Developing a robust LC-MS/MS method to quantify Zn-DTPA, a zinc chelate in human plasma and urine.

Quantitation of Zn-DTPA (zinc diethylenetriamene pentaacetate, a metal chelate) in complex biological matrix is extremely challenging on account of its special physiochemical properties. This study aimed to develop a robust and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of Zn-DTPA in human plasma and urine. The purified samples were separated on Proteonavi (250 × 4.6 mm, 5 µm; Shiseido, Ginza, Tokyo, Japan) and a C18 guard column. The mobile phase consisted of methanol-2 mm ammonium formate (pH 6.3)-ammonia solution (50:50:0.015, v/v/v), flow rate 0.45 mL/min. The linear concentration ranges of the calibration curves for Zn-DTPA were 1-100 µg/mL in plasma and 10-2000 µg/mL in urine. The intra- and inter-day precisions for quality control (QC) samples were from 1.8 to 14.6% for Zn-DTPA and the accuracies for QC samples were from -4.8 to 8.2%. This method was fully validated and successfully applied to the quantitation of Zn-DTPA in plasma and urine samples of a healthy male volunteer after intravenous infusion administration of Zn-DTPA. The result showed that the concentration of Zn-DTPA in urine was about 20 times that in plasma, and Zn-DTPA was completely (94.7%) excreted through urine in human.

Simultaneous quantification of tizoxanide and tizoxanide glucuronide in mouse plasma by liquid chromatography-tandem mass spectrometry.

Nitazoxanide (NTZ) is a broad-spectrum antimicrobial agent. Tizoxanide (T) and tizoxanide glucuronide (TG) are the major circulating metabolites after oral administration of NTZ. A rapid and specific LC-MS/MS method for the simultaneous quantification of T and TG in mouse plasma was developed and validated. A simple acetonitrile-induced protein precipitation method was employed to extract two analytes and the internal standard glipizide from 50 µL of mouse plasma. The purified samples were resolved using a C18 column with a mobile phase consisting of acetonitrile and 5 mm ammonium formate buffer (containing 0.05% formic acid) following a gradient elution. An API 3000 triple quadrupole mass spectrometer was operated under multiple reaction-monitoring mode with electrospray ionization. The precursor-to-product ion transitions m/z 264 → m/z 217 for T and m/z 440 → m/z 264 for TG were used for quantification. The developed method was linear in the concentration ranges of 1.0-500.0 ng/mL for T and 5.0-1000.0 ng/mL for TG. The intra- and inter-day precision and accuracy of the quality control samples at low, medium and high concentrations exhibited an RSD of <13.2% and the accuracy values ranged from -9.6 to 9.3%. We used this validated method to study the pharmacokinetics of T and TG in mice following oral administration of NTZ. Copyright © 2016 John Wiley & Sons, Ltd.

A sensitive LC-MS/MS method for quantifying capsaicin and dihydrocapsaicin in rabbit plasma and tissue: application to a pharmacokinetic study.

Prescription and nonprescription products for topical management of pain, including cream, lotion and patch forms, contain capsaicin (CAP) and dihydrocapsaicin (DHC). There are few in vivo studies on absorption, bioavailability and disposition of CAP and DHC. We established a sensitive and rapid LC-MS/MS assay to determine CAP and DHC levels in rabbit plasma and tissue. Bio-samples prepared by liquid-liquid extraction using n-hexane-dichloromethane-isopropanol (100: 50: 5, v/v/v) mixture were separated by isocratic chromatography with an Extend C18 column. The mobile phase was acetonitrile-water-formic acid (70: 30: 0.1, v/v/v). The method was linear from 0.125 to 50 ng/mL for a 100 µL bio-sample, and the lower quantification limit was 0.125 ng/mL. Total run time to analyze each sample was 3.5 min. We used this validated method to study pharmacokinetics and tissue distribution of CAP gel administered topically to rabbits. A very small amount of CAP and DHC was absorbed into the systemic circulation. The highest plasma concentration was 2.39 ng/mL, and the mean peak plasma concentration value after 12 h of CAP gel application was 1.68 ng/mL. Drug concentration in treated skin was relatively high, with low concentration in other tissues. Thus, topical CAP gel had strong local effects and weaker systemic effects.

