Simultaneous determination of cyadox and its metabolites in plasma by high‐performance liquid chromatography tandem mass spectrometry

Cyadox is a novel antimicrobial growth‐promoter of the quinoxalines. For food safety and pharmacokinetic studies, a convenient, sensitive and reproducible LC‐ESI‐MS/MS method was developed for the simultaneous determination of cyadox and its major metabolites, quinoxaline‐2‐carboxylic acid, 1,4‐bisdesoxycyadox, cyadox‐1‐monoxide and cyadox‐4‐monoxide in chicken plasma. Plasma sample was subjected to a simple deproteinisation with acetonitrile. Analysis was performed on a C₁₈ column by detection with mass spectrometry in multiple reaction monitoring mode. A gradient elution program with 0.2% formic acid, methanol and acetonitrile was performed at a flow rate of 0.2 mL/min. The decision limits (CCαs) of five analytes in plasma ranged from 1.0 to 4.0 μg/L, and the detection capabilities (CCβs) were <10 μg/L. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The extraction recoveries of five analytes were between 87.4 and 93.9% in plasma at the spiked levels of 5 (10)–200 μg/L with the relative standard deviations <10% for each analyte. The developed method demonstrated a satisfactory applicability in real plasma samples.     

Determination of Metoclopramide in Serum by HPLC Assay and Its Application to Pharmacokinetic Study in Rat

Abstract

A simple, sensitive, and reproducible HPLC method has been developed for the determination of metoclopramide employing reversed phase high performance liquid chromatography with UV detection at 270 nm. The separation was performed on a Novapak C₁₈, 4 μm (3.9 × 150 mm) column. Acetonitrile (18%) in 0.02 M ammonium acetate containing 0.1% triethylamine was used as the mobile phase and the run time was 7 min. Tramadol was used as the internal standard. The mean retention times of metoclopramide and tramadol were 3.4 and 4.6 min, respectively. Linear response (r > 0.997) was observed over the range of 0.025–5 μg/ml of metoclopramide. There was no significant difference (p < 0.05) between inter- and intra-day studies for metoclopramide. The mean relative standard deviations (RSD%) of the results of within-day precision and accuracy of the drug were < 10%. The applicability of the assay was demonstrated in measuring metoclopramide pharmacokinetics in rats. The elimination half-life was 2.09 ± 0.39 h with an apparent clearance of 2.45 ± 0.70 (L/h)/kg in rat.     

Simultaneous quantitative analysis of phosphocreatine,creatine and creatinine in plasma of children by HPLC–MS/MS method: Application to a pharmacokinetic study in children with viral myocarditis

A simple and rapid HPLC–MS/MS method was developed and validated for simultaneous measurement of phosphocreatine and its metabolites creatine and creatinine in children's plasma. A 50 μL aliquot of plasma was prepared by protein precipitation with acetonitrile–water (1000 μL, 1:1, v/v) followed by separation on a Hypersil Gold C₁₈ column (35°C) with gradient mobile phase consisting of 2 mm ammonium acetate aqueous solution (pH 10) and methanol at a flow rate of 0.3 mL/min and analyzed by mass spectrometry in both positive (phosphocreatine) and negative (creatine and creatinine) ion multiple reaction monitoring mode. Good linearity (r > 0.99) was obtained for the three analytes. The intra‐day and inter‐day values of CV were <5.46% (?13.09% ≤ RE ≤ 2.57%). The average recoveries of the three analytes were 70.9–97.5%. No obvious impact was found for the quantitation of three analytes in normal, hemolyzed and hyperlipemic plasma. In the end, this method was successfully applied to a pharmacokinetic study of phosphocreatine in children (six cases) with viral myocarditis of children after intravenous infusion of 2 g of the test drug. The pharmacokinetc parameters of phosphocreatine/creatine were as follows: t_1/2 0.24/0.83 h, T_max 0.49/0.55 h, C_max 47.34/59.29 μg/mL, AUC_last 17.07/59.63 h μg/mL, AUC_inf 17.16/79.01 h μg/mL and MRT 0.29/0.67 h.     

