Quantification of the neuromuscular blocking agent rocuronium and its putative metabolite 17-desacetylrocuronium in heparinized plasma by capillary gas chromatography using a nitrogen sensitive detector

We have developed a sensitive and specific capillary GC (cGC) assay for the quantification of the quarternary aminosteroidal compound rocuronium (roc), a neuromuscular blocking agent, and its putative metabolite 17-desacetylrocuronium (17OH-roc), using 3-desacetylvecuronium (3OH-vec) as an internal standard (I.S.). This novel method has been applied to a pharmacokinetic study with roc, monitoring sixty patients who were classified according to four different body mass index (BMI) groups. The isolation of these drugs from plasma was carried out using a dichloromethane liquid-liquid extraction after ion-pairing of the positively charged ammonium compounds with iodide. To achieve thermal stability, tert.-butyldimethylsilyl-ethers were formed at the 3OH- and 17OH-steroidal positions by reaction with N-methyl-N-(tert.-butyldimethylsilyl)-trifluoroacetamide at 70°C overnight. An automated cGC system fitted with a nitrogen sensitive detector with a specially prepared glass phase bead and a computer controlled data handling system was used to analyze and quantify the compounds, which were separated on a DB1 capillary column with helium as the carrier gas and a temperature program ranging from 120 to 300°C. The method is linear for 50-6400 ng/ml for roc and 80-6400 ng/ml for 17OH-roc. The detection limits were 10 ng/ml for roc and 50 ng/ml for 17OH-roc. The lower limit of quantification was 50 ng/ml for roc and 80 ng/ml for 17OH-roc. Intra-assay coefficients of variation (C.V.s) were 10% and 15% and the inter-assay C.V.s 8-18% and 16-21% for roc and 17OH-roc, respectively.     

Rapid method for the simultaneous measurement of nicotine and cotinine in urine and serum by gas chromatography–mass spectrometry

A simple, sensitive, and rapid gas chromatographic–mass spectrometric method is described for the simultaneous detection and quantitation of nicotine and its metabolite, cotinine, in urine and serum. The analytes and their respective deuterated internal standards were extracted by liquid–liquid extraction coupled to centrifugation and evaporation. The detection limit of the assay was 0.16 ng/ml for both nicotine and cotinine. The limit of quantitation for each analyte was 1.25 ng/ml.     

Simultaneous determination of a novel angiotensin II receptor blocking agent, losartan, and its metabolite in human plasma and urine by high-performance liquid chromatography

A sensitive and selective high-performance liquid chromatographic method for the simultaneous determination of a new angiotensin II receptor blocking agent, losartan (DuP 753, MK-954, I), and its active metabolite, EXP3174 (II), in human plasma or urine is described. The two analytes and internal standard are extracted from plasma and urine at pH 2.5 by liquid—liquid extraction and analyzed on a cyano column with ultraviolet detection at 254 nm. The mobile phase is composed of acetonitrile and phosphate buffer at pH 2.5. The limit of quantification for both compounds in plasma is 5 ng/ml. The limit in urine is 20 and 10 ng/ml for I and II, respectively. The assay described has been successfully applied to samples from pharmacokinetic studies.     

Determination of milnacipran, a serotonin and noradrenaline reuptake inhibitor, in human plasma using liquid chromatography with spectrofluorimetric detection

Milnacipran is an antidepressant drug belonging to the class of serotonin and noradrenaline reuptake inhibitors. A sensitive high performance liquid chromatographic during the development method coupled with a fluorimetric detection was set up, validated and then used routinely of the drug. After liquid-liquid extraction, milnacipran and its internal standard were analyzed by reversed-phase liquid chromatography (LC). The drug was derivatized with fluorescamine for fluorescence detection. The identity of the liquid chromatography peaks was controlled using mass spectrometry. The assay linearity was validated up to 1000 ng/ml. The limit of quantification was set at 5 ng/ml. Precision values (relative standard deviations) were lower than 5.4%, whereas the mean accuracy was higher than 95%. The extraction recoveries were higher than 70% for both milnacipran and the internal standard. In clinics, the LC-fluorescence method was routinely used to investigate the pharmacokinetics of milnacipran in patients and proved to be robust and capable of quantifying milnacipran in plasma for at least 36 h (four- to five-fold the elimination half-life).     

