A method for serum octanoate in hepatic cirrhosis and hepatic encephalopathy

We describe a new, more efficient, and more reproducible method for determination of octanoate in serum. This method involves ethanol extraction, followed immediately by alkali addition before concentration of the extract. The concentrate is made acidic only before it is to be steam distilled (in a special all-glass apparatus with an alkali trap). The material is acidified again just before separation by gas-liquid chromatography. The yield is 89-107%. When assayed by mass spectrometry, only octanoate was found in the fraction from chromatography. Previous methods yielded only 30-55% of the expected octanoate value and the recovered materials showed impurities by mass spectrometry. Octanoate concentrations were determined in the serum of 24 fasting controls and that of 85 fasting cirrhotic patients, of whom 50 had encephalopathy. Concentrations in arterial and venous blood were significantly higher in cirrhotic patients in coma than in those not in coma, and arterial concentrations were statistically higher than venous concentrations in the cirrhotic patients.