Measurement of bumetanide in plasma and urine by high-performance liquid chromatography and application to bumetanide disposition.

A high-performance liquid chromatographic method for the measurement of bumetanide in plasma and urine is described. Following precipitation of proteins with acetonitrile, bumetanide was extracted from plasma or urine on a 1-ml bonded-phase C18 column and eluted with acetonitrile. Piretanide dissolved in methanol was used as the internal standard. A C18 Radial Pak column and fluorescence detection (excitation wavelength 228 nm; emission wavelength 418 nm) were used. The mobile phase consisted of methanol-water-glacial acetic acid (66:34:1, v/v) delivered isocratically at a flow-rate of 1.2 ml/min. The lower limit of detection for this method was 5 ng/ml using 0.2 ml of plasma or urine. Nafcillin, but not other semi-synthetic penicillins, was the only commonly used drug that interfered with this assay. No interference from endogenous compounds was detected. For plasma, the inter-assay coefficients of variation of the method were 7.6 and 4.4% for samples containing 10 and 250 ng/ml bumetanide, respectively. The inter-assay coefficients of variation for urine samples containing 10 and 2000 ng/ml were 8.1 and 5.7%, respectively. The calibration curve was linear over the range 5-2000 ng/ml.     

Quantitative analysis of retinoids in biological fluids by high-performance liquid chromatography using column switching. II. Simultaneous determination of etretinate, acitretin and 13-cis-acitretin in plasma

An automated gradient high-performance liquid chromatographic method for the determination of etretinate, acitretin and 13-cis-acitretin in plasma was developed, using a column-switching technique. After protein precipitation with ethanol, 0.5 ml of the supernatant was injected onto a precolumn (17 mm x 4.6 mm I.D.), filled with 37-53 microns C18 Corasil. Polar plasma components were washed out using 1% ammonium acetate and 1% acetic acid-acetonitrile (8:2, v/v); the retained retinoids were then transferred to the analytical column (125 mm x 4 mm I.D., filled with 5-microns ODS material) in the backflush mode, separated by gradient elution and detected at 360 nm by UV detection. The limit of quantification was 2 ng/ml and the inter-assay precision in the concentration range 20-1000 ng/ml was between 0.9 and 4.0% for all three compounds. To optimize the recovery for etretinate (greater than 60%), protein was precipitated from plasma with ethanol before injection, instead of direct injection of plasma samples, and a mobile phase containing 20% acetonitrile, instead of pure water or buffer, was used.     

Quantitative analysis of diclazuril in animal plasma by liquid chromatography/electrospray ionization mass spectrometry

A novel, sensitive and specific method for the quantitative determination of diclazuril in animal plasma using liquid chromatography combined with electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) with negative ion detection is presented. Extraction of the samples was performed with a rapid deproteinization step using acetonitrile. Chromatography of diclazuril and the internal standard was achieved on a Nucleosil ODS 5-microm column, using a gradient elution with 0.01 M ammonium acetate and acetonitrile. To obtain the highest sensitivity and specificity possible, the mass spectrometer was operated in the multiple reaction monitoring (MRM) mode. The method was validated according to the requirements defined by the European Community. Calibration curves using plasma fortified between 1-100 ng/mL and 100-2000 ng/mL showed good linear correlation (r >or= 0.9991, goodness-of-fit coefficient 相似文献   

Simultaneous determination of antidepressants by non-aqueous capillary electrophoresis-time of flight mass spectrometry

Simultaneous determination of 20 antidepressants in plasma samples was carried out by non-aqueous capillary electrophoresis with time of flight mass spectrometry via electrospray ionization, where a mixture of 60 mM ammonium acetate and 1M acetic acid in acetonitrile, and water, as well as methanol (100:1:0.5, v/v/v) was selected as the background electrolyte. By using time of flight mass spectrometry, accurate mass information was obtained and the background noise was dramatically decreased, thus causing a great improvement in qualitative ability. As for the plasma sample, solid phase extraction with Oasis HLB was used. The limits of detection and quantification were in the range of 0.5-1 and 1-5 ng/ml, respectively. The sensitivity of the present method was found better, i.e. approximately 10-60 folds compared to that using photo diode array detectors because the analyte peak could be clearly distinguished from the background derived from the plasma. The present method was found very useful and practical as regards to routine analysis of plasma samples.     

