Simultaneous determination of luteolin and apigenin in dog plasma by RP-HPLC

A specific and accurate high-performance liquid chromatographic method has been developed and validated for the simultaneous determination of luteolin and apigenin in the plasma of dog. The sample was treated with 6.0% perchloric acid to precipitate the protein. Luteolin and apigenin were extracted with ethyl acetate. The organic layer separated was dried and reconstituted in the mobile phase. The HPLC separation was performed on C18 column and the UV detector was set at 350 nm. The standard curve for luteolin and apigenin in plasma were linear over the range of 38.5-4350 and 16.5-1860 ng/ml, with the correlation coefficients 0.9996 and 0.9999, respectively. The assay recoveries for luteolin and apigenin ranged from 102.7 to 104.5% and 93.8-101.8%, respectively. The intra- and inter-day precisions (R.S.D.) for luteolin and apigenin were all less than 7.9%. The sample was stable within 24 h at 4 degrees C storage, 30 days at -20 degrees C storage, and undergoing four freeze-thaw-assay cycles. The limits of detection (LOD) of luteolin and apigenin were 1.82 and 1.94 ng/ml, while the limits of quantification (LOQ) were 7.84 and 6.29 ng/ml, respectively. The method developed was applied successfully to study pharmacokinetics of the effective composition (luteolin) of Chrysanthemum morifolium extract in dogs after single dose of oral administration.     

Determination of quercetin and kaempferol in human urine after orally administrated tablet of ginkgo biloba extract by HPLC

A sensitive, simple and accurate method was developed for determination of quercetin and kaempferol in human urine by reversed phase high performance liquid chromatography. The urine samples were analyzed on C18 column. Quercetin and kaempferol were analyzed simultaneously with good separation. UV detector was set at 380 nm. There was a linear relationship between chromatographic area of analytes and concentration of analytes over the concentration range 1.638-81.90 and 1.872-93.60 ng/ml for quercetin and kaempferol, respectively. The recovery of the assay was 99.7+/-6.2 and 97.4+/-7.2% for quercetin and kaempferol, respectively. The within-day and between-day coefficients of variation were less than 9.7 and 16.5% (RSD), respectively. The limit of detection was 1.0 ng/ml for quercetin and 1.1 ng/ml for kaempferol. The limit of quantitation was 1.61+/-0.11 ng/ml (n=5) for quercetin and 1.85+/-0.11 ng/ml (n=5) for kaempferol. The method developed has been applied to determine quercetin and kaempferol after orally administrated tablet of Ginkgo biloba extract in human urine.     

A validated solid-phase extraction HPLC method for the simultaneous determination of the citrus flavanone aglycones hesperetin and naringenin in urine

A simple, specific, precise, accurate, and robust HPLC assay for the simultaneous analysis of hesperetin and naringenin in human urine was developed and validated. Urine samples were incubated with beta-glucuronidase/sulphatase and the analytes were isolated by solid-phase extraction using C18 cartridges and separated on a C8 reversed phase column using a mixture of methanol/water/acetic acid (40:58:2, v/v/v) at 45 degrees C. The method was found to be linear in the 50-1200 ng/ml concentration range for both hesperetin and naringenin (r > 0.999). The accuracy of the method was greater than 94.8%, while the intra- and inter-day precision for hesperetin was better than 4.9 and 8.2%, respectively and for naringenin was better than 5.3 and 7.8%, respectively. Recovery for hesperetin, naringenin and internal standard 7-ethoxycoumarin was greater than 70.9%. The method has been applied for the determination of hesperetin and naringenin in urine samples obtained from a male volunteer following a single 300 mg oral dose of each of the corresponding flavanone glycosides hesperidin and naringin. The intra- and inter-day reproducibility through enzyme hydrolysis was less than 3.9% for both total (free + conjugated) hesperetin and naringenin. Stability studies showed urine quality control samples to be stable for both hesperetin and naringenin through three freeze-thaw cycles and at room temperature for 24 h (error < or = 3.6%).     

