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PubMed1987

Rapid high-performance liquid chromatographic assay for the simultaneous analysis of non-steroidal anti-inflammatory drugs in plasma.

A high-performance liquid chromatographic assay has been developed for the determination of a number of non-steroidal anti-inflammatory drugs in plasma. The samples were prepared by adding acetonitrile and perchloric acid to 200 microliter of plasma. Diclofenac, fenoprofen, ketoprofen, naproxen, phenylbutazone, piroxicam and sulindac were quantified in the supernatant produced using a mobile phase of phosphoric acid 0.03% (pH 2.5)-acetonitrile and a detecting wavelength of 254 nm. The reproducibility, linearity, precision and specificity of the assay were determined and found to be satisfactory. Alteration of the detection wavelength to 229 nm also permitted accurate determination of ibuprofen concentration in plasma. While reduction of the organic solvent content of the mobile phase and alteration of wavelength to 313 nm produced a system capable of quantifying salicylate and its metabolites in plasma and by further reducing the detecting wavelength to 237 nm, aspirin also was quantifiable. These methods have been applied in a cross-sectional study of medication compliance among rheumatoid arthritis patients treated with non-steroidal anti-inflammatory drugs.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1991

Determination of sulfalene in plasma, red blood cells and whole blood by high-performance liquid chromatography.

A normal phase high-performance liquid chromatographic method using dichloromethane-methanol-perchloric acid (1 M) (96:9:1, v/v) at a flow-rate of 1 ml/min on a Nucleosil 100-7 column (250 x 8 x 4 mm) and UV detection at 254 nm, has been developed to determine the concentration of sulfalene in plasma, red blood cells and whole blood after oral administration of the antimalarial drug metakelfin. The coefficient of variation was 7.1% and the extraction recovery was 82%. Mean concentrations of sulfalene on days 1, 7 and 15 were: 49.56, 10.46 and 2.24 micrograms/ml in plasma, 25.02, 4.34 and 0.84 micrograms/ml in red blood cells and 21.12, 4.44 and 1.00 micrograms/ml in whole blood, respectively. Quinine, chloroquine, desethylchloroquine, mefloquine, primaquine, sulfadoxine, pyrimethamine and dapsone did not interfere in the detection of sulfalene.

Administration, Oral↗
PubMed1991

Determination of oxidized, reduced and protein-bound glutathione in eye lenses by high-performance liquid chromatography and electrochemical detection.

A method for the detection of oxidized, reduced and protein-bound glutathione in eye lenses has been developed. Homogenized lens samples are deproteinated with acetonitrile and perchloric acid. Protein-bound glutathione is reduced by 1,4-dithiothreitol. Separation of the different forms of glutathione and dithiothreitol is performed by ion-pair reversed-phase high-performance liquid chromatography with sodium octylsulphate as the ion-pairing agent. The compounds are detected amperometrically using on-line-generated bromine, which oxidizes thiols and disulphides. In this way two samples can be analysed in triplicate in a single day. The lower detection limits are 80 and 48 nmol per gram wet lens for reduced and oxidized glutathione, respectively. The amounts of free reduced and protein-bound glutathione in calf lenses, determined with this method, are 6.8 +/- 0.4 and 0.96 +/- 0.03 mumol per gram wet lens, respectively. That of oxidized glutathione is less than 0.048 mumol per gram wet lens.

Animals↗
PubMed1991

Simplified procedure for the determination of sotalol in plasma by high-performance liquid chromatography.

A simple, specific and rapid reversed-phase high-performance liquid chromatographic (HPLC) procedure for sotalol determination is described requiring small plasma volumes. The high recovery of sotalol from plasma and the high precision of measurement obviate the need for an internal standard. Plasma samples (300 microliters) were deproteinised with 50 microliters of 70% (w/w) perchloric acid in disposable glass tubes. After vortex-mixing and centrifugation, 30 microliters of 4 M K2HPO4 were added followed by gentle shaking. A 20-microliters aliquot was then injected (by autosampler) for HPLC analysis. Chromatography was performed on a glass-lined 250 mm x 4 mm 5-micron C18 steel column. The mobile phase was 6% (v/v) acetonitrile in 0.08 M KH2PO4 buffer (pH 4.6). The flow-rate was 0.8 ml/min. Detection was by fluorescence with excitation and emission wavelengths at 235 and 310 nm, respectively. The retention time for sotalol was 7.1 min. Calibration was linear from 0.16 to 10 micrograms/ml in plasma (r greater than 0.999 for detector response to sotalol). The minimum concentration for quantitation was 0.08 micrograms/ml [within assay coefficient of variation (C.V.) less than 5%]. Recovery was near quantitative (greater than 98%) and replicate (intra-assay precision was less than 5% C.V.). Analysis of samples (n = 10) at concentrations of 0.42 and 4.2 micrograms/ml gave mean values of 0.44 and 4.3 micrograms/ml, respectively. The inter-assay C.V. values were 4.5 and 2.2%, respectively. Other clinically used antiarrhythmic drugs did not interfere. This assay can be performed using other commercial C18 analytical columns by suitable adjustment of mobile phase flow-rate and acetonitrile composition.

