Liquid chromatographic/tandem mass spectrometric method for the quantitation of tranilast in human plasma

An analytical method for the determination of tranilast in human plasma using tramadol as the internal standard has been developed based on liquid chromatography/tandem mass spectrometry. Sample preparation involved protein precipitation with methanol. Separation by reversed-phase high-performance liquid chromatography using methanol/10 mM ammonium acetate (70: 30, v/v) as mobile phase was complete in a run time of 2.4 min. Detection on a Q TRAP system used multiple reaction monitoring. The method was linear in the range 0.06-20 microg/mL with intra- and inter-day precisions (as relative standard deviation) of 2.2-2.6% and 2.3-2.9%, respectively. Accuracy (as relative error) was <-2.5%. The method was applied in a pharmacokinetic study in healthy volunteers treated with a single 80 mg oral dose of tranilast.     

Analytical monitoring of the production of biodiesel by high-performance liquid chromatography with various detection methods.

Gradient elution reversed-phase high-performance liquid chromatography (RP-HPLC) was used for the determination of compounds occurring during the production of biodiesel from rapeseed oil. Individual triacylglycerols (TGs), diacylglycerols, monoacylglycerols and methyl esters of oleic, linoleic and linolenic acids and free fatty acids were separated in 25 min using a combined linear gradient with aqueous-organic and non-aqueous mobile phase steps: 70% acetonitrile+30% water in 0 min, 100% acetonitrile in 10 min, 50% acetonitrile+50% 2-propanol-hexane (5:4, v/v) in 20 min and 5 min final hold-up. Another method with a non-aqueous linear mobile phase gradient [from 100% methanol to 50% methanol+50% 2-propanol-hexane (5:4, v/v) in 15 min] was used for fast monitoring of conversion of rapeseed oil triacylglycerols to fatty acid methyl esters and for quantitation of residual TGs in the final biodiesel product. Sensitivity and linearity of various detection modes (UV detection at 205 nm, evaporative light scattering detection and mass spectrometric detection) were compared. The individual sample compounds were identified using coupled HPLC-atmospheric pressure chemical ionization mass spectrometry in the positive-ion mode.     

Supercritical fluid chromatography with post-column addition of supporting electrolyte solution for electrochemical determination of tocopherol and tocotrienol isomers

A supercritical fluid chromatography with electrochemical detection system was developed for the simultaneous determination of tocopherol and tocotrienol isomers. The supercritical fluid chromatography with electrochemical detection system was connected with an additional pump to create a flow path to add a supporting electrolyte solution. The supporting electrolyte solution was mixed with a mobile phase in a post-column fashion, enabling the independent control of the separation and detection. After optimization of the measurement conditions, vitamin E isomers and an internal standard substance (2,2,5,7,8-pentamethyl-6-hydroxychroman) were separated within 30 min using a mixture of supercritical carbon dioxide and methanol (99:1, v/v) as a mobile phase and a cyanopropyl column (4.6 mm inner diameter × 250 mm length, 5 μm). For the electrochemical detection, methanol containing 1.0 mol/L ammonium acetate was used as a supporting electrolyte solution, and the applied potential was set at +0.8 V. This analytical method showed good linearity (5–100 μg/mL) and repeatability (less than 2.5% relative standard deviation, n = 6) and was applicable to the determination of tocopherol and tocotrienol isomers in nutrition supplements.     