HPLC method for the determination of fluvoxamine in human plasma and urine for application to pharmacokinetic studies

A simple, specific and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the assay of fluvoxamine in human plasma and urine. The method was based on reaction of fluvoxamine with 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS) forming orange colored product. The fluvoxamine-NQ derivative was separated by isocratic reversed-phase HPLC and detected at 450 nm. The chromatographic conditions were as follows: Phenomenex C(18) (250 mm x 4.6 mm i.d., 5 microm) column, mobile phase consisting of acetonitrile/water (80:20 v/v) at a flow rate of 1 ml/min. Tryptamine was selected as an internal standard. The assay was linear over the concentration range of 5-145 and 2-100 ng/ml for plasma and urine, respectively. The limits of detection (LOD) were 1.4 and 1 ng/ml for plasma and urine estimation at a signal-to-noise (S/N) ratio of 3. The limits of quantification (LOQ) were 5 and 2 ng/ml for plasma and urine, respectively. The extraction recoveries were found to be 96.66+/-0.69 and 96.73+/-2.17% for plasma and urine, respectively. The intra-day and inter-day standard deviations (S.D.) were less than 1. The method indicated good performance in terms of specificity, linearity, detection and quantification limits, precision and accuracy. This assay was demonstrated to be applicable for clinical pharmacokinetic studies.     

Liquid chromatographic assay of moxidectin in human plasma for application to pharmacokinetic studies

A sensitive and selective high-performance liquid chromatography (HPLC) method is presented for the analysis of moxidectin in human plasma. Solid phase extraction using Oasis HLB cartridges is used for sample preparation. The fluorescent derivative is obtained by a dehydrative reaction with trifluoroacetic anhydride and N-methylimidazole. Separation is achieved on a Bondapak C(18) reversed-phase column with a mobile phase composed of tetrahydrafuran-acetonitrile-water (40:40:20, v/v/v). Detection is by fluorescence, with excitation at 365 nm and emission at 475 nm. The retention times of moxidectin and internal standard, ivermectin are approximately 10.7 and 18.6 min, respectively. The assay is linear over the concentration range 0.2-1000 ng/ml for moxidectin in human plasma (r=0.9999, weighted by 1/concentration). Recoveries at concentrations 0.2, 400, 1000 ng/ml are 94, 75, and 71%, respectively. The analysis of quality control (QC) samples for moxidectin (0.2, 400, and 1000 ng/ml) demonstrates excellent precision with relative standard deviations of 11.9, 5.7, and 2.7%, respectively (n=6). The method is accurate with all intra- (n=6) and inter-day (n=18) mean concentrations within (5.0%) from nominal at all QC sample concentrations. Moxidectin was found to be stable after three free-thaw cycles, and with storage at -20 and -80 degrees C for 12 weeks. The method is suitable for pharmacokinetic studies of moxidectin after oral administration to humans.     

Determination of simvastatin-derived HMG-CoA reductase inhibitors in biomatrices using an automated enzyme inhibition assay with radioactivity detection

A robust, automated enzyme inhibition assay method was developed and validated for the determination of HMG-CoA reductase inhibitory activities in plasma and urine samples following simvastatin (SV) administration. The assay was performed on Tecan Genesis 150 and 200 systems equipped with 8-probe and 96-well plates. Plasma samples containing HMG-CoA reductase inhibitors were treated with acetonitrile for protein precipitation before being incubated with HMG-CoA reductase, [14C]-HMG-CoA, and NADPH for a fixed length of time at a fixed temperature. The product, [14C]-mevalonic acid, was lactonized and separated from excess substrate via a small ion exchange resin column, and radioactivity was counted on a scintillation counter. HMG-CoA reductase inhibitors were measured before and after base hydrolysis. The two values obtained for each sample are referred to as 'active' and 'total' HMG-CoA reductase inhibitor concentrations. Simvastatin acid (SVA), the beta-hydroxy acid of SV, was used as a standard to generate a calibration curve of HMG-CoA reductase activity versus SVA concentration (ng/ml). Three calibration ranges, 0.4-20, 2-50, and 50, 100 ng/ml, in human and animal plasma and urine were validated. The assay precision was less than 8.5%, CV in plasma and less than 10.4% in urine. The assay accuracy was 93.6-103.0 and 98.1-103.9% for the 0.4 20 and 2-50 ng/ml calibration ranges, respectively, in human plasma, and was 97.3-105.1, 94.4- 105.2, and 90.2-95.7%, for calibration range 5-100 ng/ml in rat plasma, dog plasma and human urine, respectively.     