Bioanalysis of diclofenac as its fluorescent carbazole acetic acid derivative by a post-column photoderivatization high-performance liquid chromatographic method

A sensitive and selective bioanalytical liquid chromatographic method for diclofenac is described. The drug was detected as a flourescent derivative, which was demonstrated by 1H NMR and mass spectrometric studies to be carbazole acetic acid. Diclofenac was derivatized by UV irradiation of the substance performed as a post-column photoreaction. The reactor was a PTFE capillary wound around a 254-nm UV lamp. Diclofenac was isolated from the plasma samples by precipitation of the proteins with acetonitrile. A 50-microliters volume of the supernatant was injected onto a Nucleosil C18 column. The mobile phase was 32% acetonitrile in pH 6.6 buffer. Carbazole acetic acid was detected by a fluorescence detector using an excitation wavelength of 288 nm and an emission wavelength of 360 nm. The recovery was 92%, the standard curve was linear in the range 10-5500 ng diclofenac per ml plasma, and the relative standard deviation at 10 and 5000 ng of diclofenac per ml plasma was 9.0% and 3.3%, respectively. The limit of detection was 6 ng/ml at an injection volume of 50 microliters. Chromatograms of human and rat plasma containing diclofenac are shown.     

Sensitive determination of piritramide in human plasma by gas chromatography.

A selective and sensitive method for the determination of piritramide in human plasma is described. A 1-ml aliquot of plasma was extracted with 10 ml of hexane-isoamyl alcohol (99.5:0.5, v/v) (extraction efficiency 86%) after addition of 50 microliters of 2 M ammonia and 20 microliters of aqueous strychnine solution (100 ng per 10 microliters) as internal standard. Gas chromatography was performed with J&W DB-1, 30 m x 0.53 mm I.D. separation column, film thickness 1.5 microns, using an nitrogen-phosphorus-sensitive detector. The assay was linear in the concentration range 3.75-2250 ng/ml (r = 0.999), with a lower limit of detection of 1-2 ng/ml. The precision was determined using spiked plasma samples (10 and 50 ng/ml), with coefficients of variation of 3.5 and 3.1% (intra-day; n = 5) and 4.6 and 4.1% (inter-day; n = 4). In the range 3.75-150 ng/ml, the accuracy of the assay was 3.36%. The method was used for the determination of piritramide plasma concentrations in patients receiving intra- or post-operative analgesia.     

High-performance liquid chromatographic analysis of the anticancer drug oxantrazole in rat whole blood and tissues.

A reversed-phase high-performance liquid chromatographic (HPLC) assay was developed for the antitumor anthrapyrazole analogue, oxantrazole (OX), in rat whole blood and tissues. Blood samples were mixed with equal volumes of a 25% (w/v) aqueous solution of L-ascorbic acid, whereas tissue samples were homogenized with 1.5-3 volumes of an L-ascorbic acid-methanol-water (1:10:1, w/v/v) mixture to prevent oxidative degradation of OX. Samples were then treated with 60% (v/v) perchloric acid (25-30 microliters/ml of stabilized sample) to precipitate proteins, and centrifuged, with the resultant supernatants analyzed on HPLC utilizing a C8 column. The mobile phase for blood and urine samples consisted of 8% (v/v) glacial acetic acid, 13% (v/v) acetonitrile, 79% (v/v) water, 0.16% (w/v) sodium acetate, and 0.05% (w/v) L-ascorbic acid (final pH 2.7), and was pumped at 1.8 ml/min. Tissue samples were eluted at 2 ml/min with a mobile phase consisting of 8% (v/v) glacial acetic acid, 12% (v/v) acetonitrile, 80% (v/v) water, 0.16% (w/v) sodium acetate, and 0.0;5% (w/v) L-ascorbic acid. OX and internal standard were detected at 514 nm and had retention times of 2.3 and 3.1 min, respectively. The limit of quantitation of OX was 25-50 ng/g. Recovery of OX from biological samples ranged from 50 +/- 0.9% in spleen to 102.8 +/- 1.8% in RG-2 glioma. The analytical method was applied to a pharmacokinetic study in rats.     