Chromatography, High Pressure Liquid↗
PubMed1992

Determination of glycyrrhizin in rabbit plasma by high-performance liquid chromatography with photodiode-array ultraviolet detection and its pharmacokinetics application.

A simple and sensitive high-performance liquid chromatographic method for the determination of glycyrrhizin in rabbit plasma has been developed. Up to 0.1 ml of plasma containing glycyrrhizin was deproteinized by acetonitrile, which contained an internal standard (indomethacin). The supernatant was injected onto a LiChrospher RP-18 column using a methanol-water-ammonia solution (80:20:0.1, v/v, pH 3.0-3.2, adjusted with perchloric acid) as the mobile phase and ultraviolet detection at 254 nm, followed by ultraviolet spectrum identification (between 200 and 380 nm) with a photodiode-array detector. The method is rapid, easily reproduced, selective and sensitive. It was applied to pharmacokinetic studies of glycyrrhizin in rabbit, after a 2 mg/kg intravenous administration. A biphasic phenomenon with a rapid distribution followed by a slower elimination phase was observed from the plasma concentration-time curve. Compartmental analysis yielded a two-compartment model.

Animals↗
PubMed1992

Simple and sensitive determination of diacetyl and acetoin in biological samples and alcoholic drinks by gas chromatography with electron-capture detection.

Acetoin was quantitatively oxidized into diacetyl by Fe3+ in 1 M perchloric acid. The reaction of diacetyl with 4,5-dichloro-1,2-diaminobenzene afforded 6,7-dichloro-2,3-dimethylquinoxaline (DCDMQ), which was extracted by benzene containing aldrin (25 ng/ml) as an internal standard, and determined by gas chromatography with electron-capture detection. The method is very simple and sensitive. The detection limit of DCDMQ (either diacetyl or acetoin) was 10 fmol/microliters of the benzene extract, and the determination limit of DCDMQ (either diacetyl or acetoin) was 50 fmol/microliters of the extract. Both acetoin and diacetyl could be determined in 0.1 ml of normal human urine or blood, and both were found in rat liver, kidney and brain. The method was also applied to the determination of acetoin and diacetyl in alcoholic drinks.

Acetoin↗
PubMed1992

High-performance liquid chromatographic method for the determination of mangiferin, likviritin and dihydroquercetin in rat plasma and urine.

The use of reversed-phase high-performance liquid chromatography for the determination of the biologically active plant phenolic compounds mangiferin, likviritin and dihydroquercetin is described. Perchloric acid (35%) was used for deproteinization in the case of mangiferin and likviritin, and acidified methanol for dihydroquercetin. Detection was performed at 254, 275 and 290 nm for mangiferin, likviritin and dihydroquercetin in plasma, and 365, 312 and 290 nm in urine, respectively. The limit of detection was 0.2 micrograms/ml for plasma and 0.5 micrograms/ml for urine.

Animals↗
PubMed1992

New, high-sensitivity high-performance liquid chromatographic method for the determination of acyclovir in human plasma, using fluorometric detection.

A high-performance liquid chromatographic method for the determination of acyclovir in human plasma has been developed. It is the first published chromatographic method capable of determining acyclovir in plasma with sufficient sensitivity and for sufficiently long periods of time following oral administration of a standard dose of acyclovir during pharmacokinetic investigations. Following precipitations of the proteins with perchloric acid, the sample is chromatographed with a strongly acidic mobile phase on a reversed-phase column, and is then subjected to fluorometric detection (excitation 260 nm, emission 375 nm). The determination limit is 6-10 ng/ml human plasma. The calibration is linear in the range 10-12,400 ng/ml plasma, with the coefficients of variation less than 8%. The absolute recovery rate is between 102 and 113%. This method has already been used to analyse several thousand plasma samples.

Acyclovir↗
PubMed1992

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).

Buffers↗
PubMed1992

Determination of nicotinamide-adenine dinucleotide and thiazole-4-carboxamide-adenine dinucleotide in human leukocytes by reversed-phase high-performance liquid chromatography.

