Sensitive determination of d‐lactic acid and l‐lactic acid in urine by high‐performance liquid chromatography–tandem mass spectrometry

ABSTRACT d ‐Lactic acid in urine originates mainly from bacterial production in the intestinal tract. Increased d ‐lactate excretion as observed in patients affected by short bowel syndrome or necrotizing enterocolitis reflects d ‐lactic overproduction. Therefore, there is a need for a reliable and sensitive method able to detect d ‐lactic acid even at subclinical elevation levels. A new and highly sensitive method for the simultaneous determination of l ‐ and d ‐lactic acid by a two‐step procedure has been developed. This method is based on the concentration of lactic acid enantiomers from urine by supported liquid extraction followed by high‐performance liquid chromatography–tandem mass spectrometry. The separation was achieved by the use of an Astec Chirobiotic™ R chiral column under isocratic conditions. The calibration curves were linear over the ranges of 2–400 and 0.5–100 µmol/L respectively for l ‐ and d ‐lactic acid. The limit of detection of d ‐lactic acid was 0.125 µmol/L and its limit of quantification was 0.5 µmol/L. The overall accuracy and precision were well within 10% of the nominal values. The developed method is suitable for production of reference values in children and could be applied for accurate routine analysis. Copyright © 2011 John Wiley & Sons, Ltd.