High-performance liquid chromatographic method for simultaneous determination of honokiol and magnolol in rat plasma

A high-performance liquid chromatographic (HPLC) method is described for the simultaneous determination of honokiol and magnolol in rat plasma. The plasma was deproteinized with acetonitrile which contained an internal standard (diphenyl) and was separated from the aqueous layer by adding sodium chloride. Honokiol and magnolol are extracted into the acetonitrile layer with high yield, and determined by reversed-phase HPLC and ultraviolet detection. The limits of quantitation for honokiol and magnolol were 13 and 25 ng ml⁻¹ in plasma, respectively, and recovery of both analytes was greater than 93%. The assay was linear from 20 to 200 ng ml⁻¹ for honokiol and from 40 to 400 ng ml⁻¹ for magnolol. Variation over the range of the standard curve was less than 15%. The method was used to determine the concentration-time profiles of honokiol and magnolol in the plasma following rectal administration of Houpo extract at a dose of 245 mg kg⁻¹, equivalent to 13.5, 24.4 mg kg⁻¹ of honokiol and magnolol, respectively.     

A rapid determination of propiverine and its N-oxide metabolite in human plasma by high performance liquid chromatography-electrospray ionization tandem mass spectrometry

A simple, fast and sensitive high-performance liquid chromatography (HPLC)-electrospray ionization (ESI) tandem mass spectrometric method (LC-MS/MS) has been developed for determination of propiverine and propiverine N-oxide metabolite in human plasma using oxybutynin as internal standard. Instead of extracting propiverine from plasma using organic solvents, which should be separated from the aqueous phase and evaporated before injecting the sample into the chromatograph, plasma sample containing propiverine and N-oxide was directly injected after precipitating proteins with acetonitrile. Numerous compounds in the plasma did not interfere with the highly specific multiple reaction monitoring in tandem mass spectrometric detection following C₈ reversed-phase chromatographic separation under conditions that eluted propiverine, N-oxide and oxybutynin within 2 min (0.1% formic acid in water/acetonitrile, 25:75, v/v). The LC-MS/MS method and an alternative LC-MS method, using methyl-t-butyl ether extraction and selected ion monitoring, were validated over 1-250 ng ml⁻¹ of propiverine and 2 to 500 ng ml⁻¹ of N-oxide, and successfully applied in a pharmacokinetic study. The lower limit of quantitation was 1 ng ml⁻¹ for propiverine and 2 ng ml⁻¹ for N-oxide in both methods.     

Determination of clarithromycin in rat plasma by HPLC-UV method with pre-column derivatization

A novel high-performance liquid chromatographic (HPLC) method using pre-column derivatization and UV detection at 275 nm for the determination of clarithromycin in rat plasma has been validated. Clarithromycin was extracted from plasma sample spiked with internal standard (erythromycin) under alkaline condition with ethyl ether and derivatizated with trimethylbromosilane. The analyses were run on a C₁₈ column, maintained at 40 °C during elution, using a mobile phase comprised of potassium dihydrogen phosphate (50 mM, pH 6.8, contained 0.7% triethylamine), acetonitrile, and methanol (30:45:25, v/v/v). The standard calibration curve for clarithromycin was linear (r² = 0.9998) over the concentration range of 0.1-10 μg ml⁻¹ in rat plasma. The limit of detection (LOD) and limit of quantitation (LOQ) was 30 ng ml⁻¹ and 0.1 μg ml⁻¹ respectively. The intra- and inter-day assay variability range was 2.6-7.4% and 3.3-8.5%, respectively. This method has been successfully applied to a pharmacokinetic study of clarithromycin in rats.     

A simple method for the study of salbutamol pharmacokinetics by ion chromatography with direct conductivity detection

A simple method for the study of the pharmacokinetics of salbutamol using ion chromatography with direct conductivity detection without chemical suppression is presented in this paper. Baseline separation of salbutamol from plasma components was achieved by using diluted HNO₃ (2 mmol l⁻¹) as mobile phase with acetonitrile (6%, v/v) as modifier. Atenolol was utilized as internal standard. Under the optimal conditions, the linear regression coefficients of the calibration curves are 0.996 within the concentration range of 1000-3 ng ml⁻¹ salbutamol. The detection limit (signal-to-noise ratio = 3) was 1 ng ml⁻¹ salbutamol. The noncompartmental pharmacokinetic parameters for salbutamol following administration of 8 mg salbutamol to 18 subjects were tested. The results coincided most satisfactorily with the results obtained by using reversed-phase high performance liquid chromatography (HPLC) with fluorescence detection.     