A liquid chromatographic-tandem mass spectrometric method for determination of artesunate and its metabolite dihydroartemisinin in human plasma

A bioanalytical method for the analysis of artesunate and its metabolite dihydroartemisinin in human plasma using high throughput solid-phase extraction in the 96-wellplate format and liquid chromatography coupled to positive tandem mass spectroscopy has been developed and validated. The method was validated according to published FDA guidelines and showed excellent performance. The within-day and between-day precisions expressed as RSD, were lower than 7% at all tested concentrations including the lower limit of quantification. Using 50 microl plasma the calibration range was 1.19-728 ng/ml with a limit of detection at 0.5 ng/ml for artesunate and 1.96-2500 ng/ml with a limit of detection at 0.6 ng/ml for dihydroartemisinin. Using 250 microl of plasma sample the lower limit of quantification was decreased to 0.119 ng/ml for artesunate and 0.196 ng/ml dihydroartemisinin. Validation of over-curve samples in plasma ensured that accurate estimation would be possible with dilution if samples went outside the calibration range. The method was free from matrix effects as demonstrated both graphically and quantitatively.     

Direct gas chromatographic determination of dechloroethylcyclophosphamide following microsomal incubation of cyclophosphamide

A method for the sensitive determination of dechloroethylcyclophosphamide (3-DCl) in microsomal incubation mixtures was developed. 3-DCl, a side-chain oxidation product of cyclophosphamide (CP), was isolated by extraction with acetic acid ethyl ester following solid-phase extraction on C₈ cartridges. Quantification of the metabolite was performed by direct capillary gas chromatography with a nitrogen-phosphorus detector without prior derivatization. The method showed good sensitivity and reproducibility with a detection limit of 1 ng/ml and a limit of quantification of 5 ng/ml. The suitability of the method is shown for the quantification of 3-DCl following incubation of CP with human liver microsomes.     

Reliable and specific high-performance liquid chromatographic method for simultaneous determination of loratadine and its metabolite in human plasma

A high-performance liquid chromatographic (HPLC) method with fluorescence detection has been developed for the simultaneous determination of loratadine (L) and its metabolite, descarboethoxyloratadine (DCL), in human plasma. Following a two-step liquid-liquid extraction with toluene, the analytes were separated using a gradient mobile phase consisting of methanol-acetonitrile-phosphate buffer. The linearity for L and DCL was within the concentration range of 0.5-16 ng/ml. The coefficient of variation of intra- and inter-day assay was <8.3%, with accuracy ranging from 98.3 to 105.7%. The lower limit of quantification was 0.5 ng/ml for both L and DCL. This method has been demonstrated to be reliable, and is an improvement over existing methods due to its capability for determining L and DCL simultaneously in a single chromatographic run.     

Determination of (E)-5-(2-bromovinyl)-2′-deoxyuridine in plasma and urine by capillary electrophoresis

(E)-5-(2-Bromovinyl)-2′-deoxyuridine is an antiviral drug used for treatment of infections with Herpes simplex virus type 1 as well as Varicella zoster virus. Two fast methods for the determination of the drug and its metabolite in plasma and urine by capillary electrophoresis have been developed. The plasma method can be used for measurement of total as well as unbound drug and metabolite. Plasma and urine samples are prepared for measuring by liquid/liquid extraction resulting in a limit of quantification of 40 ng/ml for total and 10 ng/ml for free BVdU in plasma and 170 ng/ml in urine. Inter- as well as intra-day precision were found to be better than 10% and both methods have been used for drug monitoring of patients.     

Selective and sensitive liquid chromatography-tandem mass spectrometry method for the determination of levonorgestrel in human plasma

A selective, sensitive and rapid liquid chromatography-tandem mass spectrometry method for the determination of levonorgestrel in plasma was developed. An Applied Biosystems API 3000 triple quadrupole mass spectrometer set to multiple reaction monitoring (MRM) mode, using atmospheric pressure photospray ionisation (APPI) in the positive mode. Using 17-alpha-methyltestosterone as internal standard (IS), liquid-liquid extraction was followed by reversed phase liquid chromatography using a phenyl-hexyl column and tandem mass spectrometric detection. The mean recovery for levonorgestrel and 17-alpha-methyltestosterone was 99.5 and 62.9%, respectively. The method was validated from 0.265 to 130 ng levonorgestrel/ml plasma with the lower limit of quantification (LLOQ) set at 0.265 ng/ml. This assay method makes use of the increased sensitivity and selectivity of tandem mass spectrometric (MS/MS) detection, allowing for a rapid (extraction and chromatography) and selective method for the determination of levonorgestrel in human plasma. The assay method was used in a pharmacokinetic study to quantify levonorgestrel in human plasma samples generated after administrating a single oral dose of 1.5 mg levonorgestrel to healthy female volunteers for up to five half lives. The total chromatographic runtime of this method was 5.0 min per sample, allowing for analysis of a large number of samples per batch.     

