Question

Chromatographic techniques and recent trends

Answer 1

This chapter discusses current developments in fast and two-dimensional (2D) chromatographic techniques and their applications in the gas chromatography (GC) and liquid chromatography (LC) analyses of contaminants and chemical residues in foods. 2D GC or LC separations involve the use of two coupled columns of different selectivity (or capacity) to provide improved separation for sections (heartcuts) of one-dimensional (1D) chromatogram or for the whole first dimension separation. The chapter reviews some current approaches to overcome matrix effects that may adversely affect the quantitative GC- and LC-mass spectrometric (MS) analyses of trace components in food matrices. Basic approaches to fast LC are very similar to fast GC approaches. Differences exist because of a simple fact that LC employs liquid and not gaseous mobile phases. Apart from different physicochemical properties of the mobile phase, LC is a much more versatile technique than GC because both the stationary and mobile phases affect the separation. A myriad of stationary and mobile phase combinations can be used, enabling selectivity optimization for enhanced separation and/or increased speed. Similarly to GC, an existing method can be speeded up by employing higher than optimum mobile phase flows and/or shorter columns. Faster temperature programming in GC can be compared to faster (steeper) mobile phase gradients in LC, resulting in faster analyte elution as the mobile phase strength increases more rapidly.