Development and validation of a liquid chromatographic/electrospray ionization mass spectrometric method for the determination of benazepril, benazeprilat and hydrochlorothiazide in human plasma

A new method was developed and fully validated for the quantitation of benazepril, benazeprilat and hydrochlorothiazide in human plasma. Sample pretreatment was achieved by solid-phase extraction (SPE) using Oasis HLB cartridges. The extracts were analysed by high-performance liquid chromatography (HPLC) coupled to a single-quadrupole mass spectrometer (MS) with an electrospray ionization interface. The MS system was operated in selected ion monitoring (SIM) modes. HPLC was performed isocratically on a reversed-phase porous graphitized carbon (PGC) analytical column (2.1 x 125.0 mm i.d., particle size 5 microm). The mobile phase consisted of 55% acetonitrile in water containing 0.3% v/v formic acid and pumped at a flow rate of 0.15 ml min(-1). Chlorthalidone was used as the internal standard (IS) for quantitation. The assay was linear over a concentration range of 5.0-500 ng ml(-1) for all the compounds analysed, with a limit of quantitation of 5 ng ml(-1) for all the compounds. Quality control (QC) samples (5, 10, 100 and 500 ng ml(-1)) in five replicates from three different runs of analyses demonstrated intra-assay precision (coefficient of variation (CV) < or =14.6%), inter-assay precision (CV < or = 5.6%) and overall accuracy (relative error less than -8.0%). The method can be used to quantify benazepril, benazeprilat and hydrochlorothiazide in human plasma, covering a variety of pharmacokinetic or bioequivalence studies.     

Enantioanalysis of bisoprolol in human plasma with a macrocyclic antibiotic HPLC chiral column using fluorescence detection and solid phase extraction

A sensitive, enantioselective, high-performance liquid chromatographic (HPLC) method was developed and validated to determine S-(-)- and R-(+)-bisoprolol in human plasma. Baseline resolution was achieved using the 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 : 0.02 : 0.025, v/v/v) at a flow rate of 1.5 ml/min and fluorescence detection set at 275 nm for excitation and 305 nm for emission. All analyses with S-(-)-atenolol as the internal standard were conducted at ambient temperature. The assay involved the use of a solid-phase extraction procedure for human plasma samples prior to HPLC analysis. The C18 cartridge gave good recovery rates for both enantiomers without any interference. The method was validated over the range of 20-200 ng/ml for each enantiomer concentration. Recovery rates for S-(-)- and R-(+)-bisoprolol enantiomers were in the range of 95-102%. The method proved to be precise (within-run precision expressed as % RSD ranged from 1.0-6.2% and between-run precision ranged from 0.9-6.7%) and accurate (within-run accuracies expressed as percentage error ranged from 0.2-4.8% and between-run accuracies ranged from 0.3-1.7%). The limit of quantitation and limit of detection for each enantiomer in human plasma were 20 and 5 ng/ml, respectively.     

Quantitative analysis of ES-285, an investigational marine anticancer drug,in human,mouse, rat,and dog plasma using coupled liquid chromatography and tandem mass spectrometry