Determination of Org NC 45 (a myoneural blocking agent) in human plasma using high-performance normal-phase liquid chromatography

The assay for the quantification of Org NC 45 in human plasma is described in detail. It comprises ion-pair extraction and normal-phase liquid chromatography in conjunction with UV detection. An analogue, 17β-deacetyl-Org NC 45, is used as standard in the assay procedure. The accuracy and precision of the assay at 400 ng of Org NC 45 per ml of plasma are 0.7% and 2.8%, respectively. The detection limit is approx. 50 ng Org NC 45 per ml of plasma. The assay can be used for the pharmacokinetic evaluation of Org NC 45 in man.     

Determination of plasma levels of spirorenone,a new aldosterone antagonist,and one of its metabolites by high-performance liquid chromatography

A method for the determination of plasma concentrations of spirorenone, a new aldosterone antagonist, and one of its metabolites, chromatographically characterized as 1,2-dihydro-spirorenone, is described. The assay utilizes high-performance liquid chromatography with UV detection. Reproducible results can be obtained with standard deviations of about 5% and the limit of detection is less than 5 ng/ml. Plasma levels of drug and metabolite have been measured after oral doses of 10 and 40 mg, respectively, administered to two male volunteers.     

High-performance liquid chromatographic determination of acrolein as a marker for cyclophosphamide bioactivation in human liver microsomes

A high-performance liquid chromatographic method for the quantification of acrolein following incubation of cyclophosphamide (CP) with human liver microsomes was developed. Based on the formation of the fluorescent derivative 7-hydroxyquinoline by condensation of acrolein with 3-aminophenol quantitation was performed without prior extraction or other sample cleanup procedures. The method showed sufficient sensitivity with a limit of detection of 5 ng/ml and a limit of quantification of 10 ng/ml. The suitability of the method is shown for enzyme kinetic studies.     

Simultaneous quantification of beclomethasone dipropionate and its metabolite, beclomethasone 17-monopropionate in rat and human plasma and different rat tissues by liquid chromatography-positive electrospray ionization tandem mass spectrometry

A sensitive, rapid and selective liquid chromatography-positive electrospray ionization tandem mass spectrometry (LC-(ESI+)-MS-MS) method has been developed and validated for the simultaneous quantification of beclomethasone dipropionate (BDP) and its active metabolite, beclomethasone 17-monopropionate (17-BMP) in rat plasma and different tissues using fluticasone propionate (FP) as the internal standard. The method was validated over a linear range from 0.05 to 5 ng/ml for both analytes. A solid-phase extraction procedure was used for plasma samples and a liquid-liquid extraction procedure for tissues samples (lung, liver and kidney). The between-day and within-day coefficients of variation for all compounds were 相似文献   

Extractionless determination of 6-methoxy-2-naphthylacetic acid, a major metabolite of nabumetone, in human plasma by high-performance liquid chromatography

Following oral administration of the prodrug nabumetone, the major metabolite 6-methoxy-2-naphthylacetic acid (6-MNA) was determined in human plasma. Minimal sample preparation was followed by reversed-phase liquid chromatography and UV detection, affording high sample throughput. The lower limit of quantification (LLOQ) was 70 ng/ml, at a signal-to-noise ratio of 8:1. The assay method displayed good correlation (r=0.997), and can be readily employed in pharmacokinetic and bioequivalence studies.     

Assay of bromhexine in human plasma by capillary gas—liquid chromatography with nitrogen-selective detection and selected ion monitoring

A specific, sensitive method for the determination of bromhexine in human plasma is described. It comprises a selective extraction procedure and a specific determination with capillary gas—liquid chromatography and nitrogen-selective flame ionization detection. The detection limit of the assay is about 0.5 ng/ml. The specificity of the assay was checked by gas chromatography—mass spectrometry. The method is applied to the pharmacokinetics of bromhexine in humans.     

