Simple and rapid liquid chromatography method for determination of moxifloxacin in saliva

A high performance liquid chromatographic method for determination of moxifloxacin in human saliva was developed. The method involved deproteinisation of the sample with perchloric acid and analysis of the supernatant using a reversed-phase C18 column (150 mm) and fluorescence detection at an excitation wavelength of 290 nm and an emission wavelength of 460 nm. The assay was specific for moxifloxacin and linear from 0.25 to 10.0 μg/ml. The relative standard deviation of intra- and inter-day assays was lower than 10%. The average recovery of moxifloxacin from saliva was 101%. Due to its simplicity, the assay can be used for pharmacokinetic studies of moxifloxacin.     

Simple and rapid liquid chromatography method for determination of efavirenz in plasma

A simple and rapid high performance liquid chromatographic method for determination of efavirenz in human plasma was developed. The method involved extraction of sample with ethyl acetate and analysis using a reversed-phase C(18) column (150 mm) with UV detection. The assay was linear from 0.0625 to 10.0 microg/ml. The method was specific for efavirenz estimation and the drug was stable in plasma up to one month at -20 degrees C. The average recovery of efavirenz from plasma was 101%. Due to its simplicity, the assay can be used for pharmacokinetic studies and therapeutic drug monitoring of efavirenz.     

Simple and rapid high-performance liquid chromatography method for the determination of ofloxacin concentrations in plasma and urine

A high-performance liquid chromatographic method for the determination of ofloxacin in human plasma and urine was developed. The method involved deproteinisation of the sample with perchloric acid and analysis of the supernatant using a reversed-phase C₁₈ column and fluorescence detection at an excitation wavelength of 290 nm and an emission wavelength of 460 nm. The assay was linear from 0.5 to 10.0 μg/ml. The relative standard deviation of intra- and inter-day assays was lower than 5%. The average recovery of ofloxacin from plasma was 93%. The method was evaluated in samples from healthy subjects whose drug levels were already measured by microbiological assay.     

Simple method for determination of terbutaline plasma concentration by high-performance liquid chromatography

A method is described in which low nanomolar concentrations of terbutaline in plasma can be quantitated by use of a standard isocratic high-performance liquid chromatography system with electrochemical detection. Samples were prepared for injection by solid-phase extraction and preserved from degradation by addition of glutathione. Terbutaline and internal standard metaproterenol were resolved from plasma constituents on a single C₁₈ column by ion-pairing chromatography. The method is precise and accurate for measurement of freebase concentrations as low as 4.4 nmol/l (1 ng/ml).     

Simple,rapid and sensitive method for the determination of indomethacin in plasma by high-performance liquid chromatography with ultraviolet detection

A micro method for determination of indomethacin in plasma was developed. Following deproteinization of plasma with acetonitrile containing internal standard (mefenamic acid), the separation of indomethacin and internal standard was achieved by high-performance liquid chromatography using a 7 μm LiChrosorb-RP18 column (250×4 mm I.D.) at 50°C. The mobile phase was 6 mM phosphoric acid–acetonitrile (50:50). The flow-rate was kept at 2.0 ml/min and the column effluent was monitored at 205 nm. The coefficients of variation of the method estimated at 0.2 and 1.0 μg/ml were 4.2 and 2.3%, and the detection limit of the drug was about 0.05 μg/ml (S/N=5). The method requires minimum pretreatment of the plasma with a small sample volume (25 μl), and is very suitable for therapeutic drug monitoring of indomethacin in premature infants with symptomatic patent ductus arteriosus.     

Simple and sensitive fluorimetric liquid chromatography method for the determination of valproic acid in plasma

A simple and sensitive liquid chromatographic method is described for the analysis of valproic acid in human plasma. The method is based on the derivatization of valproic acid extracted from acidified plasma with 2-(2-naphthoxy)ethyl 2-(piperidino)ethanesulfonate. The resulting derivative is highly responsive to a fluorimetric detector (excitation at 230 nm and emission at 350 nm), giving a low detection limit of 0.6 microM (S/N = 3, 10 microl injected). The relative standard deviations of the method for intra- and inter-day analyses (n = 5) are below 3.3 and 4.1%, respectively. Toluene was used for the extraction of valproic acid from plasma and the toluene extract obtained was subjected to subsequent derivatization without solvent replacement. The simple method was applied to the analysis of valproic acid in plasma of dosed patients using only small amount of sample (10-50 microl plasma).     

