Abstract: Organic acids analysis is a powerful technique in the diagnosis of inborn errors of metabolism. Carboxylic acids in plasma or urine can be conveniently determined by capillary gas chromatography (GC), following treatment with ethyl chloroformate (ECF). We propose a rapid, simple methodology for routine analysis of human fluids to detect eleven organic acids related to metabolic disease. With this methodology, isolation of the compounds of interest is not necessary. The run time is 14 minute.