Pharmacokinetic study of a new angiotensin-AT1 antagonist by HPLC

Recently an innovative novel class angiotensin-AT(1) antagonist has been developed by Rottapharm. In this study, we present a validated method for detecting CR 3834 in biological matrices using high-performance liquid chromatography (HPLC) with diode array detection. After oral administration (30mg/kg) to Wistar rats, the plasma and urine concentrations of CR 3834 and its potential metabolic products were determined. Moreover, the plasmatic time course in rats has been determined after intravenous (IV) administration of CR 3834 (5mg/kg). Biological samples (0.5ml of plasma and 1ml of urine) were purified using solid-phase extraction (SPE) of analytes and the internal standard Idebenone, 2,3-dimethoxy-5-methyl-6-(10-hydroxydecyl)-1-4-benzoquinone. A chromatographic separation was performed on an Adsorboshere C18 at 25 degrees C, with a pre-column of the same matrix; the eluent was made up of acetonitrile/acidified water with CF(3)COOH (pH 2.01) in ratio of 75:25 (v/v); the flow rate was 1.0ml/min and a 100mul loop. The lower limit of detection (LOD) was taken as 25ng/ml in plasma and 50ng/ml in urine samples. The lower limit of quantification (LOQ) was taken as 0.1 and 0.2mug/ml in plasma and urine samples, respectively. The procedures were validated according to international standards with a good reproducibility and linear response (r=0.9916 in plasma; r=0.9997 in urine). The coefficients of variation inter assay ranged between 2.579 and 4.951% in plasma, and between 0.813 and 2.460% in urine. Mean recovery for CR 3834 was 79% in plasma and 97% in urine samples. The experiments performed demonstrated that the method presented was suitable for determining this new angiotensin-AT(1) antagonist in rat plasma and urine.     

Determination of sitagliptin in human urine and hemodialysate using turbulent flow online extraction and tandem mass spectrometry

High turbulence liquid chromatography (HTLC, or turbulent flow online extraction) and tandem mass spectrometry (MS/MS) methods for the determination of sitagliptin in human urine and hemodialysate were developed and validated to support clinical studies. A narrow bore large particle size reversed-phase column (Cyclone, 50 mm x 1.0 mm, 60 microm) and a BDS Hypersil C18 column (30 mm x 2.1 mm, 3 microm) were used as extraction and analytical columns, respectively. For the urine assay, the LLOQ was 0.1 microg/ml, the linear calibration range was 0.1 to 50 microg/ml, the interday precision (R.S.D.%, n=5) was 2.3-6.5%, and the accuracy was 96.9-106% of the nominal value. For the urine quality control samples (QCs), the intraday precision (R.S.D.%, n=5) and accuracy were 1.8-2.6% and 96.2-106% of the nominal value, respectively. The interday precision (R.S.D.%) for 56 sets of urine QCs over a 6-month period varied from 3.8% to 5.5% and the accuracy from 102% to 105% of the nominal value. For the hemodialysate assay, the LLOQ was 0.01 ng/ml, the linear dynamic range was 0.01-5.0 ng/ml, the interday precision was 1.6-4.1%, and the accuracy was 89.8-104% of the nominal value. For hemodialysate QCs, the intraday precision and accuracy varied from 2.3% to 8.9% and from 99.8% to 111% of the nominal value, respectively. These results demonstrated that both methods are selective, accurate, precise, reproducible, and suitable for quantifying sitagliptin in hemodialysate and human urine samples.     

