Determination of clindamycin in animal plasma by high-performance liquid chromatography combined with electrospray ionization mass spectrometry

A method for the quantification of clindamycin in animal plasma using high-performance liquid chromatography combined with electrospray ionization mass spectrometry (LC/ESI-MS/MS) is presented. Lincomycin is used as the internal standard. The sample preparation includes a simple deproteinization step with trichloroacetic acid. Chromatographic separation is achieved on an RP-18 Hypersil column using gradient elution with 0.01 M ammonium acetate and acetonitrile as mobile phase. Good linearity was observed in the range 0-10 microg ml(-1). The limit of quantification of the method is 50 ng ml(-1) and the limit of detection is 1.3 ng ml(-1). The method was shown out to be of use for pharmacokinetic studies of clindamycin formulations in dogs.     

Quantitation of glutathione by liquid chromatography/positive electrospray ionization tandem mass spectrometry

Glutathione (GSH) is a tripeptide composed of glutamate, cysteine, and glycine. It is present in practically all cells and has several important roles, such as preventing the oxidation of the sulfhydryl groups of proteins within a cell. Evidence for GSH deficiency or depletion has been found in a variety of diseases and toxicity-related studies, including diabetes and induction of oxidative stress to form reactive oxygen species which cause DNA, lipid, and protein oxidations. A simple, selective, and sensitive analytical method for measuring low levels of GSH in biological fluids would therefore be desirable to conduct GSH deficiency or depletion-related mechanistic toxicity studies. Here a method for both low- and high-level quantitation of GSH from cultured cells and rat liver tissues via liquid chromatography/positive electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) has been developed. The lower limit of quantitation (LOQ) of the method was 5 ng/mL. The method is linear over a wide dynamic concentration range of 5.0 to 5000.0 ng/mL, with a correlation coefficient R2 > 0.99. The intra-day assay precision relative standard deviation (RSD) values for all quality control (QC) samples were < or =16.31%, with accuracy values ranging from 94.13 to 97.80%. The inter-day assay precision RSD values for all QC samples were < or =15.94%, with accuracy values ranging from 94.51 to 100.29%. With this method, low levels of GSH from diethyl maleate (DEM)-treated mouse lymphoma cells, and GSH in rat liver tissues, were quantified.     

Determination of gentamicin in swine and calf tissues by high-performance liquid chromatography combined with electrospray ionization mass spectrometry

Gentamicin is a broad-spectrum aminoglycoside antibiotic widely used in veterinary medicine for the treatment of serious infections. The purpose of this study was to develop and validate a method to determine gentamicin residues in edible tissues of swine and calf. Extraction of gentamicin was performed using a liquid extraction with phosphate buffer containing trichloroacetic acid, followed by a solid-phase clean-up procedure on a CBA weak cation-exchange column. Tobramycin was used as the internal standard. After drying of the eluate, the residue was redissolved and further analyzed by reversed-phase liquid chromatography/electrospray ionization tandem mass spectrometry (MS/MS). Chromatographic separation of the internal standard tobramycin and the gentamicin components was achieved on a Nucleosil (5 microm) column using a mixture of 10 mM pentafluoropropionic acid in water and acetonitrile as the mobile phase. The gentamicin components C1a, C2 + C2a and C1 could be identified with the MS/MS detection, and subsequently quantified. The method was validated according to the requirements of the EC at the maximum residue limit (MRL) (100 ng g(-1) for muscle and fat, 200 ng g(-1) for liver and 1000 ng g(-1) for kidney), half the MRL and double the MRL levels. Calibration graphs were prepared for all tissues and good linearity was achieved over the concentration ranges tested (r > 0.99 and goodness of fit <10%). Limits of quantification of 25.0 ng g(-1) were obtained for the determination of gentamicin in muscle, fat, liver and kidney tissues of swine and calf, which correspond in all cases to at least half the MRLs. Limits of detection ranged between 0.5 and 2.5 ng g(-1) for the tissues. The within-day and between-day precisions (RSD) and the results for accuracy fell within the ranges specified. The method was successfully used for the determination of gentamicin in tissue samples of swines and calves medicated with gentamicin by intramuscular injection.     

