Determination of erythromycin A in rat plasma and urine by high-performance liquid chromatography with chemiluminescence detection using Tris(2,2'-bipyridine)ruthenium(II)

A simple and sensitive method was developed for the determination of erythromycin A (EA), decladinosyl erythromycin A (dClEA) and erythromycin B (EB) in rat plasma and urine by high-performance liquid chromatography with electrogenerated chemiluminescence detection using Tris(2,2'-bipyridine)ruthenium(II). The recovery rates of EA, dClEA and EB were 97, 94 and 85% from rat plasma and 89, 83 and 93% from rat urine, respectively. The calibration curves were linear over the concentration ranges 0.05-5 microg/mL for plasma and 0.5-50 microg/mL for urine. The precision and accuracy for all analytes in rat plasma were < or =9.0 and -6.3-7.2%, and those in urine were < or =9.4% and -6.1-7.6%, respectively. This method proved to be a powerful tool for determination of EA, dClEA and EB concentrations in samples from rats.     

Simple, sensitive and rapid liquid chromatography/atmospheric pressure chemical ionization mass spectrometric method for the quantitation of Ranolazine in rat plasma

A sensitive and specific method using liquid chromatography with atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) has been developed and validated for the identification and quantification of Ranolazine in rat plasma. A simple liquid-liquid extraction procedure was followed by injection of the extracts onto a C18 column with isocratic elution and detection using a single quadrupole mass spectrometer in selected ion monitoring (SIM) mode. The method was tested using six different batches of blank plasma. Linearity was established for the concentration range 0.02-10.0 microg/mL, with a coefficient of determination (r) of 0.9998 and good back-calculated accuracy and precision. The intra- and inter-day precision (relative standard deviation (RSD) %) was lower than 10%, and accuracy ranged from 85 to 115%. The lower limit of quantification was reproducible at 0.01 microg/mL with 20 microL plasma. The proposed method enables the unambiguous identification and quantification of Ranolazine for pre-clinical and clinical studies.     

Determination of ubidecarenone (coenzyme Q10, ubiquinol-10) in raw materials and dietary supplements by high-performance liquid chromatography with ultraviolet detection: single-laboratory validation

A method based on high-performance liquid chromatography with ultraviolet detection has been developed to quantify ubidecarenone [coenzyme Q10 (CoQ10)] in raw materials and dietary supplements. Single-laboratory validation has been performed on the method to determine repeatability, accuracy, selectivity, limits of detection and quantification (LOQ), ruggedness, and linearity for CoQ10. As CoQ10 can exist as the biologically active reduced form, the application of an oxidizing agent, ferric chloride, drives the equilibrium mechanics to the fully oxidized state and allows for exact quantification of total CoQ10 in the sample. This method was found to be fit and linear for the testing of materials containing CoQ10 in the range of approximately equal 50-1000 mg/g. Repeatability precision for CoQ10 was between 2.15 and 5.00% relative standard deviation. Observed recovery of CoQ10 was found to be between 93.8 and 100.9%. LOQ was found to be 9 microg/mL. Further, limited studies showed that some adulterants and degraded material could be satisfactorily separated from CoQ10 and identified.     

High-performance liquid chromatographic method for the determination of mangiferin in rat plasma and urine

A reversed-phase high-performance liquid chromatography assay for mangiferin in rat plasma and urine was developed. Rutin was employed as an internal standard. The mobile phase consisted of acetonitrile-water (16:84, v/v) containing 3% acetic acid at a flow rate of 1 mL/min. Detection was at 257 and 365 nm for mangiferin in plasma and urine, respectively. The limit of quantitation (LOQ) of mangiferin was 0.6 microg/mL in plasma, and 0.48 microg/mL in urine. The standard curve was linear from 0.6 to 24 microg/mL in plasma, and 0.48 to 24 microg/mL in urine, both intra- and inter-day precision of the mangiferin were determined and their RSD did not exceed 10%. The method provides a technique for rapid analysis of mangiferin in rat plasma and urine, which can be used in pharmacokinetic studies.     

