Determination of glycyrrhizin in dog plasma by liquid chromatography-mass spectrometry and its application in pharmacokinetic studies

A sensitive liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method was established and validated for the determination of glycyrrhizin in dog plasma. After treatment with methanol to precipitate proteins, plasma samples were analyzed on a reversed-phase C18 (ODS) column with a mobile phase of methanol:1% formic acid solution (75:25, v/v). MS determination was performed using negative electrospray ionization (negative ESI) in the selected ion monitoring mode. Glycyrrhizin was monitored at the m/z 821 channel and internal standard (gliquidone) at the m/z 526 channel. The calibration curve was linear over the range from 0.05 μg mL(-1) to 10 μg mL(-1) with a correlation coefficient above 0.99. This method was successfully applied to the pharmacokinetic studies in beagle dogs. The absolute bioavailability of glycyrrhizin in beagle dogs was 3.24%.     

Rapid and sensitive liquid chromatography-electrospray ionization-mass spectrometry method for the determination of eperisone in human plasma: method and clinical applications

A sensitive liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method for determination of eperisone in human plasma using buflomedil as the internal standard (IS) is established. After being made alkaline with saturated sodium bicarbonate solution, plasma samples are extracted with a mixture of diethyl ether-cyclohexane (1:1, v/v) and separated by high-performance liquid chromatography on a reversed-phase C(18) column with a mobile phase of 10mM ammonium acetate buffer (adjusted the pH to 3.9 with acetic acid)-methanol (20:80, v/v). Eperisone is determined using ESI in a single-quadrupole MS. LC-ESI-MS is performed in the selected ion monitoring mode using target ions at m/z 260 for eperisone and m/z 308 for the IS. Calibration curves are linear over the ranges 0.02-20 ng/mL for eperisone. The intra- and interassay variability values are less than 9.0% and 11.5%, respectively. The mean plasma extraction recovery of eperisone is 91.7 +/- 6.6%. The method has been successfully applied to study the pharmacokinetics of eperisone in healthy, male, Chinese volunteers. Pharmacokinetic parameters of the reference and test tablets have been compared.     

Determination of a new angiotensin-converting enzyme inhibitor (CS-622) and its active metabolite in plasma and urine by gas chromatography-mass spectrometry using negative ion chemical ionization

A sensitive and specific gas chromatographic-mass spectrometric method for the simultaneous determination of angiotensin-converting enzyme inhibitor (I, CS-622) and its active desethyl metabolite (II, RS-5139) in plasma and urine was developed. Compound D5-RS-5139 was used as an internal standard and measurements were made by electron-capture negative ion chemical ionization. Extraction from plasma and urine was carried out using Sep-Pak C18 and silica cartridges. The extract of plasma or urine was treated with diazomethane followed by trifluoroacetic anhydride to convert I and II into their methyl ester trifluoroacetyl derivatives. The detection limit of I and II was 0.5 ng/ml in plasma and 5 ng/ml in urine. The proposed method was satisfactory for the determination of I and II in plasma and urine with respect to accuracy and precision. Thus it is suitable for measurement of bioavailability and pharmacokinetics of I and II in body fluids.     

液相色谱-电喷雾串联质谱法测定生姜中的215种农药残留

建立了生姜中215种农药多残留测定的液相色谱-电喷雾串联质谱(LC-ESI-MS/MS)方法。样品用1%醋酸-乙腈溶液均质提取,经Sep-Pak Vac固相萃取柱净化,乙腈-甲苯(3:1, v/v)洗脱,旋转蒸发浓缩至约0.5 mL后,于室温氮气吹干,用乙腈-水(3:2, v/v)溶解,以电喷雾电离串联质谱在正离子多反应监测(MRM)模式下进行测定。在定量限水平进行添加回收率实验,方法的回收率范围为68.1%～132.6%,其中回收率在70%～120%的占94.4%,相对标准偏差(RSD)范围为0.4%～25.0%。方法的检出限(S/N=3)和定量限(S/N=10)范围分别为0.01～70.45 μg/L和0.04～234.84 μg/L。该方法操作简便,灵敏度、准确度和精密度均符合农药多残留检测技术要求,适用于生姜中215种农药多残留的快速测定。     

