Gas-chromatographic measurement of 3-hydroxybutyrate and lactate in plasma and 3-hydroxybutyrate in whole blood.

We describe two simple, rapid, and sensitive gas-chromatographic methods. One is for determining 3-hydroxybutyrate and lactate in plasma, the other for determining 3-hydroxybutyrate in perchloric acid extracts of blood. Samples are purified by adsorption onto graphitized carbon black (Carbopak B). After desorption, the two hydroxyacids are gas-chromatographically measured. Chromatography is on Carbopack B/polyethylene glycol (Mr 20 000)/trimesic acid, 94.4/ 4.8/0.8 by weight. A series of determinations of 3-hydroxybutyrate in whole blood from 15 subjects gave a mean of 59 (SD 46) mumol/L, with 97.8% analytical recovery (range 94.4-101.8%). In 15 plasma samples, we determined a mean value for 3-hydroxybutyrate of 62 (SD 72) mumol/L, with an analytical recovery of 96.4% (range 93.5-97.6%) and a mean value for lactate of 0.99 (SD 0.55) mmol/L, with an analytical recovery of 92.0 (range 91.3-97.6%). Six replicate analyses of plasma containing typical concentrations of lactate and 3-hydroxybutyrate gave respective CVs of 3.2, 2.1, 1.6, and 1.4%, and 4.9, 3.7, 2.8, and 2.0% for low, medium, high, and very high concentrations. Total analysis time for either method is less than 1 h.