Simultaneous determination of methadone, buprenorphine and norbuprenorphine in biological fluids for therapeutic drug monitoring purposes

Methadone and buprenorphine are two of the drugs most frequently used for abstinence from illicit opioids and in the treatment of pain. A sensitive and selective high-performance liquid chromatographic method with diode array detection for the simultaneous determination of methadone, buprenorphine and norbuprenorphine has been developed. Separation of the three analytes was obtained by using a reversed-phase column (C8, 250mmx4.6mm i.d., 5microm) and a mobile phase composed of 40% phosphate buffer containing triethylamine, 50% methanol and 10% acetonitrile (final apparent pH 6.0). Loxapine was used as the internal standard. An accurate pre-treatment procedure of biological samples was developed, using solid-phase extraction with C8 cartridges (100mg, 1mL) and needing small amounts of plasma or urine (300microL). The calibration curves were linear over a working range of 10.0-1500.0ng/mL for methadone and of 5.0-500.0ng/mL for buprenorphine and norbuprenorphine in both matrices. The limit of quantitation (LOQ) and the limit of detection (LOD) were 1.0 and 0.4ng/mL for methadone and 0.5 and 0.2ng/mL for both buprenorphine and norbuprenorphine, respectively. The method was successfully applied to the analysis of plasma and urine samples from patients undergoing treatment with these drugs. Precision and accuracy results were satisfactory and no interference from endogenous or exogenous compounds was found. The method is suitable for the simultaneous determination of methadone and buprenorphine in human plasma and urine for therapeutic drug monitoring purposes.     

A sensitive liquid chromatography-mass spectrometry method for simultaneous determination of two active chromones from Saposhnikovia root in rat plasma and urine

A sensitive and efficient liquid chromatography-mass spectrometry method was developed and validated for the simultaneous determination of two active chromones (prim-O-glucosylcimifugin and 4'-O-D-glucosyl-5-O-methylvisamminol) from Saposhnikovia root in rat plasma and urine. The plasma or urine samples were prepared by protein precipitation. Chromatographic separation of the two active chromones from matrix interferences was achieved on an Angilent TC-C(18) column with a mobile phase consisted of methanol, water and 0.1% formic acid. Puerarin was added as the internal standard. The method was validated with the concentration range 1.0-100 ng/mL in rat plasma and 10-1000 ng/mL in urine for prim-O-glucosylcimifugin, 1.5-150 ng/mL in plasma and 15-1500 ng/mL in urine for 4'-O-D-glucosyl-5-O-methylvisamminol. The lower limit of quantitation (LLOQ) of prim-O-glucosylcimifugin and 4'-O-D-glucosyl-5-O-methylvisamminol was 1.0 and 1.5 ng/mL in plasma, 10 and 15 ng/mL in urine, respectively. The intra- and inter-day precision across three validation days over the entire concentration range was lower than 9.0% as terms of relative standard deviation (R.S.D.). Accuracy determined at three quality control concentrations (2.0, 25 and 75 ng/mL for prim-O-glucosylcimifugin; 3.0, 37.5 and 112.5 ng/mL for 4'-O-D-glucosyl-5-O-methylvisamminol) ranged from -1.9 to 3.9% as terms of relative error (R.E.). The LC-ESI-MS method was further applied to assess pharmacokinetics and urine excretion of the two chromones after oral administration of Fangfeng extract to rats. Practical utility of this new LC-MS method was confirmed in pilot pharmacokinetic studies in rats following oral administration.     