Qualitative analysis of some carboxylic acids by ion-exclusion chromatography with atmospheric pressure chemical ionization mass spectrometric detection

A simple, selective and sensitive method for the determination of carboxylic acids has been developed. A mixture of formic, acetic, propionic, valeric, isovaleric, isobutyric, and isocaproic acids has been separated on a polymethacrylate-based weak acidic cation-exchange resin (TSK gel OA pak-A) based on an ion-exclusion chromatographic mechanism with detection using UV-photodiode array, conductivity and atmospheric pressure chemical ionization mass spectrometry (APCI-MS). A mobile phase consisting of 0.85 mM benzoic acid in 10% aqueous methanol (pH 3.89) was used to separate the above carboxylic acids in about 40 min. For LC-MS, the APCI interface was used in the negative ionization mode. Linear plots of peak area versus concentration were obtained over the range 1-30 mM (r2=0.9982) and 1-30 mM (r2=0.9958) for conductimetric and MS detection, respectively. The detection limits of the target carboxylic acids calculated at S/N=3 ranged from 0.078 to 2.3 microM for conductimetric and photometric detection and from 0.66 to 3.82 microM for ion-exclusion chromatography-APCI-MS. The reproducibility of retention times was 0.12-0.16% relative standard deviation for ion-exclusion chromatography and 1.21-2.5% for ion-exclusion chromatography-APCI-MS. The method was applied to the determination of carboxylic acids in red wine, white wine, apple vinegar, and Japanese rice wine.     

固相萃取-超临界流体色谱-质谱联用同时快速测定中成药和保健食品中的12种抗过敏化学药物

建立了固相萃取-超临界流体色谱-质谱联用（SPE-SFC-MS/MS）快速检测中成药和保健食品中12种抗过敏化学药物的分析方法。样品经甲醇超声提取,Oasis MCX固相萃取柱净化。采用Waters Trefoil CEL1色谱柱（150 mm×3.0 mm,2.5 μ m）,以CO₂为流动相A,甲醇-氨水（100：0.1,v/v）为流动相B,进行梯度洗脱。流速为1.2 mL/min,柱温和背压分别为45℃和12.4×10⁶ Pa。12种抗过敏化学药物以电喷雾离子源在正离子或负离子模式下用多反应监测（MRM）方式进行监测,整个分析过程在10 min内完成。结果表明,12种化学药物在5~250 μ g/L范围内线性关系良好,相关系数（r）均≥ 0.998,检出限（LOD）为0.141~0.262 μ g/L,定量限（LOQ）为0.703~1.308 μ g/L。3种加标水平（10、20和100 μ g/L）下,12种化学药物的平均回收率为76.1%~112.5%,相对标准偏差（RSD）为1.1%~8.3%。该法简便,灵敏性高,实用性强,可用于抗过敏类中成药和保健食品中非法添加抗过敏化学药物的检测。     

Determination of carboxylic acids in water by gas chromatography using several detectors after flow preconcentration

A novel analytical method is reported that combines continuous solid-phase extraction and gas chromatography for the determination of 22 carboxylic acids in water. The highly polar and hydrophilic analytes were preferentially sorbed on a mixture of LiChrolut EN-Supelclean ENVI-18 (1:1) sorbent column and eluted with methanol; this extraction process did not require derivatisation. The extract was analysed by gas chromatography coupled to a flame ionisation detector as well as a mass spectrometer with electron impact (EI) or positive chemical ionisation modes. The highest sensitivity was achieved when using MS-EI, with good linearity in calibration curves and low detection limits (2-40ngL(-1)) for 50mL of sample. The entire procedure from raw aqueous sample to a ready-to-inject methanol solution of the acids requires less than 15min. Another benefit of this method is the good accuracy (recoveries between 93 and 102%) and precision (relative standard deviation, 3.4-6.2%), which allows the determination of carboxylic acids in environmental water and in real chlorinated and ozonated drinking water.     

Detecting aristolochic acids in herbal remedies by liquid chromatography/serial mass spectrometry

Targeted liquid chromatography/serial mass spectrometry (LC/MS/MS) analysis, using a quadrupole ion-trap mass spectrometer, permitted the detection of aristolochic acids I and II in crude 70% methanol extracts of multi-component herbal remedies without any clean-up or concentration stages. The best ionisation characteristics were obtained using atmospheric pressure chemical ionisation (APCI) and by including ammonium ions in the mobile phase. Limits of detection for aristolochic acids were influenced by the level of interference created by other components in the sample matrix. They were determined to be between 250 pg and 2.5 ng on-column within a matrix containing compounds extracted from 2 mg of herbal remedy. With a herbal remedy that only permitted the higher limit of detection, this sensitivity was sufficient to detect the aristolochic acids extracted from 0.1% dry weight of Aristolochia manshuriensis included in the preparation.     