Anodic Stripping Potentiometric Determination of Cu,Pb, Cd and Zn In Natural Waters on a Novel Combined Electrode System

Abstract

A method is described for the reliable determination of copper, lead, cadmium and zinc in natural waters by anodic stripping potentiometry with the use of a novel combined electrode. The method involves two stripping cycles during which copper is initially determined on its own, followed by simultaneous determination of lead, cadmium and zinc after addition of gallium (III) ions. The optimum conditions include 0.01 M HCl as supporting electrolyte, 10 mg/L Hg (II) as chemical oxidant; E_dep(Cu) -700 mV vs Ag/AgCl; E_{dep(Pb,Cd,Zn)} -1200 mV vs Ag/AgCl; t_dep 10s; 150 μg/L Ga (III); sample rotation rate 5 and rest period 30s. Under these conditions, as low as 0.06 μg/L Cu (0.7% RSD); 0.2 μg/L Pb (13% RSD); 0.04 μg/L Cd (7.8% RSD) and 0.06 μg/L Zn (5.5% RSD) can be determined reliably. A linear concentration range of 0–110 μg/L was obtained for the four metals. The successful application of the method to reference fresh water, creek water and tap water is demonstrated.     

Use of micellar liquid chromatography to analyze darunavir,ritonavir, emtricitabine,and tenofovir in plasma

Danuravir, ritonavir, emtricitabine, and tenofovir are together prescribed against AIDS as a highly active antiretroviral therapy regimen. Micellar liquid chromatography has been applied to determine these four antiretroviral drugs in plasma. The sample preparation is shortened to the dilution of the sample in a micellar solution, filtration, and injection. Clean‐up steps are avoided, due to the solubilization of plasma matrix in micellar media. The drugs were analyzed in <20 min using a mobile phase of 0.06 M sodium dodecyl sulfate/2.5% 1‐pentanol (pH 7) running under isocratic mode through a C₁₈ column at 1 mL/min at room temperature. Absorbance wavelength detection was set at 214 nm. The method was successfully validated following the ICH Harmonized Tripartite Guideline in terms of selectivity, limit of detection (0.080–0.110 μg/mL), limit of quantification (0.240–0.270 μg/mL), linearity between 0.25 and 25 μg/mL (r² > 0.995), accuracy (89.3–103.2%), precision (<8.2%) and robustness (<7.5%). Real plasma sample from patients taking this therapy were analyzed. This is the first paper showing the simultaneous detection of this four drugs. Therefore, the methodology was proven useful for the routine analysis of these samples in a hospital laboratory for clinical purposes.     

An HPLC‐UV method for determining plasma dimethylacetamide concentrations in patients receiving intravenous busulfan

Dimethylacetamide (DMA) is a solvent used in the preparation of intravenous busulfan, an alkylating agent used in blood or marrow transplantation. DMA may contribute to hepatic toxicity, so it is important to monitor its clearance. The aim of this study was to develop an HPLC‐UV assay for measurement of DMA in human plasma. After precipitation of plasma proteins with acetonitrile followed by dilution (1:4) with water, the extract was injected onto the HPLC and detected at 195 nm. Separation was performed using a Cogent‐HPS 5 μm C₁₈ column (250 × 4.6 mm) preceded by a Brownlee 7 μm RP₁₈, pre‐column (1.5 cm × 3.2 mm). The mobile phase was 25 mm sodium phosphate buffer (pH 3), containing 2.5% (v /v) acetonitrile and 0.0005% (v /v) sodium‐octyl‐sulfonate. Using a flow rate of 1 mL/min, the retention times of DMA and the internal standard (IS), 2‐chloroacetamide, were 9.5 and 3.5 min, respectively. Peak area ratio (DMA:IS) was a linear function of concentration from 1 to 1000 μg/mL. There was excellent intraday precision (<5% for 5–700 μg/mL DMA), accuracy (<3% deviation from the true concentration) and recovery (74–98%). The limits of detection and quantification were 1 and 5 μg/mL, respectively. In eight children who received intravenous busulfan, DMA concentrations ranged from 110 to 438 μg/mL.     