Simple high-performance liquid chromatographic method for the determination of ranitidine in human plasma

A simple high-performance liquid chromatographic method was developed for the determination of ranitidine in human plasma. Prior to analysis, ranitidine and the internal standard (metoprolol) were extracted from alkalinized plasma samples using dichloromethane. The mobile phase was 0.05 M potassium dihydrogenphosphate–acetonitrile (88:12, v/v) adjusted to pH 6.5. Analysis was run at a flow-rate of 1.3 ml/min and at a detection wavelength of 229 nm. The method is sensitive with a detection limit of 1 ng/ml at a signal-to-noise ratio of 3:1, while the quantification limit was set at 15 ng/ml. The calibration curve was linear over a concentration range of 15–2000 ng/ml. Mean recovery value of the extraction procedure was about 90%, while the within-day and between-day coefficients of variation and percent error values of the assay method were all less than 15%.     

Simple and rapid high-performance liquid chromatographic method for determination of celecoxib in plasma using UV detection: application in pharmacokinetic studies

A rapid, sensitive and reproducible HPLC method was developed and validated for the analysis of celecoxib in human plasma. The analysis was carried out on a monolithic silica column using UV detection at 254 nm. The assay enables the measurement of celecoxib for therapeutic drug monitoring with a minimum quantification limit of 10 ng ml(-1). The method involves simple, one-step extraction procedure, and analytical recovery was 100.5 +/- 1.3%. The calibration curve was linear over the concentration range of 10-800 ng ml(-1). The coefficients of variation for inter-day and intra-day assay were found to be less than 8%. We also demonstrate the applicability of this method for pharmacokinetic studies in humans.     

High-performance liquid chromatographic assay with ultraviolet detection for the determination of etoperidone and two active metabolites, 5-(1-hydroxyethyl)etoperidone and 1-(3-chlorophenyl)piperazine, in plasma

A selective and sensitive high-performance liquid chromatographic assay with ultraviolet detection for the determination of the antidepressant drug etoperidone and two active metabolites in plasma is described. The drug, metabolites and internal standard are isolated from plasma using a two-step liquid—liquid extraction procedure. The resulting sample is chromatographed on a C₁₈ column (10 cm × 2.1 mm I.D.) with ultraviolet detection at 254 nm. Standard curves are linear for each compound over the concentration range 2–1000 ng/ml. The accuracy and precision of the assay, expressed as the percentage deviation of measured values from the true value and the relative standard deviation (inter-run), are ≤ 10% at all concentrations except the minimum quantification limit. Using an automated injector and computerized data acquisition, eighty samples can be routinely processed in one day. The assay has been successfully used for the analysis of plasma samples from pharmacokinetic studies in mice, rats, dogs and humans.     

Determination of an arylether antiarrhythmic and its N-dealkyl metabolite in rat plasma and hepatic microsomal incubates using liquid chromatography–tandem mass spectrometry

A method was developed and validated for the quantification of (±)-trans-[2-morpholino-1-(1-naphthaleneethyloxy]cyclohexane monohydrochloride (RSD1070) and its N-dealkyl metabolite in rat plasma and hepatic microsomal incubates. Chromatographic separations were achieved using reversed-phase high-performance liquid chromatography coupled with positive ion electrospray ionization and detection by tandem mass spectrometry. The assay was linear from 2.5 to 100 ng/ml and this range was used for validation. Inter- and intra-assay variability (n=6), extraction recovery, and stability in plasma were assessed. The estimated limit of quantitation was in the range 2.5–3 ng/ml for both analytes in rat plasma. The analytical method was used in a pharmacokinetic study of RSD1070 in rats after a single i.v. bolus of 12 mg/kg.     

Solid-phase extraction-liquid chromatographic method for the determination and pharmacokinetic studies of albiflorin and paeoniflorin in rat serum after oral administration of Si-Wu decoction

A sensitive and rapid high-performance liquid chromatography (HPLC) method with solid-phase extraction (SPE) to simultaneously determine albiflorin and paeoniflorin in rat serum was described. Serum samples were pretreated with solid-phase extraction using Extract-Clean cartridges, and the extracts were analyzed by HPLC on a reversed-phase C(18) column and a mobile phase of acetonitrile-0.03% formic acid (17:83 (v/v)) with ultraviolet detection at 230 nm. Pentoxifylline was used as the internal standard (IS). The linear ranges of the calibration curves were 29-1450 ng/ml for albiflorin and 10-2000 ng/ml for paeoniflorin. The intra- and inter-day precisions (R.S.D.) were 相似文献