液相色谱-串联四极杆质谱法测定牛奶中128种农药残留

建立了牛奶中128种农药残留的液相色谱-串联质谱检测方法。10 mL牛奶用20 mL乙腈(加4 g硫酸镁和1 g氯化钠)振荡提取两次,上清液浓缩后经C18固相萃取柱(2000 mg填料)净化以除去提取液中的亲脂性化合物等干扰杂质,洗脱液浓缩至约0.5 mL后,于45 ℃下用氮气吹干,加1 mL乙腈-水(体积比为3:2)定容,超声溶解30 s,经0.2 μm微孔滤膜过滤,液相色谱-电喷雾串联质谱测定。2倍检出限和8倍检出限两个添加水平的5次平行实验结果表明: 128种农药在低添加水平(0.14 μg/L～0.62 mg/L)下回收率范围为60.4%～118.4%,相对标准偏差为2.1%～24.3%;高添加水平(0.56 μg/L～2.48 mg/L)下的回收率范围为64.4%～118.5%,相对标准偏差为1.3%～24.1%。各种农药在确定的添加范围内线性关系良好,相关系数高于0.99,方法的检出限(LOD)为0.07 μg/L～0.31 mg/L。该方法通用性强、选择性好、灵敏度高,快速简便。     

液相色谱-串联质谱法快速筛查测定浓缩果蔬汁中的156种农药残留

建立了浓缩果蔬汁中156种农药多残留的液相色谱-电喷雾串联质谱(LC-ESI-MS/MS)测定方法。样品用1%醋酸乙腈溶液萃取,经Waters Sep-Pak Vac固相萃取柱净化,乙腈-甲苯(体积比为3∶1)洗脱,旋转蒸发浓缩,用乙腈-水（体积比为3∶2）溶解,以Agilent ZORBAX SB-C18色谱柱分离,以电喷雾电离串联质谱在正离子多反应监测(MRM)模式下进行测定。对156种农药在5种浓缩果蔬汁(橙汁、苹果汁、葡萄汁、白菜汁、胡萝卜汁)中两个添加水平下的回收率进行了测定,回收率范围为57.2%～122.7%,相对标准偏差范围为0.9%～19.8%。方法的检出限(S/N=3)和定量限(S/N=10)范围分别为0.10～56.77 μg/kg和0.33～189.23 μg/kg。该方法样品前处理简单、快速、分析时间短,灵敏度、准确度和精密度均符合农药多残留检测技术的要求,适用于苹果汁、橙汁、葡萄汁、白菜汁、胡萝卜汁等浓缩果蔬汁中156种农药多残留的快速筛查测定。     

Pharmacokinetic study of free-form sinomenine in rat skin by microdialysis coupled with liquid chromatography-electrospray mass spectrometry

Sinomenine (7,8-didehydro-4-hydroxy-3,7-dimethoxy-17-methylmorphinan-6-one) is a pure alkaloid extracted from the Chinese medical plant. In this report a liquid chromatography-electrospray mass spectrometry (LC-ESI-MS) method with in vivo microdialysis for the pharmacokinetic study of free-form sinomenine in rat skin has been developed. A microdialysis probe was surgically implanted into the subcutaneous tissue of the rats and an isotonic phosphate buffer (PBS) was used as the perfusion medium. Samples were collected and then analyzed off-line by LC-ESI-MS. The chromatographic separation was achieved within 4.2 min by using a narrow-bore Xterra C(18) column (2.1 x 150 mm, 5 microm) with acetonitrile-(10 mmol/L ammonium acetate buffer, 0.1% acetic acid) (15:85, v/v). Ion signal m/z 330.1 for sinomenine was measured in the positive mode. Linearity was established for the range of concentrations of 2.0-10000.0 ng/mL with a coefficient of determination (r) of 0.9989. The intra- and inter-day reproducibility of the present method was better than 6%. The lower limit of quantification (LLOQ) was 1.0 ng/mL. The proposed method described provides more authentic information on pharmacokinetics and metabolism at the site of action by using the coupling of microdialysis to LC-ESI-MS technique than the traditional sampling methods.     

