Sharing passion for separation science with Roman

Janusz Pawliszyn, Department of Chemistry, University of Waterloo, Waterloo, ON, N2L 3G1, Canada

Development of rapid analytical workflows capable of providing high quality data and at the same time resulting in minimum environmental impact is garnering interest in the scientific community. Solid phase microextraction (SPME), a sample preparation tool that combines sampling and sample preparation into a single step, has demonstrated excellent performance for both qualitative and quantitative determination of a broad range of analytes in various matrices particularly when combined with GC/MS or LC/MS techniques. The additional advantage of the hyphenated techniques would be to allow convenient calibration and/or qualitative assignment. This can be facilitated by using retention times corresponding to the separation method rather than using matrix matched calibration or other approaches requiring isotopically labelled standards. Initial work demonstrated that the distribution coefficients (K) between air and SPME fiber coating can be estimated using the linear temperature-programmed retention index system (LTPRI) [1]. This alternative approach to establishing K values significantly enhances and simplifies the use of SPME for sampling and analyzing air. Also, it was determined that there is a linear relationship between log K for each hydrocarbon series and LTPRI when using aqueous matrix. The slope of the curves for all the series are the same and they are related to the partial free energy of solution for the hydrocarbon-fiber coating solution. The y-intercept of the plots is distinct for each group of hydrocarbons and related to Henry’s law coefficients for each homologue series indicating that the K for a series of hydrocarbons can be estimated using literature Henry’s law coefficients [2]. For complex matrices quantitative structure–retention relationship (QSRR) is a technique capable of improving the identification of analytes by predicting their retention time on a liquid chromatography column (LC) based on their properties. This approach is particularly useful when LC is coupled with a high-resolution mass spectrometry (HRMS) platform, which aids in identification of the compounds based on respective retention time and the exact mass [3]. In addition, the retention time also provides information about the distribution constants, which can be calculated using QSRR models. This approach facilitates a practical and effective method for analytical chemists working with SPME hyphenated to chromatographic separation to improve predictive confidence of identification and quantitation of small molecules in range of complex matrices.

1. Anal. Chem. 69, 206-215 (1997)
2. Anal. Chem. 69, 402-408 (1997)
3. Anal. Chimica Acta 797, 13-19 (2013)