A method was developed for the quantitative analysis of the novel anticancer agent ES-285 (spisulosine; free base) in human, mouse, rat, and dog plasma using high-performance liquid chromatography/electrospray ionization tandem mass spectrometry in order to support pre-clinical and clinical studies with the drug. Sample preparation was carried out by protein precipitation with acetonitrile, containing isotopically labeled (d(3)) ES-285 as internal standard. Aliquots of 10 micro l of the supernatant were injected directly on to an Inertsil ODS-3 column (50 x 2.0 mm i.d., 5 micro m). Elution was carried out using methanol-10 mM ammonium formate (pH 4) in water (80 : 20, v/v) pumped at a flow-rate of 0.2 ml min(-1) with a run time of 8 min. Multiple reaction monitoring chromatograms obtained on an API365 triple-quadrupole mass spectrometer were used for quantification. The lower limit of quantitation (LLOQ) was 10 ng ml(-1) in human, mouse, rat, and dog plasma and the linear dynamic range extended to 500 ng ml(-1). A full validation of the method was performed in human plasma, and partial validations were performed in mouse, rat and dog plasma. Accuracies and precisions were <20% at the LLOQ concentration and <15% for all other concentrations in all matrices. ES-285 was stable during all steps of the assay. Thus far this method has been used successfully to analyze over 500 samples in pre-clinical trials, and will be implemented in the planned clinical phase I studies.     

改良的QuEChERS结合高效液相色谱-串联质谱同时测定水产品中7种阿维菌素类药物残留

建立了改良的QuEChERS结合高效液相色谱-串联质谱(HPLC-MS/MS)同时测定水产品中7种阿维菌素类药物(阿维菌素、伊维菌素、多拉菌素、塞拉菌素、乙酰氨基阿维菌素、莫西菌素和埃玛菌素)的分析方法。样品经0.2%(v/v)氨化乙腈提取,3 g无水硫酸镁和2 g无水硫酸钠除水剂和沉淀蛋白质,100 mg十八烷基硅烷(C18)和500 mg无水硫酸镁净化。以0.1%(v/v)甲酸乙腈(含5 mmol/L乙酸铵)-0.1%(v/v)甲酸水溶液(含5 mmol/L乙酸铵)为流动相,采用Varian Pursuit ULTRA C8色谱柱(100 mm×2.0 mm,2.8μm)进行分离。在加热电喷雾离子(HESI)源、正离子模式下采用多反应监测模式检测,基质匹配标准曲线外标法定量。阿维菌素、伊维菌素、多拉菌素、塞拉菌素、乙酰氨基阿维菌素和莫西菌素在2~200μg/L范围内、埃玛菌素在0.2~20μg/L范围内呈线性相关,相关系数(r)均≥0.997 2,水产品中阿维菌素类药物的加标回收率为71.6%~112.8%,相对标准偏差(RSD)为4.7%~13.1%,不同水产品的基质效应均小于15%。阿维菌素、伊维菌素、多拉菌素、塞拉菌素、乙酰氨基阿维菌素和莫西菌素的定量限均为5μg/kg,埃玛菌素的定量限为0.25μg/kg。该法操作简便,重复性好,适用于水产品中7种阿维菌素类药物残留量的同时测定。     

Quantitative determination of clenbuterol enantiomers in human plasma by high-performance liquid chromatography using the macrocyclic antibiotic chiral stationary phase teicoplanin

We report a method for the high-performance liquid chromatographic (HPLC) chiral separation of racemic clenbuterol in human plasma. Human plasma was spiked with stock solutions of clenbuterol hydrochloride and practolol as the internal standard. Following a liquid-liquid extraction procedure with 10% (+/-)-2-butanol/isopropyl ether under alkaline conditions, the dried samples were reconstituted in methanol and chromatographed using a macrocyclic antibiotic chiral stationary phase (CSP) known as Chirobiotic T(trade mark) (teicoplanin). The mobile phase composition was methanol:acetonitrile (70:30, v/v), containing 0.3% (v/v) acetic acid and 0.2% (v/v) triethylamine. The resulting chromatogram achieved baseline separation for the clenbuterol enantiomers. Calibration curves (peak area ratio vs plasma concentration, n = 10) were constructed for the (-)-R-and (+)-S-clenbuterol enantiomers with a plasma concentration range of 0. 25-10 microM. The correlation coefficient (r) range was 0.99988-0. 99999 (mean = 0.99999). The lowest concentration measured was 0.25 microM. Inter- and intra-assay variation was determined for the lowest, medium and highest plasma concentration (0.25, 2 and 10 microM) by calculating the analytical recoveries with a range of 96-104%. The percentage recoveries for the clenbuterol enantiomers were 88.4-102% over the concentration range used. Detailed methodology is presented.     