Validation of a sensitive LC-MS assay for quantification of glyburide and its metabolite 4-transhydroxy glyburide in plasma and urine: an OPRU Network study

Glyburide (glibenclamide, INN), a second generation sulfonylurea is widely used in the treatment of gestational diabetes mellitus (GDM). None of the previously reported analytical methods provide adequate sensitivity for the expected sub-nanogram/mL maternal and umbilical cord plasma concentrations of glyburide during pregnancy. We developed and validated a sensitive and low sample volume liquid chromatographic-mass spectrometric (LC-MS) method for simultaneous determination of glyburide (GLY) and its metabolite, 4-transhydroxy glyburide (M1) in human plasma (0.5 mL) or urine (0.1 mL). The limits of quantitation (LOQ) for GLY and M1 in plasma were 0.25 and 0.40 ng/mL, respectively whereas it was 1.06 ng/mL for M1 in urine. As measured by quality control samples, precision (% coefficient of variation) of the assay was <15% whereas the accuracy (% deviation from expected) ranged from -10.1 to 14.3%. We found that the GLY metabolite, M1 is excreted in the urine as the glucuronide-conjugate.     

Biocompatible in-tube solid-phase microextraction coupled to HPLC for the determination of angiotensin II receptor antagonists in human plasma and urine

A poly (methacrylic acid-ethylene glycol dimethacrylate, MAA-EGDMA) monolithic capillary was used for the in-tube solid-phase microextraction (in-tube SPME) of several angiotensin II receptor antagonists (ARA-IIs) from human plasma and urine. Under the optimized extraction condition, the protein component of the biological sample was flushed through the monolithic capillary, while the analytes were successfully trapped. Coupled to HPLC with fluorescence detection, this on-line in-tube SPME method was successfully applied for the determination of candesartan, losartan, irbesartan, valsartan, telmisartan, and their detection limits were found to be 0.1-15.3ng/mL and 0.1-15.2ng/mL in human plasma and urine, respectively. The method was linear over the range of 0.5-200ng/mL for telmisartan, 5-2000ng/mL for candesartan and irbesartan, 10-2000ng/mL for valsartan, and 50-5000ng/mL for losartan with correlation coefficients being above 0.9985 in plasma sample and above 0.9994 in urine sample. The method reproducibility was evaluated at three concentration levels, resulting in the R.S.D. <7%. The poly (MAA-EGDMA) monolithic capillary was demonstrated to be robust and biocompatible by using direct injections of biological samples.     

Development and validation of a liquid chromatographic-tandem mass spectrometric method for determination of oseltamivir and its metabolite oseltamivir carboxylate in plasma, saliva and urine

A bioanalytical method for the analysis of oseltamivir (OP) and its metabolite oseltamivir carboxylate (OC) in human plasma, saliva and urine using off-line solid-phase extraction and liquid chromatography coupled to positive tandem mass spectroscopy has been developed and validated. OP and OC were analysed on a ZIC-HILIC column (50 mm x 2.1 mm) using a mobile phase gradient containing acetonitrile-ammonium acetate buffer (pH 3.5; 10mM) at a flow rate of 500 microL/min. The method was validated according to published FDA guidelines and showed excellent performance. The lower limit of quantification for OP was determined to be 1, 1 and 5 ng/mL for plasma, saliva and urine, respectively and for OC was 10, 10 and 30 ng/mL for plasma, saliva and urine, respectively. The upper limit of quantification for OP was determined to be 600, 300 and 1500 ng/mL for plasma, saliva and urine, respectively and for OC was 10,000, 10,000 and 30,000 ng/mL for plasma, saliva and urine, respectively. The within-day and between-day precisions expressed as R.S.D., were lower than 5% at all tested concentrations for all matrices and below 12% at the lower limit of quantification. Validation of over-curve samples ensured that it would be possible with dilution if samples went outside the calibration range. Matrix effects were thoroughly evaluated both graphically and quantitatively. No matrix effects were detected for OP or OC in plasma or saliva. Residues from the urine matrix (most likely salts) caused some ion suppression for both OP and its deuterated internal standard but had no effect on OC or its deuterated internal standard. The suppression did not affect the quantification of OP.     

