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electrokinetic capillary electrophoresis (MECE) [ 26 ] time-of-flight secondary ion mass spectrometry (ToF-SIMS) [ 27 ] and desorption electrospray ionisation mass spectrometry (DESI-MS) [ 11 ] were also used. LC/MS and LC-MS/MS methods developed for

Open access
Acta Chromatographica
Authors:
Camila C. Pires
,
Moacir Kaiser
,
Lauren D. Grünspan
,
Fabiano Barreto
,
Adrine Innocente
,
Simone Gnoatto
,
João V. Laureano
,
Bibiana V. Araujo
,
Teresa Dalla Costa
, and
Leandro Tasso

An accurate and reliable LC—MS/MS assay was firstly developed and validated for quantitative determination of a new antimalarial prototype drug, 3β-hydroxyurs-12-en-28-oic acid (LAFIS 01), in rat plasma. Dexamethasone was employed as internal standard. Simple protein precipitation by acetonitrile for the sample preparation was used. Effective separation was achieved with Phenomenex Luna C18 (50 × 2 mm, 5 μm) column. The mobile phase consisted of (A) water and (B) acetonitrile, both containing 0.1% acetic acid, delivered by gradient elution. The column temperature was maintained at 40 °C. The LAFIS 01 was monitored by electrospray ionization interface, operating in the negative mode (ESI−) in multiple reactions monitoring (MRM), checking the transitions 455 > 455 for LAFIS 01 and 451 > 361 for the IS. Once LAFIS 01 demonstrated low fragmentation by collision-induced dissociation (CID) nonpresenting abundant high-intensity fragments to meet the desired concentration levels quantification, only pseudomolecular ion was monitored. The flow rate was 500 μL min−1. The lower limit of quantitation achieved was 10 ng mL−1 and linearity was observed from 10 to 500 ng mL−1. The relative standard deviation (RSD) values of the intra- and inter-assay precisions of the method were below 8.42 and 7.94%, respectively. The accuracy ranged from 92.05 to 102.94%. The extraction recovery of LAFIS 01 and IS was up to 90%. The method showed linearity, precision, accuracy, sensitivity, and stability required to quantify LAFIS 01 in preclinical pharmacokinetic study.

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water content ready to eat vegetables (tomatoes and cucumbers). The developed method involved a one-shot liquid-liquid extraction using a minute amount of a high-density solvent, clean-up with a dispersing sorbent, and subsequent LC-MS/MS for

Open access

Summary

The quantification of the main withanolide, withaferin-A, in plant extracts of Withania somnifera and Withania coagulans using high-performance liquid chromatography (HPLC)-mass spectrometry (ESI-MS/MS) is described. HPLC was used in combination with a triple quadrupole mass spectrometer in multiple reaction monitoring (MRM) mode. Additionally, mass exact determination of withaferin-A was achieved using a hybrid high-resolution mass spectrometer (Q-TOF). A combination of acetonitrile and water as the mobile phase using gradient elution was found to be successful in separating the compound of interest from the other main components. The limit of detection (LOD) in the plants was 6 ng/g and the total analysis time was 10 min.

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A new sensitive and validated liquid chromatography electro spray ion-tandem mass spectrometry (HPLC-ESI-MS/MS) method for the quantification of Vildagliptin (VG) in rat plasma has been developed and validated using repaglinide (RG) as an internal standard (IS). The analytes were extracted by liquid-liquid extraction using ethyl acetate. Elution of the VG and IS was achieved on a reverse phase Betasil (C18 50 mm 4.6 mm ID, 5 μ) column with an isocratic mobile phase composed of acetonitrile: 2 mM ammonium acetate (90:10 v/v). The analytes monitored in the Multiple Reaction Monitoring (MRM) mode were m/z 304.2→154.0 and 453.3→230.3 for VG and RG, respectively. The calibration curve was linear in the range of 1.57–501.21 ng/mL for VG with lower limit of quantification 1.57 ng/mL. The intra run and inter run precision values are within 11.70% for VG at LOQ level.

Open access

A simple and sensitive liquid chromatography—tandem mass spectrometry method was developed for the quantification of atorvastatin, ortho-hydroxyatorvastatin, para-hydroxyatorvastatin, and atorvastatin lactone in rat plasma. Solid-phase extraction was used for preparation of samples. Rosuvastatin was chosen as an internal standard. Chromatographic separation was achieved on ZORBAX Eclipse C18 Analytical, 4.6 × 100 mm (3.5 μm) column with a gradient mobile phase composed of acetonitrile and 0.1% acetic acid, at a flow rate of 400 μL min−1. The column was kept at constant temperature (25 °C), and autosampler tray temperature was set at 4 °C. The following selected reaction monitoring (SRM) transitions were selected: (m/z, Q1 → Q3, collision energy) atorvastatin (559.47 → 440.03, 22 eV), atorvastatin lactone (541.36 → 448.02, 19 eV), ortho-ohydroxyatorvastatin (575.20 → 440.18, 20 eV), para-hydroxyatorvastatin (575.54 → 440.18, 20 eV), and rosuvastatin (482.25 with selected combination of two fragments 257.77, 31 eV, and 299.81, 35 eV) in positive ion mode. The method was validated over a concentration range of 0.5–20 ng mL−1 for ortho-hydroxyatorvastatin and para-hydroxyatorvastatin and 0.1–20 ng mL−1 for atorvastatin and atorvastatin lactone with excellent linearity (r 2 ≥ 0.99). This method demonstrated acceptable precision and accuracy at four quality control concentration levels. The detection limits were 0.1 and 0.13 ng mL−1 for orth-ohydroxyatorvastatin and para-hydroxyatorvastatin, respectively, and 0.05 ng mL−1 for atorvastatin and atorvastatin lactone. All analytes were found to be stable at examined conditions. Validated method was applied for determination of atorvastatin and its metabolites in plasma of experimental animals.