Rapid and Simple Technique for the Quantitation of Polyamines in Biological Samples

Abstract

A rapid and simple technique has been developed to quantify putrescine, spermidine, and spermine in biological tissue. The method, based upon several published procedures, involves protein precipitation with perchloric acid followed by dansylation with 5-dimethylamino-1-naphthalenesulfonyl chloride (dansyl chloride). After extraction on a Waters C₁₈ Sep-Pak cartridge, the samples are analyzed by high pressure liquid chromotography using a step solvent change and a 3μ C₁₈ reverse phase column. The chromotographic conditions allowed complete analysis of the three polyamines within 10 min with a total run time of 13 min (sample injection and re-equilibrium of column). Standard curves were linear up to 1 μg polyamine and the coefficient of variation for the assay ranged from 4% at l μg polyamine per sample to 11% at 50 ng polyamine per sample. The assay is therefore both rapid and simple. Moreover, unlike other available methods, the present technique does not require duel pumps, ion pairing agents, solvent extraction or a gradient control system. The concentrations of putrescine, spermidine and spermine in rat lung, liver and kidney are reported.     

High-Performance Liquid Chromatographic Determination of Acetazolamide in Human Plasma

Abstract

A simple, rapid and specific HPLC method has been developed to determine acetazolamide concentrations in human plasma. The assay procedure requires only 250 μl of sample with direct injection of the organic supernatant after protein precipitation with acetonitrile. Chlorothiazide was used as an internal standard. A reversed-phase C₁₈ μBondapak column was employed for the chromatographic separation. The eluent was monitored at 265 nm using a UV variable wavelength detector. The retention times for acetazolamide (ACZ) and chlorothiazide (CTZ) were 6 and 8 min respectively. A linear relationship (r).995) was obtained over the 1-20 μg/ml concentration range. The limit of sensitivity for ACZ was 0.5 μg/ml, with greater than 85% recovery of ACZ and internal standard. The method was applied to human plasma samples obtained after administration of a 250 mg acetazolamide tablet.     

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.     

High‐performance liquid chromatography–tandem mass spectrometry for simultaneous determination of raltegravir,dolutegravir and elvitegravir concentrations in human plasma and cerebrospinal fluid samples

A simple sample treatment procedure and sensitive liquid chromatography–tandem mass spectrometry method were developed for the simultaneous quantification of the concentrations of human immunodeficiency virus‐1 integrase strand transfer inhibitors – raltegravir, dolutegravir and elvitegravir – in human plasma and cerebrospinal fluid (CSF). Plasma and CSF samples (20 μL each) were deproteinized with acetonitrile. Raltegravir‐d₃ was used as the internal standard. Chromatographic separation was achieved on an XBridge C₁₈ column (50 × 2.1 mm i.d., particle size 3.5 μm) using acetonitrile–water (7:3, v/v) containing 0.1% formic acid as the mobile phase at a flow rate of 0.2 mL/min. The run time was 5 min. Calibration curves for all three drugs were linear in the range 5–1500 ng/mL for plasma and 1–200 ng/mL for CSF. The intra‐ and inter‐day precision and accuracy of all three drugs in plasma were coefficient of variation (CV) <12.9% and 100.0 ± 12.2%, respectively, while those in CSF were CV <12.3% and 100.0 ± 7.9%, respectively. Successful validation under the same LC–MS/MS conditions for both plasma and CSF indicates this analytical method is useful for monitoring the levels of these integrase strand transfer inhibitors in the management of treatment of HIV‐1 carriers.     

