Isocratic HPLC assay with electrochemical detection of free gamma-aminobutyric acid in cerebrospinal fluid

Abstract A method for measuring gamma-aminobutyric acid (GABA) in human cerebrospinal fluid (CSF) by isocratic HPLC with electrochemical detection is described. The method is based on precolumn derivatization of GABA with o-phthaldialdehyde (OPA) and tert-butylthiol (t-BT), separation of the GABA-OPA complex on a reversed-phase column, and quantitation by means of a Coulochem electrochemical detector. The method is highly sensitive and specific for GABA. In three samples of human CSF containing low, medium, and high amounts of GABA, the coefficients of variation between and within runs were 4.5% and 3.6%, respectively. The concentration of GABA in 10 neurologically intact subjects was 92.5 +/- 9.4 nmol/L of CSF.

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Determination of delta-aminobutyric acid and other amino acids in cerebrospinal fluid of pediatric patients by reversed-phase liquid chromatography.

Clinical Chemistry ◽

10.1093/clinchem/33.10.1736 ◽

1987 ◽

Vol 33 (10) ◽

pp. 1736-1740 ◽

Cited By ~ 34

Author(s):

R F Goldsmith ◽

J W Earl ◽

A M Cunningham

Keyword(s):

Amino Acids ◽

Cerebrospinal Fluid ◽

Pediatric Patients ◽

Reference Intervals ◽

Reversed Phase ◽

Aminobutyric Acid ◽

Control Group ◽

Precolumn Derivatization ◽

Gamma Aminobutyric Acid ◽

Phase Liquid

Abstract The reversed-phase liquid-chromatographic system described here is capable of resolving the neurotransmitter amino acids aspartic acid, glutamic acid, and gamma-aminobutyric acid (GABA) plus 21 other amino acids in cerebrospinal fluid (CSF) in a single analysis. The amino acids, derivatized with o-phthalaldehyde, are separated in 65 min. Concentrations of glutamine less than or equal to 600 mumol/L can be measured at the same time as GABA greater than or equal to 10 nmol/L. Using this method, we have determined reference intervals for amino acids, including GABA, in CSF in a group of pediatric patients who underwent lumbar puncture before myelography, and who were subsequently shown to have normal myelograms. These intervals are generally lower than those previously reported for childhood, but we believe this results from a more rigid selection of the control group. In addition, artifactual increases in concentrations of free neurotransmitters, caused by breakdown of amino acid conjugates, are minimized by (a) immediate freezing of the CSF samples to prevent enzyme-mediated changes, (b) omission of a deproteinization step, and (c) precolumn derivatization to reduce on-column breakdown of amide and peptide forms.

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Simultaneous determination of tryptophan and its 5-hydroxy metabolites in human cerebrospinal fluid by reversed phase liquid chromatography with electrochemical detection

Scandinavian Journal of Clinical and Laboratory Investigation ◽

10.3109/00365518309168432 ◽

1983 ◽

Vol 43 (6) ◽

pp. 463-472 ◽

Cited By ~ 8

Author(s):

J. T. Laakso ◽

M. -L. Koskiniemi ◽

O. Wahlroos ◽

M. Hårkonen

Keyword(s):

Cerebrospinal Fluid ◽

Liquid Chromatography ◽

Simultaneous Determination ◽

Electrochemical Detection ◽

Reversed Phase ◽

Reversed Phase Liquid Chromatography ◽

Human Cerebrospinal Fluid ◽

Phase Liquid ◽

Hydroxy Metabolites

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Very rapid assay of gamma-aminobutyric acid in mouse brain regions within 3 minutes by high-performance liquid chromatography with electrochemical detection

Journal of Pharmacological Methods ◽

10.1016/0160-5402(89)90029-6 ◽

1989 ◽

Vol 21 (2) ◽

pp. 115-121 ◽

Cited By ~ 15

Author(s):

Shigeo Murai ◽

Hiromichi Nagahama ◽

Hiroko Saito ◽

Hiroki Miyate ◽

Yoshikatsu Masuda ◽

...