HPLC法同时测定旱莲草中木犀草素和芹菜素的含量

目的:建立同时测定旱莲草提取物中木犀草素和芹菜素含量的方法。方法:采用高效液相色谱法。色谱柱为Nucleodur100-5 C18(250 mm×4.6 mm,5μm),流动相为甲醇-0.2%磷酸水溶液(50∶50,V/V),流速为1 ml/min,检测波长为350 nm,柱温为40△。结果:木犀草素和芹菜素的质量浓度均在0.02⁵0.00μg/ml范围内与各自峰面积积分值呈良好的线性关系(r分别为0.999 5和0.999 3);精密度、稳定性、重复性试验的RSD<2%;平均加样回收率分别为97.2%和98.9%,RSD分别为2.41%和2.91%(n均为6)。结论:该方法快速、简便,结果准确,可用于不同产地旱莲草药材的质量评价。     

Development and validation of a sensitive LC-MS/MS method for the determination of adefovir in human serum and urine

A sensitive and selective liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and validated for the determination of adefovir (PMEA) in human serum and urine. The analyte was separated on a Diamonsil C(18) column (250 mm x 4.6 mm i.d., 5 microm particle size) by isocratic elution with methanol-water-formic acid (20:80:0.1, v/v/v) at a flow rate of 0.6 ml/min, and analyzed by mass spectrometry in multiple reaction-monitoring mode. The precursor-to-product ion transitions of m/z 274-->162 and m/z 226-->135 were used to measure and quantify the analyte and internal standard (I.S.), respectively. The weighted (1/x(2)) calibration curve was linear over serum concentration range 1.25-160.00 ng/ml and urine concentration range 0.05-8.00 microg/ml, with a correlation coefficient (r) of 0.9992 and 0.9978, respectively. The lower limit of quantification in human serum was 1.25 ng/ml. The inter- and intra-day precisions (R.S.D.%) in both serum and urine were lower than 8.64%, the mean method accuracies and recoveries from spiked serum samples at three concentrations ranged from 96.3 to 102.0% and 56.5 to 59.3%, respectively. The serum extract was stable when stored for 24h. The developed method was successfully applied to determine PMEA in human serum and urine, and proved suitable to clinical pharmacokinetic study.     

Stir bar sorptive extraction with in situ de-conjugation and thermal desorption gas chromatography-mass spectrometry for measurement of 4-nonylphenol glucuronide in human urine sample

4-Nonylphenol glucuronide (NP-G) in human urine samples was analyzed using stir bar sorptive extraction (SBSE) with in situ de-conjugation by beta-glucuronidase and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS). Distilled water (1 ml), 1.0 M ammonium acetate solution (100 microl) and beta-glucuronidase (10,000 units ml(-1), 10 microl) were added to human urine sample (1 ml), and extraction was commenced for 90 min at 37 degrees C while stirring at 250 rpm with a stir bar coated with a 500-microm-thick polydimethylsiloxane (PDMS) layer. Then, the stir bar was subjected to TD-GC-MS in the selected ion monitoring (SIM) mode. The calibration curve was made by SBSE method using 4-nonylphenol (NP) as the standard solution. The method showed good linearity and the correlation coefficients were 0.999 over the concentration range of 5-500 nM. Moreover, to optimize the conditions for SBSE with in situ de-conjugation and the recovery test, NP-G was synthesized by a biochemical technique in our laboratory. The limits of detection (S/N = 3) and quantitation (S/N > 10) for NP were 0.2 ng ml(-1) (1.0 nM) and 1.1 ng ml(-1) (5.0 nM), respectively. The average recoveries in the human urine samples (n = 6) spiked with NP-G at levels of 20 and 100 nM were 104.1 (R.S.D. 7.1%) and 100.6% (R.S.D. 9.2%), respectively, with correction using the added internal standard, 4-(1-methyl) octylphenol-d(5). The method enabled the precise determination of the standard and was applicable to the detection of trace amounts of NP-G in human urine samples.     

