A sensitive and simple ultra-high-performance-liquid chromatography–tandem mass spectrometry based method for the quantification of d-amino acids in body fluids

• Published in: Journal of Chromatography A Vol. 1218; no. 40; pp. 7130 - 7136
• Main Authors: Visser, Wouter F., Verhoeven-Duif, Nanda M., Ophoff, Roel, Bakker, Steven, Klomp, Leo W., Berger, Ruud, de Koning, Tom J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 07.10.2011; Elsevier
• Subjects: ( S)-NIFE; amino acids; Amino Acids - analysis; Amino Acids - blood; Amino Acids - cerebrospinal fluid; Amino Acids - urine; Biological and medical sciences; central nervous system; cerebrospinal fluid; Chiral derivatization; chromatography; Chromatography, High Pressure Liquid - methods; d-Amino acids; derivatization; detection limit; Diagnostic markers; enantiomers; Humans; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Miscellaneous. Technology; Nitro Compounds - chemistry; pathogenesis; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Reproducibility of Results; schizophrenia; sclerosis; Sensitivity and Specificity; Stereoisomerism; tandem mass spectrometry; Tandem Mass Spectrometry - methods; urine; NBD-PyNCS; OPA; METC; Diagnostic markers; MS; FAD; ( S)-NIFE; AMBI; d-Amino acids; DDO; GITC; IBLC; CV; DAO; PLP; UPLC; SNR; Chiral derivatization; E coll; NMDA; ESI; NIFE; RP; Human; Urine; Ultra performance liquid chromatography; (S)-NIFE; Biological fluid; Tandem mass spectrometry; D stereoisomer; Chemical analysis; Separation; Coupled method; Cerebrospinal fluid; Derivatization; Blood; D-Amino acids; Blood plasma; α-Aminoacid; Reversed phase chromatography; Enantiomer; Clinical biology; Diagnosis; Quantitative analysis
• ISSN: 0021-9673; 1873-3778
• DOI: 10.1016/j.chroma.2011.07.087

d-Amino acids are increasingly being recognized as important signaling molecules in mammals, including humans. d-Serine and d-aspartate are believed to act as signaling molecules in the central nervous system. Interestingly, several other d-amino acids also occur in human plasma, but very little is currently known regarding their function and origin. Abnormal levels of d-amino acids have been implicated in the pathogenesis of different diseases, including schizophrenia and amyotrophic lateral sclerosis (ALS), indicating that d-amino acid levels hold potential as diagnostic markers. Research into the biological functions of d-amino acids is hindered, however, by the lack of sufficiently sensitive, high-throughput analytical methods. In particular, the interference of large amounts of l-amino acids in biological samples and the low concentrations of d-amino acids are challenging. In this paper, we compared 7 different chiral derivatization agents for the analysis of d-amino acids and show that the chiral reagent ( S)-NIFE offers outstanding performance in terms of sensitivity and enantioselectivity. An UPLC–MS/MS based method for the quantification of d-amino acids human biological fluids was then developed using ( S)-NIFE. Baseline separation ( R s > 2.45) was achieved for the isomers of all 19 chiral proteinogenic amino acids. The limit of detection was <1 nM for all amino acids except d-alanine (1.98 nM), d-methionine (1.18 nM) and d-asparagine (5.15 nM). For measurements in human plasma, cerebrospinal fluid and urine, the accuracy ranged between 85% and 107%. The intra-assay and inter-assay were both <16% RSD for these three different matrices. Importantly, the method does not suffer from spontaneous racemization during sample preparation and derivatization. Using the described method, d-amino acid levels in human cerebrospinal fluid, plasma and urine were measured.