Determination of geniposide in rat urine after oral administration of the traditional Chinese medicinal preparation yin-zhi-ku decoction by high-performance liquid chromatography

A high-performance liquid chromatography method with solid-phase extraction is introduced for the determination of geniposide in rat urine after oral administration of yin-zhi-ku decoction. Geniposide and an internal standard (paeoniflorin) are extracted from urine using Strata cartridges. Analysis of the extract is then performed on a reversed-phase C18 column using acetonitrile-water (14:86, v/v) as eluting solvent system. UV detection is set at 238 nm. The calibration curve for geniposide is linear (r = 0.9996) in the concentration range of 2.0-240 microg/mL. Both intra- and interday precision of the geniposide are determined, and their relative standard deviation does not exceed 10%. The validated method is successfully applied to determine geniposide from rat urine after oral administration of yin-zhi-ku decoction.     

Development and validation of a liquid chromatography with tandem mass spectrometry method for the quantification of vitisin B in rat plasma and urine

A new, rapid, and sensitive liquid chromatography with tandem mass spectrometry method was developed for the determination of vitisin B and validated in rat plasma and urine using carbamazepine as an internal standard. The plasma (0.05 mL) or urine (0.2 mL) samples were extracted by liquid–liquid extraction with ethyl acetate and separated on an Eclipse Plus C₁₈ column (100 × 4.6 mm, 3.5 μm) with a mobile phase consisting of acetonitrile and 0.1% formic acid water (60:40, v/v) at a flow rate of 0.7 mL/min. Detection and quantification were performed by mass spectrometry in selected reaction‐monitoring mode with positive electrospray ionization. The calibration curves were recovered over the concentration ranges of 10?5000 ng/mL (correlation coefficients, r≥0.9833) in plasma and 5?2500 ng/mL (r≥0.9977) in urine, respectively. All validation data, including the specificity, precision, accuracy, recovery, and stability, conformed to the acceptance requirements. No matrix effects were observed. The developed method was successfully applied to pharmacokinetic studies of vitisin B following intravenous administration of 0.5 and 1 mg/kg and intraperitoneal injection of 5, 10, and 25 mg/kg to rats. This is the first report on the pharmacokinetic properties of vitisin B. The results provide a meaningful basis to evaluate preclinical or clinical applications of vitisin B.     

Analysis of lamotrigine and its metabolites in human plasma and urine by micellar electrokinetic capillary chromatography

A reliable micellar electrokinetic capillary chromatographic method was developed and validated for the determination of lamotrigine and its metabolites in human plasma and urine. The variation of different parameters, such as pH of the background electrolyte (BGE) and Sodium dodecyl sulfate (SDS) concentration, were evaluated in order to find optimal conditions. Best separation of the analytes was achieved using a BGE composed of 10 mM borate and 50 mM SDS, pH 9.5; melatonin was selected as the internal standard. Isolation of lamotrigine and its metabolites from plasma and urine was accomplished with an original solid-phase extraction procedure using hydrophilic-lypophilic balance cartridges. Good absolute recovery data and satisfactory precision values were obtained. The calibration plots for lamotrigine and its metabolites were linear over the 1-20 microg/mL concentration range. Sensitivity was satisfactory; the limits of detection and quantitation of lamotrigine were 500 ng/mL and 1 microg/mL, respectively. The application of the method to real plasma samples from epileptic patients under therapy with lamotrigine gave good results in terms of accuracy and selectivity, and in agreement with those obtained with an high-performance liquid chromatography (HPLC) method.     