Development of a sensitive liquid chromatography/tandem mass spectrometry method for the determination of fenofibric acid in rat plasma.

A rapid and sensitive LC-MS/MS method for the quantification of fenofibric acid in rat plasma was developed and validated. Plasma samples were prepared by liquid-liquid extraction with a mixture of N-hexane-dichloromethane-isopropanol (100:50:5, v/v/v). Isocratic chromatographic separation was performed on a reversed-phase Discovery C(18) column (2.1 × 50 mm, 5 µm). The mobile phase was methanol-water-formic (75:25:0.25, v/v/v). Detection of fenofibric acid and the internal standard (IS) diclofenac acid was achieved by ESI MS/MS in the negative ion mode using m/z 317 → m/z 213 and m/z 294 → m/z 250 transitions, respectively. The method was linear from 0.005 to 1.250 µg/mL when 100 µL plasma was analyzed. The lower limit of quantification was 0.005 µg/mL. The intra- and inter-day precision values were below 8.2%, and accuracy ranged from -0.9 to 2.1% in all quality control samples. The recovery was 90.3-94.7% and 83.3% for fenofibric acid and IS, respectively. Total run time for each sample analysis was 2.5 min. The validated method was successfully applied to a pharmacokinetic study in six rats after oral administration of fenofibrate, the ester prodrug of fenofibric acid (equivalent to fenofibric acid 5 mg/kg). The method permits laboratory scientists with access to the appropriate instrumentation to perform rapid fenofibric acid determination.

Determination of alamifovir disoproxil fumarate and its active metabolite 602076 in rat plasma by LC-MS/MS: application to a pharmacokinetic study.

Alamifovir disoproxil fumarate (ADF) is a novel ester prodrug of alamifovir, which is currently as a promising antiviral candidate under investigation. This paper is aimed to develop rapid, sensitive and specific LC-MS/MS methods for the quantification of ADF and its active metabolite 602076 in rat plasma. According to the significantly different chemical properties of the compounds, two sets of liquid chromatography and ionization modes were used for determining the concentration of ADF and 602076 in rat plasma, separately. Following liquid-liquid extraction with n-hexane:dichloromethane:isopropanol (100:50:5, v/v/v), the ADF and internal standard (gliclazide) were separated on a Phenomenex Gemini C(18) column (150 mm × 2.0 mm, 5 µm) with a mobile phase consisting of methanol:water:formic acid (70:30:0.1, v/v/v). A tandem mass spectrometer equipped with electrospray ionization (ESI) source was used as the detector and operated in positive ion mode. The metabolite 602076 and the internal standard ZHY81018 were extracted from plasma by protein precipitation with acetonitrile. Chromatographic separation was performed on a Capcell MG C(18) column (150 mm × 2.0 mm, 5 µm) with a mobile phase consisting of acetonitrile and water (20:80, v/v). The MS/MS detection was operated in negative ion mode using an ESI source. The linear concentration ranges of the calibration curves were 2.5-500 ng/mL for ADF and 2.5-1000 ng/mL for 602076. The intra-assay RSD for quality control (QC) samples were from 3.3% to 6.7% for ADF, and 4.0% to 6.1% for 602076. The inter-assay RSD for QC samples were from 4.9% to 14.7% for ADF, and 2.6% to 4.4% for 602076. The relative errors for QC samples were from -10.6% to 1.9% for ADF, and 0.2% to 2.6% for 602076. The methods were successfully applied in the investigation of the pharmacokinetic profile of ADF, alamifovir and 602076 in rats. The results showed that ADF was rapidly metabolized to its active metabolite 602076 after oral absorption, with no detectable unchanged drug. The oral bioavailability of ADF was about 3 times higher than that of alamifovir.

Development and validation of an LC/MS/MS method for the determination of tenofovir in monkey plasma.