High-performance liquid-chromatographic tandem-mass spectrometric methods for atropinesterase-mediated enantioselective and chiral determination of R- and S-hyoscyamine in plasma

S-hyoscyamine (S-hyo) is a toxic tropane alkaloid from plants of the solanacea family, which is extracted for pharmaceutical purposes thereby undergoing racemization (atropine). Merely the S-hyo enantiomer acts as an antagonist of muscarinic receptors (MR). Nevertheless, racemic atropine is clinically administered in e.g. ophthalmology and for symptomatic therapy of acute poisoning with organophosphorus compounds (OPCs, e.g. pesticides, nerve agents). However, very limited data are available of comparative pharmacokinetics of S- and R-enantiomers in humans or other species. Therefore, we developed an enantioselective LC-ESI-MS/MS assay making use of rabbit serum containing atropinesterase (AtrE, EC 3.1.1.10) which is suitable for stereospecific hydrolysis of S-hyo into tropine and tropic acid while R-hyo is unaffected. For sample preparation plasma was incubated with human serum (not containing AtrE, procedure A) and with rabbit serum (procedure B). Afterwards, hyoscyamines were quantified by a validated previously published non-chiral LC-ESI-MS/MS method. Following procedure A the concentration of total hyo and following procedure B remaining R-hyo were determined. S-hyo was calculated by the difference between these concentrations. This assay design allowed reproducible, precise (RSD 2-9%), accurate (93-101%) and selective determination of total and individual hyoscyamines. Potential therapeutics for OPC poisoning (carbamates, oximes) and thiono-pesticides did not interfere with the assay whereas some oxon-pesticides inhibited S-hyo hydrolysis. A control experiment was designed allowing to be aware of such interferences thus avoiding the use of false results. To validate this assay, results were compared to those from a novel isocratic chiral LC-ESI-MS/MS method. Separation of S-hyo (t(R) 31.1 ± 0.2 min) and R-hyo (t(R) 33.4 ± 0.2 min) was achieved on α-glycoprotein (AGP) chiral stationary phase at 40°C (selectivity factor α 1.07). Ammoniumformate (0.01 M, pH 8.0) with 3.75% (v/v) acetonitrile served as mobile phase (300 μL min(-1)). Hyoscyamines were detected in the positive multiple reaction monitor mode. The enantioselective assay was applied to the analysis of atropine degradation in diluted rabbit serum in vitro as well as to human in vivo plasma samples from a pesticide-poisoned patient treated with atropine.     

Determination of AJ-3941, a possible agent for the treatment of cerebrovascular disorders, in plasma and brain by means of high-performance liquid chromatography with fluorescence detection.

A sensitive and selective high-performance liquid chromatographic method with fluorescence detection is described for the determination of AJ-3941 (I), a possible agent for the treatment of cerebrovascular disorders, in plasma and brain tissue. A simple hexane extraction was used for plasma, and for brain homogenate the hexane extract was further purified by solid-phase extraction. The determination limit was ca. 3 ng/ml for both plasma (0.5 ml) and 10% (w/v) brain homogenate (1 ml). The method was applied to the determination of I in plasma and brain samples of experimental animals.     

Stability-indicating methods for determination of tiapride in pure form, pharmaceutical preparation, and human plasma

Four different stability-indicating procedures are described for determination of tiapride in pure form, dosage form, and human plasma. Second derivative (D2), first derivative of ratio spectra (1DD), spectrofluorimetric, and high-performance column liquid chromatographic (LC) methods are proposed for determination of tiapride in presence of its acid-induced degradation products, namely 2-methoxy-5-(methylsulfonyl) benzoic acid and 2-diethylaminoethylamine. These approaches were successfully applied to quantify tiapride using the information included in the absorption, excitation, and emission spectra of the appropriate solutions. In the D2 method, Beer's law was obeyed in the concentration range of 1.5-9 microg/mL with a mean recovery of 99.94 +/- 1.38% at 253.4 nm using absolute ethanol as a solvent. In 1DD, which is based on the simultaneous use of the first derivative of ratio spectra and measurement at 245 nm in absolute ethanolic solution, Beer's law was obeyed over a concentration range of 1.5-9 microg/mL with mean recovery 99.64 +/- 1.08%. The spectrofluorimetric method is based on the determination of tiapride native fluorescence at 339 nm emission wavelength and 230 nm excitation wavelength using water-methanol (8 + 2, v/v). The calibration curve was linear over the range of 0.2-3 microg/mL with mean recovery of 99.66 +/- 1.46%. This method was also applied for determination of tiapride in human plasma. A reversed-phase LC method performed at ambient temperature was validated for determination of tiapride using methanol-deionized water-triethylamine (107 + 93 + 0.16, v/v/v) as the mobile phase. Sulpiride was used as an internal standard at a flow rate of 1 mL/min with ultraviolet detection at 214 nm. A linear relation was obtained over a concentration range of 2-30 microg/mL with mean recovery of 99.66 +/- 0.9%. Results were statistically analyzed and compared with those obtained by applying the reference method. They proved both accuracy and precision.     

