Measurement of lumefantrine and its metabolite in plasma by high performance liquid chromatography with ultraviolet detection

Artemether-lumefantrine (ARM-LUM) has in recent years become the first-line treatment for uncomplicated malaria in many Sub-Saharan African countries. Vigorous monitoring of the therapeutic efficacy of this treatment is needed. This requires high-quality studies following standard protocols; ideally, such studies should incorporate measurement of drug levels in the study patients to exclude the possibility that insufficient drug levels explain an observed treatment failure. Several methods for measuring lumefantrine (LUM) in plasma by HPLC are available; however, several of these methods have some limitations in terms of high costs and limited feasibility arising from large required sample volumes and demanding sample preparation. Therefore, we set out to develop a simpler reversed phase high performance liquid chromatography (RP-HPLC) method based on UV detection for simultaneous measurement of LUM and its major metabolite the desbutyl LUM (DL) in plasma. Halofantrine was used as an internal standard. Liquid–liquid extraction of samples was carried out using hexane–ethyl acetate (70:30, v/v). Chromatographic separation was carried out on a Synergi Polar-RP column (250 mm × 300 mm, particle size 4 μm). The mobile phase consisted of acetonitrile–0.1 M ammonium acetate buffer adjusted to pH 4.9 (85:15%, v/v). Absorbance of the compounds was monitored at 335 nm using a reference wavelength of 360 nm. Absolute extraction recovery for LUM and DL were 88% and 90%, respectively. Inter- and intraday coefficients of variation for LUM and DL were ≤10%. The lower limits of quantification for LUM and DL were 12.5 and 6.5 ng/ml, respectively. After validation, the methodology was transferred to a local laboratory in Tanga Tanzania and samples from a small subset of malaria patients were analysed for LUM. The method appears to be applicable in settings with limited facilities.     

Development and validation of a bioanalytical LC-UV method with solid-phase extraction for determination of valproic acid in saliva

A bioanalytical HPLC method with UV detection for the determination of the antiepileptic drug valproic acid in human saliva has been developed and validated. Saliva represents an alternative matrix for therapeutic monitoring of antiepileptic drugs due to the increasing interest in free drug concentration. The proposed method involved solid-phase extraction for sample preparation and yielded very good mean recoveries of 99.4 % and 97.9 % for valproic acid and IS, respectively. The calibration function for valproic acid was linear over the concentration range of 1.0-50.0 μg mL(-1) (R(2) = 0.9989). Within-run and between-run precision and accuracy were studied at four concentrations and RSDs were less than 7.3 and 2.2 %, while accuracy values were higher than 96.8 and 97.5 %, respectively. The described method provides sensitivity, linearity, precision, accuracy and is suitable for analyses of valproic acid in saliva samples.     

固相萃取HPLC-UV法测定人血浆中比阿培南浓度及其药代动力学研究(英文)

比阿培南是一种新型经胃肠外吸收的碳青霉烯类抗生素,广泛用于治疗多种细菌感染。本试验建立了一种简便、有效、精确的固相萃取HPLC法测定人血浆中比阿培南的浓度。样品和内标物Vitamin B6经固相萃取后通过Capcell Pak C18柱进行分离。测定方法以0.05mol/L磷酸二氢钠(pH5.7)–甲醇(98:2,v/v)为流动相,流速为1.0mL/min,检测波长为300nm。比阿培南在0.04~50.00μg/mL浓度范围内线性关系良好,最低定量限可至0.04μg/mL,0.10、5.00和25.00μg/mL三个浓度的提取回收率均在70%左右。这种测定方法成功地应用于12名健康志愿者单次静脉滴注三剂量(150、300和600mg)比阿培南后的药动学研究。本方法具有良好的精密度和准确度,并且保证样品处理后的稳定性,因此能广泛应用于临床研究。     

Development and validation of an automated method for the liquid chromatographic determination of sotalol in plasma using dialysis and trace enrichment on a cation-exchange pre-column as on-line sample preparation