Isolation of tetracyclines in milk using a solid-phase extracting column and water eluent

An isolating method using a solid-phase extraction (SPE) ISOLUTE® C8 endcapped syringe-column for routine monitoring of residual tetracyclines (TCs) (oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC), and doxycycline (DC)) in cow's milk is presented. In the simplest and most environmentally harmless method, milk samples could be applied directly to the SPE column, following which all TCs were eluted with water. No organic solvents were used at all. The purified sample was injected into a high-performance liquid chromatography (HPLC) with a photo-diode array detector (PDAD). For the HPLC determination/identification, a LiChrospher® 100 RP-8 endcapped column and a mobile phase of acetonitrile −7% (v v⁻¹) acetic acid solution (in water) (35:65, v v⁻¹) with a PDAD was used. The total time required for the analysis of one sample was <40 min. Average recoveries (spiked 0.1-1.0 μg ml⁻¹ each drug) and their standard deviations were >80 and <5%, respectively.     

Simultaneous determination of sulfamonomethoxine, sulfadimethoxine, and their hydroxy/N(4)-acetyl metabolites with gradient liquid chromatography in chicken plasma, tissues, and eggs

A simultaneous determination of sulfamonomethoxine, sulfadimethoxine, and their hydroxy/N⁴-acetyl metabolites in chicken plasma, muscle, liver, and eggs using gradient high-performance liquid chromatography (HPLC) with a photo-diode array detector is developed. All the compounds are extracted by a handheld ultrasonic homogenizer with ethanol followed by centrifugation. The separation is performed by a reversed-phase C4 column with a gradient elution (ethanol:1% (v/v) acetic acid, v/v; 10:90 → 20:80). Average recoveries from samples spiked at 0.1-1.0 μg g⁻¹ or μg ml⁻¹ for each drug were >90% with relative standard deviations within 4%. The limits of quantitation were <30 ng g⁻¹ or ng ml⁻¹.     

Separation and determination of terbinafine and its four impurities of similar structure using simple RP-HPLC method

A novel reversed-phase HPLC method for the simultaneous determination of active component terbinafine, its one impurity 1-methylaminomethylnaphtalene and three degradation products, β-terbinafine, Z-terbinafine and 4-methyl-terbinafine occurring in pharmaceutical formulations after long-term stability tests, was developed and validated using propylparaben as an internal standard.The chromatographic separation was performed on a NUCLEOSIL 100-5-CN column, mobile phase for separation of all compounds consisted of a mixture of tetrahydrofurane, acetonitrile and citrate buffer pH 4.50 (10:20:70, v/v/v). The analysis time was less than 32 min at flow-rate of 0.8 ml min⁻¹. UV detection was performed at 226 nm. The method was validated and system suitability parameters were investigated. Method robustness and short-term standard solution stability were verified. Limits of detection for terbinafine degradation products/impurity were from 0.023 to 0.098 μg ml⁻¹, limits of quantitation were from 0.078 to 0.327 μg ml⁻¹. The method was applicable for routine determination of terbinafine and all its found impurities of similar structure with sufficient selectivity, precision and accuracy.     

Enantioselective high-performance liquid chromatographic method for the determination of baclofen in human plasma

A new analytical method for the separation and determination of R-(−)- and S-(+)- baclofen enantiomers in human plasma by high-performance liquid chromatography (HPLC) with UV detection was developed. Enantioselective resolution of the baclofen enantiomers was achieved by using teicoplanin macrocyclic antibiotic chiral stationary phase (CSP) known as Chirobiotic T with a polar ionic mobile phase (PIM) consisting of methanol: glacial acetic acid: triethylamine, 100:0.1:0.1, (v/v/v) at a flow rate of 0.5 ml min⁻¹ and UV detection set at 220 nm. The analytes of interest with S-(+)-sulpiride as the internal standard were extracted from human plasma using liquid-liquid extraction procedure with ethyl ether under alkaline condition prior to HPLC analysis. Recoveries for R-(−)- and S-(+)-baclofen enantiomers were in the ranges of 96-103% at 60-2500 ng ml⁻¹ level. Intra-day and inter-day precision calculated as %RSD was in the ranges of 1.2-5.2 and 1.3-4.3% for both enantiomers, respectively. Intra-day and inter-day accuracy calculated as percentage error were in the ranges of 1.2-3.9 and 1.1-3.9% for both enantiomers, respectively. Linear calibration curves in the concentration ranges of 20-3000 ng ml⁻¹ for each enantiomer showed correlation coefficient (r) of 0.9997. The limit of quantitation (LOQ) and limit of detection (LOD) for each enantiomer in human plasma were 20 and 10 ng ml⁻¹ (S/N=3) respectively.     