Development and validation of an LC-MS method with electrospray ionization for quantitation of digoxin in human plasma and urine: application to a pharmacokinetic study

A highly sensitive and specific LC-MS method was developed and validated for the quantification of digoxin in human plasma and urine using d5-dihydrodigoxin as internal standard (IS). The assay procedure involved extraction of digoxin and IS from human plasma with chloroform-isopropanol (95:5, v/v). Chromatogrphic separation was achieved on a Spherisorb ODS2 column using a gradient mobile phase with 5 mmol/L ammonium acetate in water with 1% acetic acid and acetonitrile. The mass spectrometer was operated in the selected ion monitoring mode using the respective [M+K](+) ions, m/z 819.4 for digoxin and m/z 826.4 for IS. The method was proved to be accurate and precise at linearity range of 0.12-19.60 ng/mL in plasma with a correlation coefficient (r(2)) of >or=0.9968 and 1.2-196.0 ng/mL in urine. The limit of quantification achieved with this method was 0.12 ng/mL in plasma and 1.2 ng/mL in urine. The intra- and inter-assay precision and accuracy values were found to be within the assay variability limits as per the FDA guidelines. The developed assay method was successfully applied to a pharmacokinetic study in human volunteers following intravenous administration of digoxin.     

LC/MS/MS measurement of penicillin G in bovine plasma, urine, and biopsy samples taken from kidneys of standing animals

Methods for the measurement of penicillin concentration in bovine plasma, kidney and urine were developed and validated. Detection was based on liquid chromatography/tandem mass spectrometry (LC/MS/MS). Phenethecillin was used as an internal standard. Plasma was extracted with acetonitrile using a method with a calculated limit of quantitation (LOQ) of 12 ng/mL. Kidney samples were homogenized in water and acetonitrile, then cleaned up on C18-bonded silica SPE cartridges. The LOQ of this procedure was 10 ng/g. Urine samples were diluted, filtered, and analyzed directly. The LOQ of this procedure was 63 ng/mL. The overall accuracy for plasma was 103% with coefficient of variation (CV) of 3%; for kidney, 96% and 11%, respectively, and for urine, 98% and 4%, respectively. These methods were applied to the analysis of plasma, urine, and kidney biopsy samples taken from standing animals that had been dosed with penicillin.     

Development of a high-performance liquid chromatographic method to determine the concentration of karenitecin,a novel highly lipophilic camptothecin derivative,in human plasma and urine

Karenitecin is a novel, highly lipophilic camptothecin derivative with potent anticancer potential. We have developed a sensitive high-performance liquid chromatographic method for the determination of karenitecin concentration in human plasma and urine. Karenitecin was isolated from human plasma and urine using solid-phase extraction. Separation was achieved by gradient elution, using a water and acetonitrile mobile phase, on an ODS analytical column. Karenitecin was detected using fluorescence detection at excitation and emission wavelengths of 370 and 490 nm, respectively. Retention time for karenitecin was 16.2±0.5 min and 8.0±0.2 min for camptothecin, the internal standard. The karenitecin peak was baseline resolved, with the nearest peak at 3.1 min distance. Using normal volunteer plasma and urine from multiple individuals, as well as samples from the 50 patients analyzed to date, no interfering peaks were detected. Inter- and intra-day coefficients of variance were <4.4 and 7.1% for plasma and <4.9 and 11.6% for urine. Assay precision, based on an extracted karenitecin standard plasma sample of 2.5 ng/ml, was +4.46% with a mean accuracy of 92.4%. For extracted karenitecin standard urine samples of 2.5 ng/ml assay precision was +2.35% with a mean accuracy of 99.5%. The mean recovery of karenitecin, at plasma concentrations of 1.0 and 50 ng/ml, was 81.9 and 87.8% respectively. In urine, at concentrations of 1.5 and 50 ng/ml, the mean recoveries were 90.3 and 78.4% respectively. The lower limit of detection (LLD) for karenitecin was 0.5 ng/ml in plasma and 1.0 ng/ml in urine. The lower limit of quantification (LLQ) for karenitecin was 1 ng/ml and 1.5 ng/ml for plasma and urine, respectively. Stability studies indicate that when frozen at −70°C, karenitecin is stable in human plasma for up to 3 months and in human urine for up to 1 month. This method is useful for the quantification of karenitecin in plasma and urine samples for clinical pharmacology studies in patients receiving this agent in clinical trials.     

