Determination of Ritodrine in Plasma Using HPLC

Abstract

An HPLC instrument coupled with an electrochemical detector was used to determine ritodrine (erythro-p-hydroxy-α-[1-[(p-hydroxyphenethyl)-amino]ethyl] benzyl alcohol hydrochloride) at nanogram levels in serum. Extraction of ritodrine was accomplished using a multistep ethyl acetate procedure, and the mobile phase consisted of acetonitrile, ammonium acetate, glacial acetic acid, and a counterion. The stationary phase was a Biophase ODS 5 μm column at ambient temperature. Nalbuphine hydrochloride (Nubain®) was used as an internal standard to quantitate the ritodrine levels of pregnant patients receiving ritodrine. The procedure's linearity for both ritodrine standards and spiked plasma samples was demonstrated. The precision of the assay was found to be 3.4% at 20 ng/ml ritodrine. The minimum detectable concentration, with a signal-to-noise ratio of 6, was determined to be 0.31 ng per 50 μl injected, corresponding to a concentration of 0.6 ng/ml plasma. The sensitivity, precision, and reproducibility of the assay were all found to be acceptable for determining ritodrine in patient serum.     

Determination of Cefmenoxime in Human Serum by Ion-Pair Reverse-Phase High Performance Liquid Chromatography

Abstract

A highly reproducible ion-pair reverse-phase high performance liquid chromatographic assay for cefmenoxime in human serum has been developed. A simple sample cleanup procedure is employed. Cefoxitin is the internal standard and separation is achieved using a C-18 μ-Bondapak column. The mobile phase consists of 20% acetonitrile and 80% 0.05 M ammonium acetate buffer containing 0.005 M tetrabutylammonium hydrogen sulphate as the ion-pair agent. Samples are quantitated by UV detector at 254 nm and 0.02 aufs with an assay sensitivity of 0.625 μg/ml. The method has been successfully applied in a clinical setting.     

A Stability-Indicating Liquid Chromatographic Method for the Analysis of Erythromycin in Stored Biological Fluids Using Amperometric Detection

Abstract

A simple, sensitive and reliable high-performance liquid chromatographic procedure has been developed for the determination of erythromycin in human serum and urine using amperometric detection. A solid-phase extraction procedure was used followed by chromatography on a reverse-phase column. The mean recovery of erythromycin from serum and urine was 80%. Calibration plots for erythromycin base in serum and urine were linear over the ranges 0.25–5.0 μg/ml and 1.25–25.0 μg/ml respectively, with a sensitivity limit of 0.1 μg/ml.

This method allows both erythromycin and its principle degradation product, anhydroerythromycin, to be determined during a period of sample storage at 4°C and ?15°C. The method is sufficiently sensitive and precise and is thus highly suited for use in both pharmacokinetic and stability studies.     

Analysis of erythromycin in biological fluids by high-performance liquid chromatography with electrochemical detection

A simple and sensitive high-performance liquid chromatographic assay was developed for the quantitative determination of major erythromycin components and their potential metabolites or degradation products in plasma and urine. An ether extract of alkalized plasma sample was chromatographed on a reversed-phase column and the components in the column effluent were monitored by an electrochemical detector. The recovery of the drug from extraction was virtually 100%. The detection limits for erythromycin A in plasma were 5-10 ng/ml and 30 ng/ml using 1 and 0.2 ml of sample, respectively. For urine samples, a simple one-step deproteinization with two volumes of acetonitrile was satisfactory for analysis. The method has been evaluated in plasma and urine from dogs receiving oral or intravenous erythromycin A. The standard curves for potential metabolites or degradation products were not constructed due to the lack of sufficient samples.     