High-resolution liquid chromatography/electrospray ionization time-of-flight mass spectrometry combined with liquid chromatography/electrospray ionization tandem mass spectrometry to identify polyphenols from grape antioxidant dietary fiber

Grape antioxidant dietary fiber (GADF) is a dietary supplement that combines the benefits of both fiber and antioxidants that help prevent cancer and cardiovascular diseases. The antioxidant polyphenolic components in GADF probably help prevent cancer in the digestive tract, where they are bioavailable. Mass spectrometry coupled to liquid chromatography is a powerful tool for the analysis of complex plant derivatives such as GADF. We use a combination of MS techniques, namely liquid chromatography/electrospray ionization time-of-flight mass spectrometry (LC/ESI-TOF-MS) and liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) on a triple quadrupole, for the identification of the polyphenolic constituents of the soluble fraction of GADF. First, we separated the mixture into four fractions which were tested for phenolic constituents using the TOF system in the full scan mode. The high sensitivity and resolution of the TOF detector over the triple quadrupole facilitate the preliminary characterization of the fractions. Then we used LC/ESI-MS/MS to identify the individual phenols through MS/MS experiments (product ion scan, neutral loss scan, precursor ion scan). Finally, most of the identities were unequivocally confirmed by accurate mass measurements on the TOF spectrometer. LC/ESI-TOF-MS combined with MS/MS correctly identifies the bioactive polyphenolic components from the soluble fraction of GADF. High-resolution TOF-MS is particularly useful for identifying the structure of compounds with the same LC/ESI-MS/MS fragmentation patterns.     

Determination of bencycloquidium bromide in dog plasma by liquid chromatography with electrospray ionization tandem mass spectrometry

A rapid, selective and sensitive liquid chromatography/tandem mass spectrometry (LC‐MS/MS) method was developed and validated for determining bencycloquidium bromide (BCQB) in beagle dog plasma. The plasma sample was deproteinized with methanol which contained l‐ethyl‐bencycloquidium bromide as internal standard, and supernantant was assayed by LC‐MS/MS. The chromatographic separation was performed on a Phenomenex C₁₈ column (100 × 2.0 mm, i.d., 3.0 μm) with a gradient programme mobile phase consisting of methanol and ammonium acetate (5 mm) containing 0.15% acetic acid and at a flow rate of 0.3 mL/min. Electrospray ionization in positive ion mode and selective reaction monitoring was used for the quantification of BCQB with a monitored transitions m/z 330.2 → 142.1 for BCQB and m/z 344.2 → 126.2 for IS. Validation results indicated that the lower limit of quantification was 0.05 ng/mL and the assay exhibited a linear range of 0.05–10.0 ng/mL and gave a correlation coefficient of 0.9998. The intra‐ and inter‐run precisions of the assay were 1.7–4.6 and 3.2–15.6%, respectively, and the intra‐ and inter‐day accuracies were ?8.8 to 1.1 and ?5.0 to 4.6%, respectively. The developed method was applied for the pharmacokinetic study of BCQB in beagle dogs following a single intranasal dose. Copyright © 2009 John Wiley & Sons, Ltd.     

液相色谱-电喷雾电离三重四级杆质谱测定畜禽肝脏中维吉尼亚霉素M1的残留量

建立了动物肝脏组织中维吉尼亚霉素M1残留的液相色谱-电喷雾电离三重四级杆质谱(LC-ESI-MS/MS)的测定方法。样品经0.2 mol/L NH4H2PO4和乙酸乙酯提取,分散型固相萃取PSA填料净化,采用正离子扫描多反应监测(MRM)模式下液质联用仪进行定性和定量分析。该方法省去耗时的固相萃取过程,回收率在67.2%～90.3%之间,RSD<10.0%;检测限为0.5μg/kg,定量限为1.0μg/kg。     

Analysis of phenolic compounds in rhubarbs using liquid chromatography coupled with electrospray ionization mass spectrometry

Rhubarb is an important herbal medicine for the treatment of constipation, inflammation, and cancer. In this study, a facile method based on liquid chromatography coupled with electrospray ionization tandem mass spectrometry has been established for the analysis of bioactive phenolic compounds in rhubarbs. From six rhubarb species, official (Rheum officinale, R. palmatum, and R. tanguticum) and unofficial (R. franzenbachii, R. hotaoense, and R. emodi), a total of 107 phenolic compounds were identified or tentatively characterized based on their mass spectra. These compounds include sennosides, anthraquinones, stilbenes, glucose gallates, naphthalenes, and catechins. Ion chromatograms for the identified compounds of different rhubarbs were then compared. Consistent with previous reports, sennosides and rhein were only detected in official rhubarbs. Unexpectedly, we found that R. officinale contained very different phenolic compounds from the other two official species. Sennoside A, which has been considered as the major purgative component of rhubarb, was only detected in R. officinale, while its close isomers were observed in R. palmatum and R. tanguticum. In addition, the predominant anthraquinone glycosides in R. officinale were found to be rhein 8-O-glucoside and emodin 1-O-glucoside, whereas those in R. palmatum and R. tanguticum were rhein 1-O-glucoside and emodin 8-O-glucoside. Stilbenes, which are the major constituents of unofficial rhubarbs, were also different among the species. Our results clarify the chemical composition of rhubarbs comprehensively for the first time. Due to the significant differences in chemical components of rhubarbs, we suggest that different Rheum species be used separately in clinical practice.     

