| Title: | Using labelled internal standards to improve needle trap micro-extraction technique prior to gas chromatography/mass spectrometry |
| Author(s): | Biagini D; Lomonaco T; Ghimenti S; Onor M; Bellagambi FG; Salvo P; Di Francesco F; Fuoco R; |
| Address: | "Department of Chemistry and Industrial Chemistry, University of Pisa, Via Giuseppe Moruzzi 13, Pisa, Italy. Department of Chemistry and Industrial Chemistry, University of Pisa, Via Giuseppe Moruzzi 13, Pisa, Italy. Electronic address: tommaso.lomonaco@unipi.it. Institute of Chemistry of Organometallic Compounds, CNR, Via Giuseppe Moruzzi 3, Pisa, Italy. Institute of Clinical Physiology, CNR, Via Giuseppe Moruzzi 3, Pisa, Italy" |
| DOI: | 10.1016/j.talanta.2019.03.046 |
| ISSN/ISBN: | 1873-3573 (Electronic) 0039-9140 (Linking) |
| Abstract: | "When working with humid gaseous samples, the amount of water vapour collected in a needle trap along with volatile analytes may vary from sample to sample and decrease during the storage. This has a major impact on desorption efficiency and recovery. We propose the addition of a labelled internal standards to nullify the effect of variable humidity on the analytical performance of needle trap micro-extraction combined with gas chromatography mass spectrometry. Triple-bed (Divinylbenzene/Carbopack X/Carboxen 1000) and single-bed (Tenax GR) needles were tested with standard gaseous mixtures prepared at different relative humidity levels (85%, 50% and 10%). The standard mixtures contained twenty-five analytes representative of breath and ambient air constituents, including hydrocarbons, ketones, aldehydes, aromatics, and sulphurs, in the concentration range 0.1-700 ppbv. The two needles showed different behaviours, as recovery was independent of humidity for single-beds, whereas a low recovery (10-20%) was observed when triple-beds trapped very volatile compounds at low humidity (e.g. pentane and ethanol, 10% relative humidity. Triple-beds showed an almost quantitative recovery (>90%) of all the analytes at 50% and 85% relative humidity. This big difference was probably due to the reduced action of water vapour pressure during the desorption step. The addition of (6)D-acetone and (8)D-toluene to the sorbent material before gas sampling and the normalization of raw data nullified this effect, thereby lowering the variations of analyte recovery at different humidity levels down to 20%. Internal standards were also exploited to limit within 10-20% alterations in peak areas of very volatile compounds during needle storage at room temperature. This variation may results from a loss of water vapour either retained from the sorbent material and/or condensed on triple-bed needle walls. After normalization, the inter- and intra-day precision were halved to 5% and 10% in the case of single-beds, respectively, and to 15% and 20% with three-beds. The addition of an internal standard to the sorbent helps to keep the overall analytical procedure under control and improves the reliability of needle trap micro-extraction for the analysis of volatile organic compounds at ultra-trace levels" |
| Keywords: | Breath analysis Gc-ms Labelled internal standards Needle trap micro-extraction Volatile organic compounds; |
| Notes: | "PubMed-not-MEDLINEBiagini, Denise Lomonaco, Tommaso Ghimenti, Silvia Onor, Massimo Bellagambi, Francesca G Salvo, Pietro Di Francesco, Fabio Fuoco, Roger eng Netherlands 2019/05/01 Talanta. 2019 Aug 1; 200:145-155. doi: 10.1016/j.talanta.2019.03.046. Epub 2019 Mar 12" |
