GC–MS Measurement of 13C-Enrichment of Lactic Acid in Sepsis Plasma

Improved conventional and microwave-assisted silylation protocols for simultaneous gas chromatographic determination of tocopherols and sterols: Method development and multi-response optimization

This paper reports on improved conventional thermal silylation (CTS) and microwave-assisted silylation (MAS) methods for simultaneous determination of tocopherols and sterols by gas chromatography. Reaction parameters in each of the methods developed were systematically optimized using a full factorial design followed by a central composite design. Initially, experimental conditions for CTS were optimized using a block heater. Further, a rapid MAS was developed and optimized. To understand microwave heating mechanisms, MAS was optimized by two distinct modes of microwave heating: temperature-controlled MAS and power-controlled MAS, using dedicated instruments where reaction temperature and microwave power level were controlled and monitored online. Developed methods: were compared with routine overnight derivatization. On a comprehensive level, while both CTS and MAS were found to be efficient derivatization techniques, MAS significantly reduced the reaction time. The optimal derivatization temperature and time for CTS found to be 55°C and 54min, while it was 87°C and 1.2min for temperature-controlled MAS. Further, a microwave power of 300W and a derivatization time 0.5min found to be optimal for power-controlled MAS. The use of an appropriate derivatization solvent, such as pyridine, was found to be critical for the successful determination. Catalysts, like potassium acetate and 4-dimethylaminopyridine, enhanced the efficiency slightly. The developed methods showed excellent analytical performance in terms of linearity, accuracy and precision.

Microwave-assisted derivatization procedures for gas chromatography/mass spectrometry analysis

In this review, published applications of microwave-assisted derivatization procedures for gas chromatography/mass spectrometry (GC/MS) are summarized. Among the broad range of analytical techniques available, GC/MS is still the method of choice for most high-throughput screening procedures in forensic/clinical toxicology, doping control and food and environmental analysis. Despite the many advantages of the GC/MS method, time-consuming derivatization steps are often required in order to obtain desirable chromatographic characteristics or to improve the stability and detectability of the target analytes. These derivatization processes typically require reaction times from 30 min up to several hours at elevated temperature. In contrast, microwave protocols have demonstrated to be able to reduce the time required for derivatization to a few minutes, and can thus very effectively shorten the overall analysis time, in particular when carried out in a high-throughput format. Herein, the literature in this field is summarized and recent experimental techniques for performing parallel GC/MS derivatization protocols are discussed.