Determination of arteether in blood plasma by high-performance liquid chromatography with ultraviolet detection after hydrolysis acid

A reversed-phase high-performance liquid chromatographic method is described for determination of the antimalarial agent arteether in blood plasma based on its decomposition in acidic medium and measurement of the major decomposition product, which has been identified as an alpha,beta-unsaturated decalone. Linear calibration curves were obtained in the range 0-250 ng/ml arteether and the recovery of the drug from plasma was found to be quantitative. There is no interference from desoxyarteether, the putative major metabolite of arteether. The method has been applied to the measurement of arteether in the plasma of rats given 110 mg/kg by intramuscular injection of the drug as a solution in sunflower oil.     

Determination of ximoprofen and its metabolites in human urine by high-performance liquid chromatography with ultraviolet absorbance detection

A simple, sensitive and selective method for the determination of ximoprofen and its keto and hydroxy metabolites in human urine has been developed using high-performance liquid chromatography in the reversed-phase mode. The limit of reliable determination of ximoprofen and each of its metabolites in urine is about 1 microgram/ml (4 nmol/ml). The method has been applied to urine samples obtained from human volunteers after administration of single intravenous doses of 30 mg of ximoprofen and about 70% dose was accounted for in terms of these compounds and their glucuronic acid conjugates.     

Determination of zopiclone in plasma using column liquid chromatography with ultraviolet detection.

A reversed-phase liquid chromatographic method with ultraviolet detection for the determination of zopiclone in plasma is described. It is rapid, sensitive, reproducible and linear over a wide range. The method was used to study plasma zopiclone concentrations in a case of acute intoxication after oral ingestion of 300 mg of the drug. The plasma level was 1600 ng/ml 4.5 h after the dose and the elimination half-life was 3.5 h.     

Determination of clindamycin in plasma or serum by high-performance liquid chromatography with ultraviolet detection

A simple, sensitive high-performance liquid chromatographic assay for the determination of clindamycin in human plasma or serum has long been hampered by inability to separate it from endogenous compounds. We describe here such an assay. Proteins from a 200-microliters sample were precipitated by addition of acetonitrile containing the internal standard, triazolam. The sample was then vortex-mixed and centrifuged at approximately 3000 g for 10 min. The supernatant was evaporated to about 250 microliters under nitrogen, and 10-30 microliters were analyzed using an autoinjector. An octadecylsilane column with acetonitrile-water-phosphoric acid-tetramethylammonium chloride as mobile phase and ultraviolet detection at 198 nm provided a reproducibly quantifiable peak corresponding to 0.17 micrograms/ml. Retention times for clindamycin and triazolam averaged 8 and 11.8 min, respectively. Replicate standard curves run over a 36-h period showed no loss of integrity; r2 values generally exceeded 0.999. The method has successfully been applied to the analysis of samples taken up to 12 h after administration of intravenous infusions of 600-1200 mg in healthy volunteers.     

Determination of cetirizine in serum using reversed-phase high-performance liquid chromatography with ultraviolet spectrophotometric detection.

A method using reversed-phase high-performance liquid chromatography with ultraviolet detection for the determination of ceterizine in serum is described. The method is sensitive down to 50 ng/ml (250-microliter loop). Sample preparation involves only serum deproteination with perchloric acid and injection of the centrifuged supernatant. Elution is at pH 2.5 with acetonitrile-methanol-0.05 M phosphate buffer (33:9:58, v/v) on a 25 cm x 4.6 mm I.D. Spherisorb S5 ODS2 column. Detection is at 211 nm, its lambda max. For levels above 300 ng/ml the serum sample size is 100 microliter and a 200-microliter sample is necessary for concentrations less than 300 ng/ml. At the 2 micrograms/ml concentration the intra-assay relative standard deviation is better than 2.2%, whilst the inter-assay deviation is 2.6% over eight samples. At 200 ng/ml the intra-assay relative standard deviation is 6% over seven samples. Detector response is linear from 100 ng/ml to 10 micrograms/ml (100-microliter loop).     

Determination of pindolol in human plasma and urine by high-performance liquid chromatography with ultraviolet detection

This paper presents a rapid, simple and economical method for assaying pindolol concentrations in plasma and urine by high-performance liquid chromatography using ultraviolet detection. It is sensitive enough for use in single-dose pharmacokinetic studies and may also be used to determine pindolol concentrations in the plasma from patients taking the drug, provided that the patient is not taking any of the drugs which interfere with the method. Drugs which were found to interfere with the pindolol peak are quinidine, n-acetylprocainamide and lidocaine. Disopyramide, oxprenolol and levobunolol interfered with the internal standard peak.     

Determination of naphazoline in rat plasma using column liquid chromatography with ultraviolet detection.

A sensitive (1 ng/mL) and rapid method for the determination of naphazoline in rat plasma is described. Following extraction, the compound is analysed by reversed phase high performance liquid chromatography and ultraviolet detection at 214 nm.     

Determination of quinolones in chicken tissues by liquid chromatography with ultraviolet absorbance detection

This paper presents an analytical method for the determination of quinolones in chicken tissues. The procedure involves pre-treatment by solid-phase extraction (SPE) and subsequent liquid chromatography (LC) with UV absorbance detection. Different SPE disposable cartridges and extractants of the tissue samples were tested, and various columns were systematically tested. The mobile phase was composed of acetonitrile and citric buffer at pH 4.5, with an initial composition of acetonitrile-water (12:88, v/v) and using linear gradient elution. Recoveries were 66-91% in the concentration range 30-300 microg kg(-1). The detector response was linear in this range. The limits of detection were 16-30 microg kg(-1). These values were lower than the maximum residue limits established by the European Union.     