A fully automated method for the determination of sotalol in human plasma was developed, involving dialysis through a cellulose acetate membrane, clean-up and enrichment of the dialysate on a strong cation-exchange pre-column and subsequent liquid chromatographic (LC) analysis with UV detection. All sample handling operations were carried out by means of an ASTED system. Before starting dialysis, the trace enrichment column (TEC) was conditioned. The plasma sample, to which the internal standard (atenolol) was automatically added, was then loaded in the donor channel and was kept static while the dialysis liquid, consisting of 0.017 M acetic acid, was passed through the acceptor channel in successive pulses. After each pulse, the dialysate was dispensed onto the TEC. When dialysis was discontinued, the analytes were eluted from the TEC by the LC mobile phase by rotation of a switching valve and transferred to the analytical column packed with octyl silica. The LC mobile phase was a mixture of methanol and pH 7.0 phosphate buffer containing 1-octanesulfonate at a concentration of 7.5×10⁻⁴ M (19:81; v/v). The UV detection was performed at 230 nm. The influence of several parameters of the dialysis and trace enrichment processes on analyte recovery and method selectivity was investigated. The method was then validated. The mean absolute recovery for sotalol was about 60%. The limit of quantitation was 25 ng/ml and R.S.D. for repeatability and intermediate precision obtained at a concentration level of 50 ng/ml were 4.3 and 5.8%, respectively.     

Development and validation of a fully automated LC method for the determination of cloxacillin in human plasma using anion exchange restricted access material for sample clean-up

In the framework of a preliminary investigation on the plasma profile of cloxacillin after oral administration, a simple and rapid LC method was developed for the direct determination of this compound in human plasma. The on-line sample clean-up was carried out using a weak anion exchanger (diethylaminoethyl groups) as restricted access material (RAM). The effects of the washing liquid pH, the ionic strength and the addition of organic modifier to the washing liquid were studied in order to obtain an efficient sample clean-up and a high recovery of cloxacillin. The separation was achieved on octadecylsilica stationary phase using a mobile phase consisting in a mixture of phosphate buffer (pH 4.0; 25 mM) and acetonitrile (72:28, v/v). The UV detection was performed at 215 nm. The most appropriate regression model of the response function as well as the limit of quantitation (LOQ) were first selected during the pre-validation step. These criteria were then assessed during the formal validation step. The LOQ was 50 ng/ml. The method was also validated with respect to analyte recovery, precision, trueness, accuracy and linearity. Finally, it was successfully applied for the analysis of the first plasma samples obtained from patients having taken an oral dose of 500 mg cloxacillin.     

Development and validation of an anion-exchange LC-UV method for the quantification and purity determination of the DNA plasmid pDERMATT

The pDERMATT (plasmid DNA encoding recombinant MART-1 and tetanus toxin fragment-c) plasmid is a novel in-house developed anti-cancer vaccine which encodes a melanoma associated epitope (Mart-1) and an immuno stimulatory sequence (tetanus toxin fragment-c). The pharmaceutical development of pDERMATT necessitated the availability of an assay for the quantification and purity determination of pDERMATT active pharmaceutical ingredient (API), the produced bulk drug and its pharmaceutical dosage form. An anion-exchange liquid chromatographic method (AEX-LC) with ultraviolet (UV) detection was developed, which is based on separation on a non porous anion-exchange (NPR AEX) column with a mobile phase gradient of 0.45–0.53 M NaCl in 20 mM Tris–HCl 10% isopropanol (IPA) pH 9 and UV detection at 260 and 280 nm. The method was found to be precise, accurate and linear over a concentration range of 5–150 μg/ml. The supercoiled topoisoform of pDERMATT was well separated from the linear and open-circular form, the main degradation products formed during stress testing, confirming its stability-indicating capability. The use of photo diode array (PDA) detection enabled us to confirm all visible peaks to contain DNA. Additionally capillary gel electrophoresis (CGE) showed the same peak profile as the developed HPLC method. The developed LC-UV method will be used for the pharmaceutical quality control of pDERMATT API, bulk drug and its pharmaceutical dosage form.     

