A RECIRCULATING SYSTEM FOR CONCENTRATING VOLATILE SAMPLES

A recirculating system powered by a diaphragm pump which may be readil y dismantled for cleaning, is described. The results of operating this system for dynamic headspace sampling in the closed or open mode to l oad volatiles onto a Tenax trap over a range of temperatures and loadi ng volumes are shown. The system was-designed to facilitate the analys is of volatiles in natural products and tested using an equimolar solu tion of 7 esters of boiling points ranging from 120 degrees C to 299 d egrees C. The results showed that compounds in the boiling point range 120-200 degrees C could be loaded onto the trap at 30 degrees C by pa ssing 1-21 of carrier gas through. In order to trap compounds of boili ng points approaching 300 degrees C, a temperature of 50-70 degrees C and a loading volume of 2.5-3 l was necessary. Using the apparatus, hu man sweat was analysed to show the degree of concentration possible wi th a natural sample and the variation in the chromatogram profiles of successive trapping from the same sample. Twelve chromatograms from th e sweat of two pairs of identical twins were pattern matched to show t he high degree of reproducibility possible using this apparatus to tra p biological volatiles.