An HPLC method for the determination and pharmacokinetic study of lehmannine in rat plasma

A high-performance liquid chromatographic (HPLC) method for determining lehmannine (LMN) in rat plasma was developed for application in the pharmacokinetics study. The plasma was deproteinized with acetonitrile that contained an internal standard and was separated from the aqueous layer by adding sodium chloride. The HPLC assay was carried out using a VP-ODS column at 40 degrees C. The mobile phase was acetonitrile-0.02 mol/L ammonium acetate buffer-triethylamine (35:65:0.04, v/v/v). The flow rate was 1.0 mL/min. The detection wavelength was set at 220 nm. The method was used to determine the concentration-time profiles of LMN in the plasma following oral administration or bolus injection of LMN aqueous solution. The pharmacokinetic parameters of LMN were calculated for the first time by Drug and Statistics 1.0 program.     

High-performance liquid chromatographic method for the simultaneous determination of cyclosporine A and its four major metabolites in whole blood

This study aimed to develop a simple and efficient optimized high-performance liquid chromatograph (HPLC) method for simultaneous determination of cyclosporine A (CyA) and its major, partly active metabolites AM1, AM9, AM4N, and AM19 in whole blood from transplant patients using cyclosporine D (CyD) as internal standard. The method used a CN analytical column maintained at 60 °C with hexan-isopropanol (93:7, v/v) as mobile phase; detection was at 212 nm. Linearity for all five compounds was tested in the range of 31-1500 ng ml⁻¹ for CyA and of 31-1000 ng ml⁻¹ for metabolites. The limit of detection was found to be 15 ng ml⁻¹ for all compounds.This modified, inexpensive method is also suitable for measuring cyclosporine A and metabolite concentrations in routine monitoring of patients undergoing treatment with CyA.     

Simple HPLC‐UV for the quantification of a new leishmanicidal candidate (E)‐1‐4(trifluoromethyl) benzylidene)‐5‐(2‐4‐dichlorozoyl) carbonylhydrazine (LASSBio‐1736) in rat plasma for pharmacokinetics assessment

In this study, a sensitive HPLC‐UV assay was developed and validated for the determination of LASSBio‐1736 in rat plasma with sodium diclofenac as internal standard (IS). Liquid–liquid extraction using acetonitrile was employed to extract LASSBio‐1736 and IS from 100 μL of plasma previously basified with NaOH 0.1 M. Chromatographic separation was carried on Waters Spherisorb^®S5 ODS2 C₁₈ column (150 × 4.6 mm, 5 μm) using an isocratic mobile phase composed by water with triethylamine 0.3% (pH 4), methanol and acetonitrile grade (45:15:40, v/v/v) at a flow rate of 1 mL/min. Both LASSBio‐1736 and IS were eluted at 4.2 and 5 min, respectively, with a total run time of 8 min only. The lower limit of quantification was 0.2 μg/mL and linearity between 0.2 and 4 μg/mL was obtained, with an R² > 0.99. The accuracy of the method was >90.5%. The relative standard deviations intra and interday were <6.19 and <7.83%, respectively. The method showed the sensitivity, linearity, precision, accuracy and selectivity required to quantify LASSBio‐1736 in preclinical pharmacokinetic studies according to the criteria established by the US Food and Drug Administration and European Medicines Agency. Copyright © 2016 John Wiley & Sons, Ltd.     

Determination of quinolizidine alkaloids in Sophora medicinal plants by capillary electrophoresis

A new capillary electrophoresis (CE) method for the determination of quinolizidine alkaloids in Sophora medicinal plants was developed. A total of seven alkaloid components (cytisine, sophocarpine, matrine, lehmannine, sophoranol, oxymatrine and oxysophocarpine) were separated within 15 min. The running buffer was a 50 mM phosphate buffer containing 1%HP-β-CD and 3.3% isopropanol. The linear calibration ranges were 5.50-88.0 μg ml⁻¹ for cytisine and lehmannine, 5.00-88.0 μg ml⁻¹ for sophocarpine and sophoranol, 5.60-89.6 μg ml⁻¹ for matrine and oxysophocarpine, and 24.0-384 μg ml⁻¹ for oxymatrine. The recoveries of the seven alkaloids were 96.0-102.9% with relative standard deviations from 1.50 to 3.00% (n = 5). The method was successfully applied to different Sophora medicinal plants including Sophora flavescens, Sophora tonkinensis and Sophora alopecuroides.     