Validation of a chromatographic method to determine E-6006 and its metabolite E-6332 in rat and dog plasma by solid-phase extraction and capillary gas chromatography. Application in pharmacokinetics

E-6006, 5-{-[2-(dimethylamino)ethoxy]-2-thienylmethyl}-1-methyl-1H-pyrazole is a new antidepresive compound and E-6332, 5-{-[2-(methylamino)ethoxy]-2-thienylmethyl}-1-methyl-1H-pyrazole is its desmethylate metabolite. With the aim of quantifying E-6006 and E-6332, simultaneously in rat or dog plasma, a method of analysis based on solid-phase extraction coupled with capillary gas chromatographic system with N–P detection was developed and validated. E-6006, E-6332 and its internal standard (E-4018) were isolated from plasma using an off-line semiautomatic solid-phase extraction method. Gas chromatography separations were carried out by means of 12 m length, 0 2 mm (i.d.) and 0.33 μm (f.t.) ULTRA 1 type capillary column in splitless mode of injection at 190°C, with a TSD or specific nitrogen–phosphorus detector. No peaks interfering with the quantification of E-6332 and E-6006 were observed. The limit of quantification was 5 ng/ml with a precision and accuracy <17%. The peak height ratios were proportional to E-6332 and E-6006 concentration over the range from 5 to 600 ng/ml (r²>0.998). Mean recoveries of E-6332, E-6006 and internal standard from rat plasma were between 57.1 and 82.6. Intra-assay precision coefficients were <8.0 and <11.8%, respectively, for E-6332 and E-6006, with an accuracy <12.6 and <9.7%. Both inter-assay precision and accuracy were within acceptable limits (<15%). In dog, the results were very similar to those obtained in rat. To show an example of the suitability of the method to determine E-6332 and E-6006, plasma profiles obtained after single oral and intravenous administration of 20 mg/kg to rats and 25 mg/kg to dogs are reported.     

Development and validation of an automated solid-phase extraction and liquid chromatographic method for determination of lumefantrine in capillary blood on sampling paper

A bioanalytical method for the determination of lumefantrine in 100 microl blood applied onto sampling paper, by solid-phase extraction and liquid chromatography, has been developed and validated. Whatman 31 ET Chr sampling paper was pre-treated with 0.75 M tartaric acid before sampling capillary blood to enable a high recovery of lumefantrine. Lumefantrine was extracted from the sampling paper, then further purified using solid-phase extraction and finally quantified with HPLC. The between-day variation was below 10% over the range 0.4-25 microM. The lower limit of quantification was 0.25 microM in 100 microl capillary blood. No decrease in lumefantrine concentration in dried blood spot is seen after 4 months storage at 22 degrees C. The method was also evaluated in field samples from patients in Tanzania after treatment with lumefantrine/artemether. Lumefantrine could be estimated accurately enough to assess bioavailability and treatment compliance on day 7 (i.e. 4 days after the last dose) after a standard regimen with the lumefantrine/artemether combination.     

Development and validation of a reversed-phase HPLC method for simultaneous estimation of ambroxol hydrochloride and azithromycin in tablet dosage form

A simple, precise and accurate reversed-phase liquid chromatographic method has been developed for the simultaneous estimation of ambroxol hydrochloride and azithromycin in tablet formulations. The chromatographic separation was achieved on a Xterra RP18 (250 mm × 4.6 mm, 5 μm) analytical column. A Mixture of acetonitrile–dipotassium phosphate (30 mM) (50:50, v/v) (pH 9.0) was used as the mobile phase, at a flow rate of 1.7 ml/min and detector wavelength at 215 nm. The retention time of ambroxol and azithromycin was found to be 5.0 and 11.5 min, respectively. The validation of the proposed method was carried out for specificity, linearity, accuracy, precision, limit of detection, limit of quantitation and robustness. The linear dynamic ranges were from 30–180 to 250–1500 μg/ml for ambroxol hydrochloride and azithromycin, respectively. The percentage recovery obtained for ambroxol hydrochloride and azithromycin were 99.40 and 99.90%, respectively. Limit of detection and quantification for azithromycin were 0.8 and 2.3 μg/ml, for ambroxol hydrochloride 0.004 and 0.01 μg/ml, respectively. The developed method can be used for routine quality control analysis of titled drugs in combination in tablet formulation.     

