Development and validation of a high-throughput liquid-absorption preconcentrator for the detection of trace air contaminants

This paper discusses a high-throughput liquid-absorption preconcentrator (HTLAP) developed for rapid and/or ultrasensitive detection and analysis of trace air contaminants. The HTLAP consists of an internally wetted (6 cm I.D., 30 cm long) glass tube through which the sampled air is drawn in a swirling, highly turbulent motion that facilitates material transfer to a liquid film covering and draining down the inner wall of the tube. The liquid is collected at a rate of 0.1-2 (usually 0.1) mL/min. For validation, carrier gas (nitrogen) from a vapor generator, containing known analyte concentrations and flowing at an adjustable rate of 0.05-0.5 L/min, was mixed at the preconcentrator inlet with ambient air drawn at a rate of 600-800 L/min. The HTLAP's collection efficiency was measured by comparing the amount of analyte collected in the liquid with the amounts collected by sorbent tubes over comparable periods of time before and after each experimental run. For cocaine and heroin vapor concentrations of 0.1-150 parts per trillion by volume, the collection efficiency was 55 ± 30%, as measured by liquid chromatography with electrochemical detection. The HTLAP should reduce the detection limit and/or the sampling time for trace air contaminants by several orders or magnitude