A simple and rapid liquid chromatography method for simultaneous determination of zidovudine and nevirapine in plasma

We describe a simple, fast, isocratic, reversed-phase high performance liquid chromatographic method for simultaneous determination of plasma zidovudine and nevirapine with UV detection at 260 nm. The method involves liquid-liquid extraction with ethyl acetate and using 3-isobutyl 1-methyl xanthine as internal standard. The system requires a C(18) column (150 mm x 4.6 mm I.D.) and a mobile phase composed of potassium dihydrogen phosphate (15 mM; pH 7.5) and acetonitrile in the ratio of 80:20 (v/v). The assay was linear from 0.025 to 10.0 microg/ml for zidovudine and 0.05 to 10.0 microg/ml for nevirapine. The intra- and inter-day variations were less than 10% for both the drugs. The method was specific and sensitive enough to allow quantification of zidovudine and nevirapine in concentrations observed clinically. The average recoveries of zidovudine and nevirapine from plasma were 95 and 94%, respectively. The method was applied to a pharmacokinetic study in HIV-infected patients who were receiving antiretroviral treatment with zidovudine and nevirapine containing regimens. The method spans the blood concentration range of clinical interest. Due to its simplicity, the assay can be used for pharmacokinetic studies and therapeutic drug monitoring in patients taking a combination treatment of zidovudine and nevirapine.     

Simple,rapid procedure for the determination of valproate and ethosuximide in plasma by gas—liquid chromatography

A simple method based on high-performance liquid column chromatography with electrochemical detection is described for the simultaneous determination of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in discrete brain regions of rats. The supernatant of a tissue homogenate is injected directly onto a liquid chromatograph, thus omitting the commonly adopted adsorption step. Of the four different supports tested Nucleosil C₁₉ (5 μm) was found superior with respect to chromatographic performance. The effects of pH, methanol and the ion-pairing agent hexyl sulfate on the retention were studied. The mobile phase used in the final studies consisted of citrate buffer pH 4.25—methanol (92:8, v/v) containing hexyl sulfate (1.7 · 10^?3M). Standard curves of dopamine, DOPAC and HVA were found linear up to about 600 pmol per injection for each compound. The precisions of the chromatographic step were (s_rel. %): 0.72% (dopamine), 1.26% (DOPAC) and 2.69% (HVA).     

Simple method for determination of paraquat in plasma and serum of human patients by high-performance liquid chromatography

A simple and fast HPLC system is presented for quantifying paraquat in human plasma and serum using 1,1'-diethyl-4,4'-bipyridyldiylium (diethyl paraquat) as an internal standard. An octadecyl-silica column is used with an eluent of 10% acetonitrile (v/v) containing sodium 1-octanesulphonic acid (3.0 mM) and a diethylamine-orthophosphoric acid buffer (pH 3). Unlike with other techniques, sample treatment requires only the precipitation of protein contents by 6% perchloric acid (v/v) in methanol. The method has a limit of detection of 0.1 microg/ml and is linear up to 10 microg/ml. The serum of four patients and the plasma of one patient with paraquat intoxication's were analysed and positive identification and quantification was readily achieved. One of those patients survived, partially given the rapid disclosure of his levels of paraquat. Therefore, this method is suitable for quantification of paraquat in toxicological samples. It may be used as a prognostic tool in critical case detoxification and to quickly identify potentially salvageable patients for enrollment in new hemofiltration studies.     

