title: Simultaneous quantification of acylcarnitine isomers containing dicarboxylic acylcarnitines in human serum and urine by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry.
abstract: Tandem mass spectrometry (MS/MS) has become a prominent method for screening newborns for diseases such as organic acidemia and fatty acid oxidation defects, although current methods cannot separate acylcarnitine isomers. Accurate determination of dicarboxylic acylcarnitines such as methylmalonylcarnitine and glutarylcarnitine has not been carried out, because obtaining standards of these acylcarnitines is difficult. We attempted the individual determinations of acylcarnitines with isomers and dicarboxylic acylcarnitines by applying high-performance liquid chromatography (HPLC). Chromatographic separation was performed by gradient elution using a mixture of 0.08% aqueous ion-pairing agent and acetonitrile as the mobile phase. Mass transitions of m/z 161.8-->84.8 for carnitine and m/z 164.8-->84.8 for deuterated carnitine were monitored in positive ion electrospray ionization mode. One carnitine and 16 acylcarnitines were quantified. The limit of quantitation (LOQ) was 0.1 micromol/L for methylmalonylcarnitine and 0.05 micromol/L for the other acylcarnitines. Intra-day and inter-day coefficients of variance (CVs) were <8.3% and <8.8%, respectively, for all acylcarnitines in serum, and both were <9.2% in urine. Mean recoveries were >90% for all acylcarnitines. Human samples were quantified by this method. After addition of deuterated acylcarnitines as internal standards, acylcarnitines in serum or urine were extracted using a solid-phase extraction cartridge. In healthy adult individuals, isobutyryl-, 2-methylbutyryl- and isovalerylcarnitine were detected in serum and urine. Dicarboxylic acylcarnitines were detected in urine. High concentrations of methylmalonylcarnitine and propionylcarnitine were found in both the serum and the urine of a patient with methylmalonic acidemia. The described HPLC/MS/MS method could separate most acylcarnitine isomers and quantify them, potentially allowing detailed diagnoses and follow-up treatment for those diseases.
authors.affiliation: Laboratory of Hospital Pharmacy, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Maeda
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ito
authors.forename: Atsuko
authors.initials: A
authors.lastname: Suzuki
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Kurono
authors.forename: Akihito
authors.initials: A
authors.lastname: Ueta
authors.forename: Kyoko
authors.initials: K
authors.lastname: Yokoi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sumi
authors.forename: Hajime
authors.initials: H
authors.lastname: Togari
authors.forename: Naruji
authors.initials: N
authors.lastname: Sugiyama
mesh_terms: D000328:Adult; D002331:Carnitine / Q000031:analogs & derivatives* / Q000097:blood / Q000737:chemistry / Q000652:urine; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007536:Isomerism; D008297:Male; D008661:Metabolism, Inborn Errors / Q000097:blood / Q000201:enzymology / Q000652:urine; D008764:Methylmalonic Acid / Q000097:blood; D008765:Methylmalonyl-CoA Mutase / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: C116917:acylcarnitine; D008764:Methylmalonic Acid; D008765:Methylmalonyl-CoA Mutase; D002331:Carnitine