Determination of Cloretazine (VNP40101M) and its active metabolite (VNP4090CE) in human plasma by liquid chromatography electrospray tandem mass spectrometry (LC-ESI-MS/MS)

A sensitive method for the determination of Cloretazine (VNP40101M) and its metabolite (VNP4090CE) with an internal standard (ISTD) in human plasma was developed using high-performance liquid chromatographic separation with tandem mass spectrometric detection. Acidified plasma samples (500 microL) were prepared using solid phase extraction (SPE) columns, and 25 microL of the reconstituted sample was injected onto an Ascentis C18 HPLC column (3 microm, 5 cmx2.1 mm) with an isocratic mobile phase. Analytes were detected with an API-3000 LC-MS/MS System at unit (Q1) and low (Q3) resolution in negative multiple reaction monitoring mode: m/z 249.0 (precursor ion) to m/z 114.9 (product ion) for both Cloretazine (at 3.64 min) and VNP4090CE (at 2.91 min), and m/z 253.0 (precursor ion) to m/z 116.9 (product ion) for the ISTD. The mean recovery for Cloretazine (VNP40101M) and its metabolite (VNP4090CE) was greater than 87% with a lower limit of quantification of 1.0 ng/mL for Cloretazine (S/N=9.7, CV相似文献   

Determination of methylnaltrexone in clinical samples by solid-phase extraction and high-performance liquid chromatography for a pharmacokinetics study

A high-performance liquid chromatographic (HPLC) method with electrochemical detection and solid-phase extraction (SPE) using cartridges of weak cation-exchange capacity as the primary retention mechanism is described for the separation and determination of methylnaltrexone (MNTX) in small clinical samples of plasma or urine. The procedure was performed using a Phenomenex Prodigy ODS-2, 5 microm, 150x3.2 mm analytical column and 50 mM potassium acetate buffer, with 11% methanol as organic modifier at pH* 4.5 at a flow-rate of 0.5 ml/min. The detection potential was 700 mV. The six-point standard calibration curves were linear over three consecutive days in the range from 2 to 100 ng/ml. The average goodness of fit (r) was 0.9993. The lower limit of detection (LOD) and limit of quantification (LOQ) were found to be 2.0 and 5.0 ng/ml, respectively. At the LOQ, the coefficient of variation for the entire method was 8.0% and the accuracy was 10.0% (n = 10). Recovery of the drug from plasma was in the region of 94%. The method was applied to a pharmacokinetics study of methylnaltrexone after subcutaneous administration and in numerous assays of analytes in blood plasma and urine. The pharmacokinetics parameters for a single dose of 0.1 or 0.3 mg/kg in plasma were C(max) = 110 (+/-55) and 287 (+/-101) ng/ml and t(max) = 16.7 (+/-10.8) and 20.0 (+/-9.5) min, respectively. The method is simple, yet sensitive for the detection and determination of methylnaltrexone in biological samples at the level of the physiological response.     

HPLC-ESI-MS/MS validated method for simultaneous quantification of zopiclone and its metabolites, N-desmethyl zopiclone and zopiclone-N-oxide in human plasma