Liquid chromatographic determination of flumetsulam in soybeans

A liquid chromatography (LC) method with UV detection is reported for the determination of the sulfonamide herbicide flumetsulam in soybeans. The ground soybean sample was partitioned between methanol and hexane. The hexane removed the lipids, and the methanol layer containing the analyte was further partitioned between dichloromethane and aqueous phosphate buffer at pH 7.0. The aqueous layer, containing the analyte, was acidified to pH 2.2 and partitioned with fresh dichloromethane. The dichloromethane layer containing the analyte was evaporated, and the residue was dissolved in the LC mobile phase for analysis. A polar embedded C18 column was used with a mobile phase of pH 2.2 aqueous phosphate buffer-acetonitrile (68 + 32), run isocratically with detection at 225 nm. The average recovery was 82% with a relative standard deviation (RSD) of 10%. A coefficient of determination of R2 = 0.9992 was achieved for the analyte calibration curve, from 0.005 to 1 microg/mL. The limit of detection, determined from 3 times the standard deviation of 7 replicate extractions of the lowest fortification level (0.01 microg/g), was 0.005 microg/g with an RSD of 22%. LC/electrospray ionization/mass spectrometry in the positive-ion mode was used for identity confirmation of flumetsulam in the fortified soybean extract. The ions at m/z 326, 348, and 129 were observed.     

Quantitative determination of acetylcholine in microdialysis samples using liquid chromatography/atmospheric pressure spray ionization mass spectrometry

A fast, simple and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for the determination of acetylcholine in rat brain microdialysis samples. The chromatographic separation was achieved in 3 min on a reversed-phase column with isocratic conditions using a mobile phase containing 2% (v/v) of acetonitrile and 0.05% (v/v) of trifluoroacetic acid (TFA). A stable isotope-labeled internal standard was included in the analysis and detection was carried out with a linear ion trap mass spectrometer using selected reaction monitoring (SRM). Analyte ionization was performed with an atmospheric pressure chemical ionization (APCI) source without applying discharge current (atmospheric pressure spray ionization). This special ionization technique offered significant advantages over electrospray ionization for the analysis of acetylcholine with reversed-phase ion-pairing chromatography. The lower limit of quantification was 0.15 nM (1.5 fmol on-column) and linearity was maintained over the range of 0.15-73 nM, providing a concentration range that is significantly wider than that of the existing LC/MS methods. Good accuracy and precision were obtained for concentrations within the standard curve range. The method was validated and has been used extensively for the determination of acetylcholine in rat brain microdialysis samples.     

Supercritical fluid chromatography coupled with tandem mass spectrometry: A high‐efficiency detection technique to quantify Taxane drugs in whole‐blood samples

We present a technique to rapid determine taxane in blood samples by supercritical fluid chromatography together with mass spectrometry. The aim of this study was to develop a supercritical fluid chromatography with mass spectrometry method for the analysis of paclitaxel, cabazitaxel, and docetaxel in whole‐blood samples of rats. Liquid‐dry matrix spot extraction was selected in sample preparation procedure. Supercritical fluid chromatography separation of paclitaxel, cabazitaxel, docetaxel, and glyburide (internal standard) was accomplished within 3 min by using the gradient mobile phase consisted of methanol as the compensation solvent and carbon dioxide at a flow rate of 1.0 mL/min. The method was validated regarding specificity, the lower limit of quantification, repeatability, and reproducibility of quantification, extraction recovery, and matrix effects. The lower limit of quantification was found to be 10 ng/mL since it exhibited acceptable precision and accuracy at the corresponding level. All interday accuracies and precisions were within the accepted criteria of ±15% of the nominal value and within ±20% at the lower limit of quantification, implying that the method was reliable and reproducible. In conclusion, this method is a promising tool to support and improve preclinical or clinical pharmacokinetic studies with the taxanes anticancer drugs.     