Determination of morphine 3-esters in rabbit plasma by high-performance liquid chromatography with ultraviolet detection

A sensitive high-performance liquid chromatographic (HPLC) method for the quantitation of the morphine 3-esters 1[3-(2, 2-dimethylvaleroyl)-morphine (A), 3-(2-phenylbenzoyl)-morphine (B) and 3-(2,2-diphenylpropionyl)-morphine (C)] in rabbit plasma is described. Sample preparation was based on reversed-phase solid-phase extraction. The compounds were separated on C(18) reversed-phase analytical columns and then determined by ultraviolet detection. The recovery from plasma was 78.7 +/- 7.4%, 69.1 +/- 6.9% and 75 +/- 7.2% (mean +/- SD) for A, B, and C, respectively. The present method enabled the detection limit of 0.2, 0.2 and 0.1 ng and quantification limit of 20, 10 and 10 ng/ml for A, B and C, respectively. The developed method was used for determination of the plasmakinetics of these morphine 3-esters in rabbits.     

Determination of prostaglandins and thromboxane in whole blood by high-performance liquid chromatography with fluorimetric detection

A highly sensitive and specific assay for the quantitation of prostaglandins (PGs) such as PGE1, PGE2, PGF1 alpha, PGF2 alpha, 6-keto-PGF1 alpha, and including thromboxane B2, is described. The method involves the addition of PGF1 alpha and PGE1 as the internal standards, extraction from whole blood and purification by silica gel column chromatography. Following conversion into the methoximes, purification by reversed-phase chromatography and esterification with panacyl bromide, samples are analysed by high-performance liquid chromatography with fluorimetric detection. The lower limit of detection of the eicosanoids 6-keto-PGF1 alpha, thromboxane B2 and PGF2 alpha in blood is ca. 50 pg/ml and that of PGE2 is 100 pg/ml. Assay linearity is demonstrated over a range from 60 pg to 60 ng of eicosanoid injected. The method allows simultaneous assessment of prostaglandins and thromboxane extracted from complex biological fluids at picogram levels.     

Determination of 5-fluorouracil in plasma and whole blood by ion-pair high-performance liquid chromatography

5-Fluorouracil in blood or plasma was determined by extraction and column liquid chromatography. Acetonitrile was added to blood or plasma and the mixture was stirred and centrifuged. Zinc sulfate addition was followed by stirring and centrifuging. The acetonitrile was salted out with ammonium sulfate, and an aliquot was evaporated with nitrogen. The residue was dissolved in mobile phase and chromatographed. The stationary phase was a styrene-divinylbenzene copolymer, and the mobile phase was 10 mM tetrabutylammonium hydroxide-methanol (74:26). 5-Fluorouracil was detected by UV absorption at 266 nm. Time of the assay was less than 30 min. The detection limit was 10 ng/ml and the relative standard deviation was 4 to 10% depending on the concentration.     

Determination of vancomycin in human plasma using high-performance liquid chromatography with fluorescence detection

A high-performance liquid chromatographic (HPLC) method with fluorescence detection for the quantification of vancomycin in human plasma was developed and validated. The method includes an extraction of vancomycin by deproteinization with acetonitrile. The analyses were carried out at 258 nm as the emission wavelength while exciting at 225 nm on a reversed-phase column (30 cm × 4 mm i.d. × 10 μm Waters Associates μBondapak C18) using a mobile phase composed of methanol and phosphate buffer at pH 6.3. Vancomycin was quantitatively recovered from human plasma samples (>96%) with high values of precision. The separation was completed within 27 min. The calibration curve was linear over the range from 5 to 1,000 ng/mL with the detection and quantification limits of 2 ng/mL and 5 ng/mL, respectively. This method is suitable for the routine assay of plasma samples. Figure The effect of the deproteinization solvent on the signal of the interference peak at retention time of 15.0 min. The peak which interferes with the peaks of Erythromycin and Vancomycin has been disappeared by using 2 mL acetonitrile as the deproteinization solvent.     

Determination of different species of homocysteine in human plasma by high-performance liquid chromatography with ultraviolet detection

This assay measures reduced, free oxidized, protein-bound, and total homocysteine in human plasma. Oxidized species of homocysteine are converted to reduced form by sodium borohydride, and, after precolumn derivatization with 2-chloro-1-methylquinolinium tetrafluoroborate, homocysteine 2-S-quinolinium derivative is separated from those of other plasma thiol derivatives, and quantitated by ion-paired reversed-phase high-performance liquid chromatography with ultraviolet detection. The reduced homocysteine sulfhydryl groups are trapped with minimal oxidation by derivatizing blood samples at the time of collection. With the use of this precise and sensitive HPLC method utilizing popular ultraviolet detection, homocysteine in plasma can be detected and quantitated at the level of 0.1 and 0.2 for reduced fraction, and 0.3 and 0.5 nmol/ml for total homocysteine, respectively. The method is applied for determination of different fractions of homocysteine in plasma of apparently healthy men and women.     

Determination of acysole in whole blood by high-performance liquid chromatography

A method is developed for the determination of a carbon monoxide antidote acysole in whole blood using hydrophilic interaction high-performance liquid chromatography with UV detection. Two methods were used for sample preparation: protein precipitation with acetonitrile and solid-phase extraction (SPE) with an acysole recovery of 95.8 and 89.8%, respectively. Chromatographic determination was performed in the isocratic mode on a Nucleodur HILIC column and with an acetonitrile: water 95: 5 mobile phase at 225 nm. The calibration graphs are linear in the concentration range 0.056–111.1 μg/mL. The limits of detection and determination of acysole were 0.050 and 0.120 μg/mL after protein precipitation with acetonitrile and 0.071 and 0.169 μg/mL with SPE, respectively.