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J Chromatogr A

Title:		Construction of an automated gas chromatography/mass spectrometry system for the analysis of ambient volatile organic compounds with on-line internal standard calibration
Author(s):		Su YC; Chang CC; Wang JL;
Address:		"Department of Chemistry, National Central University, Chungli 320, Taiwan"
Journal Title:		J Chromatogr A
Year:		2008
Volume:		20080329
Issue:		2
Page Number:		134 - 140
DOI:		10.1016/j.chroma.2008.03.071
ISSN/ISBN:		0021-9673 (Print) 0021-9673 (Linking)
Abstract:		"An automated sampling and enrichment apparatus coupled with a gas chromatography/mass spectrometry (GC/MS) technique was constructed for the analysis of ambient volatile organic compounds (VOCs). A sorbent trap was built within the system to perform on-line enrichment and thermal desorption of VOCs onto GC/MS. In order to improve analytical precision, calibration accuracy, and to safe-guard the long-term stability of this system, a mechanism to allow on-line internal standard (I.S.) addition to the air sample stream was configured within the sampling and enrichment apparatus. A sub-ppm (v/v) level standard gas mixture containing 1,4-fluorobenzene, chloropentafluorobenzene, 1-bromo-4-fluorobenzene was prepared from their pure forms. A minute amount of this I.S. gas was volumetrically mixed into the sample stream at the time of on-line enrichment of the air sample to compensate for measurement uncertainties. To assess the performance of this VOC GC/MS system, a gas mixture containing numerous VOCs at sub-ppb (v/v) level served as the ambient air sample. Various internal standard methods based on total ion count (TIC) and selective ion monitoring (SIM) modes were attempted to assess the improvement in analytical precision and accuracy. Precision was improved from 7-8% RSD without I.S. to 2-3% with I.S. for the 14 target VOCs. Uncertainties in the calibration curves were also improved with the adoption of I.S. by reducing the relative standard deviation of the slope (Sm%) by an average a factor of 4, and intercept (Sb%) by a factor of 2 for the 14 target VOCs"
Keywords:		Calibration Gas Chromatography-Mass Spectrometry/*methods Organic Chemicals/*analysis/isolation & purification;
Notes:		"MedlineSu, Yuan-Chang Chang, Chih-Chung Wang, Jia-Lin eng Research Support, Non-U.S. Gov't Netherlands 2008/04/15 J Chromatogr A. 2008 Aug 8; 1201(2):134-40. doi: 10.1016/j.chroma.2008.03.071. Epub 2008 Mar 29"