Quantification of the plant-derived hallucinogen Salvinorin A in conventional and non-conventional biological fluids by gas chromatography/mass spectrometry after Salvia divinorum smoking

A gas chromatography method with mass spectrometric detection is described for the determination of Salvinorin A, the main active ingredient of the hallucinogenic mint Salvia divinorum. The method was validated in plasma, urine, saliva and sweat using 17-alpha-methyltestosterone as internal standard. The analytes were extracted from biological matrices with chloroform/isopropanol (9:1, v/v). Chromatography was performed on a 5% phenyl methyl silicone capillary column and analytes were determined in the selected ion monitoring mode. The method was validated over the concentration range 0.015-5 microg/mL plasma, urine and saliva and 0.01-5 microg/patch in the case of sweat. Mean recoveries ranged between 77.1 and 92.7% for Salvinorin A in different biological matrices, with precision and accuracy always better than 15%. The method was applied to the analysis of urine, saliva and sweat from two consumers after smoking 75 mg plant leaves to verify the presence of the active ingredient of S. divinorum in human biological fluids as a biomarker of plant consumption. Salvinorin A was detected in urine (2.4 and 10.9 ng/mL) and saliva (11.1 and 25.0 ng/mL), but not in sweat patches from consumers.     

Identification and quantification of 34 drugs and toxic compounds in blood,urine, and gastric content using liquid chromatography with tandem mass spectrometry

A liquid chromatography with tandem mass spectrometry method was developed for the simultaneous screening of 34 drugs and poisons in forensic cases. Blood (0.5 mL, diluted 1:1 with water) or 1.0 mL of urine was purified by solid‐phase extraction. Gastric contents (diluted 1:1 with water) were treated with acetonitrile, centrifuged, and supernatant injected. Detection was achieved using a Waters Alliance 2695/Quattro Premier XE liquid chromatography tandem mass spectrometry system equipped with electrospray ionization, operated in the multiple reaction monitoring modes. The method was validated for accuracy, precision, linearity, and recovery. The absolute recovery of drugs and toxic compounds in blood was greater than 51% with the limit of detection in the range of 0.02–20 ng/mL. The absolute recovery of drugs and toxic compounds in urine was greater than 61% with limit of detection in the range of 0.01–10 ng/mL. The matrix effect of drugs and toxic compounds in urine was 65–117% and 67–121% in blood. The limit of detection of drugs and toxic compounds in gastric content samples were in the range of 0.05–20 ng/mL. This method was applied to the routine analysis of drugs and toxic compounds in postmortem blood, urine, and gastric content samples. The method was applied to actual forensic cases with examples given.     

Rapid determination of five probe drugs and their metabolites in human plasma and urine by liquid chromatography/tandem mass spectrometry: application to cytochrome P450 phenotyping studies

A liquid chromatography/mass spectrometry method, for rapid determination of five cytochrome P450 (CYP) probe drugs and their relevant metabolites in human plasma and urine, is described. The five specific probe substrates/metabolites, caffeine/paraxanthine (CYP1A2), tolbutamide/4-hydroxytolbutamide/carboxytolbutamide (CYP2C9), omeprazole/5-hydroxyomeprazole (CYP2C19), debrisoquine/5-hydroxydebrisoquine (CYP2D6) and midazolam/1'-hydroxymidazolam (CYP3A), together with the internal standards (phenacetin and paracetamol), in plasma and urine, were extracted using solid-phase extraction. The chromatography was performed using a C18 column with an isocratic mobile phase consisting of acetonitrile and 0.1% formic acid in water (70:30). The triple-quadrupole mass spectrometer was operated in both positive and negative modes, and multiple reaction monitoring was used for quantification. The method was validated over the concentration ranges 0.05-5 microg/mL for caffeine and paraxanthine, 0.02-2 microg/mL for tolbutamide, 0.1-20 microg/mL for 4-hydroxytolbutamide, carboxytolbutamide, debrisoquine and 5-hydroxydebrisoquine, 5-2500 ng/mL for omeprazole and 5-hydroxyomeprazole, and 1-100 ng/mL for midazolam and 1'-hydroxymidazolam. The intra- and inter-day precision were 0.3-13.7% and 1.9-14.3%, respectively, and the accuracy ranged from 93.5-107.2%. The lower limit of quantification varied between 1 and 100 ng/mL. The present method provides a robust, fast and sensitive analytical tool for the five-probe drug cocktail, and has been successfully applied to a clinical phenotyping study in 16 subjects.     

