Electrochemical detection techniques in high-performance liquid chromatography

Determination of vincristine in infant plasma by liquid chromatography-atmospheric pressure chemical ionization-mass spectroscopy

An LC-MS method using APCI has been developed and validated for the determination of the anticancer drug vincristine in human plasma, using vinblastine as internal standard. Following solid-phase extraction (SPE) of the sample, the lower limit of quantitation (LLOQ) was 0.18 ng/ml, the lower limit of detection was 0.09 ng/ml, and the linear calibration range was 0.18-180 ng/ml. This method has been used to measure plasma concentrations of vincristine from 0.08 to 24 h post bolus in 29 infants as part of a pharmacokinetic study. Concentrations of vincristine at 24 h were 0.2-1.36 ng/ml.

Validation of a high-performance liquid chromatographic assay method for quantification of total vincristine sulfate in human plasma following administration of vincristine sulfate liposome injection

The validation of a high performance liquid chromatographic (HPLC) assay method for quantitation of total vincristine sulfate (VINC) in human plasma is described. VINC was extracted from plasma using BondElut CBA solid phase cartridges with vinblastine as the internal standard. Chromatography was accomplished using a Waters Symmetry C8 (250 mm x 4.6 mm i.d.) analytical column, a Waters Delta-Pak ODS guard column with a mobile phase of 34.9% water-0.1% diethylamine (pH 7.0)-40% acetonitrile-25% methanol pumped isocratically at 1.0 ml min(-1) with ultraviolet detection at 297 nm. Above the limit of quantitation of 28.6 ng ml(-1), the area ratio precision (R.S.D. range 3.33-11.6%) and accuracy of predicted values (R.S.D. range 8.56-23.8% with the limit of quantitation being the only value above 20%) were acceptable. The assay was linear from 28.6-2860 ng ml(-1) VINC in plasma. Recovery of VINC from plasma and VINC from plasma spiked with vincristine sulfate liposome injection ranged from 74.9-87.1%. Stability of VINC in plasma stored at -20 degrees C for at least 49 days and of extracted plasma samples was demonstrated. Potential interference in quantitation of VINC from commonly co-administered drugs was evaluated along with day-to-day variability. The assay procedure was found suitable for evaluation of VINC clinical pharmacokinetics in plasma following administration of vincristine sulfate liposome injection prepared using distearoylphosphatidylcholine (DSPC)/cholesterol liposomes for injection.

Thin-layer polarographic detector for the high-performance liquid chromatographic detection of thiourea derivatives

A polarographic thin-layer detector for high-performance liquid chromatography, was devised. The detector has a sandwich structure with a working surface area of the mercury electrode of 0.25 mm2. The detector was applied to the direct amperometric detection and for detection with reactivation of the electrode surface by voltage pulses. It is shown that the latter detection mode is suitable for the determination of compounds that form insoluble or complex mercury salts, e.g., thiourea. Thiourea and its derivatives can be separated and determined in a wide concentration range and the detection limit for thiourea corresponds to 2 ng injected. Thiourea can be determined directly in urine.

Structural influences on the amperometric detection of opiates in high-performance liquid chromatography

The oxidation reactions of a series of opiates occurring at a glassy-carbon electrode in amperometric high-performance liquid chromatographic detection has been investigated. A structure-reactivity correlation has been drawn for morphone, morphinan and benzomorphan derivatives. Polarography and hydrodynamic voltammography were used to show the importance of phenolic groups to this reaction. Acyl substitution on the phenol did not prevent amperometric detection.

Determination of some tricyclic neuroleptics by reversed-phase high-performance liquid chromatography with ultraviolet and polarographic detection

The liquid chromatographic behaviour of various neuroleptics from the classes of tricyclic dibenzothiepins, -oxepins, -selenepins and similar substances was studied in an ion-pair reversed-phase system using a C4180 chemically bonded stationary phase and a methanol-water-acetic acid mobile phase. The best separation was attained with 70% methanol, 1.8% acetic acid and water, containing 0.005 M sodium pentanesulphonate, 1.2 X 10(-4) M EDTA and 0.5 g/l Na2SO4. For the detection, an ultraviolet spectrophotometric and a polarographic detector were connected in series. The detection was carried out at 254 nm and at a potential of a dropping mercury electrode of -1.0 V (vs. Ag/AgCl). The UV detector is universal, while the polarographic detector does not respond to compounds simultaneously containing two heteroatoms (O, S) in the central seven-membered ring. The detection limits are of the order of one to tens of nanograms, the polarographic detector being somewhat more sensitive for most of the compounds; the error of the determination is a few per cent. The method was applied to the determination of isofloxythepin and oxyprothepin in pharmaceutical preparations.