Development and validation of a high-performance liquid chromatographic method for bioanalytical application with rimonabant

A simple and feasible high-performance liquid chromatographic method with UV detection was developed and validated for the quantification of rimonabant in human plasma. The chromatographic separation was carried out in a Hypersil BDS, C₁₈ column (250 mm × 4.6 mm; 5 μm). The mobile phase was a mixture of 10 mM phosphate buffer and acetonitrile (30:70, v/v) at a flow rate of 1.0 ml/min. The UV detection was set at 220 nm. The extraction recovery of rimonabant in plasma at three quality control (QC) samples was ranged from 84.17% to 92.64%. The calibration curve was linear for the concentration range of 20–400 ng/ml with the correlation coefficient (r²) above 0.9921. The method was specific and sensitive with the limit of quantification of 20 ng/ml. The accuracy and precision values obtained from six different sets of QC samples analyzed in separate occasions ranged from 88.13% to 106.48% and 0.13% to 3.61%, respectively. In stability tests, rimonabant in human plasma was stable during storage and assay procedure. The method is very simple, sensitive and economical and the assay was applied to human plasma samples in a clinical (pharmacokinetic) study of rimonabant.     

Development and validation of a new HPLC analytical method for the determination of alprazolam in tablets

A new analytical method is developed together with its latter validation study, by means of a high resolution liquid chromatography (HPLC) of reverse phase to quantify alprazolam (8-chloro-1-methyl-6-phenyl-4H-[1,2,4] triazole [4,3,-]-[1,4] benzodiazepine) in tablets. Determination is carried out by means of an ODS C18 column (200 mm×4.6 mm i.d., 5 μm particle size); the mobile phase consisted of a mixture of 0.02 M buffer solution of phosphates (pH 6.0) and acetonitrile (45:55, v/v). It is pumped through the chromatographic system at a flow rate of 0.50 ml min⁻¹. The UV detector is operated at 254 nm. The validation study is carried out fulfilling the ICH guidelines in order to prove that the new analytical method, meets the reliability characteristics, and these characteristics show the capacity of an analytical method to keep, throughout the time, the fundamental criteria for validation: selectivity, linearity, precision, accuracy and sensitivity. The method is applied during the working day for the quality control of commercial alprazolam tablets in order to quantify the drug and its degradation products and to check the content uniformity test.     

Development and validation of UPLC method for determination of primaquine phosphate and its impurities

With the objective of reducing analysis time and maintaining good efficiency, there has been substantial focus on high-speed chromatographic separations. Recently, commercially available ultra-performance liquid chromatography (UPLC) has proven to be one of the most promising developments in the area of fast chromatographic separations. In this work, a new isocratic reverse phase chromatographic method was developed using UPLC for primaquine phosphate bulk drug. The newly developed method is applicable for assay and related substance determination of the active pharmaceutical ingredient. The chromatographic separation of primaquine and impurities was achieved on a Waters Acquity BEH C18, 50 x 2.1mm, 1.7 microm column within a short runtime of 5 min. The method was validated according to the regulatory guidelines with respect to specificity, precision, accuracy, linearity and robustness. Forced degradation studies were also performed for primaquine phosphate bulk drug samples to demonstrate the stability indicating power of the UPLC method. Comparison of system performance with conventional HPLC was made with respect to analysis time, efficiency and sensitivity.     

Fast chiral chromatographic method development and validation for the quantitation of eszopiclone in human plasma using LC/MS/MS

Traditional chiral chromatographic separation method development is time consuming even for an experienced chromatographer. This paper describes the application of computer software ACD Lab^® to facilitate the development of chiral separation for the quantitation of eszopiclone using LC–MS/MS technology. Assisted by ACD/Chrom Manager and LC Simulator software, the optimal chiral chromatographic development was completed within hours. The baseline chiral separation was achieved with a total cycle time of 3 min. For sample extraction method development, a Waters Oasis^® Sorbent Selection Plate containing four different sorbents was utilized. Optimal conditions were determined using a single plate under various load, wash and elution conditions. This was followed by a GLP validation which demonstrated excellent intra- and inter-day accuracy and precision for the quantitation of eszopiclone in human plasma at 1.00–100 ng/mL range using LC/MS/MS technology. This method was utilized to support multiple clinic bioequivalence studies.     