Determination of melamine in pet food by enzyme immunoassay, high-performance liquid chromatography with diode array detection, and ultra-performance liquid chromatography with tandem mass spectrometry

Melamine in pet food (fortified or originally contaminated) was determined by enzyme immunoassay (EIA), high-performance liquid chromatography with diode array detection (HPLC-DAD), and ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS). The limits of detection (LOD) for EIA and HPLC-DAD were 0.02 and 0.1 microg/mL, respectively. The linear ranges of the calibration curves for EIA and HPLC-DAD were 0.02-0.5 and 0.1-500 microg/mL, respectively. The coefficient of determinations (r2) of the standard curves for EIA and HPLC were 0.9991 and 0.9999, respectively. Coefficient of variations from both inter- and intra-assay were <9.31%, and recovery range for all concentrations was between 71 and 105%. The r2 values between the EIA and HPLC-DAD methods for melamine analysis of the fortified and originally contaminated samples were 0.9973 and 0.9885. The r2 values for UPLC-MS/MS with HPLC-DAD and with EIA were 0.9566 and 0.9489, respectively.     

Validated procedure for simultaneous trace level determination of the anti-cancer agent gemcitabine and its metabolite in human urine by high-performance liquid chromatography with tandem mass spectrometry

A sensitive, accurate and reproducible procedure has been developed for the quantitative determination of gemcitabine (2',2'-difluorodeoxycytidine, dFdC) and its metabolite 2',2'-difluorodeoxyuridine (2dFdU) in human urine. The samples (2 mL) were extracted by solid-phase extraction (SPE) and analyzed by reversed-phase high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC/MS/MS), operating in multiple reaction monitoring (MRM mode). This procedure was validated using 2'-deoxycytidine as internal standard (IS). The urine assay was linear over the range 0-50 microg/L, with a limit of quantification (LLOQ) of 0.2 microg/L for gemcitabine and 1.0 microg/L for the metabolite. The respective limits of detection (LODs) for dFdC and 2dFdU were 0.05 and 0.3 microg/L. The precision and accuracy of the assay were determined on three different days. The within-series precision was found to be always less than 8.5 and 12.7% for gemcitabine and 2dFdU, respectively. The overall precision expressed as relative standard deviation (CVr) was always less than 7.1% for both analytes. The recovery of gemcitabine was always greater than 90% with a CVr <6.3%. The measurement uncertainty determined from the validation data assessed the possibility of determining this drug and its metabolite at trace levels in urine, considering that the combined uncertainty of the whole procedure was always less than 30%.     

超高效液相色谱-三重四极杆质谱法测定大鼠海马和大脑皮层中生物胺类及氨基酸类神经化学物质

建立了超高效液相色谱-三重四极杆质谱法检测大鼠海马和大脑皮层中生物胺类及氨基酸类神经化学物质含量的方法。选用Hypercarb (100 mm×2.1 mm,5μm)色谱柱,以0.1%甲酸-甲醇为流动相,梯度洗脱。电喷雾离子源( ESI)在正离子模式下,选择多反应监测模式( MRM)扫描,对检测的6种生物胺类和11种氨基酸类神经化学物质分别选择一个定性离子对和一个定量离子对。测定Wistar大鼠海马和大脑皮层中6种生物胺类和11种氨基酸类神经化学物质的含量,对比两种不同脑组织样品前处理方法对神经化学物质含量测定结果的影响。17种神经化学物质在10 min内即可完成同时测定,检测方法线性关系良好,日内和日间精密度、加标回收率和重复性满足分析要求。本方法准确、灵敏度高、专属性强、重复性好,适用于脑组织中生物胺类及氨基酸类神经化学物质的含量测定,可为生物胺类及氨基酸类神经化学物质提供有效的样品前处理方法和检测手段。     

High-performance liquid chromatography of coenzyme Q-related compounds and its application to biological materials