Simultaneous determination of 17 bisphenols in polycarbonate by ultra‐high performance supercritical fluid chromatography with tandem mass spectrometry

A novel method was developed for the first time for the determination of 17 bisphenols by ultra‐high performance supercritical fluid chromatography with tandem mass spectrometry. Under the optimal conditions, 17 bisphenols were separated successfully on a high density diol column in 9 min using methanol and carbon dioxide as mobile phase. 0.02% ammonium hydroxide/methanol v/v was used as the post‐column compensation solvent to improve response of mass spectrometry. Linear relations of matrix‐matched calibration curve were favorable over the selected concentration range of 1–100 μg/kg with correlation coefficients greater than 0.9981. The method limit of detection and limit of quantitation were 0.1–0.5 μg/kg and 0.5–2.5 μg/kg, respectively. The average recoveries at three spiked levels in polycarbonate were in the range of 81.8–114.5%. Intra‐day and inter‐day precisions for six replicates were below 15.0%. This method was successfully applied to determine bisphenols in polycarbonate.     

Simultaneous quantitation of the diastereoisomers of scholarisine and 19‐epischolarisine,vallesamine, and picrinine in rat plasma by supercritical fluid chromatography with tandem mass spectrometry and its application to a pharmacokinetic study

Dengtaiye tablet has been used to treat chronic bronchitis cough. Scholarisine, 19‐epischolarisine, vallesamine, and picrinine are the representative constituents of Dengtaiye. A rapid and sensitive assay based on supercritical fluid chromatography with tandem mass spectrometry has been developed and validated for the determination of the diastereoisomers of scholarisine and 19‐epischolarisine, vallesamine, and picrinine in rat plasma using lamotrigine as internal standard. The analysis in a run time of only 6 min was performed on an ACQUITY UPC² Trefoil^TM BEH 2‐EP column (3.0 × 150 mm, 2.5 μm) at 50ºC. The mobile phase consisting of carbon dioxide and methanol (2 mM ammonium formate) was performed as follows: 15% methanol (2 mM ammonium formate) maintained at 0–2 min, 15–19% methanol (2 mM ammonium formate) at 2–4 min, 19–15% methanol (2 mM ammonium formate) at 4–6 min. The flow rate was 1.50 mL/min. The assay was linear over the concentration ranges 50–10000 pg/mL for scholarisine, 19‐epischolarisine, vallesamine, and picrinine with corresponding lower limits of quantitation of 50 pg/mL. Intra‐ and interday precisions were in the range 1.42–12.85% with accuracies in the range –11.71–2.48%. The method was successfully applied to a pharmacokinetic study involving a single oral administration of 108 mg/kg Dengtaiye tablet to rats.     

超高效液相色谱-串联质谱法测定食用植物油中胆固醇含量

提出了食用植物油中胆固醇的超高效液相色谱-串联质谱测定方法。食用植物油经皂化后用石油醚-乙醚(1+1)溶液提取,以Waters ACQUITY UPLC BEH C18色谱柱(50mm×2.1mm,5μm)为分离柱,以甲酸-甲醇(0.1+99.9)溶液为流动相,以2,2,3,4,4,6-d6胆固醇为内标,采用大气压化学电离源在多反应监测负离子模式下进行测定,胆固醇和内标的定量离子对分别为m/z369.2/146.9,369.2/160.9和375.2/166.5。胆固醇在0.1～5mg·L-1范围内呈线性,测定下限(10S/N)为0.02ng。在3个浓度水平上对方法做回收试验,测得回收率在102%～110%之间。     

Capillary column supercritical fluid chromatography-atmospheric pressure ionisation mass spectrometry interface performance of atmospheric pressure chemical ionisation and electrospray ionisation.