Analysis of Erythromycin II. Determination of Erythromycin in Human Blood Serum by Competitive Displacement of [14C]-Erythromycin from E. Coli Ribosomes

Abstract

A sensitive and selective method for the determination of erythromycin in human blood serum, in the range of 0.1 to 1.0 μg/ml, is described. The procedure is based on extraction of drug into ether and competitive displacement of [¹⁴C]-erythromycin from E. coli ribosomes. The method provides accurate, precise and rapid analyses and should be readily adaptable to bioavailability studies with erythromycin and its salts in man.     

Improved and Rapid Liquid Chromatographic Determination of Indomethacin in Serum

Abstract

A rapid, specific and sensitive reversed-phase liquid chromatographic (LC) assay for the quantitative determination of indomethacin in serum without extraction was developed. Chromatographic separation using flunixin meglumine as the internal standard was achieved on octadecylsilane-coated particles with a mobile phase of 0.15 M acetate buffer pH 3.0 (50% v/v), acetonitrile (30% v/v) and methanol (20% v/v). The recovery of indomethacin from serum samples in the concentration range of 0.1-25 μg/ml was 95.5 ± 5.8% and as little as 100 ng/ml of indomethacin in serum samples can be quantitated by this procedure. A serum level versus time profile of dog with intravenously administered indomethacin demonstrated the applicability of the assay.     

High Performance Liquid Chromatographic Determination of Oxamniquine in Plasma Samples

Abstract

A sensitive and reliable liquid chromatographic assay procedure for the quantitation of oxamniquine in plasma or urine was developed. Chromatographic separation was achieved on a reversed-phase phenyl colum using U.V. Detection at 254 nm. The eluting solvent was the mixture of 0.05 M acetate buffer pH 5 and acetonitrile (3:7). With this mobile phase the drug and its external standard were well separated from the interference of the blank samples. The average recovery of oxamniquine from 3 or more replicate dog plasma samples of different concentration (0.125 ? 4.00 μg/ml) was 95.5% and its coefficient of variation was 4.17%. The reproducibility of the assay was confirmed by the analysis of variance test for the slopes of the three standard plots obtained from plasma samples at three different occasions (F=4.2, p > 0.01). The detection limit for plasma samples was approximately 20 ng/ml. The method was applied to measure the plasma level vs, time profile of this drug following a single bolus intravenous dose of 16 mg/kg to a dog.     

Determination of Ascorbic Acid and Dehydroascorbic Acid in Blood Plasma Samples

Abstract

Following the stabilization of the plasma samples with HClO₄ and EDTA, the samples could be directly analyzed by HPLC using electrochemical detection and reversed-phase columns. The accuracy and precision of the method was evaluated using plasma samples spiked with ascorbic acid (10 μg/ml) and the results were also compared to the classical colorimetric procedure. Dehydroascorbic (5 μg/ml) was determined in plasma samples using UV detection following derivatization at room temperature for 45 minutes with o-phenylenediamine.     

A Stability-Indicating Hplc Analysis of Famotidine and Its Application to Kinetic Studies

Abstract

A stability-indicating HPLC analytical method has been developed for the determination of the H₂-receptor antagonist, famotidine in the presence of its degradation products. the method utilizes reversed phase chromatography with UV detection and internal calibration techniques. the mobile phase was comprised of 84% ammonium acetate buffer (pH 2.9) and 16% acetonitrile and pumped at a flow rate of 1.5 ml/min. Quantitation was performed by measuring the peak height ratio of drug to internal standard (salicylic acid). the limit of famotidine detection was determined to be 10 ng (0.4 ug/ml) with a signal to noise ratio of 3:1. Within day coefficient of variation of the method was 2.22% (2.5 μg/ml) and 0.82% (10 μg/ml). Between day coefficient of variation based on the slopes of daily prepared standard curves was 4.70%. the developed method was used to determine the drug content of famotidine tablets. Further, it was used to investigate the kinetics of degradation of the drug in an acidic solution.     

