Determination of total organic acids in urine by extraction with organic solvents.

Metabolic carboxylic acids are extracted, with a mixture of equal volumes of t-amyl alcohol-chloroform, from an acidifiedsample of as littleas 200 tI of urine that has been adsorbed to a short column of silicagel. Total acid in the extract is measured by titrationwith tetramethylammonium hydroxide (10 mmol/liter) to a phenolphthalein end point.There is no interferencefrom protein,creatinine, creatine, bicarbonate, or amino acids, and no pretreatment of the sample is required. Results compared well (r = 0.94) with those obtained by the Palmer-Van Slyke method for total organic acids. This procedure should prove useful as a simple, rapid screening test for those metabolic disturbances and inborn errors of metabolism characterized by increased excretion of organic acids.