Determination of underivatized glucosamine in human plasma by high-performance liquid chromatography with electrochemical detection: application to pharmacokinetic study.

A simple, rapid and sensitive high-performance liquid chromatography method with electrochemical detection was developed for the determination of glucosamine in human plasma. Plasma samples were analyzed after a simple two-step procedure of protein precipitation with subsequent dilution. The chromatographic separation was performed on a Carbopack column (3 mm x 150 mm) with a mobile phase consisting of water and 200 mM sodium hydroxide. Detection was performed electrochemically in a pulsed voltammetry mode. The limit of detection was 2.0 ng/ml, inter- and intra-day precision were less than 10%. The method was successfully applied to the investigation of the pharmacokinetics of glucosamine in healthy man volunteers.

Optical photothermal detection in HPLC.

A mode-mismatched parallel dual-beam thermal lens spectrometer with a far-field single-channel detector system was used as a detector in HPLC. An expert estimation of the measurement results was applied to optimize the optical-scheme configuration of the spectrometer to achieve the longest linear calibration range and highest repeatability under chromatographic flow conditions. Chelates with 4-(2-pyridylazo)resorcinol were separated and determined with the limits of detection of n x 10(-8)- n x 10(-7) mol L(-1); the relative standard deviation of measurements was 46%. Xylenol Orange, 4-(2-thiazolylazo)resorcinol, and dithizone were studied as post-column reagents in thermal lens detection in ion chromatography. The limits of detection were n x 10(-8)- n x 10(-7) mol L(-1); the linear calibration ranges were about three orders; the relative standard deviation of measurements was 3-7%. A combined photothermal-refractometric detector for HPLC based on a polarization interferometer is proposed. Metal complexes as 4-(pyridylazo)resorcinol chelates (limits of detection of n x 10(-8)- n x 10(-7) mol L(-1)) and sugars (limits of detection of 10-20 ng L(-1)) were investigated as model substances. Obtained results were compared with results for traditional detectors, which show that photothermal detection has higher sensitivity than photometric and other absorption detectors.