Determination of femtomole concentrations of catecholamines by high-performance liquid chromatography with peroxyoxalate chemiluminescence detection.

A highly sensitive method for determination of the plasma catecholamines, norepinephrine (NE), epinephrine (E) and dopamine (DA) is described. The method consists of the extraction of the catecholamines, using 3,4-dihydroxybenzylamine as internal standard, from plasma with alumina (5 mg), followed by a reversed-phase column separation, on-column fluorogenic derivatization with ethylenediamine (ED) and post-column peroxyoxalate chemiluminescent reaction detection utilizing bis[4-nitro-2-(3,6,9-trioxadecyl-oxycarbonyl)phenyl] oxalate (TDPO) and hydrogen peroxide. In order to optimize the reaction conditions for high-performance liquid chromatography to obtain highly sensitive detection, the effects of changing reagent compositions on the chemiluminescence yield were investigated. The following are the optimized conditions. Eluent, a mixture of 50 mmol l-1 potassium acetate (pH 3.20)-50 mmol l-1 potassium phosphate (pH 3.20)-acetonitrile (90.15 + 4.85 + 3 v/v/v) containing 1 mmol l-1 sodium hexanesulfonate (40 degrees C) and flow rate, 0.5 ml min-1. Fluorogenic reagent solution, 105 mmol l-1 ED and 175 mmol l-1 imidazole in acetonitrile-ethanol (90 + 10 v/v) and flow rate, 0.25 ml min-1. Reaction coil (15 m x 0.5 mm i.d.) heated at 80 degrees C. Chemiluminogenic reagent solution, 0.25 mmol l-1 TDPO, 150 mmol l-1 hydrogen peroxide and 110 mmol l-1 trifluoroacetic acid in dioxane-ethyl acetate (50:50 v/v) and flow rate, 1.4 ml min-1. The detection limits for all the catecholamines were 1 fmol (signal-to-noise ratio at 2). The standard deviations of the method for the determination of NE, E and DA added to rat plasma (2.5 nM) were 3, 3 and 4%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

LC-ESI-MS Determination of Bilobalide and Ginkgolides in Canine Plasma

A sensitive and selective method using liquid chromatography with electrospray ionization mass spectrometric detection was developed for the quantification of bilobalide and ginkgolides in canine plasma. The analytes were extracted with diethyl ether-dichloromethane-isopropanol (6:3:1, v/v) after spiking the samples with daidzein (internal standard). The lower limit of quantification (LLOQ) of the method was 2.5 μg L⁻¹ for ginkgolide B and 10.0 μg L⁻¹ for bilabolide, ginkgolide A and ginkgolide C. The accuracy of the method was within 15% of the actual values over a wide range of plasma concentrations. The intra-day and inter-day precision was better than 15% (R.S.D.). Finally, the LC-ESI-MS method was successfully applied to study the pharmacokinetics of ginkgolides and bilabolide after administration of Ginkgo biloba extracts to dogs.     