Keyword(s):

High Performance Liquid Chromatography ◽

Liquid Chromatography ◽

Electrochemical Detection ◽

Mouse Brain ◽

High Performance ◽

Brain Regions ◽

Aminobutyric Acid ◽

Gamma Aminobutyric Acid ◽

Rapid Assay

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Determination of Dephosphate Bromofenofos in Milk by Liquid Chromatography with Electrochemical Detection

Journal of AOAC International ◽

10.1093/jaoac/77.4.904 ◽

1994 ◽

Vol 77 (4) ◽

pp. 904-908 ◽

Cited By ~ 2

Author(s):

Kazue Takeba ◽

Takeshi Itoh ◽

Masao Matsumoto ◽

Hiroyuki Nakazawa

Keyword(s):

Liquid Chromatography ◽

Electrochemical Detection ◽

Potassium Dihydrogen Phosphate ◽

Reversed Phase ◽

Gas Chromatography Mass Spectrometry ◽

Dihydrogen Phosphate ◽

Specific Method ◽

Coefficients Of Variation ◽

The Matrix

Abstract A sensitive, specific method for the determination of dephosphate bromofenofos (DBFF) in milk by liquid chromatography (LC) with electrochemical detection is described. DBFF, the only metabolite of bromofenofos (BFF, a fasciolicide), was extracted from milk by liquid–liquid partition with acetone, acetonitrile, and dichloromethane and purified by using a C18 cartridge. The compound was separated from the matrix peaks by reversed-phase LC and detected by dual-electrode coulometric detection on a Kaseisorb LC ODS-300-5 (250 × 4.6 mm id, 5 μm) column. The mobile phase was acetonitrile–0.05M potassium dihydrogen phosphate (55 + 45, v/v) at pH 3.0. The flow rate was 1 mL/min at 40°C. The applied potentials of detectors 1 and 2 were maintained at 0.30 and 0.45 V, respectively. Average recoveries (n = 5) of DBFF from milk spiked at 1 and 10 ng/mL were 73.1 and 82.7%, respectively; and coefficients of variation were 8.4 and 2.8%, respectively. The detection limit of DBFF in milk was 0.2 ng/mL. Fifty-nine raw and 181 commercial milks were analyzed. DBFF was detected in 4 raw milks (0.2–1.5 ng/mL; average, 0.6 ng/mL) and in 3 normal liquid commercial milks (0.3–0.7 ng/mL; average, 0.5 ng/mL). The identity of DBFF from milk was confirmed by gas chromatography/mass spectrometry.

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Liquid-chromatographic quantification of piracetam.

Clinical Chemistry ◽

10.1093/clinchem/29.4.664 ◽

1983 ◽

Vol 29 (4) ◽

pp. 664-666 ◽

Cited By ~ 7

Author(s):

R M Nalbandian ◽

M F Kubicek ◽

W J O'Brien ◽

B Nichols ◽

R L Henry ◽

...

Keyword(s):

Clinical Laboratory ◽

Reversed Phase ◽

Molar Absorptivity ◽

Aminobutyric Acid ◽

Detector Response ◽

Gamma Aminobutyric Acid ◽

Biological Extracts ◽

Liquid Chromatographic ◽

Direct Quantification ◽

Detection And Quantification

Abstract Piracetam, an analog of gamma-aminobutyric acid, absorbs maximally at 197 nm. Its molar absorptivity at 208 nm and pH 4.5 is 3576 (SD 251) L . mol-1 cm-1, approximately 45% of its absorptivity at 197 nm. Direct quantification of piracetam at 197 nm in biological extracts is complicated by the fact that many other compounds absorb between 190 and 220 nm due to carbon-nitrogen bonding. Chromatography of methanol extracts of serum and aqueous humor on a reversed-phase C-18 column developed isocratically with KH2PO4 (0.1 mol/L, pH 4.8) allows detection and quantification of 0.2 mmol of piracetam per liter. Under these conditions the retention time of piracetam is about 5 min. The detector response is linear for quantities between 5 and 15 nmol. The method is rapid, inexpensive, and convenient for the clinical laboratory.

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