Development and validation of a LC method for the enantiomeric purity determination of S-ropivacaine in a pharmaceutical formulation using a recently commercialized cellulose-based chiral stationary phase and polar non-aqueous mobile phase

Ropivacaine is the first enantiomerically pure long-acting local anaesthetic used for surgical anaesthesia and post-operative pain relief.     

An interlaboratory study on the suitability of a gradient LC-UV method as a compendial method for the determination of erythromycin and its related substances

A liquid chromatographic (LC) method for the analysis of erythromycin and related substances has been adapted from an isocratic method developed by Chepkwony et al. (2001) [1]. The suitability of the method for general application as a compendial (pharmacopoeia) method has been assessed by means of an interlaboratory (collaborative) study. The method involves LC separation on a XTerra C18 column kept at 65 °C and UV detection at 210 nm. Five laboratories, located in Europe and the United States (US), participated in the study. Four erythromycin samples were tested. The main components (erythromycin A (EA), erythromycin B (EB), erythromycin C (EC)) and the impurities were determined. The analysis of variance was carried out on the results of the five laboratories to evaluate the between-laboratory consistencies and the laboratory-sample interaction. The estimates for the repeatability and reproducibility of the method, expressed as relative standard deviation (RSD) of the result of the determination of EA, were calculated to be 0.8% and 1.4% respectively. It is concluded that the method examined is a good replacement for the methods currently described in the European Pharmacopoeia (Ph. Eur.) and the United States Pharmacopoeia (USP), especially for its enhanced selectivity.     

Development and validation of a stability indicating capillary electrophoresis method for the determination of metformin hydrochloride in tablets

A simple and a stability indicating capillary electrophoresis method was developed and validated for the analysis of metformin hydrochloride in tablet formulation. The method employed 40 mM citrate buffer at pH 6.7 as a background electrolyte with an applied voltage of 15 kV (positive polarity). The capillary used was of 68.5 cm length (60 cm to detector) and the detection wavelength was 230 nm. The method was validated in accordance with the ICH requirements, which involved accuracy, precision, linearity, selectivity and both limit of detection and limit of quantitation. The current method was linear over the concentration range of 0.2–2.0 mg/ml of metformin hydrochloride. The method was precise as reflected by inter-day and intra-day relative standard deviation (RSD) of less than 2%. The limit of detection and limit of quantitation were 2.0 μg/ml and 8.0 μg/ml, respectively. The stability indicating capability of the method was established by enforced degradation studies combined with peak purity assessment using photodiode array detection.     

LC-MS method for the determination of albuterol enantiomers in human plasma using manual solid-phase extraction and a non-deuterated internal standard

A sensitive enantioselective liquid chromatography–mass spectrometry (LC–MS) assay using a manual solid-phase extraction (SPE) procedure, a non-deuterated internal standard and an ion trap LC–MS was developed to measure (R)- and (S)-albuterol in plasma. Sample extraction from plasma was achieved by a manual SPE extraction procedure with methoxyphenamine added as the internal standard. Chiral separation was achieved using a teicoplanin-based stationary phase and a mobile phase consisting of methanol, acetic acid and 28% (w/v) ammonia (1000:5:1, v/v/v). Samples were analyzed by selected reaction monitoring of product ions from the protonated molecular ions. The detection limit of the assay was 0.1 ng/ml with a conservative lower limit of quantification of 0.25 ng/ml for each enantiomer. Recovery of albuterol enantiomers from plasma spiked at 10 ng/ml of racemate was determined to be 89±5.8% (mean±S.D.). Reproducibility at 10 ng/ml of racemate assessed by the coefficient of variation was found to be 6.5% (n=5). Instrument precision (measured as coefficient of variation) was 1.4% (n=5). The correlation coefficient r² determined from the calibration curve over the range 0.5–50.0 ng/ml racemate in plasma was 0.998. This assay allows adequate sensitivity, recovery and reproducibility for the application to studies of inhaled albuterol.     

Application of solid-phase extraction to the isolation and determination of paracetamol and its metabolites

A series of clean-up columns for solid-phase extraction (SPE) were packed with various C₁₈ phases of different physico-chemical surface properties. These SPE columns were used for the isolation and determination of paracetamol and its metabolites from biological samples. The packing with a monomeric structure of chemically bonded phase showed the best recovery of tested substances in urine.