title: Improved separation and detection of picolinic acid and quinolinic acid by capillary electrophoresis-mass spectrometry: application to analysis of human cerebrospinal fluid.
abstract: "Quinolinic acid (QA)", a metabolite of the kynurenine pathway (KP), is implicated as a major neurological biomarker, which causes inflammatory disorders, whereas there is an increase evidence of the role of picolinic acid (PA) in neuroinflammation. Therefore, there is an urgent need to develop new clinical test for early diagnosis of neuroinflammatory disorders. A comparison is made between three different platforms such as high performance liquid chromatography-electrospray mass spectrometry (HPLC-ESI-MS/MS), nano LC-Chip/ESI-MS/MS, as well as the use of cationic (quaternary ammonium) and anionic (sulfonated) coated capillaries in capillary electrophoresis (CE)-ESI-MS/MS. The comparison revealed that CE-ESI-MS/MS method using a quaternary ammonium coated capillary is the best method for analysis of PA and QA. A simple stacking procedure by the inclusion of acetonitrile in the artificial cerebrospinal fluid (CSF) sample was employed to improve the peak shape and sensitivity of KP metabolites in CE-ESI-MS/MS. The developed CE-ESI-MS/MS assay provided high resolution, high specificity and high sensitivity with a total analysis time including sample preparation of nearly 12 min. In addition, excellent intra-day and inter-day repeatability of migration times and peak areas of the metabolites were observed with respective relative standard deviation (RSD) of less than 2.0% and 2.5%. Somewhat broader variations in repeatability for a 3 independently prepared coated capillary (total 35 runs each) with % RSD up to 3.8% and 5.8% was observed for migration time and peak areas, respectively. Artificial CSF was used as a surrogate matrix to simultaneously generate calibration curves over a concentration range of 0.02-10 μM for PA and 0.4-40 μM for QA. The method was then successfully applied to analyze PA and QA in human CSF, demonstrating the potential of this CE-ESI-MS/MS method to accurately quantitate with high specificity and sensitivity.
authors.affiliation: Center of Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, Atlanta, GA 30303, USA.
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Wang
authors.forename: Ian
authors.initials: I
authors.lastname: Davis
authors.forename: Aimin
authors.initials: A
authors.lastname: Liu
authors.forename: Andrew
authors.initials: A
authors.lastname: Miller
authors.forename: Shahab A
authors.initials: SA
authors.lastname: Shamsi
mesh_terms: D000097:Acetonitriles; D002851:Chromatography, High Pressure Liquid; D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D057230:Limit of Detection; D016014:Linear Models; D010848:Picolinic Acids / Q000134:cerebrospinal fluid / Q000302:isolation & purification; D000644:Quaternary Ammonium Compounds; D017378:Quinolinic Acid / Q000134:cerebrospinal fluid / Q000302:isolation & purification; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000097:Acetonitriles; D010848:Picolinic Acids; D000644:Quaternary Ammonium Compounds; D017378:Quinolinic Acid; C030614:picolinic acid; C032159:acetonitrile
keywords: Capillary electrophoresis-tandem mass spectrometry; Cerebrospinal fluid; Picolinic acid; Quaternary ammonium coated capillary; Quinolinic acid