Liquid chromatographic assay of ivermectin in human plasma for application to clinical pharmacokinetic studies

There is a need for an accurate, sensitive and selective high-performance liquid chromatography (HPLC) method for the quantitation of ivermectin in human plasma that separates the parent drug from metabolites. Ivermectin and the internal standard, moxidectin, were extracted from 0.2 ml of human plasma using Oasis HLB solid phase extraction cartridges. After extraction, fluorescent derivatives of ivermectin and moxidectin were made by reaction with trifluoroacetic anhydride and N-methylimidazole. Separation was achieved on a Alltech Ultrasphere C18 5mu column with a mobile phase composed of tetrahydrofuran-acetonitrile-water (40:38:22 v/v/v). Detection is by fluorescence, with an excitation of 365 nm and emission of 475 nm. The retention times of ivermectin and internal standard, moxidectin are approximately 24.5 and 12.5 min, respectively. The assay is linear over the concentration range of 0.2-200 ng/ml of ivermectin in human plasma (r = 0.9992, weighted by 1/concentration). Recoveries of ivermectin are greater than 80% at all concentrations. The analysis of quality control samples for ivermectin 0.2, 25, and 200 ng/ml demonstrated excellent precision with coefficient of variation of 6.1, 3.6 and 2.3%, respectively (n = 6). The method is accurate with all intra-day (n = 6) and interday (n = 12) mean concentration within 10% of nominal values at all quality control sample concentrations. Storage stability for 30 days at -80 degrees C and after three freeze-thaw cycles are within acceptable limits. The method separates ivermectin from multiple less and more polar unidentified metabolites. This method is robust and suitable for clinical pharmacokinetic studies. The analytical procedure has been applied to a pharmacokinetic study of ivermectin in healthy volunteers and to the analysis of plasma specimens from patients with disseminated strongyloidiasis.     

Simultaneous determination of rosuvastatin and fenofibric acid in human plasma by LC-MS/MS with electrospray ionization: assay development, validation and application to a clinical study

A simple, sensitive and specific LC-MS/MS method for simultaneous determination of rosuvastatin (RST) and fenofibric acid (FFA) was developed and validated with 500 microL human plasma using carbamazepine as an internal standard (IS). The assay procedure involved a simple one-step liquid/liquid extraction of RST and FFA and IS from plasma into ethyl acetate. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected onto X-Terra MS C-18 column (4.6 mm x 50 mm, 5.0 microm). Separation of RST, FFA and IS was achieved with a mobile phase consisting of 0.05 M formic acid:acetonitrile (45:55, v/v) at a flow rate of 0.40 ml/min. The API-3000LC-MS/MS was operated under the multiple reaction-monitoring mode (MRM) using the electrospray ionization technique. Positive ion acquisition chromatographic run was used in the present method. Nominal retention times of RST, FFA and IS were 2.35, 4.70 and 2.32 min, respectively. Absolute recovery of RST, FFA and IS was 74, 61 and 69%, respectively. The lower limit of quantification (LLOQ) of RST and FFA was 1.00 ng/ml and 0.50 microg/ml, respectively. Response function was established for the range of concentrations 1.00-50.0 ng/ml and 0.50-20.0 microg/ml for RST and FFA, respectively, with a coefficient of determination (r2) of 0.999 for both the compounds. The inter- and intra-day precision in the measurement of RST quality control (QC) samples 5, 15, 400 and 800 ng/ml, were in the range 8.93-9.37% relative standard deviation (R.S.D.) and 1.74-16.1% R.S.D., respectively. Similarly, the inter- and intra-day precision in the measurement of FFA quality control (QC) samples 0.5, 1.5, 8.0 and 15.0 microg/ml, were in the range 9.78-11.6% relative standard deviation (R.S.D.) and 0.22-17.4% R.S.D., respectively. Accuracy in the measurement of QC samples for RST and FFA were in the range 88.1-108 and 87-115%, respectively, of the nominal values. RST and FFA were stable in the battery of stability studies, viz., bench-top, auto-sampler and freeze/thaw cycles. Stability of RST and FFA was established for 1 month at -80 degrees C. The application of the assay to a clinical study confirmed the utility of the assay.     

