NEEDLE TRAP MICRO-EXTRACTION: A NEW STRATEGY FOR THE COLLECTION AND PRECONCENTRATION OF BREATH SAMPLES

The chemical characterization of volatile compounds in human breath is a potential tool for modern medicine to obtain clinically relevant information on ongoing body physiological processes in a non-invasive way. Pre-concentration is the crucial step when volatile organic compounds (VOCs) occurring at concentrations in the ppbv or pptv range have to be determined. The needle trap devices (NTDs), i.e. stainless steel needles (internal diameter 0.22 μm and length 6 cm) packed with suitable sorbent materials, represent a new promising tool for a robust and reproducible sample preparation since they combine the advantages of SPE (active adsorption) and SPME (small volume, direct injection in the GC injector) [1]. In this work, the needle trap micro-extraction technique was optimized for the simultaneous collection and pre-concentration of VOCs in exhaled breath. In particular, the effect of different packing materials on the efficacy and reproducibility of VOCs analysis was investigated. Double and triple bed NTDs packed with different combinations of sorbents (e.g. DVB, PDMS, Carbopack X and Carboxene 1000) were tested to evaluate the influence of sampling parameters such as flow rate and sample volume on the adsorption process, as well as the effect of different GC inlet temperatures onto the analyte desorption from NTDs. Particular attention was paid to the use of an internal standard for the normalization of data. All the tests were carried out using a humid standard gaseous mixture composed by 18 VOCs with different chemical and physical properties. Needle trap devices were automatically desorbed by a CONCEPT NT-sampler and VOCs were detected by an Agilent 7010 Series Triple Quadrupole GC/MS. Detection limits in the range of pptv and ppbv for all the investigated compounds were observed.