A Simple Electrochemical Method for the Quantitative Determination of Acetaminophen in Serum

Abstract

A simple electrochemical method for the determination of acetaminophen in serum is described. The eleotrode and associated electronics are simple, reliable, and inexpensive to build. The apparatus can be operated at a rate of 2–3 determinations per minute using only 10 μl serum per determination. The procedure includes extraction of acetaminophen in ethyl acetate and subsequent oxidative amperometric detection of the drug by a form of flow-injection analysis. The system parameters of buffer, pH, and redox potential have been optimized to permit measurement of less than 10 μg/ml of acetaminophen. The determination is linear over the range of 10–300 μg/ml with a C.V. of less than 3% for replicate analysis of the same sample.     

A Simple HPLC Method for the Determination of Trazodone Human Serum

Abstract

A simple HPLC method with minimal sample preparation and good reproducibility for the determination of trazodone in serum is described. Basified serum samples were extracted using ethyl acetate containing diazepam as the internal standard (IS). Chromatography was performed on a cyanopropylsilane column with 15 μL sample injection. The mobile phase consisted of 0.02 M ammonium phosphate, pH 7.5 : acetonitrile (70:30 v/v). The eluent was monitored at 220 nm. The serum standard curve was linear from 10.0 to 8000.0 ng/mL serum. The overall within-run quality control CV was 6.3% for five concentrations (20.0, 40.0, 100.0, 250.0 and 1000.0 ng/mL) and the overall recovery from serum was 85.4%. This method has been applied to the analysis of human serum samples.     

Determination of nadolol in serum by high-performance liquid chromatography with fluorimetric detection.

A sensitive high-performance liquid chromatographic method for a routine assay of nadolol in serum is described. Serum samples spiked with atenolol (internal standard) were extracted with diethyl ether. After centrifugation, the organic layer was evaporated to dryness. The residue was redissolved in the mobile phase and injected onto an octadecyl silica column (150 mm x 4.6 mm I.D.). The mobile phase was 0.05 M ammonium acetate (pH 4.5)-acetonitrile (85:15, v/v). Fluorometric detection (excitation 230 nm, emission 300 nm) was used. The minimum detectable level of nadolol in serum was 1 ng/ml.     

A Validated Ion-Pairing High Performance Liquid Chromatographic Method for the Determination of Enoxacin and its Metabolite Oxo-Enoxacin in Plasma and Urine

Abstract

A rapid, sensitive, and specific determination of enoxacin and its principal metabolite, oxo-enoxacin, in plasma and urine is described. the method, which employs the structurally related compound ciprof loxac in as internal standard, involves a protein precipitation step for plasma and solid-phase extraction for urine. Liquid chromatographic analysis is carried out on a C-18 bonded silica column; the mobile phase consists of 0.1 M citric-acid/acetonitrile employing ammonium perchlorate and tetrabutyl-ammonium hydroxide as ion-pairing agents. Quantitation is performed by UV-detection at 340 nm.

The analytical method was validated by examining the performance characteristics specificity, linearity, precision, accuracy, sensitivity, and recovery. Enoxacin calibration curves were linear between 0.02 and 3.2 μg/ml of plasma and from 0.5 to 125 μg/ml of urine. Limits of quantitation in plasma and urine were 0.01 and 0.5 μg/ml, respectively. For oxo-enoxacin, linear of calibration curves were obtained i n the range 0.05 to 1.6 μg/ml (plasma) and 1 to 50 μg/ml (urine); the respective quantitation limits were approximately 0.02 and 1 μg/ml.

The present assay procedure has been applied to monitoring plasma and urine concentrations in several pharmacokinetic studies in humans and different animal species.     