A validated SPE-LC-MS/MS assay for Eplerenone and its hydrolyzed metabolite in human urine

An automated LC-MS/MS assay was validated to quantitate the first selective aldosterone blocker Eplerenone (I) and its hydrolyzed metabolite (II) in human urine. After the addition of the stable isotope labeled internal standards, human urine samples were extracted on a C(18) solid phase extraction (SPE) cartridge using a Zymark RapidTrace automation system. The extraction eluates were diluted with 20 mM ammonium acetate aqueous solution and directly injected onto the LC-MS/MS system. The chromatographic separation was performed on a reverse phase Zorbax XDB-C(8) HPLC column (2.1 x 50 mm, 5 microm) with a mobile phase of acetonitrile:water (40:60, v/v) containing 10 mM ammonium acetate (pH 7.4). I and II were ionized using positive and negative ionization mass spectrometry, respectively, to achieve the best sensitivity. The ionization polarity was switched during the run at approximately 2.5 min after the injection. Multiple reaction monitoring (MRM) with a tandem mass spectrometer was used to detect the analytes. The precursor to product ion transitions of m/z 415-->163 and m/z 431-->337 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 50-10000 ng/ml of urine for both of I and II. The lower limit of quantitation (LLOQ) was 50 ng/ml for I and II. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. Sample analysis time for each injection was 5 min; a throughput of 100 human urine standards and samples per run was achieved.     

High-throughput simultaneous determination of the HIV protease inhibitors indinavir and L-756423 in human plasma using semi-automated 96-well solid phase extraction and LC-MS/MS

A method for the simultaneous determination of the HIV protease inhibitors indinavir and L-756423, in human plasma has been developed. Plasma samples (0.5 ml) were extracted using a 3M Empore 96-well plate in the mixed phase cation exchange (MPC) format. The extraction method was automated through the application of both the Packard 204DT and TOMTEC Quadra 96 work stations, and the resulting extracts were analyzed using a PE-Sciex API-3000 LC-MS/MS with a heated nebulizer interface (500 degrees C). The assay was linear in the concentration range 1-2500 ng/ml for indinavir and 5 2500 ng/ml for L-756423 when 0.5-ml aliquots of plasma were extracted. Recoveries of indinavir and L-756423 were greater than 76 and 80%, respectively, over the calibration curve range when using the described sample preparation method. Within-batch precision and accuracy for the quantitation of indinavir over the range 1-2500 ng/ml were 5.4% R.S.D. or less and within 4.0%, respectively. Within-batch precision and accuracy for the quantitation of L-756423 over the range 5-2500 ng/ml were 5.3% R.S.D. or less and within 3.4%, respectively. Interbatch variability for the analysis of indinavir QC samples at low (3 ng/ml), middle (250 ng/ml) and high (2250 ng/ml) were 3.2, 2.9, and 1.9%, respectively. Interbatch variability for the analysis of L-756423 QC samples at low (15 ng/ml), middle (250 ng/ml) and high (2250 ng/ml) concentration were 2.0, 2.5, and 3.3%, respectively. The validated assay was used in support of human clinical trials.     