A environmentally friendly reversed-phase liquid chromatography method for phthalates determination in nail cosmetics

A simple and rapid analytical method was developed for the determination of phthalates, usually employed in nail cosmetic products. The method is based on an ultrasonic extraction of the sample with ethanol-water (90:10, v/v) followed by HPLC separation and quantitation. HPLC was carried out using a C18 column and spectrophotometric detection at 254 nm. A linear gradient elution was performed with ethanol-water starting from 50 to 95% ethanol in 30 min. Standard calibration curves were linear for all the analytes over the concentration range 5-200 μg ml⁻¹ with LOD values of about 0.5 μg ml⁻¹.The proposed green analytical method has been successfully applied for the analysis of commercial samples in order to check the presence of phthalates and to determine their concentration.     

Colorimetric Determination of Propofol in Bulk form,Dosage Form and Biological Fluids

ABSTRACT

Propofol is coupled with 2, 6-dichloroquinone-4-chlorimide (DCQ) in a reaction buffered at pH 9.6 to give a colored product having an analytically useful maximum at 635 nm. The factors affecting the color generation were optimized and incorporated in the procedure. The reacted propofol has a molar absorptivity of 3.9 × 10^?4 L mol^?1 cm^?1, and Beer's law is obeyed for concentrations 1-5 μg ml^?1 with detection limit 0.25 μg ml^?1. The method was found applicable to biological fluids (plasma and urine) spiked with propofol at concentration levels 1-5 μg ml^?1 for plasma and 1-5 μg 0.5 ml^?1 urine (less sensitivity is obtained with urine volumes above 0.5 ml) with detection limits 0.28 μg ml^?1 for plasma and 0.4 μg 0.5 ml^?1 urine. The average recovery for the commercial preparation (1% w/v propofol emulsion intravenous injection for infusion) was 99.54% with an RSD of 1.05%. The method was validated by an adopted HPLC method. The results obtained by the HPLC method for the commercial preparation were statistically compared with the proposed method and evaluated at the 95% confidence limits.     

High performance liquid chromatographic determination of sodium benzoate, methylparaben and propylparaben as preservative components in nystatin suspensions

A simple and sensitive method was developed for the analysis of preservatives sodium benzoate, methylparaben and propylparaben in nystatin suspensions by reversed-phase high performance liquid chromatography (HPLC), equipped with a C18 column and PDA detector. The mobile phase was a mixture of acetonitrile and acetate buffer of pH 4.4 (35:65 v/v). Under the optimized experimental conditions, separation of the preservatives was achieved in less than 20 min. The limits of quantifications (LOQs) and the linear dynamic ranges (LDRs) of sodium benzoate, methylparaben and propylparaben were 0.3 and 50–1000 μg Ml^?1, 0.5 and 50–600 μg ml^?1 and 0.3 and 50–900 μg ml^?1, respectively; the respective precisions (%RSD) at 500 μg ml^?1 level were 0.72%, 0.73% and 0.51% (n = 6). The average recoveries of sodium benzoate, methylparaben and propylparaben for spiked nystatin samples were obtained as 98%, 97% and 98%, respectively.     

On-line gradient liquid chromatography-Fourier transform infrared spectrometry determination of sugars in beverages using chemometric background correction

An on-line gradient reversed phase liquid chromatography-Fourier transform infrared spectrometry (LC-FTIR) method was developed for the determination of fructose, glucose, sucrose and maltose in beverages. Improved chromatographic resolution was obtained using a linear gradient from 75 to 55% (v/v) acetonitrile in water in 15 min. Changes in the background spectra were corrected employing “univariate background correction based on the use of a reference spectra matrix” (UBC-RSM) and using the ratio of absorbance (AR) at 2256 and 2253 cm⁻¹ for the identification of the eluent spectra within the RSM. The method provided limits of detection in the order of 0.75 mg ml⁻¹. The precision (as relative standard deviation) ranged between 3.3 and 4.1% for glucose and fructose, respectively at a concentration level of 3.0 mg ml⁻¹. Quantitative recovery values on spiked samples confirmed the accuracy of the method. A set of samples from the Spanish market were analysed to test the suitability of the procedure.     

