient and environmentally friendly approach.’

Combined with the chemometric analysis, samples can be classed with regard to their characteristics without any expert being on hand to smoke them. The method can also be used to determine the geographical origin of samples of doubtful provenance, which could well prove useful for other plant species.

Related Links

J. Sep. Sci., 2016, 39, 4192-4201. Yang et al. Multivariate analysis of the volatile components in tobacco based on infrared-assisted extraction coupled to headspace solid-phase microextraction and gas chromatography-mass spectrometry.

Nordqvist, Medical News Today, July 13, 2015: “What chemicals are in cigarette smoke?”

Wikipedia, Principal Component Analysis

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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