Development and validation of a highly sensitive and robust LC-MS/MS with electrospray ionization method for quantification of rosuvastatin in small volume human plasma samples and its application to a clinical study

A high-throughput, simple, highly sensitive and specific LC-MS/MS method (liquid chromatography coupled with tandem mass spectrometry) has been developed for the estimation of rosuvastatin (CAS 287714-41-4, RST) with 100 microl human plasma using atorvastatin (CAS 134523-00-5) as an internal standard (IS). The API-4000 LC-MS/MS was operated under the multiple reaction-monitoring mode (MRM) using the electro spray ionization technique. The assay procedure involved direct precipitation of RST and IS from plasma with acetonitrile. Sample preparation with this method yielded clean extracts and consistent recoveries: 91.39% for RST and 99.28% for IS. The total chromatographic run time was 3.5 min and the elution of RST and IS occurred at 2.5 and 3.1 min, respectively; this was achieved with a mobile phase consisting of 0.05 mol/L formic acid: acetonitrile (20:80, v/v) at a flow rate of 0.50 ml/min on an Inertsil ODS-3 column (4.6 x 100 mm, 3.0 microm). The developed method was validated in human plasma with a limit of quantitation of 0.05 ng/ml. A linear response function was established for the range of concentrations of 0.05 to 50.0 ng/ml with a correlation coefficient (r) of 0.999. The inter- and intra-day precision in the measurement of RST quality control (QC) samples at 0.05, 0.15, 25 and 40 ng/ml were in the range of 6.55 to 11.40% relative standard deviation (RSD) and 1.76 to 11.17% RSD, respectively. Accuracy in the measurement of QC samples for RST was in the range of 95.02 to 101.37% of the nominal values. RST was stable in the battery of stability studies viz., bench-top, auto-sampler and freeze-thaw cycles. The stability of RST was established for 1 month at -80 degrees C. The application of the assay to a clinical study confirmed the utility of the assay to derive human pharmacokinetic parameters.     

A sensitive fluorescence optosensor for analysing propranolol in pharmaceutical preparations and a test for its control in urine in sport

We describe a simple and selective method for analysing propranolol and a sensitive test for its control in urine. A flow-through fluorescence optosensor based on on-line immobilization in a non-ionic-exchanger (Amberlite XAD-7) solid support in a continuous flow was used in both cases. Determination was made in 5 mM H(2)PO(4)(-)/HPO(4)(2-) buffer solution at pH 6 at a working temperature of 20 degrees C. Fluorescence intensities were measured at lambda(ex/em) = 300/338 nm with a response time of 80 s, thus obtaining a linear concentration range of between 0 and 250.0 ng ml(-1) with a detection limit of 1.3 ng ml(-1), an analytical sensitivity of 6.0 ng ml(-1) and a standard deviation of 2.40% at a 150 ng ml(-1) concentration level for propranolol. We also propose a test to detect propranolol in urine with a linear concentration range between 0 and 100.0 ng ml(-1), a detection limit of 0.2 ng ml(-1), an analytical sensitivity of 1.0 ng ml(-1), and a standard deviation of 0.84% at a 75 ng ml(-1) concentration level. The effect of proteins presents in urine samples were evaluated. The two proposed methods were satisfactorily applied to commercial formulations and urine samples respectively.     

Validation of a method for the determination of zolpidem in human plasma using LC with fluorescence detection

A sensitive and selective high-performance liquid chromatography (HPLC) method was developed for the determination of zolpidem in human plasma. Zolpidem and the internal standard (trazodone) were extracted from human plasma that had been made basic. The basic sample was loaded onto a conditioned Bond Elut C18 cartridge, rinsed with water and eluted with methanol. Forty microliters were then injected onto the LC system. Separation was achieved on a C18 column (150 x 4.6 mm, 5 microm) with a mobile phase composed of acetonitrile:50 mM potassium phosphate monobasic at pH 6.0 (4:6, v/v). Detection was by fluorescence, with excitation at 254 nm and emission at 400 nm. The retention times of zolpidem and internal standard were approximately 4.7 and 5.3 min, respectively. The LC run time was 8 min. The assay was linear in concentration range 1-400 ng/ml for zolpidem in human plasma. The analysis of quality control samples for zolpidem (3, 30, and 300 ng/ml) demonstrated excellent precision with relative standard deviations (RSD) of 3.7, 4.6, and 3.0%, respectively (n = 18). The method was accurate with all intraday (n = 6) and overall (n = 18) mean concentrations within 5.8% from nominal at all quality control sample concentrations. This method was also performed using a Gilson Aspec XL automated sample processor and autoinjector. The samples were manually fortified with internal standard and made basic. The aspec then performed the solid phase extraction and made injections of the samples onto the LC system. Using the automated procedure for analysis, quality control samples for zolpidem (3, 30, and 300 ng/ml) demonstrated acceptable precision with RSD values of 9.0, 4.9, and 5.1%, respectively (n = 12). The method was accurate with all intracurve (n = 4) and overall (n = 12) mean values being less than 10.8% from nominal at all quality control sample concentrations.     

