Abstract 1187

Background: Methodologic problems with gas chromatographic assay of trace gases in the presence of environmental contaminants have complicated attempts to quantitate products of lipid peroxidation (ethane and pentane) in exhaled breath. Our group has been studying this problem for a number of years. In 1996 we reported ( Pinney, Johnson, Bhutani et al) the presence of ethylene oxide in environmental air from degassing of ethylene dioxide (ETO) sterilized plastic disposables and tubing. ETO interfered with the measurement of pentane by the technique we were then using and was a potential health hazard. Identifying the source of ETO contamination, elimination of ETO contaminated equipment from collection and measuring circuits and increasing air flow rate and frequency of filter changes in the ICN eliminated the ETO problem. However problems of interference with pentane assay by gases such as isoprene remained (Nelson et al, Pediatr Res 1998). Methods: We developed a simplified, automated methodology using a Shimadzu GC-14A gas chromatograph equipped with a liquid nitrogen cryogenically cooled oven. Two 50ml breath samples are cryofocused onto the head of a silica-gel column. The GC oven heats, allowing the hydrocarbon mix to desorb onto a Poraplot-Q column. The separation occurs with oven temperature programming followed by flame ionization detection. Data is collected using a high resolution data processor (Shimadzu CR-501). Results: Accuracy and precision of the ethane and pentane assay is confirmed by calibration using prepared hydrocarbon gas standards. A qualitative limit of detection for both ethane and pentane was determined to be on the order of 10 to 15 ppb. Resolution and reproducibility are also excellent for propane, butane and hexane. Resolution of isoprene at low levels was observed to be 100%. The entire procedure, including post run burn-out and return to -90C in preparation for introduction of the next sample can be accomplished in one hour. Samples of environmental air consistently show contamination with isoprene, usually pentane, occasionally butane and rarely propane and ethane. A peak (probably isopentane) is observed in exhaled breath at a retention time preceeding that of pentane by 0.2 seconds. Conclusions: This sensitive, completely automated procedure for measuring trace gases will facilitate assessment of oxidant radical production in health and disease. (Supported by the Newborn Pediatric Fund, PA. Hospital).