High-performance liquid chromatographic analysis of amiloride in plasma and urine

A high-performance liquid chromatographic method has been developed for amiloride in rabbit plasma and urine which uses a reversed-phase C18 column, a mobile phase (flow-rate 2 ml/min) consisting of 32% acetonitrile in 0.15 M perchloric acid, pH 2.2, and spectrofluorometric detection via excitation at 286 nm. A simple extraction step with ethyl acetate eliminates interfering peaks. Short retention times of about 2.3 and 3.8 min are observed for amiloride and the internal standard, triamterene, respectively. The method can measure 4 ng/ml amiloride in plasma. This assay has been used to explore the pharmacokinetics of amiloride in rabbits. The plasma disposition profile is biexponential after a 50-mg intravenous bolus dose and there is no evidence for saturable elimination at zero-order infusion rates of 1.8, 3.6 and 7.2 mg/h.     

High-performance liquid chromatographic analysis of hippuric acid in human blood plasma

A method has been developed for the isocratic high-performance liquid chromatographic analysis of hippuric acid in human blood plasma. After the addition of an internal standard (3-methoxysalicylic acid), plasma samples (1 ml) were made alkaline and extracted stepwise with methylene chloride and ethyl acetate. The detection limit was 50 pmol of hippuric acid per ml of plasma. The concentrations of hippuric acid in plasma from house painters (n = 8), with long-term exposure to solvent vapours from alkyd paints, were in the range 1-21 nmol/mol (median 11 nmol/ml). These values were statistically significantly higher than those for controls (n = 9): 2-8 nmol/ml (median 3 nmol/ml).     

High-performance liquid chromatographic analysis of trilostane and ketotrilostane in rat plasma

A simple high-performance liquid chromatographic (HPLC) method for assaying trilostane, a synthetic steroid, and one of its metabolites, ketotrilostane, in small volumes of rat plasma has been developed. A single liquid-liquid extraction was used to isolate the two compounds from acidified plasma prior to the quantitative analysis. The HPLC conditions involved the use of a Spherisorb ODS column (250 mm x 4.6 mm I.D.) and a mobile phase of 1,4-dioxan-Sorenson's buffer at pH 5.0 (52:48, v/v). Ethisterone was used as an internal standard. Trilostane and ketotrilostane were detected by their ultraviolet absorbance at 255 nm. Recoveries greater than 80% and detection limits of 50 ng/ml were obtained for both compounds. Inter-day coefficients of variation were less than 10%.     

High-performance liquid chromatographic analysis of isoxicam in human plasma and urine

A sensitive, selective, and rapid high-performance liquid chromatographic procedure was developed for the determination of isoxicam in human plasma and urine. Acidified plasma or urine were extracted with toluene. Portions of the organic extract were evaporated to dryness, the residue dissolved in tetrahydrofuran (plasma) or acetonitrile (urine) and chromatographed on a mu Bondapak C18 column preceded by a 4-5 cm X 2 mm I.D. column packed with Corasil C18. Quantitation was obtained by UV spectrometry at 320 nm. Linearity in plasma ranged from 0.2 to 10 micrograms/ml. Recoveries from plasma samples seeded with 1.8, 4 and 8 micrograms/ml isoxicam were 1.86 +/- 0.077, 4.10 +/- 0.107 and 8.43 +/- 0.154 micrograms/ml with relative standard deviations of 3.3%, 2.5% and 5.4%, respectively. The linearity in urine ranged from 0.125 to 2 micrograms/ml. The precision of the method was 3.3-9.0% relative standard deviation over the linear range.     

High-performance liquid chromatographic analysis of isoxazolylpenicillins in plasma and urine samples

Summary A simple and fast liquid chromatographic method is described, applicable to the routine analysis of isoxazolylpenicillins (cloxacillin, dicloxacillin, flucloxacillin) in biological fluids (plasma, urine). The method is based on a simple dilution step employed to destroy the protein binding, which is over 95%, and allows the detection of concentrations down to 10μg/ml. In order to analyze concentrations of less than 10μg/ml, a liquid-liquid extraction with dichloromethane must be executed prior to the reversed-phase analysis with absorbance detection at 206nm. The minimum detectable amounts of the isoxazolylpenicillins with this procedure are between 2.5 and 5.1 ng in 100μl plasma samples. The stability of the penicillin samples in aqueous solutions (stock solutions, eluents) was investigated and no significant degradation was observed during the storage and analysis of the samples. Furthermore, the degree of protein binding was established by using a suitable ultrafiltration technique, and the usefulness of the developed procedures in pharmacokinetic studies was demonstrated.     

High-performance liquid chromatographic determination of pentaerythritol in plasma

A sensitive analysis of pentaerythritol in plasma has been devised, based on the formation or its tetra-p-methoxybenzoate derivative and high-performance liquid chromatography employing an ultraviolet photometric detector. The method permits analysis of pentaerythritol in the ppm range.     

High-performance liquid chromatographic determination of busulfan in plasma

Summary Busulfan (Myleran; 1,4-bis-(methanesulfonyloxy) butane; BU) is a bifunctional alkylating agent used in clinical practice since 1959. It is currently included at high doses in conditioning regimens for bone marrow transplantation, usually in combination with cyclo-phosphamide. A high-performance liquid chromatographic method has been developed for the determination of BU in plasma. The basis of the assay is a derivatization with sodium diethyldithiocarbamate at 32°C in the presence of 1-bromo-1-deoxy-3,6-anhydrogalactitol as internal standard. Analysis is performed on a cyano column with heptane-isopropanol-glacial acetic acid as mobile phase and UV detection at 280 nm. The calibration graph was linear in the concentration range 0.18–46.40 μM BU in plasma. The limit of detection was 0.1 μM. The precision and accuracy were between the limits required by good laboratory practice. Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, september 1–3, 1999     

High-performance liquid chromatographic analysis of 5-ethylpyrimidines and 5-methylpyrimidines in plasma

A high-performance liquid chromatographic (HPLC) method employing a C18 reversed-phase column, a mobile phase of sodium acetate and methanol, and an ultraviolet detector was developed for the analysis of 5-ethylpyrimidines and 5-methylpyrimidines in plasma. Samples were prepared for HPLC by sequential cation-exchange and anion-exchange column chromatography. Linear standard curves were obtained for samples containing 0.05-50 micrograms/ml 5-ethyl-2'-deoxyuridine and 5-ethyluracil, 0.05-10 micrograms ml 5-(1-hydroxyethyl)uracil, and 0.1-50 micrograms/ml thymidine, thymine and 5-hydroxymethyluracil. Applicability of the method to determination of the kinetics of 5-ethyl-2'-deoxyuridine elimination by the isolated perfused rat liver was demonstrated; clearance of the drug was 1.29 ml/min.