Analytical approach in diagnosis of inherited metabolic diseases: Maple syrup urine disease (MSUD) – simultaneous analysis of metabolites in urine by enantioselective multidimensional capillary gas chromatography‐mass spectrometry (enantio‐MDGC‐MS)

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Abstract
Maple Syrup Urine disease (USUD) is an autosomal recessive inherited metabolic disorder of branched‐chain amino acid (L‐valin, L‐leucine, and L‐isoleucine metabolism named after the characteristic smell of affected patients urine. MSUD is caused by a deficiency of the branched‐chain α‐keto acid dehydrogenase compex resulting in an accumulation of branched‐chain aamino acids and the corresponding α‐keto‐and α‐hydroxy acids in blood, urine and cerebrospinal fluid causing neurological damage and mental retardation. The enantioselective analysis of chiral MSUD metabolites and analysis of achiral compounds as corresponding N,O‐methoxycarbonyl methyl esters by derivatization with methyl chloroformate (MCF) has been achieved simultaneusly by enantioselective multidimensional gas chromatography‐mass spectrometry using heptakis (2,3‐di‐O‐methyl‐6‐O‐tert‐butyl‐dimethyl‐silyl)‐β‐cyclodextrin as chiral stationary phase. Derivatization with MCF allows the analysis of the structurally different metabolitetes such as branched‐chain‐carboxylic‐, α‐oxo‐, α‐hydroxy‐ and α‐amino acids in a single chromaatographic run. Mass selective detection immensely improves the unequivocaaal identification of metabolites even when they occur as trace compound. The described method allows a reliable screening of MSUD metabolites in patients' urine without time consuming sample preparation and is also suitable for label enrichment analysis without any methodical changes. During this investigation urine sample from three MSUD paatients were analyzed.

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