High Performance Liquid Chromatographic Determination of Flurbiprofen in Pharmaceutical Dosage Forms

Abstract

A rapid, specific and reliable high performance liquid chromatographic assay of flurbiprofen in dosage forms has been developed. Reversed-phase chromatography was conducted using a mobile phase of 0.05 M ammonium acetate and acetonitrile, (40% v/v) PH 5.2 and detection at λ 247 nm. The recovery and coefficient of variation from six placebo tablets spiked with 100 mg of flurbiprofen were 100.1% and 0.4% respectively. Replicate regression analyses of three standard plots in the concentration range 0.5 - 9 mcg/ml obtained on three different days gave a correlation coefficient (0.99996) and the coefficient of variation of the slopes 0.159%. The assay was precise within day and between days as indicated by ANOVA test. It is suggested that the proposed HPLC method should be used for routine quality control and dosage form assay of flurbiprofen.     

Simultaneous determination of three naturally occurring estrogens in environmental waters by high-performance liquid chromatography

A simple, sensitive and accurate reversed-phase high-performance liquid chromatographic (HPLC) method for simultaneous determination of three naturally occurring estrogenic steroids including estrone (E1), 17β-estradiol (E2) and estriol (E3) in environmental water samples was developed. Analytes were extracted with ethyl acetate solvents and preconcentrated prior to HPLC analysis. Separations were accomplished in <20 min using a reversed-phase C(18) column (4.6×250 mm id, 5 μm) with a gradient elution of mobile phase containing 3.0 mM ammonium acetate/acetonitrile mixtures (flow rate, 1.0 mL/min). UV light absorption responses at 205 nm were linear over a wide concentration range from 100,000 μg/L to the detection limits of 0.96 μg/L E1, 0.64 μg/L E2 and 0.78 μg/L E3. Quantitation was carried out by the peak area method. The relative standard deviation for the analysis of three estrogens was <3.0%. This method was applied for the simultaneous determination of estrogens in environmental water samples collected in Zhejiang, China. The higher concentrations of both E2 and E3 were found in Tang River and West Lake waters, and E1 was detected in lake water only. All three estrogens were below the detection limits in rain waters.     

An Optimized Method for the quantitation of Carboxyamidotriazole (CAI) in Human Plasma with Solid Phase Extraction and reversed Phase HPLC

Abstract

The anticancer agent CAI was quantitated from human plasma using a C-18 column with a mobile phase consisting of acetonitrile and water (each containing 0.01M ammonium acetate) pumped over a gradient at a flow rate of 1.0 mL min. The detection of CAI and the internal standard, harmine, was accomplished using a photodiode-array detector set at 264 and 323 nm, respectively. The chromatographic run time was 17.5 minutes. The plasma samples were prepared for HPLC analysis using a C-18 solid phase extraction procedure. Two calibration curves were prepared. and the assay was shown to be linear in the concentration range of 0.02 to 0.5 μg/mL for the low curve and 0.25 to 10.0 μg/mL for the high curve, with average correlation coefficients of 0.9933 and 0.9938, respectively. Intra-assay and inter-assay imprecisions were less than 10.0% with an error of accuracy of less than 11.0%. The assay was reproducible with the sensitivity needed for the prediction of CAI levels in the plasma of cancer patients.     

Simultaneous determination of malachite green, crystal violet, methylene blue and the metabolite residues in aquatic products by ultra-performance liquid chromatography with electrospray ionization tandem mass spectrometry

This work describes solid-phase extraction-ultra-performance liquid chromatography with electrospray ionization tandem spectrometry for determination of malachite green and metabolite leucomalachite green, crystal violet and metabolite leucocrystal violet, methylene blue and metabolites including azure A, azure B and azure C in aquatic products. Samples were extracted with acetonitrile and ammonium acetate buffer and purified by liquid extraction with dichloromethane, and then on MCAX solid-phase extraction cartridges. Then the extract was evaporated at 45°C by nitrogen blow. The residue was dissolved and separated by an Acquity BEH C18 column. The mobile phase was acetonitrile (A) and 5 mmol/L of ammonium acetate containing 0.1% formic acid (B). Analytes were confirmed and quantified using a tandem mass spectrometry system in multiple reaction mode with triple quadrupole analyzer using positive polarity mode. The limits of detection of malachite green, leucomalachite green, crystal violet and leucocrystal violet were 0.15 μg/kg, the limits of quantification were 0.50 μg/kg, and the average recoveries were more than 75% with spiked residues from 0.5 to 10 μg/kg. The relative standard deviations were less than 13%. The limits of detection of methylene blue, azure A, azure B and azure C were 0.3 μg/kg, the limits of quantification were 1.0 μg/kg, the average recoveries were more than 70% with spiked residues from 1.0 to 10 μg/kg and the relative standard deviations were less than 15%. The method has the merits of simplicity, sensitivity and rapidity, and can be used for simultaneous determination of the analytes in aquatic products.     

