Liquid/air partition coefficients of acetaldehyde: values and limitations in estimating blood concentrations from analysis of breath.

We report liquid/air partition coefficients for dilute solutions of acetaldehyde in water, saline (0.9% wt/vol NaCl), human plasma, and corn oil. Equilibrium was studied at 34 degrees C and 37 degrees C with various concentrations of acetaldehyde in the liquid phases. At 37 degrees C, the liquid/air partition ratios for water, saline, plasma, and oil were 143 +/- 7.1, 132 +/- 6.6, 183 +/- 3.6, and 64 +/- 9.9 (mean +/- SE), respectively. At 34 degrees C, all the values were higher and the temperature coefficients of solubility were 3.7%, 3.3%, and 4.0% per 1 degree C for water, saline, and plasma solutions of acetaldehyde, respectively. The partition coefficients were independent of the concentration of acetaldehyde in the liquids, and the solubility was higher in water than in oil. The results are discussed with emphasis on the usefulness of expired breath as a biological specimen for the quantitative determination of acetaldehyde.