Liquid Chromatographic Determination of 4-Amino-N-(2,6-dimethylphenyl)-benzamide in Rat Serum and Urine

Abstract

The compound 4-amino-N-(2,6-dimethylphenyl)-benzamide has shown potential as a new anticonvulsant. A method for the liquid chromatographic determination of serum and urine concentrations of the compound and its N-acetylated metabolite was developed for pharmacokinetic studies. Quantitation was achieved via UV detection at 275 nm following isocratic reversed phase (C₁₈) separation using a ternary solvent system of water:acetonitrile:acetic acid (60:39:1) at a flow rate of 1.5 mL/min. The compounds were isolated from a 50 μL sample of serum using solid phase extraction with prior protein precipitation. The compounds and internal standard were eluted from the extraction column with acetonitrile. Isolation from urine was achieved similarly with the exclusion of protein precipitation. The assay procedure is useful for the determination of concentrations of parent compound from 0.68 to 204.6 μg/mL.     

HPLC Determination of Valproic Acid in Human Serum Using Ultraviolet Detection

Abstract

A sensitive HPLC method with minimal sample preparation and good reproducibility for the determination of valproic acid in serum is described. Serum samples were precipitated using acetonitrile containing diazepam as the internal standard. Chromatography was performed on a Hewlett Packard model 1090 equipped with an octadecylsilane column and a Beckman model 163 variable wavelength detector. The drug and internal standard were eluted isocratically using a mobile phase consisting of 0.01M sodium phosphate monobasic solution, pH 2.3 and acetonitrile (63:37 v/v) followed by a gradient to flush the column before the next sample injection. The flow rate was 2.5 mL/min, the injection volume was 25 μL and the effluent was monitored at 210 nm. The serum standard curve was linear from 2.5-200.0 μg/mL with a correlation coefficient of 0.9994. Day-to-day precision for quality control samples (10.0, 25.0, 75.0 μg/mL serum) ranged from 5.6-9.6% CV. Possible interferences from other drugs which might be administered concurrently were studied. The method has been applied to the analysis of human serum samples.     

Simultaneous determination of peroxydisulfate and conventional inorganic anions by ion chromatography with the column‐switching technique

The application of ion chromatography with the column‐switching technique for the simultaneous analysis of peroxydisulfate and conventional inorganic anions in a single run is described. With this method, conventional inorganic anions were separated by consecutive elution through both the guard column and separation column, but peroxydisulfate that only passed through the guard column had a good peak shape and short retention time. A series of standard solutions consisting of target anions of various concentrations from 0.01 to 75 mg/L were analyzed, with a correlation coefficient (r) ≥ 0.9990. The limits of detection were in the range of 0.49–9.84 μg/L based on the S/N of 3 and a 25 μL injection volume. RSDs for retention time, peak area, and peak height were all <1.77%. A spiking study was performed with satisfactory recoveries between 97.6 and 103.4% for all anions. The quantitative determination of peroxydisulfate and conventional inorganic anions in surface waters was accomplished within 18 min by this column‐switching technique.     

Simultaneous determination of trace level bromate and chlorinated haloacetic acids in bottled drinking water by ion chromatography

A convenient and sensitive method for the simultaneous determination of trace level of bromate and chlorinated haloacetic acids in bottled drinking water with ion chromatography is presented. With a high capacity anion-exchange column and 11.5 mmol/l Na₂CO₃ eluent, all the 16 analytes could be separated in one injection within 31 min. By employing a microwave based evaporation technique, the bottled drinking water sample could be concentrated tenfold in 10 min. The recoveries of the compounds ranged from 90.6 to 107.2%. With a 500 μl large volume injection and high performance anion Atlas electrolytic suppressor, the detection limits were 0.06, 0.08, 0.06, 0.14 and 0.85 μg/l for BrO₃⁻, ClO₃⁻, monoacetic acid, dichloroacetic acid and trichloroacetic acid, respectively.     

dual stage preconcentration system for flame atomic absorption spectrometry using flow injection on-line ion-exchange followed by solvent extraction