A convenient and precise method for the separation and determination of coenzyme Q (CoQ)-related compounds (CoQ homologues, plastoquinone-9, ubichromenol-9, etc.) was developed using high-performance liquid chromatography (HPLC). All compounds tested were separated using a reverse-phase column with a suitable mobile phase and detected at a wavelength of 275 nm. CoQ extracts in plasma and erythrocytes were purified by thin-layer chromatography prior to HPLC analysis, but such purification was not necessary when determining CoQ in urine and tissues. Hydroquinone forms of CoQ existing in animal tissues were oxidized to the corresponding quinone forms with potassium hexacyanoferrate(III). This HPLC method was applied satisfactorily to the determination of the contents of CoQ homologues in human and animal samples. CoQ10 was the only homologue detected in human samples, and CoQ8, CoQ9 and CoQ10 were native homologues of CoQ in rat tissues. Ubichromenol-9 and plastoquinone-9 were not detected in these samples.     

Alcohol biomarker analysis: simultaneous determination of 5-hydroxytryptophol glucuronide and 5-hydroxyindoleacetic acid by direct injection of urine using ultra-performance liquid chromatography-tandem mass spectrometry

A direct ultra-performance liquid chromatography-tandem mass spectrometry method (UPLC-MS/MS) for simultaneous measurement of urinary 5-hydroxytryptophol glucuronide (GTOL) and 5-hydroxyindoleacetic acid (5-HIAA) was developed. The GTOL/5-HIAA ratio is used as an alcohol biomarker with clinical and forensic applications. The method involved dilution of the urine sample with deuterated analogues (internal standards), reversed-phase chromatography with gradient elution, electrospray ionisation and monitoring of two product ions per analyte in selected reaction monitoring mode. The measuring ranges were 6.7-10 000 nmol/l for GTOL and 0.07-100 micromol/l for 5-HIAA. The intra- and inter-assay imprecision, expressed as the coefficient of variation, was below 7%. Influence from ion suppression was noted for both compounds but was compensated for by the use of co-eluting internal standards. The accuracy in analytical recovery of added substance to urine samples was 96 and 98%, respectively, for GTOL and 5-HIAA. Method comparison with GC-MS for GTOL in 25 authentic patient samples confirmed the accuracy of the method with a median ratio between methods (GC-MS to UPLC-MS/MS) of 1.14 (r(2) = 0.975). The difference is explained by the fact that the GC-MS method also measures unconjugated 5-hydroxytryptophol naturally present in urine. The comparison with data for 5-HIAA obtained by an HPLC method demonstrated a median ratio of 1.05 between the methods. The UPLC-MS/MS method was capable of measuring endogenous GTOL and 5-HIAA levels in urine, which agreed with the literature data. In conclusion, a fully validated and robust direct method for the routine measurement of urinary GTOL and 5-HIAA was developed.     

A high-performance liquid chromatographic method for saikosaponin a quantification in rat plasma

A high-performance liquid chromatographic method with UV detection has been developed for the determination of saikosaponin a in rat plasma. Saikosaponin a and internal standard jujuboside A were isolated from plasma samples by solid-phase extraction. The chromatographic separation was achieved on a reversed-phase C(18) column with the mobile phase of acetonitrile-water (35:65, v/v) at a flow rate of 1 mL/min and UV detection was set at 205 nm. The standard curve for saikosaponin a was linear over the concentration range 0.25-10 microg/mL and the limit of detection was 0.05 microg/mL. The absolute recovery was greater than 82%. The precision and accuracy ranged from 3.05 to 9.59% and 95.61 to 110.00%, respectively. The validated method was used to determine saikosaponin a in plasma samples in a pharmacokinetic study of saikosaponin a administered to Sprague-Dawley rats.     