On-line liquid chromatography-electrospray ionization mass spectrometry for determination of the brevetoxin profile in natural “red tide” algae blooms

Reversed-phase liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) was employed to analyze brevetoxin compounds associated with naturally occurring red tide blooms collected from Sarasota Bay, FL, USA. The LC-ESI-MS method utilizes a C₁₈ microbore column with a mobile phase consisting of methanol-water (85:15, v/v), a flow-rate of 8 μl/min and a post-column split ratio of 3:1 (UV-absorbance detector-mass spectrometer). Three known brevetoxins Btx-2, Btx-1 and Btx-3 were detected at 60 μg/l, 10 μg/l and 5.7 μg/l levels, respectively, in the natrual red tide bloom samples. This distribution differed quantitatively from that found in red tide culture extract samples. Btx-9 was not detected either in natural red tide bloom extracts or in red tide culture extracts, possibly due to the instability of this compound. An unknown component with a molecular mass of 941 found in the natural bloom extract was postulated to have the structure of a reduced form (hydrogenation of two double bonds in the alkyl side chain) of Btx-5.     

High-performance liquid chromatographic determination of pipotiazine in human plasma and urine

A high-performance liquid chromatographic method has been developed for the determination of pipotiazine in human plasma and urine. After selective extraction, pipotiazine and the internal standard (7-methoxypipotiazine) and chromatographed on a column packed with Spherosil XOA 600 (5 micrometers) using a 7:3 (v/v) mixture of diisopropyl either--isooctane (1:1, v/v + 0.2% triethylamine and diisopropyl ether--methanol (1:1, v/v) + 0.2% triethylamine + 2.6% water. The eluted compounds are measured by fluorescence detection. The sensitivity of the method was established at 0.25 ng/ml pipotiazine in plasma and 2 ng/ml pipotiazine in urine (C.V. less than 5%). The method has been successfully applied to a pharmacokinetic study following a single oral administration of 10 mg of pipotiazine.     

Determination of the R-(-) and S-(+) enantiomers of the monohydroxylated metabolite of oxcarbazepine in human plasma by enantioselective high-performance liquid chromatography.

An enantioselective liquid chromatographic assay for the simultaneous determination of the S-(+) and R-(-) enantiomers of the monohydroxylated metabolite of oxcarbazepine in human plasma is described. The metabolite is the active principle. The method is based on the extraction of plasma with diethyl ether-dichloromethane (2:1, v/v), separation of the organic phase, evaporation of the solvent and dissolution of the residue in the mobile phase. The two enantiomers were resolved on a Chiralcel OD (250 mm x 4.6 mm I.D.) high-performance liquid chromatographic column. The separation was achieved by isocratic elution with n-hexane-2-propanol (77:23, v/v). The flow-rate of the mobile phase was 1.0 ml/min and the two enantiomers were detected by ultraviolet absorbance at 210 nm. The analytical method is suitable for the quantitative and simultaneous determination of the two enantiomers in plasma at concentrations down to 0.4 mumol/l after administration of oxcarbazepine.     

Determination of ivermectin B(1a) in animal plasma by liquid chromatography combined with electrospray ionization mass spectrometry

A novel, sensitive and specific method for the quantitative determination of ivermectin B(1a) in animal plasma using liquid chromatography combined with positive electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) is presented. Abamectin was used as the internal standard. Extraction of the samples was performed with a deproteinization step using acetonitrile. Chromatographic separation was achieved on a Nucleosil ODS 5 microm column, using gradient elution with 0.2% (v/v) acetic acid in water and 0.2% (v/v) acetic acid in acetonitrile. The method was validated according to the requirements defined by the European Community. Calibration curves using plasma fortified between 1 and 100 ng ml(-1) showed a good linear correlation (r > or = 0.9989, goodness-of-fit coefficient < or =8.1%). The trueness at 2 and 25 ng ml(-1) (n = 6) was +4.2 and -17.1%, respectively. The trueness and between-run precision for the analysis of quality control samples at 25 ng ml(-1) was -4.0 and 11.0%, respectively (n = 16). The limit of quantification of the method was 1.0 ng ml(-1), for which the trueness and precision also fell within acceptable limits. Using a signal-to-noise ratio of 3 : 1, the limit of detection was calculated to be 0.2 ng ml(-1). The specificity was demonstrated with respect to ivermectin B(1b).The method was successfully used for the quantitative determination of ivermectin B(1a) in plasma samples from treated bovines, demonstrating the usefulness of the developed method for application in the field of pharmacokinetics.     

