title: Determination of nitrite and nitrate in cerebrospinal fluid by microchip electrophoresis with microsolid phase extraction pre-treatment.
abstract: A new method for the determination of nitrite and nitrate, indicators of various neurological diseases (meningitis, multiple sclerosis, Parkinson's disease) in cerebrospinal fluid (CSF) on an electrophoresis chip was developed. An on-line combination of isotachophoresis (ITP) with capillary electrophoresis (CE) on a poly(methylmethacrylate) chip assembled with coupled separation channels (CC) and contact conductivity detectors was employed. ITP separations performed at low pH (3.6) in the first separation channel enabled a highly selective transfer of the analytes to the second CE stage working under micellar conditions implemented by zwitterionic surfactant, 3-(N,N-dimethyldodecylammonio)-propanesulfonate. The proposed method achieved low limits of detection varied from 0.2 to 0.4μgL(-1) when the sample volume injected onto the chip (9.9μl) was almost the same as the volume of both separation channels. Preferable working conditions on the CC chip (suppressed hydrodynamic and electroosmotic flow) contributed for reproducible migration velocities (intra-day reproducibility up to 2.1% RSD) and determinations of trace concentrations of nitrite and nitrate (intra-day precision up to 3.0% RSD). Huge amount of chloride present in CSF (approx. 4.5gL(-1)) was removed from analyzed CSF samples by microsolid phase extraction performed on silver-form resin prior to the ITP-CE analysis. Developed method provided fast (approx. 20min total analysis time) and reliable determinations of trace nitrite and nitrate and could be fully integrated into the analysis of CSF samples.
authors.affiliation: Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Bratislava, Slovak Republic.
authors.forename: Peter
authors.initials: P
authors.lastname: Troška
authors.forename: Richard
authors.initials: R
authors.lastname: Chudoba
authors.forename: Ladislav
authors.initials: L
authors.lastname: Danč
authors.forename: Róbert
authors.initials: R
authors.lastname: Bodor
authors.forename: Michal
authors.initials: M
authors.lastname: Horčičiak
authors.forename: Eva
authors.initials: E
authors.lastname: Tesařová
authors.forename: Marián
authors.initials: M
authors.lastname: Masár
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000134:cerebrospinal fluid; D046209:Electrophoresis, Microchip / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D057230:Limit of Detection; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D019636:Neurodegenerative Diseases / Q000134:cerebrospinal fluid; D009566:Nitrates / Q000134:cerebrospinal fluid*; D009573:Nitrites / Q000134:cerebrospinal fluid*; D015203:Reproducibility of Results; D052617:Solid Phase Microextraction / Q000379:methods*
chemical_list: D015415:Biomarkers; D009566:Nitrates; D009573:Nitrites