Determination of isoprene in human breath by thermal desorption gas chromatography with ultraviolet detection.

We describe a new, highly sensitive and specific method for the analysis of isoprene (2-methyl-1,3-butadiene) in human breath. A known volume of expired air (150 ml) was drawn through a solid sorbent material to capture trace organic substances, followed by thermal desorption at 200 degrees C and subsequent determination of isoprene by gas chromatography with diode-array ultraviolet detection. The calibration plot was linear (r = 0.99) over a wide range of breath isoprene concentrations (0-12 nmol/l), and levels down to 0.10 nmol/l were easily measurable. In sixteen healthy subjects (six men and ten women), all of whom were non-smokers, the mean, median and spread of breath isoprene concentrations were 3.73, 3.36 and 1.60-10.33 nmol/l, respectively. No statistically significant differences in the concentrations of breath isoprene were observed between the sexes. The mean (+/- S.D.) concentration of breath isoprene in nine consecutive tests with the same subject was 3.69 +/- 0.60 nmol/l, and the coefficient of variation was 16.3%. Much larger variations in exhaled isoprene were seen during the day and also between days when the same subject was tested repeatedly. The excretion patterns of isoprene in human breath can be investigated with high selectivity and sensitivity with this new analytical method.