A simple, specific, sensitive LC/MS/MS method for the quantitation of tenofovir (TFV) in monkey plasma was developed and validated. After the addition of adefovir as an internal standard (IS), methanol was used to produce a protein-free extract. Isocratic chromatographic separation was performed on a reverse-phase Discovery C(18) column (4.6×250 mm, 5 µm). The mobile phase consisted of methanol-water-formic acid (20 : 80 : 0.5, v/v/v). Detection of TFV and the IS was achieved with electrospray ionization (ESI)-MS/MS in the positive ion mode using 288/176 and 274/162 transitions, respectively. The analytical range was set at 0.005-1.250 µg/ml using a 200 µl plasma sample. The intra- and inter-day precision values were less than 11.4%, and accuracy ranged from 0.4 to 2.9% in all quality control samples. The method was fully validated for its sensitivity, selectivity, accuracy and precision, matrix effect, recovery, and stability. Due to the high polarity of TFV, the major challenge was to circumvent ion suppression when quantitating the plasma concentration of TFV using the LC/MS/MS method. To avoid ion suppression, sufficient chromatographic separation was the most effective means for the present purposes. Moreover, it was found that the reconstitution solvents of the dried residue had a significant impact on LC peak shapes. The validated method was successfully applied to a bioequivalence study in 6 monkeys after the oral administration of two ester prodrugs of TFV (equivalent to TFV 20 mg/kg). The method permits laboratory scientists with access to the appropriate instrumentation to perform rapid TFV determination.

Simultaneous quantification of tracheloside and trachelogenin in rat plasma using liquid chromatography/tandem mass spectrometry.

We developed and validated a quantitative method for simultaneously determining the concentrations of tracheloside and trachelogenin in rat plasma. Plasma samples were prepared by liquid-liquid extraction with ethyl acetate. Isocratic chromatographic separation was performed on a reversed-phase Diamonsil C(18) column (4.6×200 mm, 5 µm). The mobile phase consisted of methanol and 10mM aqueous ammonium formate (80:20, v/v). Analyte detection was achieved by positive electrospray ionization (ESI) tandem mass spectrometry. Calibration was performed by internal standardization with glipizide, and regression curves ranging from 0.625 to 625 ng/mL were constructed for both the analytes. The intra- and inter-day precision values were below 8%, and accuracy ranged from -5.33% to 2.53% in all quality control samples. In this study, the validated method was successfully applied to determine the pharmacokinetic profile of tracheloside and trachelogenin in rat plasma after oral and intravenous administration of trachelospermi total lignans.

[Determination of icaritin in rat plasma by HPLC-MS/MS].

The paper is to report the development of a high-performance liquid chromatographic/tandem mass spectrometry (HPLC-MS/MS) method for the determination of icaritin (ICT) in rat plasma. After precipitated with acetonitrile from the plasma, ICT was isolated chromatographically on a Dikma C18 column. The mobile phase consisted of acetonitrile-water-acetic acid (72 : 28 : 1.5, v/v/v). Electrospray ionization (ESI) source was applied and operated in the positive ion mode. Multiple reaction monitoring (MRM) mode with the transitions of m/z 387 --> m/z 313 and m/z 331 --> m/z 315 were used to quantify ICT and the internal standard, respectively. The linear calibration curve was obtained in the concentration range of 2.5-1,000 ng x mL(-1). The lower limit of quantification was 2.5 ng x mL(-1). The inter- and intra-day precision (RSD) were less than 9.63%, and the accuracy (relative error) was within +/-7.42%. The method was proved to be suitable for the pharmacokinetics of ICT, which offers advantages of high sensitivity and selectivity.

Pharmacokinetics and tissue distribution of a water-soluble flavonol triglycoside, CTN986, in mice.

The pharmacokinetics and bioavailability of CTN986, a highly water-soluble flavonol triglycoside that has shown interesting antidepressant effects, were determined in mice after intravenous ( I. V.), intraperitoneal ( I. P.) and oral administrations. Concentrations of CTN986 in the biological samples were determined by a validated LC/MS/MS method. Non-compartmental methods were used to perform pharmacokinetic data analysis. The dose-dependent pharmacokinetics of CTN986 was characterized after I. V. administrations (0.16, 0.4 and 1.0 mg/kg) to mice. There was no significant difference in clearance (CL) with increasing dose [252.66 +/- 42.82 mL/h (0.16 mg/kg) versus 241.73 +/- 14.93 mL/h (1.0 mg/kg)] after I. V. administrations. The absolute bioavailability of CTN986 after I. P. and oral administrations was 96.57 % and 1.31 %, respectively. CTN986 was found to distribute widely in the internal organs of mice 10 min after oral dosage, with tissue concentrations in the order of duodenum, stomach, small intestine, kidney, lung, liver, brain, heart and spleen (from the highest to the lowest). In conclusion, CTN986 could be absorbed and extensively distributed into tissues as its intact form in mice.

