ABSTRACT
This chapter reviews techniques that have been published in the technical literature and developed in laboratory for the isolation and concentration of samples prior to analysis by gas chromatography. It emphasizes those techniques that are easy to employ, require minimal equipment, and produce reproducible, meaningful results. The chapter also reviews techniques for isolating and concentrating aromatics, which include various distillation and extraction procedures. Direct injection is by far the most convenient technique and works particularly well for essential oils. The sample may have to be diluted with a solvent to obtain response within the limits of the detector. Carbonated beverages, fruit juices, and caffeinated beverages can often be extracted directly. Fruits and vegetables can be homogenized with water, treated with a pectinase enzyme to destroy the pectins, and filtered through a bed of diatomaceous earth to remove particulates. High-boiling impurities both in solvent and sample will also be concentrated along with the desired analytes.