A simple, selective and sensitive isocratic HPLC method with triple quadrupole mass spectrometry detection has been developed and validated for simultaneous quantification of zopiclone and its metabolites in human plasma. The analytes were extracted using solid phase extraction, separated on Symmetry shield RP8 column (150 mm x 4.6 mm i.d., 3.5 microm particle size) and detected by tandem mass spectrometry with a turbo ion spray interface. Metaxalone was used as an internal standard. The method had a chromatographic run time of 4.5 min and linear calibration curves over the concentration range of 0.5-150 ng/mL for both zopiclone and N-desmethyl zopiclone and 1-150 ng/mL for zopiclone-N-oxide. The intra-batch and inter-batch accuracy and precision evaluated at lower limit of quantification and quality control levels were within 89.5-109.1% and 3.0-14.7%, respectively, for all the analytes. The recoveries calculated for the analytes and internal standard were > or = 90% from spiked plasma samples. The validated method was successfully employed for a comparative bioavailability study after oral administration of 7.5 mg zopiclone (test and reference) to 16 healthy volunteers under fasted condition.     

Quantitative determination of Astragaloside IV, a natural product with cardioprotective activity, in plasma, urine and other biological samples by HPLC coupled with tandem mass spectrometry

Astragaloside IV is a novel cardioprotective agent extracted from the Chinese medical herb Astragalus membranaceus (Fisch) Bge. This agent is being developed for treatment for cardiovascular disease. Further development of Astragaloside IV will require detailed pharmacokinetic studies in preclinical animal models. Therefore, we established a sensitive and accurate high performance liquid chromatography (HPLC) coupled with tandem mass spectrometry (LC/MS/MS) quantitative detection method for measurement of Astragaloside IV levels in plasma, urine as well as other biological samples including bile fluid, feces and various tissues. Extraction of Astragaloside IV from plasma and other biological samples was performed by Waters OASIS(trade mark) solid phase extraction column by washing with water and eluting with methanol, respectively. An aliquot of extracted residues was injected into LC/MS/MS system with separation by a Cosmosil C18 5 microm, 150 mm x 2.0 mm) column. Acetonitrile:water containing 5 microM NaAc (40:60, v/v) was used as a mobile phase. The eluted compounds were detected by tandem mass spectrometry. The average extraction recoveries were greater than 89% for Astragaloside IV and digoxin from plasma, while extraction recovery of Astragaloside IV and digoxin from tissues, bile fluid, urine and fece ranged from 61 to 85%, respectively. Good linearity (R2>0.9999) was observed throughout the range of 10-5000 ng/ml in 0.5 ml rat plasma and 5-5000 ng/ml in 0.5 ml dog plasma. In addition, good linearity (R2>0.9999) was also observed in urine, bile fluid, feces samples and various tissue samples. The overall accuracy of this method was 93-110% for both rat plasma and dog plasma. Intra-assay and inter-assay variabilities were less than 15.03% in plasma. The lowest quantitation limit of Astragaloside IV was 10 ng/ml in 0.5 ml rat plasma and 5 ng/ml in 0.5 ml dog plasma, respectively. Practical utility of this new LC/MS/MS method was confirmed in pilot pharmacokinetic studies in both rats and dogs following intravenous administration.     

Development and validation of a liquid chromatography-mass spectrometry assay for the determination of pyronaridine in human urine

A reliable method has been developed for the determination of pyronaridine in human urine using amodiaquine as an internal standard. Liquid-liquid extraction was used for sample preparation. Analysis was performed on a Shimadzu LCMS-2010 in single ion monitoring positive mode using atmospheric pressure chemical ionization (APCI) as an interface. The extracted ion for pyronaridine was m/z 518.20 and for amodiaquine was m/z 356.10. Chromatography was carried out using a Gemini 5 microm C18 3.0 mmx150 mm column using 2 mM perflurooctanoic acid and acetonitrile mixture as a mobile phase delivered at a flow rate of 0.5 mL/min. The mobile phase was delivered in gradient mode. The retention times of pyronaridine and amodiaquine were 9.1 and 8.1 min respectively, with a total run time of 14 min. The assay was linear over a range of 14.3-1425 ng/mL for pyronaridine (R2>or=0.992, weighted 1/Concentration). The analysis of quality control samples for pyronaridine at 28.5, 285, 684 and 1140 ng/mL demonstrated excellent precision with relative standard deviation of 5.1, 2.3, 3.9 and 9.2%, respectively (n=5). Recoveries at concentrations of 28.5, 285, 684 and 1140 ng/mL were all greater than 85%.This LC-MS method for the determination of pyronaridine in human urine has excellent specifications for sensitivity, reproducibility and accuracy and can reliably quantitate concentrations of pyronaridine in urine as low as 14.3 ng/mL. The method will be used to quantify pyronaridine in human urine for pharmacokinetic and drug safety studies.     