[Studies on bioassay-guided anti-inflammatory fraction in bark of Albizia julibrissin combined determination with LC-MS-MS].

OBJECTIVE: To search the anti-inflammatory fraction of Albizia julibrissin. METHOD: Inflammatory model of Kunming mice ear edema induced by croton oil and determination combined with the LC-MS-MS-guided fractionation and isolation were used. RESULT: The n-butanol fraction (AJ-B) obtained from the ethanolic extract of the Cortex albiziae was the major active fraction. The lignan glycosides fraction (AJ-B-1), which was further isolated from AJ-B, showed significant anti-inflammatory activity and exhibited dose-dependent relationship in the dose of 5 to 20 mg x kg(-1). CONCLUSION: The method of bioassay-guided fractionation and isolation combined with the LC-MS-MS determination may be of benefit to the logical studies on the bioactive fractions or constituents of traditional Chinese materia medica.

Simultaneous quantification of CTN986 and its deglycosylation products in rat serum using liquid chromatography/tandem mass spectrometry.

A quantitative method for the simultaneous determination of CTN986, a flavonol triglycoside, and its two deglycosylation products rutin and hirsutin in rat serum was developed and validated for the investigation of the pharmacokinetics of CTN986. Analytes were isolated from the serum samples (200 microL) prior to analysis by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using C(18) solid-phase extraction, and were separated on a Zorbax C(8) reversed-phase column with an isocratic mobile phase consisting of methanol/isopropanol/water/formic acid (20:10:70:0.1, v/v/v/v). The protonated analytes generated in the positive ion mode were monitored through multiple reaction monitoring in an eletrospray ionization source. Calibration was performed by internal standardization with CTN987, a flavonoid structurally similar to CTN986, and regression curves were constructed ranging from 2 to 1000 ng/mL in 200 microL serum samples. The intra- and inter-day precision values were below 11% and accuracy was between -2.37 and 1.4% for all quality control samples. This quantitation method was successfully applied to pharmacokinetic studies of CTN986 in rats following oral and intravenous administration. Rutin and hirsutin were not detected in rat serum.

Determination of rizatriptan in human plasma by liquid chromatographic-eletrospray tandem mass spectrometry: application to a pharmacokinetic study.

A sensitive liquid chromatographic-tandem mass spectrometry(LC-MS/MS) method was developed for the determination of rizatriptan in human plasma. The analytes were extracted from plasma samples by liquid-liquid extraction, separated on a Zorbax XDB C8 column (150 x 4.6 mm i.d.) and detected by tandem mass spectrometry with an electrospray ionization interface. Zomitriptan was used as the internal standard. The method had a lower limit of quantitation of 50 pg/mL for rizatriptan, which showed more sensitivity and speed of analysis compared with reported methods. The within- and between-day precision was measured to be below 11.71% and accuracy between -5.87 and 0.86% for all quality control samples. This quantitation method was successfully applied to the evaluation of the pharmacokinetic profiles of rizatriptan after single oral administration of 5, 10 and 15 mg rizatriptan tablets to 10 healthy volunteers (five males and five females).

Chiral melamine derivatives: design, synthesis, and application to mass spectrometry-based chiral analysis.

A novel class of chiral melamine derivatives has been designed and synthesized. The ability of these compounds to perform chiral recognition toward 19 natural chiral alpha-amino acids has been investigated by electrospray ionization tandem mass spectrometry for the first time. The enantioselectivities of these new chiral selectors are encouraging. To elucidate some mechanism and regularity in the chiral recognition process using chiral melamine derivatives as chiral selectors, the effect of different noncovalent interactions caused by various chiral or achiral moieties in melamine derivatives on the chiral recognition in the gas phase has been studied at the same time. The result shows that electrostatic, hydrogen bond, pi-pi stacking, and steric interaction between selector and analyte play important roles in the association and enantioselective recognition of amino acids with the chiral melamine derivatives as chiral selectors. Enantiodiscrimination for analytes with different structures and properties could be improved by modifying substituents in melamine derivatives on purpose.

[Rapid identification of the isomeric impurity in raw drug of cefepime dihydrochloride by liquid chromatography-tandem mass spectrometry].

