On‐line solid phase extraction ‐ thermal desorption for introduction of large volumes of aqueous samples into a gas chromatograph

Abstract

AbstractA new approach to the introduction of large aqueous samples into a gas chromatograph, solid phase extraction ‐ thermal desorption, is presented. Carrier gas pushes the sample through a packed liner mounted in a programmed temperature vaporizer; analytes retained by the packing material are thermally desorbed after drying of the adsorbent. The sorption properties and thermal stability of some packing materials have been studied off‐line. Tenax GC®, and octyl‐modified silica silylated with diphenyltetramethyldisilazane to improve its thermal stability, appeared to be suitable materials.The drying period and the desorption temperature are critical for satisfactory performance of the method. When Tenax GC® is used as packing material, thermal desorption at 250°C for 15 min gives quantitative recovery for methyl esters up to hexacosanoic acid methyl ester. With the silylated octyl‐modified silica, the application range is limited to the methyl esters of decanoic to octadecanoic acids.