The first part of this chapter presents the main objectives for performing derivatization of a sample to be analyzed by gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS). The derivatization is typically done to change the analyte properties for a better separation and also for enhancing the method sensitivity. In GC/MS, derivatization may improve the capability of compound identification. Examples illustrating such improvements are included. The second part describes several types of derivatization that are more frequently used in analytical practice. These include alkylation (e.g., methylation), formation of aryl derivatives, silylation (e.g., formation of trimethylsilyl derivatives), acylation (e.g., reactions with acyl chlorides or with chloroformates), and several other types of derivatizations. The chapter also presents typical derivatizations for analytes with specific functional groups and discusses artifact formation in certain derivatization reactions.

A new reference cigarette, 2R4F, has been designed to replace the 1R4F Kentucky reference cigarette. This new cigarette has virtually the same blend composition as the 1R4F cigarette. However, the 1R4F cigarette was made in 1983 and the variation in the tobacco from crop year to crop year as well as the difference in the age of the two cigarettes were expected to generate differences in the smoke chemistry. A study done for the quantitation of more than 44 analytes in smoke, including most compounds considered as biologically active, is presented in this report. The analyses were performed by six independent laboratories using a variety of analytical techniques. The smoking was performed using International Standard (ISO) recommendations. The results showed only small differences between the two cigarettes regarding ‘tar', nicotine and carbon monoxide (CO), as well as for aminonaphthalenes, resorcinol, and some aldehydes. Although the two reference cigarettes were made as close as possible, the concentrations of a significant number of analytes in the smoke differed between 10% to 30%. Specific trace compounds in the blend such as metals and tobacco specific nitrosamines (TSNA), which may influence the smoke composition, were also different between the two cigarettes. The level of lead, in particular, was very different in tobacco between 1983 and 2002.

In HPLC, the nonlinear behavior of the retention factor k′ with temperature (dependence of ln k′ on 1/T) can be attributed to the multiple interactions of a unique analyte in the separation process and/or to the existence in solution of multiple forms of the analyte (also leading to different free enthalpies of interaction). In this study, several examples of nonlinear retention–temperature dependence are evaluated for both reversed-phase (RP) and hydrophilic interaction chromatography (HILIC) separations. The potential explanation for nonlinear retention–temperature behavior is evaluated for each example, some caused by multiple interactions in the separation system of a unique analyte and others by multiple forms of the analyte. In cases where the analyte does not have more forms and the separation is based predominantly on one type of interaction (e.g., hydrophobic interaction in RP-HPLC), the dependence is linear, as expected. By studying the changes in the chemical structure of a compound as a function of pH it is possible to decide, in many cases, if a unique form or multiple forms of a compound are present in the solution. The use of this information allows us to determine when the lack of linearity (when present) is caused by multiple interactions in the separation system (for one form of the compound) and when more forms are causing the lack of linearity. The approximation with a quadratic form for the nonlinear dependence has been verified in most cases to be good, and only minor improvements were obtained when using higher polynomial dependencies.