Electrochemical sensor for predicting transformer overload by phenol measurement

Transformer overload is a significant problem to the power transmission industry, with severe safety and cost implications. Overload may be predicted by measuring phenol levels in the transformer-insulating oil, arising from the thermolytic degradation of phenol-formaldehyde resins. The development of two polyphenol oxidase (PPO) sensors, based on monitoring the enzymatic consumption of oxygen using an oxygen electrode, or reduction of enzymatically generated o-quinone at a screen-printed electrode (SPE), for the measurement of phenol in transformer oil is reported. Ex-service oils were prepared either by extraction into aqueous electrolyte-buffer, or by direct dilution in propan-2-ol, the latter method being more amenable to simple at-line operation. The oxygen electrode, with a sensitivity of 2.87 nA μg⁻¹ ml⁻¹, RSD of 7.0-19.9% and accuracy of ±8.3% versus the industry standard International Electrotechnical Commission (IEC) method, proved superior to the SPE (sensitivity: 3.02 nA μg⁻¹ ml⁻¹; RSD: 8.9-18.3%; accuracy: ±7.9%) and was considerably more accurate at low phenol concentrations. However, the SPE approach is more amenable to field-based usage for reasons of device simplicity. The method has potential as a rapid and simple screening tool for the at-site monitoring of phenol in transformer oils, thereby reducing incidences of transformer failure.     

A liquid chromatography/positive ion tandem mass spectrometry method for the determination of cilazapril and cilazaprilat in human plasma

A simple, rapid, and sensitive high-performance liquid chromatography (HPLC)-electrospray ionization (ESI) tandem mass spectrometric method (LC-MS/MS) has been developed for simultaneous determination of cilazapril levels and its active metabolite, cilazaprilat, in human plasma using enalapril as internal standard. The acquisition was performed in the multiple reaction monitoring mode; monitoring the transitions: m/z 418.4 > 211.1 for cilazapril and m/z 390.3 > 211.1 for cilazaprilat. The method involves a simple single-step liquid-liquid extraction with ethyl acetate. The analyte was chromatographed on an YMC C₈ reversed-phase chromatographic column by isocratic elution with 10 mM ammonium formate buffer-methanol (10:90, v/v; pH 3.2 with formic acid). Numerous compounds did not interfere with specific multiple reaction monitoring in tandem mass spectrometric detection following C₈ reversed-phase chromatographic separation under conditions that eluted cilazapril, cilazaprilat, and enalapril within 2 min. This method was validated over 0.1-500 ng ml⁻¹ of cilazapril and 0.5-50 ng ml⁻¹ of cilazaprilat. Cilazapril and cilazaprilat were stable in standard solution and in plasma samples under typical storage and processing conditions. The assay was successfully applied to a pharmacokinetic study of cilazapril given as a single oral dose (5 mg) to healthy volunteers.     

Determination of N-methylcarbamate insecticides in water samples using dispersive liquid–liquid microextraction and HPLC with the aid of experimental design and desirability function

A rapid and simple method for the extraction and preconcentration of N-methylcarbamates (NMCs) (carbofuran, carbaryl and promecarb) in water samples using dispersive liquid–liquid microextraction (DLLME) using chemometrics was developed. Influence variables such as volume of extracting (CHCl₃) and dispersing solvents (ACN), pH and ionic strength, extraction time and centrifugation time and speed were screened in a 2^7–4 Plackett–Burman design was investigated. The significant variables were optimized by using a central composite design (CCD) combined with desirability function (DF). At optimum conditions values of variables set as 126 μL chloroform, 1.5 mL acetonitrile, 1 min extraction time, 10 min centrifugation at 4000 rpm min⁻¹, natural pH, 4.7% (w/v) NaCl, the separation was reached in less than 14 min using a C₁₈ column and an isocratic binary mobile phase (acetonitrile: water (50:50, v/v)) with flow rate of 1.0 mL min⁻¹. At optimum conditions method has linear response over 0.001–10 μg mL⁻¹ with detection limit between 0.0001 and 0.0005 μg mL⁻¹ with relative standard deviations (RSDs) in the range 2.18–5.06% (n = 6).     

Development and validation of bioanalytical method for quantification of cycloserine in human plasma by liquid chromatography–tandem mass spectrometry: Application to pharmacokinetic study

A selective, sensitive and high‐throughput liquid chromatography–tandem mass spectrometry bioanalytical method has been developed for the estimation of cycloserine in human plasma, employing cytosine as the internal standard. The extraction of the analyte was facilitated by solid‐phase extraction using 100 μL of human plasma. The separation was carried out on a BDS Hypersil C₁₈ (150 × 4.6 mm, 5 μm) column using a mixture of 0.2% formic acid in HPLC‐grade water, methanol and acetonitrile (70:15:15, v/v/v) as mobile phase at a flow rate of 1.0 mL/min. The method was linear over the range of 0.20–20 μg/mL with r² > 0.99. Complete validation of the method was performed as per US Food and Drug Administration guidelines and the results met acceptance criteria. Applying the present method, the clinical pharmacokinetics of cycloserine following oral administration of 250 mg cycloserine was studied under fasting conditions. Assay reproducibility was also verified by incurred sample reanalysis.