A high-performance liquid chromatographic assay for cellular nicotinamide-adenine dinucleotide and thiazole-4-carboxamide-adenine dinucleotide is presented that is appropriate for analysis of these dinucleotides in extracts of Ficoll-purified human leukemic cells. The separation, which is effected by reversed-phase chromatography, is highly reproducible and the limit of quantitation is as low as 10-15 pmol. The stability of these compounds in neutralized perchloric acid extracts is addressed and the applicability of the procedure to clinical specimens is demonstrated.

Adenine Nucleotides↗
PubMed1993

Specific and sensitive high-performance liquid chromatographic method with fluorescence detection for measurement of lometrexol and its polyglutamates in biologic samples.

A reversed-phase high-performance liquid chromatographic (HPLC) assay is described for the quantitative determination of lometrexol in biological samples; the assay is rapid, simple, specific, and highly sensitive. The method requires the dissociation of lometrexol from folate-binding proteins present in blood and formation of a fluorescent oxidized derivative of the compound. The dissociation of lometrexol from folate-binding proteins was achieved by acidification to pH 3.5 using ammonium formate, followed by serum protein precipitation with perchloric acid. The protein-free lometrexol was subsequently oxidized by MnO2 at 90 degrees C for 10 min. Chromatographic separation of lometrexol without interference was achieved on a C18 reversed-phase column with a convex gradient, using acetonitrile-0.1% ammonium formate, pH 7.0, as the mobile phase. In human serum and urine the calibration curve was linear between 5 and 300 nM. The lower limit of quantification was 5 nM. The method has been applied successfully to measure serum and urinary levels of lometrexol in patients.

Chromatography, High Pressure Liquid↗
PubMed1993

Two-dimensional high-performance liquid chromatographic method for assaying S-adenosyl-L-methionine and its related metabolites in tissues.

S-Adenosyl-L-methionine (SAM) is a methyl-donor compound which is actively involved in a variety of biochemical reactions. An assay has been developed permitting the quantitative measurement of SAM and its related metabolites (S-adenosylhomocysteine, decarboxylated SAM, methylthioadenosine, adenosine and adenine) in liver and cell cultures. As gradient reversed-phase chromatographic or cation-exchange chromatographic methods often resulted in overlapping peaks, a two-dimensional high-performance liquid chromatographic (HPLC) procedure was developed involving gradient reversed-phase chromatographic separation followed by ion-exchange chromatography. After precipitating large molecules in the sample by perchloric acid, gel permeation was carried out on a Sephadex G 25 column to separate small water-soluble metabolites from proteins and membrane fragments. The freeze-dried sample was injected onto an ODS column and a 0-10% acetonitrile gradient in 10 mM ammonium formate buffer (pH 2.9) (20 min, linear) was applied. The relevant fractions were collected and injected onto a cation-exchange column (Partisil SCX, 10 microns, 250 mm x 4.6 mm I.D.). Elution and quantification were carried out using ammonium formate buffers of various concentration (15-400 mM), pH 2.9. The detector response (254 nm) as a function of concentration was linear over the concentration range 30-500 pmol. The detection limits of the compounds after the two-dimensional chromatographic procedure ranged from 10 to 60 pmol and the recovery was higher than 70%. The reproducibility of the results obtained from given samples was within 9-22% for rat liver and 6-24% for mast cells.

Animals↗
PubMed1993

Determination of tryptophan in human serum by high-performance liquid chromatography with pre-column fluorescence derivatization using phenylglyoxal.

A high-performance liquid chromatographic method based on pre-column fluorescence derivatization with phenylglyoxal is described for the sensitive and selective quantification of total (free plus albumin-bound) and free tryptophan in serum. Serum was deproteinized with perchloric acid for total tryptophan and by ultrafiltration for free tryptophan, and then subjected to fluorescence derivatization. The reaction mixture was separated on a reversed-phase column by isocratic elution and the tryptophan derivative was then detected by fluorimetry. The method was at least ten-fold more sensitive than other conventional chromatographic methods with no derivatization. The lower limit of determination (signal-to-noise ratio = 3) for endogenous tryptophan in human serum was 72 nmol/l, which corresponds to 200 fmol on-column.

Adult↗
PubMed1993

Determination of propranolol, labetalol and clenbuterol in rat brain by high-performance liquid chromatography.

A rapid and simple HPLC method for the measurement of adrenergic drugs (propranolol, labetalol and clenbuterol) in rat brain is described. This method was applied to establish if these drugs can pass the blood-brain barrier in prenatal or early post-natal life. The chromatography was performed using a C18 column and a phosphate buffer (pH 3)-acetonitrile (65:35, v/v) mixture. After homogenization of the brain tissue in perchloric acid, the supernatant was buffered at pH 9 and extracted with diethyl ether, followed by back-extraction in sulphuric acid. Recoveries of between 80 and 100% were achieved. The method was found to be accurate (100%) and precise (coefficient of variation around 10%). All three drugs were readily detected in the brain of neonatal rats after peripheral administration. In addition, we demonstrated the presence of propranolol in the fetal brain after maternal administration.