Determination of cefquinome in pig plasma and bronchoalveolar lavage fluid by high-performance liquid chromatography combined with electrospray ionization mass spectrometry

The aim of this study was to develop a rapid and sensitive method for the quantification of cefquinome in animal plasma and bronchoalveolar lavage (BAL) fluid using high-performance liquid chromatography combined with electrospray tandem mass spectrometry (LC-ESI-MS/MS). Cefadroxil is used as internal standard. For plasma, the sample preparation includes a simple deproteinization step with a Microcon filter. This allows detecting the unbound cefquinome concentration, which is correlated with the concentration in other body fluids, such as BAL fluid. To be able to detect the total plasma concentration, deproteinization with acetonitrile, followed by a back-extraction of actonitrile with dichloromethane was performed. The BAL fluid is centrifuged to precipitate floating particles. Chromatographic separation is achieved on a PLRP-S column using 0.005% formic acid and methanol as mobile phase. For plasma, good linearity was observed in the range of 5-2500 ng ml(-1) for both the unbound and total concentration. The response in BAL fluid was linear in the range of 4-1000 ng ml(-1). The limit of quantification (LOQ) was set at 5.00 ng ml(-1) for plasma and at 4.00 ng ml(-1) for BAL fluid. The limit of detection (LOD) was 3.12 ng ml(-1) and 0.41 ng ml(-1) for the unbound and total concentration in plasma, respectively, and was 1.43 ng ml(-1) for BAL fluid. The method was shown to be of use in a pharmacokinetic study in pigs, where the correlation between cefquinome concentrations in plasma and BAL fluid of pigs was studied.     

Determination of flomoxef in human plasma by liquid chromatography/electrospray ionization tandem mass spectrometry

A specific, sensitive, rapid and reproducible method for the determination of flomoxef in human plasma using high‐performance liquid chromatography–tandem mass spectrometry was developed and validated. Flomoxef was detected using an electrospay ionization method operated in negative‐ion mode. Chromatographic separation was performed in gradient elution mode on a Luna® C₁₈(2) column (3 μm , 20 × 4.0 mm) at a flow rate of 1 mL/min and runtime 3.5 min. The mobile phase consisted of acetonitrile and water containing 0.1% formic acid as additive. Extraction of flomoxef from plasma and precipitation of plasma proteins was performed with acetonitrile with an absolute recovery of 86.4 ± 1.6%. The calibration curve was linear with a correlation coefficient of 0.999 over the concentration range 10–5000 ng/mL and the lower limit of quantification was 10 ng/mL. The intra‐ and inter‐day precisions were <11.8%, while the accuracy ranged from 99.6 to 109.0%. A stability study of flomoxef revealed that it could be successfully analyzed at 4ºС over 24 h, but it was unstable in solutions at room temperature during short‐term storage (4 h) and several freeze–thaw cycles. Copyright © 2013 John Wiley & Sons, Ltd.     

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.     

Characterization of phenolic compounds in Erigeron breviscapus by liquid chromatography coupled to electrospray ionization mass spectrometry

Erigeron breviscapus is an important herbal drug for the treatment of cardiovascular and cerebral vessel diseases. In this study, phenolic compounds were extracted from the whole plant of E. breviscapus and analyzed by high-performance liquid chromatography/electrospray ionization mass spectrometry. A total of 53 compounds were identified or tentatively characterized based on their UV and mass spectra. These compounds included caffeoylquinic acids (CQAs), CQA glucosides, malonyl-CQAs, acetyl-CQAs, caffeoyl-2,7-anhydro-3-deoxy-2-octulopyranosonic acids (CDOAs), caffeoyl-2,7-anhydro-2-octulopyranosonic acids (COAs), flavones, flavonols and flavonones. Most of them were reported for the first time from E. breviscapus and nineteen of them belonged to new compounds. The MS(n) spectra of CQA glucosides were similar to CQAs and they were discriminated by their retention times. No caffeic acid related ions (X(0) (-), Y(0) (-) and Z(0) (-)) were observed in MS(n) spectra of acyl-CQAs compared to those of CQAs. Fragment ions ((2,5)O(-), (3,6)O(-) and (4,6)O(-)) corresponding to ring cleavage were shown in MS(n) spectra of CDOAs and COAs, characteristic of this class of compounds. The 5,6,7-trihydroxyl-substituted flavones were dominant in E. breviscapus. Their [A--H](-) ions underwent the loss of a molecule of H(2)O, followed by the loss of CO, which was used to discriminate from other hydroxyl-substituted flavones. Our results are the first comprehensive analysis of E. breviscapus constituents and will be helpful for the quality control of the herb of E. breviscapus and its related preparations.     