Simple and sensitive high-performance liquid chromatography method for the determination of docetaxel in human plasma or urine

Several methods for quantification of docetaxel have been described mainly using HPLC. We have developed a new isocratic HPLC method that is as sensitive and simpler than previous methods, and applicable to use in clinical pharmacokinetic analysis. Plasma samples are spiked with paclitaxel as internal standard and extracted manually on activated cyanopropyl end-capped solid-phase extraction columns followed by isocratic reversed-phase HPLC and UV detection at 227 nm. Using this system, the retention times for docetaxel and paclitaxel are 8.5 min and 10.5 min, respectively, with good resolution and without any interference from endogenous plasma constituents or docetaxel metabolites at these retention times. The total run time needed is only 13 min. The lower limit of quantification is 5 ng/ml using 1 ml of plasma. The validated quantitation range of the method is 5–1000 ng/ml with RSDs≤10%, but plasma concentrations up to 5000 ng/ml can be accurately measured using smaller aliquots. This method is also suitable for the determination of docetaxel in urine samples under the same conditions. The method has been used to assess the pharmacokinetics of docetaxel during a phase I/II study of docetaxel in combination with epirubicin and cyclophosphamide in patients with advanced cancer.     

Simple and rapid method determination for metformin in human plasma using high performance liquid chromatography tandem mass spectrometry: application to pharmacokinetic studies

A rapid and simple method for quantitation of metformin (MET) in human plasma by HPLC-MS/MS was developed and validated. The sample preparation consists of plasma deproteinization using acetonitrile. The mobile phase consisted of water-acetonitrile and formic acid (55/45/0.048, v/v/%) and the run time was 3 min. A pursuit C(18) (100 mm x 2.0 mm i.d., 3 microm) column connected to a guard column MS-pursuit (0.20 mm x 0.20 mm i.d., 5 microm) was used. The range of the calibration curve was from 20 to 5000 ng/mL, the limit of quantitation being 20 ng/mL. The detection was performed on a mass spectrometer (ESI+), using metoprolol as internal standard. The calibration curves have r(2) values of 0.995 (CV=0.24%, n=10). The accuracy and precision were between 90.74 and 106.7% and coefficients of variations (CV) of 1.10 and 4.35%, respectively. The method was applied to determine the pharmacokinetic parameters: C(max) (1667.25 ng/mL) and T(max) (3.89 h).     

Simple high-performance liquid chromatography method for the simultaneous determination of serum caffeine and paraxanthine following rapid sample preparation

A simple reversed-phase high-performance liquid chromatography (HPLC) method for the simultaneous determination of caffeine and paraxanthine in human serum is described. Serum proteins are precipitated with perchloric acid and the resulting supernatant neutralized for direct injection onto an HPLC column. The method uses a phosphate–methanol mobile phase (85:15, v/v) at pH 4.9 with a flow-rate of 1.75 ml/min and quantitation is by UV absorbance at 274 nm. Elution times are approximately 18 min for caffeine and 8 min for paraxanthine. Theobromine and theophylline have elution times of 5.4 and 9.4 min and do not interfere in the assay. The intra-assay and between-assay means for precision and accuracy for both drugs are: 4.5% C.V. and 3.3% deviation. The sensitivity of the method is 50 ng/ml for each drug.     

Simple determination of terbutaline in dog plasma by column-switching liquid chromatography

Terbutaline is a beta-adrenergic receptor antagonist that acts as a bronchodilator in the treatment of asthma and chronic bronchitis. In the present work, a column-switching high-performance liquid chromatographic method was developed to monitor terbutaline sulphate in dog plasma. The system consists of a C2 pre-column (PC) and a C18 analytical column connected in series via a switching valve. Atenolol was used as the internal standard. Good linearity was achieved in the range of 5-800 ng/ml plasma. The mean intra- and inter-assay variation coefficients for this analysis were 2.3 and 4.7%, respectively. The average recovery for terbutaline was 87.4% from plasma. The mean concentration after three freeze-thaw cycles was 99.4% of the normal value. The analytical sensitivity and accuracy of this assay is adequate for characterisation of the pharmacokinetics of oral administration of terbutaline to dogs and has been successfully used to provide pharmacokinetic data using pulsatile and immediate-release tablets.     