A sensitive and rapid liquid chromatography tandem mass spectrometry method for quantitative determination of 7-ethyl-10-hydroxycamptothecin (SN-38) in human plasma containing liposome-based SN-38 (LE-SN38)

7-Ethyl-10-hydroxycamptothecin (SN-38) is an active metabolite of Irinotecan (CPT-11), an anticancer pro-drug. To support clinical pharmacokinetic studies for liposome based formulation of SN-38 (LE-SN38) in cancer patients, a rapid, simple and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the quantification of total SN-38 in human plasma. Sample preparation was carried out by one-step protein precipitation using cold acetonitrile with 0.5% acetic acid (v/v). Camptothecin was used as an internal standard (IS). Chromatographic separation of SN-38 and IS was achieved using a Synergi Hydro-RP column (C(18), 50 x 2 mm, 4 micro m), with a gradient elution of acetonitrile and 0.1% acetic acid. After ionization in electrospray source (positive ions), the acquisition was performed in the multiple reactions monitoring mode. Quantitation was accomplished using the precursor-->product ion combinations of m/z 393.1-->349.2 for SN-38 and 349.1-->305.1 for IS. The quantification limit of 0.05 ng/mL was achieved by using much lower volume (0.2 mL) of plasma and in the presence of LE-SN38. The method was validated over the concentration range of 0.05-400 ng/mL. Accuracy was within +/-12% of nominal at all concentration levels. Inter-day and intra-day precisions expressed as percentage coefficient of variation (%CVs) for quality control (QC) samples were less than 14 and 5%, respectively.     

Solid-phase extraction with liquid chromatography and ultraviolet detection for the assay of antidepressant drugs in human plasma

A solid-phase extraction (SPE) method for sample clean-up followed by a reversed-phase high-performance liquid chromatography (HPLC) procedure for the assay of five antidepressant drugs (trazodone, doxepin, desipramine, maprotiline and imipramine) is reported. The drugs were recovered from plasma buffered at a suitable pH using C18 Bond-Elut cartridges and mixtures of methanol-aqueous buffer as washing and elution solvents. The recoveries of the drugs using other sorbent materials (C8, C2, cyclohexyl, cyanopropyl and phenyl Bond Elut and copolymer HLB waters cartridges) were also examined. The selectivity of SPE was examined by using spiked plasma samples and the CH cartridge gave rise to the cleanest extracts. Cyclohexyl cartridges were conditioned successively with 2 ml of methanol and 1 ml of acetic acid-sodium acetate buffer (0.1 M, pH 4.0). Plasma sample was buffered at pH 4.0 and then applied to the sorbent. The washing step was performed subsequently with 1.5 ml of acetate buffer (0.1 M, pH 4.0), 100 microl of acetonitrile and 1 ml of methanol-acetate buffer (30:70, v/v). Finally, the analytes were eluted with 0.5 ml of methanol-acetate buffer (70:30, v/v). The extract was evaporated to dryness, reconstituted in mobile phase, and chromatographed on a reversed-phase C18 column with ultraviolet detection at 215 nm. The recoveries of trazodone, doxepin, desipramine, maprotiline and imipramine from spiked plasma samples using the CH cartridge were 58 2, 84 3, 83 3, 83 3 and 82 2%, respectively. The within-day and between-day repeatabilities were lower than 6% and 9%, respectively. The linearity of calibrations for the five antidepressants was between 0.005 and 2 microg/ml. The limits of detection were 1 ng/ml for trazodone, doxepin and desipramine and 2 ng/ml for maprotiline and imipramine.     