A validated stability‐indicating ultra performance liquid chromatography method for the determination of potential process‐related impurities in eplerenone

A simple, sensitive, and accurate stability‐indicating analytical method has been developed and validated using ultra high performance liquid chromatography. The developed method is used to evaluate the related substances of eplerenone (EP). The degradation behavior of EP under stress conditions was determined, and the major degradants were identified by ultra high performance liquid chromatography with tandem mass spectrometry. The chromatographic conditions were optimized using an impurity‐spiked solution, and the samples, generated from forced degradation studies. The resolution of EP, its potential impurities, and its degradation products was performed on a Waters UPLC BEH C₁₈ column (50 × 2.1 mm, 1.7 μm) by linear gradient elution using a mobile phase consisting of 10 mmol/L ammonium acetate adjusted to pH 4.5, methanol and acetonitrile. A photo‐diode array detector set at 245 nm was used for detection. The flow rate was set at 0.3 mL/min. The procedure had good specificity, linearity (0.02–3.14 μg/mL), recovery (96.1–103.9%), limit of detection (0.01–0.02 μg/mL), limit of quantitation (0.03–0.05 μg/mL), and robustness. The correction factors of the process‐related substances were calculated.     

高效液相色谱法测定食品中的姜黄素

食品中的姜黄素经甲醇提取、净化后,以液相色谱-紫外检测器外标法定量检测.色谱条件:反相C<,18>色谱柱(250 mm x4.6 mm,5μm),以乙腈-0.05%乙酸氨水溶液为流动相等度洗脱,流速为1.0 mL/min.姜黄素质量浓度在0.5-50.0μg/mL范围内与峰面积呈线性关系,回归方程y=7440x-295...     

Ion-Paired Liquid Chromatographic Determination of Cefazolin in Canine Serum and Tissues

Abstract

Cefazolin is commonly used as a prophylactic antibiotic in dogs undergoing total hip arthroplasty.

A sensitive high-performance liquid chromatographic method was developed for the determination of cefazolin in canine serum and tissues. The tissues were those in contact with the hip prothesis; namely, the coxofemoral joint capsule, cancellous bone from the acetabulum and bone marrow from the femoral canal.

The method involved filtration of diluted serum or tissue extracted with ethanol:acetonitrile:water (40:10:50) through a 30,000 molecular weight cut-off filter. Separation of cefazolin from other components was by ion-paired (dodecanosulfonate) high performance liquid chromatography using a reversed-phase column eluted with acetonitrile/water solution. The ultraviolet absorbance of the column effluent was monitored at 230 nm. Recovery of cefazolin spiked at 10 μg/ml from serum was 89.8% with a coefficient of variation (CV) of 5.3% (n=10). Recovery of cefazolin spiked at 5 μg/ml from tissue extracts of joint capsule, cancellous bone and bone marrow was: 93.9%, 98.2%, and 104.2% respectively, with a CV of 6.7%, 10.2% and 10.6% respectively (n=10). A correlation coefficient of 0.9999 occurred with cefazolin in aqueous solution (n=5). The limit of detection for cefazolin was approximately 10 ng/ml of serum or tissue extract.