Determination of β2-Agonists in Porcine Urine by Molecularly Imprinted Solid Phase Extraction Followed Ultra-Performance Liquid Chromatography–Tandem Mass Spectrometry Detection

A novel, sensitive, and robust method has been developed to detect 9 β₂-agonists in porcine urine to monitor illegal use of β₂-agonists in swine rearing. The method based on the molecular imprinted polymer (MIP) rapid extraction followed ultra-performance liquid chromatography coupled tandem mass spectrometry (UPLC-MS/MS) detection. The cleaning efficiency of MIP cartridges was demonstrated by comparing with common ion exchange solid phase extraction. The presented method was validated in accordance with the European Commission Decision 2002/657/EC. The linearity, decision limit (CCα), detection capability (CCβ), recovery, precision, robustness, and stability were studied in detail. CCα and CCβ values were from 0.006 ng/mL to 0.03 ng/mL and from 0.02 ng/mL to 0.08 ng/mL, respectively. The mean recoveries and repeatability varied from 68.8% to 94.2% and from 2.8% to 10.1%. The proposed method was applied to test 170 porcine urine samples from the Shaanxi province in China and two urine samples were confirmed as clenbuterol positive and the concentrations of clenbuterol in positive urine samples were about 0.08 ng/mL and 0.1 ng/mL, respectively. The developed method was demonstrated to be more sensitive and robust for the determination of 9 β₂-agonists in porcine urine. The method was proven to be simple and easy in operation with high selectivity and good reproducibility.     

A rapid LC-MS-MS method for the determination of nicotine and cotinine in serum and saliva samples from smokers: validation and comparison with a radioimmunoassay method

The development and validation of a rapid liquid chromatography (LC)-tandem mass spectrometry (MS-MS) method for determination of nicotine and cotinine in smokers' serum is described. The method is based on solid-phase extraction in a 96-well plate format and requires only 100 microL of serum. Using normal-phase chromatography, both analytes elute in less than 1 min, which permits high sample throughput applications. The calibrated range is 2-100 ng/mL nicotine and 20-1,000 ng/mL cotinine. For known samples, recovery is 95-116% for nicotine and 93-94% for cotinine. The method is extended to rat serum and human saliva (cotinine only) using partial validation techniques. When compared with an existing radioimmunoassay method in our laboratory, the LC-MS-MS method gives improved accuracy, precision, and sample throughput.     

Sensitive liquid chromatography/tandem mass spectrometry method for the determination of two novel highly lipophilic anticancer drug candidates in rat plasma and tissues

A simple and sensitive liquid chromatography/electrospray ionization tandem mass spectrometry (LC‐ESI‐MS/MS) method was developed and validated for determination of two highly lipophilic anticancer drug candidates, LG1980 and GH501, in rat plasma and tissues (liver, kidney and femur bones). LG1980 and GH501 were extracted from rat plasma and tissue homogenates using liquid–liquid extraction. The method provided a linear range of 1.0–200.0 ng/mL for GH501 in plasma and LG1980 in plasma and liver. For both analytes in other tissue homogenates the linear range was 2.0–400.0 ng/mL. The method was validated with precision within 15% relative standard deviation, accuracy within 15% relative error and a consistent recovery. This method has been successfully applied in two preclinical studies for LG1980 and GH501 to determine their concentrations in rat plasma, liver, kidney and bone over 24 h after intravenous injection of compounds.     

Determination of ephedrine alkaloids in human urine and plasma by liquid chromatography/tandem mass spectrometry: collaborative study

A collaborative study was conducted to evaluate the accuracy and precision of a method for ephedrine-type alkaloids (i.e., norephedrine, norpseudoephedrine, ephedrine, pseudoephedrine, methylephedrine, and methylpseudoephedrine) in human urine and plasma. The amount of ephedrine-type alkaloids present was determined using liquid chromatography (LC) with tandem mass selective detection. The test samples were diluted to reflect a concentration of 5.00-100 ng/mL for each alkaloid. An internal standard was added and the alkaloids were separated using a 5 microm phenyl LC column with an ammonium acetate, glacial acetic acid, acetonitrile, and water mobile phase. Eight blind duplicates of human urine and eight blind duplicates of human plasma were analyzed by 10 collaborators. In addition to negative controls, test portions of urine and plasma were fortified at 3 different levels with each of the 6 ephedrine-type alkaloids at approximately 1, 2, and 5 microg/mL for urine and 100, 200, and 500 ng/mL for plasma. On the basis of the accuracy and precision results for this collaborative study, it is recommended that this method be adopted Official First Action for the determination of 6 different ephedrine-type alkaloids in human urine and plasma.