A capillary gas chromatography-selected ion monitoring mass spectrometry method for the analysis of atractylenolide I in rat plasma and tissues, and application in a pharmacokinetic study

The aim of this paper is to investigate the characteristics of atractylenolide I (AO-I) in the body by a GC-MS method. All bio-samples were cleared up with a liquid-liquid extraction procedure. The calibration curves were linear within a range of 5-1000 ng/mL for plasma samples, 0.06-16.00 microg/g for cerebellum samples, and 0.03-8.00 microg/g for other tissue samples. The limit of quantification (LOQ) for AO-I was 1.0 ng/mL or 1.0 ng/g (S/N>micro=10) in the bio-samples. In the applications, the main pharmacokinetic parameters were firstly obtained as follows: Tmax=0.37+/-0.19 h, Cmax=0.26+/-0.05 microg/mL, AUC=1.95+/-0.30 microgh/mL and ka=10.08+/-5.60 h(-1). The tissue distribution of AO-I in rats after the oral administration of 50.0mg/kg was from 0.225 to 0.031microg/g with a decreasing tendency in different tissues like liver>kidney>spleen>cerebellum>heart>cerebrum>lung. The protein binding in rat plasma, human plasma and bovine serum albumin was 80.8+/-3.9, 90.6+/-3.1 and 60.9+/-5.1%, respectively.     

Quantitative HPLC-UV method for the determination of firocoxib from horse and dog plasma

A sensitive reversed-phase HPLC-UV method was developed for the determination of firocoxib, a novel and highly selective COX-2 inhibitor, in plasma. A 1.0 mL dog or horse plasma sample is mixed with water and passed through a hydrophobic-lipophilic copolymer solid-phase extraction column to isolate firocoxib. Quantitation is based on an external standard curve. The method has a validated limit of quantitation of 25 ng/mL and a limit of detection of 10 ng/mL. The validated upper limit of quantitation was 2500 ng/mL for horses and 10,000 ng/mL for dogs. The average recoveries ranged from 88-93% for horse plasma and 96-103% for dog plasma. The coefficient of variation in all cases was less than 10%. This method is suitable for the analysis of clinical samples from pharmacokinetic and bioequivalence studies and drug monitoring.     

Efficient assay for the determination of atenolol in human plasma and urine by high-performance liquid chromatography with fluorescence detection

An efficient method for the determination of atenolol in human plasma and urine was developed and validated. α-Hydroxymetoprolol, a compound with a similar polarity to atenolol, was used as the internal standard in the present high-performance liquid chromatographic analysis with fluorescence detection. The assay was validated for the concentration range of 2 to 5000 ng/ml in plasma and 1 to 20 μg.ml in urine. For both plasma and urine, the lower limit of detection was 1 ng/ml. The intra-day and inter-day variabilities for plasma samples at 40 and 900 ng/ml, and urine samples at 9.5 μg/ml were <3% (n=5).     

