Development of a syringe pump assisted dynamic headspace sampling technique for needle trap device

• Published in: Journal of Chromatography A 2008-07, Vol.1196, p.10-14
• Main Authors: Eom, In-Yong, Niri, Vadoud H., Pawliszyn, Janusz
• Format: Article
• Language: English
• Subjects: Benzene Derivatives - chemistry; Chemical Fractionation - instrumentation; Chemical Fractionation - methods; Chromatography, Gas; Dynamic headspace sampling; Needle trap device (NTD); Needles; Purge and trap; Reproducibility of Results; Syringe pump; Temperature; Water analysis; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2008.03.036

This paper describes a new approach that combines needle trap devices (NTDs) with a dynamic headspace sampling technique (purge and trap) using a bidirectional syringe pump. The needle trap device is a 22-G stainless steel needle 3.5-in. long packed with divinylbenzene sorbent particles. The same sized needle, without packing, was used for purging purposes. We chose an aqueous mixture of benzene, toluene, ethylbenzene, and p-xylene (BTEX) and developed a sequential purge and trap (SPNT) method, in which sampling (trapping) and purging cycles were performed sequentially by the use of syringe pump with different distribution channels. In this technique, a certain volume (1 mL) of headspace was sequentially sampled using the needle trap; afterwards, the same volume of air was purged into the solution at a high flow rate. The proposed technique showed an effective extraction compared to the continuous purge and trap technique, with a minimal dilution effect. Method evaluation was also performed by obtaining the calibration graphs for aqueous BTEX solutions in the concentration range of 1–250 ng/mL. The developed technique was compared to the headspace solid-phase microextraction method for the analysis of aqueous BTEX samples. Detection limits as low as 1 ng/mL were obtained for BTEX by NTD-SPNT.