Sensitive Determination of Piritramide in Human Plasma by High-Performance Liquid Chromatography

Abstract

A selective and sensitive method for the determination of piritramide in human plasma is described. After addition of 50 μl of 2 M ammonia and 20 μl of aqueous promethazine solution (100 ng/10 μ1) as an internal standard, 1 ml of plasma was extracted with 5 ml of toluene (extraction efficiency: 93.9 × 2.6%; mean × S. D.; n = 5). HPLC was performed with a phenyl hypersil NC-04 column, particle size 5 μm, 250 × 4 mm I. D.; mobile phase: 8 parts of acetonitrile and 2 parts of 10 mM potassium phosphate buffer (pH 3. 3). The flow rate was set to 2 ml/min and the column temperature was 22°C. The assay was linear in a concentration range of 3.75 ? 3000 ng/ml (r = 0.999), with a lower limit of detection of 3 ng/ml. The precision was determined using spiked plasma samples (15 ng/ml; 300 ng/ml), with coefficients of variation of 6.1 and 5.9% (intraday; n = 5) and 6.5 and 0.2% (interday; n = 3). In the range of 5.6 ? 1500 ng/ml, the accuracy of the assay was 2.82%. The method was used for the determination of piritramide plasma concentrations in patients receiving intra- or postoperative analgesia.     

Quantitative determination of dihydrostreptomycin in bovine tissues and milk by liquid chromatography-electrospray ionization-tandem mass spectrometry

Dihydrostreptomycin (DHS) is an aminoglycoside antibiotic used in veterinary medicine in combination with benzylpenicillin for the treatment of bacterial infections in cattle, pigs and sheep. A method to determine its residues in edible tissues of cattle, as well as in milk, was developed and validated. Extraction of DHS from the tissues was performed using a liquid extraction with a 10 mM phosphate buffer containing 2% (w/v) trichloroacetic acid, while milk samples were treated with a 50% (w/v) trichloroacetic acid solution, followed by a solid-phase clean-up procedure on a carboxypropyl (CBA) weak cation exchange column. Ion-pair chromatography, using a mixture of 20 mM pentafluoropropionic acid in water and acetonitrile as the mobile phase, was used to retain DHS and the internal standard streptomycin (STR) on a Nucleosil (5 microm) reversed-phase C18 column. The components were detected and quantified by electrospray ionization (ESI) tandem mass spectrometry. The method could be validated according to EC (European Community) requirements with respect to linearity, trueness and precision, the latter evaluated at the maximum residue limit (MRL) - 1000 ng g(-1) for kidney, 500 ng g(-1) for muscle, liver and fat, and 200 ng g(-1) for milk -, at one-half of the MRL and at one and a half times the MRL. A limit of quantification of 10 ng g(-1) and 1 ng ml(-1) was obtained for all tissues and for milk, respectively, which is far below one-half of the MRL as requested, while the limit of detection was in the low ppb range, varying between 1.9 and 4.2 ng g(-1) for the different tissues tested, and being 0.6 ng ml(-1) for milk. The method was used for the monitoring of DHS residues in incurred tissue and milk samples coming from cattle medicated with DHS in combination with benzylpenicillin by intramuscular injection, in order to evaluate withdrawal times.     

Simultaneous Determination of Flunixin,Phenylbutazone, Oxyphenbutazone and γ-Hydroxyphenylbutazone in Equine Plasma by High-Performance Liquid Chromatography: With Application to Pharmacokinetics

Abstract

A high performance liquid chromatographic method was developed for the simultaneous determination of flunixin, phenylbutazone, oxyphenbutazone and γ-hydroxyphenylbutazone in equine plasma. Samples of plasma or sera were deproteinated by addition of acetonitrile containing the internal standard naproxen. The concentration step consisted of taking an aliquot of deproteinated plasma, evaporating under nitrogen to dryness and redissolving in mobile phase. The extracts were chromatographed on a Spherisorb 5 μm ODS column using an isocratic mobile phase of methanol (30% v/v), acetonitrile (20% v/v) and pH 3.0 1% acetate buffer (50% v/v) at a flow rate of 1.2 ml/min using naproxen as the internal standard. The detection limit for flunixin, phenylbutazone, oxyphenbutazone and γ-hydroxyphenylbutazone was 50 ng/ml.