Animals↗
PubMed1993

Determination of quinine in serum, plasma, red blood cells and whole blood in healthy and Plasmodium falciparum malaria cases by high-performance liquid chromatography.

A normal-phase high-performance liquid chromatographic method using dichloromethane-methanol-1 M perchloric acid (100:9:0.4, v/v) at a flow-rate of 0.8 ml/min on a Zorbax-Sil column with fluorescence detection has been developed for the separation of quinine and quinidine from other antimalarials. Within-day and day-to-day coefficients of variation averaged 0.74 and 7.56%, respectively. The extraction recovery of quinine for plasma, serum, red blood cells and whole blood (filter paper) was 88.13, 87.12, 78.0 and 77.5%, respectively. The method is capable of separating quinine from dihydroquinine, a compound usually found as an impurity in authentic quinine samples. The method has been used for the determination of quinine in plasma, serum, red blood cells and whole blood (filter paper) of six healthy and twenty Plasmodium falciparum malaria cases. The average quinine concentration in P. falciparum malaria cases was three to four times higher than that in healthy volunteers. Quinine was absorbed much less in red blood cells than in plasma or serum.

Adult↗
PubMed1993

High-performance liquid chromatographic determination of chlorzoxazone and 6-hydroxychlorzoxazone in serum: a tool for indirect evaluation of cytochrome P4502E1 activity in humans.

Chronic alcohol consumption is known to induce the enzyme cytochrome P4502E1 (CYP2E1), which is involved in the toxicity and carcinogenicity of a number of solvents and xenobiotics. It was recently suggested that in vivo chlorzoxazone metabolism could be a potential tool as a non-invasive probe for measuring CYP2E1 activity in humans. Therefore, a simple and sensitive method was developed for the determination of chlorzoxazone and its major metabolite 6-hydroxychlorzoxazone in both serum and urine. Biological samples were hydrolysed by Helix pomatia juice, deproteinized with perchloric acid, and then extracted using ethyl acetate. The compounds were separated by high-performance liquid chromatography on an octadecylsilane column with a mobile phase of acetonitrile-0.5% acetic acid in water (30:70, v/v) and detected at 287 nm. The linearity of the method was tested in the concentration range 0.5-20 micrograms/ml, and the limit of detection in biological samples was found to be 0.5 microgram/ml. Within- and between-run precision was below 5% and 10%, respectively, for both compounds at three concentrations (0.5, 10 and 20 micrograms/ml). The accuracy of the procedure was in the range 0.3-6%. Serum levels and urinary excretion of chlorzoxazone and its metabolite were studied in five healthy controls and five alcoholic patients, following oral administration of 500 mg of chlorzoxazone. The concentration ratio 6-hydroxychlorzoxazone/chlorzoxazone in blood was shown to be a valuable tool for the evaluation of CYP2E1 activity in humans.

Administration, Oral↗
PubMed1993

High-performance liquid chromatography of the quinazolinocarboline alkaloid dehydroevodiamine.

A high-performance liquid chromatographic method has been developed for the determination of dehydroevodiamine (DeHE), an active principle from Evodia fruit. Plasma was denatured with acetonitrile and centrifuged, the supernatant was separated and blown dry, and the residue was redissolved in water. Bile was acidified with perchloric acid and centrifuged to yield the supernatant. Aliquots were used for analysis. Elution was isocratic on a reversed-phase column with acetonitrile-water-phosphoric acid (64:35:0.8, v/v) adjusted to pH 3.5 as the mobile phase. Ultraviolet detection was at a wavelength of 367 nm. The detection limits were 2 ng/ml for plasma and 10 ng/ml for bile. The intra-day and inter-day variations were mostly below 10%.

Alkaloids↗
PubMed1994

High-performance liquid chromatographic determination of ganciclovir nucleotides in human myocardial tissue.

A method for the analysis of ganciclovir nucleotides in myocardial tissues was developed. The antiviral effect of ganciclovir is attributed to intracellular ganciclovir nucleotides. The procedure is based on perchloric acid deproteinization and enzymatic hydrolysis of the ganciclovir nucleotides to ganciclovir. Then, the parent drug was analyzed on a Hypersil ODS column using potassium dihydrogenphosphate buffer as mobile phase. The mean analytical recovery of ganciclovir from myocardial tissue was 101 +/- 2% and the detection limit was 2 pmol. The sample treatment procedure described is simple and presents a suitable analytical tool for the investigation of the ganciclovir nucleotides pool in tissues.

Alkaline Phosphatase↗