Determination of oxatomide in human plasma by high-performance liquid chromatography-electrospray ionization mass spectrometry

A rapid, sensitive and specific high-performance liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method has been developed and validated for the determination of oxatomide in human plasma. Flunarizine hydrochloride was employed as the internal standard (IS). The analytes were chromatographically separated on a Shimadzu Shim-pack VP-ODS C18 column (250 x 2.0 mm i.d.) with a mobile phase consisting of methanol and aqueous ammonium acetate solution (10 mm, pH 4.0; 85:15, v/v). Detection was performed on a single quadrupole mass spectrometer using an electrospray ionization interface with the selected-ion monitoring (SIM) mode. The method showed excellent linearity (r = 0.9995) over the concentration range of 0.5-500 ng/mL with good accuracy and precision. The intra- and inter-batch precisions were within 10% relative standard deviation. The recoveries were more than 90%. The validated method was successfully applied to a preliminary pharmacokinetic study of oxatomide in Chinese healthy male volunteers.     

Development and validation of high-performance liquid chromatography/electrospray ionization mass spectrometry for assay of madecassoside in rat plasma and its application to pharmacokinetic study

A rapid, sensitive and specific high-performance liquid chromatography/electrospray ionization mass spectrometric (LC-ESI-MS) method was developed and validated for the quantification of madecassoside, a major active constituent of Centella asiatica (L.) Urb. herbs, in rat plasma. With paeoniflorin as an internal standard (IS), a simple liquid-liquid extraction process was employed for the plasma sample preparation. Chromatographic separation was achieved within 6 min on a Shim-pack CLC-ODS column using acetonitrile and water (60:40, v/v) containing 0.1% (v/v) formic acid as the mobile phase. The detection was performed by MS with electrospray ionization interface in negative selected ion monitoring (SIM) mode. The linear range was 11-5500 ng/mL with the square regression coefficient (r(2) ) of 0.9995. The lower limit of quantification was 11 ng/mL. The intra- and inter- day precision ranged from 4.99 to 9.03%, and the accuracy was between 95.82 and 111.80%. The average recoveries of madecassoside and IS from spiked plasma samples were >92%. The developed method was successfully applied to the pharmacokinetic study of madecassoside in rats after an oral administration.     

Simultaneous determination of 18alpha- and 18beta-glycyrrhetic acid in human plasma by LC-ESI-MS and its application to pharmacokinetics

A highly sensitive and selective LC-ESI-MS was developed, validated for the simultaneous determination of 18alpha-glycyrrhetic acid (alpha-GA) and 18beta-glycyrrhetic acid (beta-GA) for pharmacokinetic studies in healthy subjects. Sample preparation was performed by liquid-liquid extraction with ethyl acetate and the separations were achieved using a C(18) column with the mobile phase composed of 10 mmol/L ammonium acetate solution-methanol-acetonitrile (40:36:24, v/v/v) at a flow rate of 1 mL/min. The internal standard was honokiol and the epimers were quantified using a single quadrupole mass spectrometer employing ESI in the negative ion mode. The separation factor, alpha, was 1.512 for alpha- and beta-GA. The standard curves were linear for both epimers with coefficients of determination (r >or= 0.9998) over the concentration range of 1-150 ng/mL. The precision and accuracy were 相似文献   

Liquid chromatographic/mass spectrometric assay of rabeprazole in dog plasma for a pharmacokinetic study

In order to evaluate the pharmacokinetic (PK) profile of rabeprazole (RA) sterile powder for injection, a rapid, sensitive and specific assay for quantitative determination of RA in dog plasma was developed and validated. After a liquid-liquid extraction procedure, samples were analyzed by liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) using omepazole as the internal standard (IS). The analyte and IS was chromatographed on a ZORBAX Extend-C(18) analytical column (50 x 2 mm i.d, 5 microm, Agilent Technologies, USA). The assay was linear in the range 1-2000 ng/mL. The lower limit of quantification of RA was 1 ng/mL. The recovery of RA was greater than 70%. The within- and between-batch accuracy was 102.7-107.4% and 103.5-105.7%, respectively. The plasma samples for the PK study were collected at defined time points during and after an intravenous injection (1 mg/kg) to beagle dogs and analyzed by LC-ESI-MS method. The PK parameters, such as half-life, volume of distribution, total clearance and elimination rate constant, were determined. The PK profile of RA gave insights into the application in the clinics.