高效液相色谱-串联质谱法测定纺织品中的致癌芳香胺

建立了高效液相色谱-串联质谱法(LC/MS/MS)测定纺织品中致癌芳香胺的检测方法.纺织品中的偶氮染料在柠檬酸缓冲液中用连二亚硫酸钠还原为芳香胺,用硅藻土提取还原液中的芳香胺,用乙醚洗脱,浓缩至近干后用甲醇定容.使用液相色谱-串联质谱进行测定,色谱柱为XTerra MS C18柱,流动相为甲醇和0.025 mol/L乙...     

Pharmacokinetics and metabolism of ulixertinib in rat by liquid chromatography combined with electrospray ionization tandem mass spectrometry

The purpose of this study was to develop and validate a simple and sensitive liquid chromatography tandem mass spectrometry method for the determination of ulixertinib in rat plasma. The plasma samples were precipitated with acetonitrile and then separated on a C₁₈ column with water containing 0.1% formic acid and acetonitrile as mobile phase at a flow rate of 0.3 mL/min. Analytes were monitored on a TSQ Vantage triple quadrupole tandem mass spectrometer operated in positive electrospray ionization mode. Selected reaction monitoring transitions were m/z 433.1→262.1 for ulixertinib and m/z 450.1→260.1 for internal standard. The assay achieved good linearity over the concentration range of 0.1‐1000 ng/mL with correlation coefficient > 0.9991. The validated assay has been successfully applied to pharmacokinetic study of ulixertinib in rat after oral and intravenous administration. The results revealed that ulixertinib showed high exposure in rat plasma, low clearance, moderate oral bioavailability (45.13%), and dose‐independent pharmacokinetic profiles over the oral dose range of 1‐15 mg/kg. In addition, six metabolites from rat plasma and hepatocytes were detected and structurally identified by ultra‐high performance liquid chromatography combined with high‐resolution mass spectrometry. The metabolic pathways of ulixertinib referred to hydroxylation and dealkylation and glucuronidation.     

Determination of polar organic compounds in atmospheric aerosols by gas chromatography with ion trap tandem mass spectrometry

A gas chromatography with ion trap mass spectrometry method has been developed and validated for the analysis of 27 polar organic compounds in atmospheric aerosols. The target analytes were low‐molecular‐weight carboxylic acids and methoxyphenols, as relevant markers of source emissions and photochemical processes of organic aerosols. The operative parameters were optimized in order to achieve the best sensitivity and selectivity for the analysis. In comparison with the previous gas chromatography with mass spectrometry procedure based on single ion monitoring detection, the tandem mass spectrometry technique increased the analytical sensitivity by reducing detection limits for standard solutions from 1–2.6 to 0.1–0.4 ng/μL ranges (concentrations in the injected solution). In addition, it enhanced selectivity by reducing matrix interferences and chemical noise in the chromatogram. The applicability of the developed method in air quality monitoring campaigns was effectively checked by analyzing environmental samples collected in the Po Valley (Northern Italy) in different seasons. The obtained results indicate that the ion trap mass spectrometer may be an ideal alternative to high‐resolution mass spectrometers for the user‐friendly and cost‐effective determination of a wide range of molecular tracers in airborne particulate matter.     

Determination of deltamethrin residues in plant materials by liquid chromatography/tandem mass spectrometry with electrospray ionization

This paper describes a selective and sensitive method that uses liquid chromatography/tandem mass spectrometry with positive electrospray ionization (ESI+) for the determination of deltamethrin in a variety of crops. Samples were extracted by conventional high-speed blending. Some samples required no further cleanup; others were cleaned up by gel permeation chromatography, strong cation-exchange cartridges, or partitioning with n-hexane. In the determinative step, the buffered neutral mobile phase, consisting of 10 mM ammonium acetate (pH 6.8) and methanol, and ESI+ provided strong ammonium adduct formation to [M+NH4]+ at m/z 523, and the multiple-reaction monitoring (MRM) transition at m/z 523/281 was used for the quantitation of deltamethrin. A second MRM transition at m/z 525/283 was used for confirmation. The limit of quantitation (LOQ) values were 0.01 mg/kg for edible materials and 0.05 mg/kg for nonedible materials. Mean overall recoveries at the LOQ and the 10-fold LOQ ranged from 73 to 96%, and the relative standard deviations were <10% for all samples materials analyzed.     