A supercritical fluid chromatography interface probe for atmospheric pressure ionisation mass spectrometry (API-MS) with the advantage of convenient switch between ionisation modes [atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI)] has recently been reported [P.J.R. Sj?berg, K.E. Markides, J. Chromatogr. A, 785 (1997) 101]. In order to obtain a stable ion signal and a low minimum detectable quantity, the design of the spray devise has to be optimised. For easy optimisation in the APCI mode, the corona needle was mounted directly on the interface probe. To compensate for the adiabatic cooling of the expanding mobile phase in the APCI mode, a heated region around the restrictor tip was used. In comparison, ESI required no additional heat, which might also prevent fragmentation for thermolabile compounds. As the mobile phase used was neat CO2, a low flow of make-up liquid was utilised in the ESI mode for transfer of the analytes from the expanding CO2 gas to the liquid phase before ionisation. The low make-up liquid flow in the ESI mode was sufficient for preventing the restrictor from becoming blocked. Factors that influence the ion signal intensity and stability have been studied. In APCI mode, corona needle position, nebuliser gas flow and gas additives were studied and in ESI mode, spray capillary assembly dimension and position, liquid flow-rate and composition were studied. The achievable detection limits were in the 50-0.1 pg (i.e., 290 fmol-140 amol) range. The detection limit in APCI mode was improved by a factor of about 20-25 compared to an earlier design [L.N. Tyrefors, R.X. Moulder, K.E. Markides, Anal. Chem. 65 (1993) 2835].     

Column liquid chromatography coupled on-line with mass spectrometry using post-column phosphate suppression

The coupling of column liquid chromatography on-line with mass spectrometry using post-column phosphate suppression is described. A membrane suppressor is used to remove the non-volatile phosphate ions from the mobile phase after the chromatographic separation prior to introduction into the mass spectrometer. Using post-column phosphate suppression by a membrane device phosphate concentrations up to 10 mM phosphate, at a mobile phase flow rate of 0.1 ml/min, could be removed for more than 99% without any decay of the sensitivity of the MS detection. Using a new antidepressant tetracyclic basic compound, ORG 4428, and some structure related compounds as model compounds electron impact as well as chemical ionisation spectra of all compounds could be obtained. The set-up could be used for several weeks running, using a phosphate containing mobile phase, without any loss of performance.     

反相高效液相色谱法测定康肾颗粒中的葛根素

建立了反相高效液相色谱分离、质谱定性、紫外检测定量测定康肾颗粒中葛根素含量的方法。采用YMC-ODS色谱柱(4.6 mm i.d.×100 mm,10 μm),选用甲醇(含0.1%三氟醋酸)和水(含0.1%三氟醋酸)体系为流动相,非线性梯度洗脱分离,流速1.0 mL/min,检测波长250 nm;用基质辅助激光解吸离子化飞行时间质谱(MALDI-TOF MS)分析鉴定对照品和样品的馏分,在确定目标峰后进行紫外检测定量测定。结果表明,葛根素在0.132 ~1.32 μg范围内其峰面积与进样量呈良好的线性关系（r=0.9997）,平均加标回收率高于103%,相对标准偏差低于2.0%(n=6)。应用该方法测定康肾颗粒中葛根素,其平均含量为3.09 mg/g。该方法简单、快速、重现性好。     

A liquid chromatography-mass spectrometry method for the quantitation of aristololactam-I in rat plasma

A sensitive method with liquid chromatography-electrospray ionization mass spectrometry has been developed and validated for the determination of aristololactam-I in rat plasma after oral administration of aristolochic acid-I using finesteride as the internal standard. Chromatographic separation was achieved on a Lichrospher C(18) column using methanol:0.05% acetic acid in water (71:29, v/v) as a mobile phase delivered at a flow rate of 1 mL/min. The assay was linear for aristololactam-I over the range 0.3-300 ng/mL. The analysis of quality control samples demonstrated precision with coefficient of variation less than 20% (n = 5). Absolute recovery of aristololactam-I was 90.4-97.3%. The LC-MS method for the determination of aristololactam-I is sensitive, specific and can be used to investigate the toxicokinetics of aristololactam-I.     