Rapid preparation of human urine and plasma samples for analysis of F2-isoprostanes by gas chromatography-mass spectrometry

Reliable MS-based methods have been developed for the measurement of free and esterified F2-isoprostanes. However, prior to sample analysis several steps of purification, including solid-phase extraction followed by TLC or HPLC, are usually required, making it tedious to analyze large sample numbers, e.g., for population studies. We report a quick sample purification method using anion exchange solid phase extraction (SPE), which is highly selective for acidic compounds. Urine and hydrolyzed plasma of healthy individuals were acidified before SPE extraction, washed with 4 different solvent mixtures and finally eluted with ethyl acetate. The eluted samples were first derivatized with pentafluorobenzyl bromide followed by a second derivatization with bis-(trimethylsilyl)trifluoroacetamide. F2-isoprostanes were analyzed by GC-MS-NCI. The method was highly sensitive; the limit of detection at 5:1 signal-to-noise ratio was 0.037 ng/ml and 0.007 ng/mg creatinine for plasma and urine, respectively. Anion exchange SPE extraction for F2-isoprostane showed recovery of 55-65% and high linearity for concentration 0-1.0 ng/ml for urine (CV=4.08%, r2=0.990) and 0-0.5 ng/ml for plasma (CV=4.07%, r2=0.998). Fasting for 6h significantly increased plasma F2-isoprostanes levels, which has implications for the design of intervention studies using this biomarker.     

Quantification of riboflavin in human urine using high performance liquid chromatography-tandem mass spectrometry

We developed a selective method to measure riboflavin in human urine. Sample preparation involved solid phase extraction and concentration of the target analyte in urine. The urine concentrate was analyzed using high performance liquid chromatography-tandem mass spectrometry. Riboflavin concentrations were quantified using an isotopically labeled internal standard. The limit of detection was 11 ng/mL, and the linear range was 4.4-20,000 ng/mL. The relative standard deviation at 100, 1000, and 5000 ng/mL was 17%, 17%, and 12%, respectively. The accuracy was 90%. On average, 100 samples, including calibration standards and quality control samples, were prepared per day. Using our method, we measured concentrations of riboflavin in human urine samples that were collected from participants in a study where riboflavin was used as a surrogate chemical to simulate exposure to an environmental toxicant.     

Determination of Salvinorin A in body fluids by high performance liquid chromatography-atmospheric pressure chemical ionization

Salvinorin A was quantitated in human and rhesus monkey plasma, rhesus monkey cerebrospinal fluid, and human urine by negative ion LC-MS/APCI. The method for Salvinorin A has been fully validated, the LLOQ using FDA guidelines is 2 ng/mL for 0.5 mL plasma samples. The linear range was from 2 to 1000 ng/mL. Several derivatives in the Salvinorin family can also be analyzed by this method; d(3)-Salvinorin A was prepared and used as internal standard. The metabolite Salvinorin B can be semi quantitatively determined. The method has been used to establish that Salvinorin B is the principal metabolite of Salvinorin A ex vivo and to establish the analytical method to study in vivo samples.     

Development and validation of a liquid chromatography-tandem mass spectrometry method for the determination of xanthinol in human plasma and its application in a bioequivalence study of xanthinol nicotinate tablets

A sensitive, rapid liquid chromatographic-electrospray ionization mass spectrometric method for the determination of xanthinol in human plasma was developed and validated. Xanthinol nicotinate in plasma (0.5mL) was pretreated with 20% trichloroacetic acid for protein precipitation. The samples were separated using a Lichrospher silica (5mum, 250mmx4.6mm i.d.). A mobile phase of methanol-water containing 0.1% formic acid (50: 50, v/v) was used isocratically eluting at a flow rate of 1mL/min. Xanthinol and its internal standard (IS), acyclovir, were measured by electrospray ion source in positive selected reaction monitoring mode. The method demonstrated that good linearity ranged from 10.27 to 1642.8ng/mL with r=0.9956. The limit of quantification for xanthinol in plasma was 10.27ng/mL with good accuracy and precision. The mean plasma extraction recovery of xanthinol was in the range of 90.9-100.2%. The intra- and inter-batch variability values were less than 4.8% and 7.9% (relative standard deviation, R.S.D.), respectively. The established method has been successfully applied to a bioequivalence study of two xanthinol nicotinate tablets for 20 healthy volunteers.