Development and validation of an automated SPE-LC-MS/MS assay for valdecoxib and its hydroxylated metabolite in human plasma

A sensitive and specific liquid chromatography-tandem mass spectrometry assay was developed to quantitate valdecoxib (I) and its hydroxylated metabolite (II) in human plasma. The analytes (I and II) and a structurally analogue internal standard (IS) were extracted on a C(18) solid phase extraction (SPE) cartridge using a Zymark RapidTrace automation system. The chromatographic separation was performed on a narrow-bore reverse phase Zorbax XDB-C(8) HPLC column with a mobile phase of acetonitrile:water (50:50, v/v) containing 10 mM ammonium acetate. The analytes were ionized using negative electrospray mass spectrometry, then detected by multiple reaction monitoring (MRM) with a tandem mass spectrometer. The precursor to product ion transitions of m/z 313-->118 and m/z 329-->196 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 0.5-200 ng/ml of I and II in human plasma with absolute recoveries from plasma at 91 and 86%, respectively. The lower limit of quantitation was 0.5 ng/ml for I and II. Acceptable precision and accuracy were obtained for concentrations over the calibration curve ranges (0.5-200 ng/ml). Sample analysis time for each injection was 5 min, a throughput of 70 human plasma standards and samples per run was achieved. The assay has been successfully used to analyze human plasma samples to support clinical phase I and II studies.     

Determination of ABT-089 in human plasma by high performance liquid chromatography using in situ precolumn derivatization with 7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole

ABT-089 is a potent, selective neuronal cholinergic channel modulator with cognition enhancing activity in several animal paradigms. A simple and sensitive chromatographic method for the specific determination of ABT-089 in human plasma has been developed and validated. The method utilizes in situ precolumn fluorescence derivatization of the sample with 7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-F) prior to liquid-liquid extraction followed by reverse phase HPLC and fluorescence detection (lambda(ex) 495 nm, lambda(em) 533 nm). The described method significantly simplifies sample preparation. The derivatized product was separated from interference using a YMC ODS-AQ, 5 microm, 250x4.6 mm i.d. column using a mobile phase consisting of 30:5:65 (v:v:v) acetonitrile/methanol/aqueous buffer at a flow rate of 0.75 ml min(-1). The aqueous buffer consisted of 0.01 M tetramethylammonium perchlorate, 0.1% (v:v) trifluoroacetic acid, pH 3.0. An Alltech Absorbosphere CN, 5 microm, cartridge guard column was also used before the analytical column. Plasma samples were alkalinized with 0.1 M NaHCO3, 300 microl of a 1 mg ml(-1) ethanolic solution of NBD-F was added and the samples were heated in a water bath for 10 min at 50 degrees C. The samples were then extracted with tert-butylmethylether, evaporated to dryness and then reconstituted in mobile phase. For 1 ml of plasma, a limit of quantitation (LOQ) of 1.6 ng ml(-1) was obtained. The method was linear from 1.6 to 836 ng ml(-1). Inter and intra-day assay RSD (n = 6) were less than 9%. Accuracy determinations showed the quality control samples to range between 88-114% of the theoretical concentration.