An accurate, automated, simultaneous gas chromatographic headspace measurement of whole blood ethanol and acetaldehyde for human in vivo studies.

Simultaneous assessment of ethanol and acetaldehyde concentrations is necessary to address hypotheses in alcohol research. Accurate measurement of in vivo acetaldehyde following ethanol exposure is problematic because acetaldehyde is present in blank blood, is volatile, and is formed enzymatically and nonenzymatically in blood containing ethanol. Because acetaldehyde is carried in red blood cells, previously reported plasma methods may not reflect total body acetaldehyde. We developed an accurate, sensitive, automated gas chromatographic whole blood method using headspace injection and flame ionization detection. Sensitivity was 5.4 mumol/L and 1.13 mumol/L for ethanol and acetaldehyde, respectively. Linearity (r2 > 0.99, both) and reproducibility (coefficients of variation = 1.6-7.7%) were acceptable. Because a whole blood method completely inhibiting in vitro oxidation of ethanol has not been reported, we evaluated multiple reported sample processing methods. The optimum method, which uses saturated sodium nitrite as the inhibitor, resulted in a 30% in vitro increase in acetaldehyde in blood containing 21.7 mmol/L (0.1 g/dL) ethanol, in contrast to the 9-40-fold increase observed with other inhibitors (p = 0.001). Using the described technique, the median acetaldehyde and ethanol peak concentrations in six African-American women following a 0.5 g/kg oral ethanol dose were 6.1 microM and 17.1 mM, respectively.