Analysis of phenolic compounds in Epimedium plants using liquid chromatography coupled with electrospray ionization mass spectrometry

A new method based on HPLC coupled with electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) has been established for the analysis of phenolic compounds in Epimedium plants. The characteristic fragmentation pathways of 29 phenolic compounds were studied, and 126 compounds were identified or tentatively characterized based on their mass spectra from fourteen samples including the aerial samples and the underground parts of the seven species. Furthermore, the differences in phenolic compound profiles between different Epimedium plants and two parts of the seven species were reported for the first time. Due to their significant chemical differences, these Epimedium species should be used separately in clinical practice.     

Determination of chlorantraniliprole residues in crops by liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry/mass spectrometry

An analytical method is presented for the determination of chlorantraniliprole residues in crops. Chlorantraniliprole residues were extracted from crop matrixes with acetonitrile after a water soak. The extracts were passed through a strong anion-exchange (SAX) SPE cartridge stacked on top of a reversed-phase (RP) polymer cartridge. After both cartridges were rinsed and vacuum-dried, the SAX cartridge was removed, and chlorantraniliprole was eluted from the RP polymer cartridge with acetonitrile. The acetonitrile eluate was evaporated to dryness, reconstituted, and analyzed using an LC/MS/MS instrument equipped with an atmospheric pressure chemical ionization source. The method was successfully validated at 0.010, 0.10, and 10 mg/kg for the following crop matrixes: potatoes, sugar beets (tops), lettuce, broccoli, soybeans, soybean forage, tomatoes, cucumbers, oranges, apples, pears, peaches, almonds (nutmeat), rice grain, wheat grain, wheat hay, corn stover, alfalfa forage, cottonseed, grapes, and corn grain. The average recoveries from all crop samples fortified at the method LOQ ranged from 91 to 108%, with an overall average recovery of 97%. The average recoveries from all crop samples fortified at 10 times the method LOQ ranged from 89 to 115%, with an overall average recovery of 101%. For all of the fortified control samples analyzed in this study, the overall average recovery was 99%.     

Quantitative analysis of oxytetracycline and its 4-epimer in calf tissues by high-performance liquid chromatography combined with positive electrospray ionization mass spectrometry

Tetracycline antibiotics are commonly used in veterinary medicine because of their broad spectrum activity and cost effectiveness. Oxytetracycline (OTC) is one of the most important members of this antibiotic family. The purpose of this study was to develop and validate a method to determine OTC residues in edible tissues of calf. Extraction of OTC and its 4-epimer (4-epiOTC), in the presence of the internal standard demethylchlortetracycline (DMCTC), was performed using a liquid extraction with sodium succinate solution (pH 4.0), followed by protein removal with trichloroacetic acid and paper filtration. Further solid-phase extraction clean-up on an HLB polymeric reversed phase column was performed to obtain an extract suitable for LC-MS-MS analysis. Chromatographic separation of the internal standard, and especially OTC and its 4-epimer, was achieved on a PLRP-S polymeric reversed phase column, using a mixture of 0.001 M of oxalic acid, 0.5% (v/v) of formic acid and 3% (v/v) of tetrahydrofuran in water (mobile phase A) and tetrahydrofuran (mobile phase B) as the mobile phase, and at a column temperature of 60 degrees C. OTC and its 4-epimer could be identified using the MS-MS detection technique, and were subsequently quantified. The method has been validated according to the requirements of the EC at the MRL (maximum residue limit, 100 ng g(-1) for muscle, 300 ng g(-1) for liver and600 ng g(-1) for kidney), half the MRL and double the MRL levels, as well for OTC as for 4-epiOTC. Calibration graphs were prepared for all tissues and good linearity was achieved over the concentration ranges tested (r > 0.99 and goodness of fit < 10%). Limits of quantification of half the MRLs were obtained for the analysis of OTC and 4-epiOTC in muscle, liver and kidney tissues of calf. Limits of detection ranged for both components between 0.8 and 48.2 ng g(-1). The within-day and between-day precisions, expressed as RSD values, were all below the maximum allowed RSD values calculated according to the Horwitz equation. The results for accuracy fell within the -20% to +10% range. Recoveries were between 47 and 56% for OTC, and between 52 and 62% for 4-epiOTC, depending on the tissue. The method has been successfully used for the quantitative determination of OTC and 4-epiOTC in tissue samples of calves medicated with OTC by intramuscular injection.