A dual stage preconcentration system based on flow injection on-line ion-exchange and solvent-extraction has been developed for flame atomic absorption spectrometry. Lead is taken as a model trace element. A column packed with Amberlite IRC-718 cation exchanger is incorporated into the FI manifold. The analyte is retained on the column by time-based sample loading and eluted by 1 mol/L HNO₃. The eluate is subsequently merged with potassium iodide and tetrabutylammonium bromide (TBABr), and isobutyl methyl ketone (IBMK). Lead is extracted on-line into IBMK as the ion-pair formed between the iodoplumbate anion and tetrabutylammonium cation. The organic phase is separated from the aqueous phase by a gravity phase separator. 50 μL of concentrate is introduced into the nebulizer-burner system of the spectrometer. An enhancement factor of 550 is achieved with a 30 mL sample consumption at a sampling frequency of 30/h. The precision (relative standard deviation) is 2.4% at 10 μg/L level and the detection limit is 0.3 μg/L (3 σ). The method was successfully applied to the determination of lead in water samples.     

高效液相色谱法快速同时检测全血中两种免疫抑制剂

环孢素A和西罗莫司是许多器官移植手术中广泛使用的免疫抑制剂,且一起使用时会产生协同效应,但这两种免疫抑制剂的治疗窗口都非常窄,仅在特定的血药浓度范围内有预期的治疗效果。因此,快速同时检测全血中这两种免疫抑制剂的浓度,可为患者器官移植手术后的给药方案提供有价值的信息。该工作首先考察了环孢素A和西罗莫司在生物液相色谱柱和传统液相色谱柱上的色谱行为,然后基于生物液相色谱柱,建立了可快速分离和检测全血中环孢素A和西罗莫司的高效液相色谱分析方法。全血样品经样品前处理后进样分析,采用ZORBAX 300SB C8柱（250 mm×4.6 mm, 5.0 μm）进行分离,以乙腈-水（70∶30, v/v）为流动相进行等度洗脱,柱温为60 ℃,流速为1.0 mL/min,检测波长为205 nm和278 nm,进样量为20 μL。结果表明,环孢素A和西罗莫司在6 min内可实现较好的分离;环孢素A和西罗莫司在各自的浓度范围内具有良好的线性关系（r>0.997）,检出限（S/N=3）分别为10 ng/mL和1 ng/mL,定量限（S/N=10）分别为30 ng/mL和2 ng/mL, 3个水平的平均加标回收率分别为83.5%~89.7%和95.8%~97.8%,相对标准偏差（RSD）分别为3.2%~9.0%和3.4%~6.7%（n=5）。该方法操作简便,流动相简单,分析时间短,线性范围宽,灵敏度高,可用于全血中环孢素A和西罗莫司的含量检测。     

Development and validation of a bioanalytical method by LC‐MS/MS for the quantification of the LAFIS 10 – an antimalarial candidate – and its pharmacokinetics first evaluation

A rapid and highly sensitive method by LC‐MS/MS was developed and validated for the quantification of an antimalarial candidate (LAFIS10) in rat plasma using dexamethasone as internal standard (IS). The chromatographic separation was performed with a Poroshell 120 EC‐C₁₈ column. The mobile phase consisted of water (A) and acetonitrile (B), both containing 10 m m of ammonium formate and 0.1% formic acid, delivered in the form of elution gradient. The LAFIS10 was monitored using an electrospray ionization interface operating in the positive mode in multiple reaction monitoring mode, monitoring the transitions 681.47 → 538.2 for LAFIS10 and 393.20 → 355.30 for the IS. The flow rate was 500 μL/min. The column temperature was kept at 40 °C and the injection volume was 2 μL. The lower limit of quantification was of 10 ng/mL and linearity between 10 and 1000 ng/mL was observed, with an R² > 0.99. The accuracy of the method was >90%. The relative standard deviations intra‐ and interday were <8.80 and <6.37%, respectively. The method showed sensitivity, linearity, precision, accuracy and selectivity required to quantify LAFIS 10 in preclinical pharmacokinetic studies according to criteria established by the US Food and Drug Administration and European Medicines Agency. Copyright © 2014 John Wiley & Sons, Ltd.     