The developed chromatographic method was applied to the determination of equine nonsteroidal anti-inflammatory treatment. Plasma samples from clinically treated horses administered flunixin and phenylbutazone simultaneously are reported. Effect of different anticoagulants used in sampling is reported.     

Determination of RSD921 in human plasma by high-performance liquid chromatography-tandem mass spectrometry using tri-deuterated RSD921 as internal standard: application to a phase I clinical trial.

A fast, sensitive and specific method is presented for the quantification of RSD921 in human plasma by liquid chromatography coupled with tandem mass spectrometry using tri-deuterated RSD921 (3d-RSD921) as an internal standard. A single-step liquid/liquid extraction was performed with diethyl ether/hexane (80 : 20, v/v) using 0.5 ml of plasma. The plasma calibration curves were linear from 0.1 to 20 ng ml(-1) (r > 0.999). Between-run precision, based on the percent relative deviation for replicate (n = 40) quality controls, was < or =7.27% (0.5 ng ml(-1)), < or =7.39% (5.0 ng ml(-1)), and < or =5.06% (20.0 ng ml(-1)). Between-run accuracies, based on the relative error, were +/-2.59%, +/-1.23% and +/-1.64% respectively. The method was developed to evaluate the pharmacokinetic profile after 15 min of intravenous stepwise-ascending infusion dose of RSD921 in 18 healthy volunteers. A dissociation study of protonated RSD921 and 3d-RSD921 by collision-induced dissociation using in-source fragmentation and tandem mass spectrometry is also presented.     

Development and validation of a UPLC‐MS/MS method for the determination of 7‐hydroxymitragynine,a μ‐opioid agonist,in rat plasma and its application to a pharmacokinetic study

A simple, sensitive and specific ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) method was developed and validated to determine the concentrations of 7‐hydroxymitragynine in rat plasma. Following a single‐step liquid–liquid extraction of plasma samples using chloroform, 7‐hydroxymitragynine and the internal standard (tryptoline) were separated on an Acquity UPLC^TM BEH C₁₈ (1.7 µm, 2.1 × 50 mm) column using an isocratic elution at a flow rate of 0.2 mL/min. The mobile phase consisted of 0.1% acetic acid in water and 0.1% acetic acid in acetonitrile (10:90, v/v). The run time was 2.5 min. The analysis was carried out under the multiple reaction‐monitoring mode using positive electrospray ionization. Protonated ions [M + H]⁺ and their respective product ions were monitored at the following transitions: 415 → 190 for 7‐hydroxymitragynine and 173 → 144 for the internal standard. The calibration curve was linear over the range of 10–4000 ng/mL (r² = 0.999) with a lower limit of quantification of 10 ng/mL. The extraction recoveries ranged from 62.0 to 67.3% at concentrations of 20, 600 and 3200 ng/mL). Intra‐ and inter‐day assay precisions (relative standard deviation) were <15% and the accuracy was within 96.5–104.0%. This validated method was successfully applied to quantify 7‐hydroxymitragynine in rat plasma following intravenous administration. Copyright © 2013 John Wiley & Sons, Ltd.     

High Performance Liquid Chromatographic Determination of Amiodarone in Plasma and Tissues

Abstract

A simple and rapid high-performance liquid chromatographic (HPLC) method for the determination of amiodarone (AD) in plasma and tissues was developed. The method involved deproteinization of plasma or homogenized tissue with acetonitrile containing an internal standard (N-Cetylpyridinium chloride) followed by reversed phase chromatography using μ bondapack C₁₈ column (10μm) with a mobile phase consisting of acetonitrile - methanol - sodium dihydrogen phosphate buffer (70:10:20%, v/v), the pH adjusted to 4.0 and pumped at flow rate of 1.0 ml/min. The column effluent was monitored at 242 nm. A linear relationship was obtained between peak height ratios (drug to internal standard) versus drug levels over the concentration range of 50–750 ng/ml. The detection limit of AD in plasma and tissues by this method was 20 ng/ml.