A recirculating system for concentrating volatile samples

Summary A recirculating system powered by a diaphragm pump which may be readily dismantled for cleaning, is described. The results of operating this system for dynamic headspace sampling in the closed or open mode to load volatiles onto a Tenax trap over a range of temperatures and loading volumes are shown. The system was designed to facilitate the analysis of volatiles in natural products and tested using an equimolar solution of 7 esters of boiling points ranging from 120°C to 299°C. The results showed that compounds in the boiling point range 120–200°C could be loaded onto the trap at 30°C by passing 1–21 of carrier gas through. In order to trap compounds of boiling points approaching 300°C, a temperature of 50–70°C and a loading volume of 2.5–3 1 was necessary. Using the apparatus, human sweat was analysed to show the degree of concentration possible with a natural sample and the variation in the chromatogram profiles of successive trapping from the same sample. Twelve chromatograms from the sweat of two pairs of identical twins were pattern matched to show the high degree of reproducibility possible using this apparatus to trap biological volatiles.