Supercritical fluid chromatography with tandem mass spectrometry combined with postcolumn compensation and one‐step acetone protein precipitation to evaluate the bioavailability of probucol solid dispersion tablet

Solid dispersion technology was used to improve the bioavailability of probucol due to its low hydrophilicity and high lipophilicity. In this study, a highly rapid and sensitive supercritical fluid chromatography with tandem mass spectrometry method was optimized and validated for the determination of probucol in beagle dog plasma with diazepam as an internal standard. The analyte and internal standard were extracted by acetone and then separated on a polar 2‐ethylpyridine phase column (100 mm × 3 mm, 1.7 μm) at a flow rate of 1.0 mL/min using CO₂ (≥99.99%) and methanol (95:5, v/v) as the mobile phase. The mass transition ion‐pair was m/z 515.6→236.2 and 285.2→193.1 for probucol and internal standard, respectively. Excellent linearity was observed over the concentration range of 5–5000 ng/mL (r² ≥ 0.9999) with a lower limit of quantification of 5 ng/mL. The intra‐ and inter‐day accuracy and precision for all quality control samples were within ±15%. The proposed method was accurate, rapid and reproducible, which was successfully applied to a bioavailabilty evaluation of probucol solid dispersion tablets.     

Development and validation of an LC‐APCI‐MS/MS method for the determination of phenethyl isothiocyanate in human plasma

Phenethyl isothiocyanate (PEITC) is a promising chemopreventive agent present in cruciferous vegetables. This paper describes the development of a method for the determination of PEITC in human plasma by liquid chromatography/tandem mass spectrometry (LC‐MS/MS). Atmospheric‐pressure chemical ionization was found more suitable for ionization of PEITC than electrospray ionization. Because of the lability of PEITC, a combination of low temperature and acidification was applied to minimize the degradation during the sample collection and preparation procedure. A simple protein precipitation with acetonitrile was used for the preparation of plasma samples. The analyte and 1‐phenylpropyl isothiocyanate as internal standard (IS) were subjected to chromatographic analysis on a C₁₈ column (50 × 2.1 mm, 5 µm) using 85% methanol as mobile phase at a flow rate of 0.3 mL/min. The total analysis time for each chromatograph was 3 min and the results were linear over the studied range (5.00–250 ng/mL). The intra‐ and inter‐day precision values were acceptable as per US Food and Drug Administration guidelines. This method was successfully applied in the determination of PEITC concentrations in plasma samples from healthy chinese Volunteers. Copyright © 2014 John Wiley & Sons, Ltd.     

超临界流体色谱法分析非对映异构体d4T-5’-N-磷酰化苯丙氨酸甲酯

采用超临界CO2流体色谱技术,分析d4T-5’-N-磷酰化苯丙氨酸甲酯手性磷的非对映异构体。色谱柱为Hpersil ODS2(250 mm×4.6 mm,5μm),流动相为夹带改性剂甲醇、乙醇和异丙醇的超临界CO2流体。以容量因子、选择性和分离度为指标,考察改性剂、背压和柱温对分离的影响。在甲醇、乙醇和异丙醇3种改性剂中,甲醇为最好的改性剂,其中在7%甲醇改性剂下,该化合物的分离度可达到3.35。在7%甲醇改性剂条件下,考察了压力(10～20 MPa)和温度(303.15～318.15 K)的影响。在优化的分离条件(改性剂为7%甲醇,流速为2 mL/min,柱温为308.15 K,背压为15 M Pa)下,d4T-5’-N-磷酰化苯丙氨酸甲酯的两种非对映异构体完全达到基线分离,分离时间约15 min。