Simple methodology for the therapeutic drug monitoring of the tyrosine kinase inhibitors dasatinib and imatinib

A simple HPLC method has been developed to measure imatinib and N‐desmethylimatinib (norimatinib) in plasma or serum at concentrations attained during therapy. Adaptation of this method to LC‐MS/MS also allows dasatinib assay. A small sample volume (100 μL HPLC‐UV, 50 μL LC‐MS/MS) is required and analysis time is <5 min in each case. Detection was by UV (270 nm) or selective reaction monitoring (two transitions per analyte) tandem mass spectrometry. Assay calibration was linear (0.05–10 mg/L imatinib, 0.01–2.0 mg/L norimatinib and 1–200 µg/L dasatinib), with acceptable accuracy (86–114%) and precision (<14% RSD) for both methods. A comparison between whole blood and plasma confirmed that plasma is the preferred sample for imatinib and norimatinib assay. For dasatinib, although whole blood concentrations were slightly higher, plasma is still the preferred sample. Despite considerable variation in the (median, range) plasma imatinib and norimatinib concentrations in patient samples [1.66 (0.02–4.96) and 0.32 (0.01–0.99) mg/L, respectively, N = 104], plasma imatinib was >1 mg/L (suggested target for response) in all but one sample from patients achieving complete molecular response. As to dasatinib, the median (range) plasma dasatinib concentration was 13 (2‐143) µg/L (N = 33). More observations are needed to properly assess the potential role of therapeutic drug monitoring in guiding treatment with dasatinib. Copyright © 2012 John Wiley & Sons, Ltd.     

Preconcentration and Spectrophotometric Determination of Chromium (VI) and Total Chromium in Drinking Water by the Sorption of Chromium Diphenylcarbazone with Surfactant Coated Alumina

Abstract

A simple and inexpensive method for determining chromium (VI) in drinking water by spectrophotometry after preconcentration with sodium dodecyl sulphate (SDS) coated alumina column is described. Chromium(VI) is reacted with diphenylcarbazide (DPC) and the Cr-DPC complex is quantitatively adsorbed onto a SDS coated alumina column from 800 ml of sample solution. The complex is then eluted with a 8 ml mixture of methanol, acetone and hydrochloric acid and determined by spectrophotometry. Total chromium can be determined after oxidation of chromium (III) to chromium (VI) by KMnO₄. The relative standard deviation (10 replicate analyses) at the 10 μg l^?1 of chromium (VI) and 10 μg l^?1 of total chromium were 3.5% and 3.4% and corresponding limits of detection (based on 3 σ) were 0.040 μg l^?1 and 0.033 μg l^?1, respectively.     

Vortex‐ and CO2‐gas‐assisted liquid–liquid microextraction with salt addition for the high‐performance liquid chromatographic determination of furanic compounds in concentrated juices and dried fruits

A novel microextraction method based on vortex‐ and CO₂‐assisted liquid–liquid microextraction with salt addition for the isolation of furanic compounds (5‐hydroxymethyl‐2‐furaldehyde, 5‐methyl‐2‐furaldehyde, 2‐furaldehyde, 3‐furaldehyde, 2‐furoic and 3‐furoic acids) was developed. Purging the sample with CO₂ was applied after vortexing to enhance the phase separation and mass transfer of the analytes. The optimum extraction conditions were: extraction solvent (volume), propyl acetate (125 μL); sample pH, 2.4; vortexing time, 45 s; salt concentration, 25% w/v and purging time, 5 min. The analytes were separated using an ODS Hypersil C₁₈ column (250×4.6 mm i.d, 5 μm) under gradient flow. The proposed method showed good linearities (r² >0.999), low detection limits (0.08–1.9 μg/L) and good recoveries (80.7–122%). The validated method was successfully applied for the determination of the furanic compounds in concentrated juice (mango, date, orange, pomegranate, roselle, mangosteen and soursop) and dried fruit (prune, date and apricot paste) samples.