Abstract: The main biomarker of Methylmalonic acidemia was known as methylmalonic acid. Therefore, a rapid, selective and accurate method is developed to determine methymalonic acid in urine by using electrospray tandem mass spectrometry with n-butyl ester derivation and stable isotope dilution. The concentration of creatinine in urine was also determined without derivation. With this quantitative method of c(MMA)/c(creatinine), the urines samples of two MMAemia patients were analyzed through the process of treatment. The result shows that it can be used not only for the screening of inborn errors of metabolism, but also in the treatment process of MMAuria patients.

Key words: Methylmalonic acidemia, Derivation, Tandem mass spectrometry