AIM: To establish a sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of isomeric impurity in raw drug material of cefepime dihydrochloride. METHODS: The HPLC separation experiments were performed on a reversed phase C18 column, with acetonitrile-10 mmol x L(-1) ammonium acetate (5:95) as mobile phase (a flow rate of 0.8 mL x min(-1)). The analytes were determined by electrospray ionization tandem mass spectrometry in positive mode. The chromatogram and mass spectra of cefepime dihydrocloride and its isomeric impurity were obtained by LC-MS/MS. RESULTS: The method can be used for the separation and identification of cefepime dihychrocloride and its isomeric impurity, of which the retention times were 15.28 min and 9.18 min, respectively. Based on the MS/MS spectra of their molecular ions, the different fragmentation pathways of cefepime dihydrocloride and its isomeric impurity were compared and proposed. CONCLUSION: The method was rapid, sensitive and specific. It can be used for the identification of the isomeric purity in raw drug material of cefepime dihydrochloride.

Identification of rat faecal, urinary and biliary metabolites of thionorphine, a novel mixed agonist-antagonist analgesic, using liquid chromatography/electrospray ionization tandem mass spectrometry.

The biotransformation of thionorphine (N-cyclopropylmethyl-7alpha-[(s)-1-hydroxy-1-methyl-3-(2thiophene)-propyl]-6,14-endo-ethano tetrahydrooripavine), a new analgesic, was in-vestigated in rats. The results of metabolite analysis by liquid chromatography/electrospray ionization tandem mass spectrometry with positive ion mode, in which a mobile phase of 10 mM ammonium acetate (pH 3.0)/acetonitrile (25/75) was used, suggested that thionorphine is biotransformed to two potentially active metabolites, the N-dealkylated thionorphine (M-I) and the oxidized thionorphine (M-II), and subsequently form conjugates with glucuronic acid of both thionorphine and the metabolites.

[Determination of glycosides in traditional Chinese medicine liu-wei di-huang by RP-HPLC].

OBJECTIVE: To establish a RP-HPLC method for determination of glycosides in Traditional Chinese Medicine Liu-wei Di-huang. METHOD: The samples were analyzed on an ODS column at 30 degrees C, with mobile phase of methanol/water (33:67) at flow rate 1.0 mL.min and detection at wavelength of 236 nm. RESULT: Three major components reached base-line separation and were identified to be mononiside, loganin, paeoniflorin. Respectively for the three components, linear correlations were found between peak areas and concentrations in the ranges of 7.4-60, 7.7-62 mg.L-1 and 8.5-68 mg.L-1, and the recoveries were 98.8%, 98.3%, 99.6%. CONCLUSION: The established method is proved to be suitable for simultaneous quantification of three major glycosidic components in Liuwei Dihuang decoction and can be used for evaluation of the quality of Liuwei Dihuang preparations.

[Identification of the metabolites of penehyclidine hydrochloride raceme in rats by LC-MS/MS and ion cluster].

AIM: To study the metabolites of penehyclidine hydrochloride (PH) raceme, a new anticholinerigic drug invented by the Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences. METHODS: Three healthy rat urine samples were collected within 24 h after a single i.m. dose of PH raceme and PH-d5 [(5 + 5) mg.kg-1] simultaneously. The eight metabolites of PH raceme were identified by the methods of LC-MS/MS, GC-MS, FAB-MS and the stable isotope ion cluster. Mass spectrometry was operated in the positive mode for the method of LC-MS/MS. RESULTS: M1 and M1* were identified as the oxygenated products of PH in the cyclopentyl group; M2 and M2* were as the hydroxylated products of PH in the cyclopentyl group; M3 and M3* were as the oxygented and hydroxylated products of PH at the meta-position of cyclopentyl group; M4 and M4* were identified as the dihydroxylated metabolites of PH, the hydroxylated position were at the cyclopentyl group and quiniuclidinol ring of PH. Among them, M1 and M1*, M2 and M2*, M3 and M3*, M4 and M4* were the isomers of each other. CONCLUSION: These characteristics can be used for future structure elucidation in studies of the metabolites of PH optical isomers. The structure data of PH metabolites provide important information for the clinical use and for developing better anticholinerigic drug.