Transportmechanismen und Ausbeuten beim TAS — Verfahren

In the TAS procedure, substances which can be separated from a sample by thermal increase of the vapour pressure can be transported to the TLC layer in different ways and with varying effectiveness. “Forced Convection” gives the lowest yields, results improve considerably with the so-called carrier gas extraction, and a carrier gas extraction in a stream of helium results in optimal yields. Nipagin^®, Sudan red, Dimethyl yellow, Menadione^® and Diphenyl were used as model substances. An almost quantitative thermoextraction from samples can only be achieved with amounts of less than 20 μg. Following scraping off and elution of the corresponding TLC-zones a photometric assay is carried out for quantitative determination.