Simple liquid chromatography method for the rapid simultaneous determination of prednisolone and cortisol in plasma and urine using hydrophilic lipophilic balanced solid phase extraction cartridges

This article describes the development and validation of a simple solid phase extraction (SPE) and HPLC method for the extraction and the specific determination of prednisolone and hydrocortisone (cortisol) in both plasma and urine using one washing step with Oasis hydrophilic lipophilic balanced (HLB) cartridges (1 ml/30 mg, 30 microm). Recoveries of prednisolone and cortisol from plasma and urine exceeded 82%. The limit of quantification (LOQ) in plasma and urine was 9.9 and 6.7 ng/ml for cortisol, respectively, and 11.6 and 8.0 ng/ml for prednisolone, respectively. The intraday and interday precision (measured by CV%) for both prednisolone and cortisol in both plasma and urine was always less than 7%. The accuracy (measured by relative error %) for both prednisolone and cortisol in both plasma and urine was always less than 8%. The advantages of the developed method are the use of a one step washing SPE utilising HLB cartridges which do not suffer the drying out problems of conventional SPE cartridges and the time saving when compared with solvent extraction (SE), in addition to the simultaneous determination of prednisolone and cortisol in both plasma and urine.     

Simple high-performance liquid chromatographic method for determination of ketoconazole in human plasma

A simple high-performance liquid chromatographic method using fluorescence detection was developed for the determination of ketoconazole in human plasma. The method entailed direct injection of the plasma sample after deproteinization using acetonitrile. The mobile phase comprised 0.05 M disodium hydrogen orthophosphate and acetonitrile (50:50, v/v) adjusted to pH 6. Analysis was run at a flow-rate of 1.5 ml/min with the detector operating at an excitation wavelength of 260 nm and an emission wavelength of 375 nm. The method is specific and sensitive with a quantification limit of approximately 60 ng/ml and a detection limit of 40 ng/ml at a signal-to-noise ratio of 3:1. Mean absolute recovery value was about 105%, while the within-day and between-day coefficient of variation and percent error values of the assay method were all less than 14%. The calibration curve was linear over a concentration range of 62.5–8000 ng/ml.     

Simple,rapid and micro high-pressure liquid chromatographic method for the simultaneous determination of tolbutamide and carboxy tolbutamide in plasma

A rapid high-pressure liquid chromatographic (HPLC) assay is described for the quantitative analysis of tolbutamide and its major metabolite, carboxy tolbutamide, in plasma. An aliquot (25–100 μl) of plasma was prepared for chromatography by deproteinization as follows. One volume of plasma and 2.5 volumes of acetonitrile were vortex mixed for a few seconds and then centrifuged for approx. 1 min. A 50-μl sample of the clear supernatant was injected into the chromatograph. A μBondapak C₁₂ reversed-phase column was used with a mobile phase of acetonitrile-0.05% phosphoric acid (45:55) at a flow-rate of 1.5 ml/min. The column effluent was monitored by a variable-wavelength UV detector set at 200 nm. Tolbutamide and its metabolite had retention times of 5.75 and 3.25 min, respectively. The procedure yields reproducible results with sensitivity adequate for routine clinical monitoring of plasma levels or for single-dose pharmacokinetic studies. A number of commonly used drugs do not interfere with the method. A single plasma sample can be analyzed in approx. 9 or 10 min.     

A simple and rapid determination of biapenem in plasma by high-performance liquid chromatography

A simple, rapid and precise HPLC method using ultrafiltration to remove plasma protein was developed to determine biapenem concentrations in human plasma. Plasma was separated by centrifugation at 4 degrees C from blood collected in heparinized vacuum tubes, and biapenem was stabilized by immediate mixing the plasma with 1M 3-morpholinopropanesulfonic acid (MOPS) buffer (pH 7.0) (1:1). Biapenem was detected by ultraviolet absorbance at 300nm with no interfering plasma peak. The calibration curve of biapenem in human plasma was linear from 0.04 to 50microg/mL. The limit of detection was 0.01microg/mL, which was more than 40-fold lower than that of conventional plasma protein precipitation using ammonium sulfate. The assay has been clinically applied to pharmacokinetic studies in patients.