Sensitive detection of amino acids in human serum and dried blood disc of 3 mm diameter for diagnosis of inborn errors of metabolism.

Sensitive high-performance liquid chromatographic determination of amino and imino acids in human serum (5 microliters) and dried blood (2.6-2.8 microliters) on a paper disc (3 mm diameter) of normal and abnormal newborns with inborn errors of metabolism (phenylketonuria, maple syrup urine disease and tyrosinosis) is described. Amino and imino acids in the biological specimens were extracted with ethanol and derivatized with 4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole at 60 degrees C and at pH 8.0 for 1 min. The fluorescent derivatives were separated on mu Bondapak C18 and detected fluorometrically (530 nm/470 nm). The method was about one order of magnitude more sensitive than the similar method using o-phthalaldehyde. The amino acid contents obtained by the proposed method were comparable to those obtained by the amino acid analyser with use of o-phthalaldehyde.