Open access

Abstract  

In the present work, the thermal behavior of prednicarbate was studied using DSC and TG/DTG. The solid product remaining at the first decomposition step of the drug was isolated by TG, in air and N2 atmospheres and was characterized using LC-MS/MS, NMR, and IR spectroscopy. It was found that the product at the first thermal decomposition step of prednicarbate corresponds to the elimination of the carbonate group bonding to C17, and a consequent formation of double bond between C17 and C16. Structure elucidation of this degradation product by spectral data has been discussed in detail.

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High-performance liquid chromatography coupled with fluorescence (HPLC-FD) and tandem mass spectrometric detection (LC-MS/MS) was studied as a versatile tool for fast and reliable determination of nine regulated quinolones in food of animal origin (Council Regulation 2377/90/ECC). The sample pre-treatment protocol includes double step extraction with acetonitrile followed by solid phase extraction (SPE) cleanup on hydrophobic-lipophilic balance (HLB) cartridge. The separation of quinolones in HPLC-FD determination was performed on C18 Zorbax column with a gradient mixture of aqueous formic acid, methanol, and acetonitrile. A multi-wavelength excitation/emission program was used for sensitive quinolones detection. The separation efficiency of newly available chromatographic columns: Gemini C18 and Synergi Polar RP (fully porous particles), as well as Kinetex PFP and Poroshell 120 EC-C18 (core-shell particles), was studied in liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis. Appropriate gradient elution program was designed for each column. Multiple reaction monitoring was used for selective determination of each quinolone. LC-MS/MS allowed quinolones determination in less than 5 min. Both methods showed detection limits below maximum residue limits for quinolones residues in food commodities.

Open access

Summary

Capsaicin has been reported to exhibit an inhibitory effect on the P-glycoprotein (P-gp) function in vitro. To investigate its concentration-dependent effect in vivo, a sensitive assay that can characterize the absorption and disposition of capsaicin needs to be developed. This study reports the development of a sensitive LC-MS/MS assay for the determination of capsaicin in mouse plasma. The sample pretreatment involved a one-step extraction of 20 μL plasma with t-butyl methyl ether. Separations were achieved on a C18 column and the detection was performed on an LC-ESI-MS/MS by multiple reaction monitoring. The assay was linear over a wide concentration range from 0.325 to 650 ng mL−1 (r > 0.999), with a LLOQ of 0.325 ng mL−1. The developed method was applied to i.v. (dose 0.325 and 0.65 mg kg) and oral absorption (dose 40 mg kg) studies in mice. After i.v. injection, the t 1/2,λz, V z and CL s ranged from 0.13–0.16 h, 127.6–141.8 mL, and 547.3–775.4 mL/h, respectively. After oral administration, a secondary peak was observed and the terminal half-life was prolonged (1.51 h). Capsaicin was poorly absorbed, with the absolute oral bioavailability (F) ranging from 1.02% to 1.56%. The developed assay may be useful in studies where sample volumes are limited.

Open access

Summary

Galantamine hydrobromide was subjected to oxidative stress degradation using hydrogen peroxide and analyzed as per the chromatographic conditions described in European Pharmacopoeia. The drug showed considerable degradation at ambient temperature resulting in the formation of two degradation products at relative retention times (RRTs) 0.63 and 2.52. The minor degradant at RRT 0.63 was identified as galantamine N-oxide. The principal degradant formed at RRT 2.52 was found to be unknown and has not been reported previously. The unknown impurity was identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) followed by isolation using semi-preparative high-performance liquid chromatography (HPLC). The isolated impurity was characterized using one-dimensional, two-dimensional nuclear magnetic resonance spectroscopy (1D and 2D NMR) and elemental analysis (EA). The principal degradant was found to be formed due to the generation of bromine and subsequent attack on the aromatic ring via in situ reaction between hydrogen bromide and hydrogen peroxide. The unknown impurity was characterized as (4aS,6R,8aS)-5,6,9,10,11,12-hexahydro-1-bromo-3-methoxy-11-methyl-4aH-[1]benzofuro [3a,3,2-ef] [2] benzazepin-6-ol.

Open access