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is the most hydrophobic between them [ 6 ]. The determination of drug concentrations in plasma or other biological samples through liquid chromatography coupled with mass spectrometry (LC-MS/MS) methods is now considered a technological

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Examination of heat shock and PR (“pathogenesis-related”) proteins is of special interest in food science. Many food allergens have a similar or the same structure as PR proteins, which are produced in the plants as a response to pathogenesis or certain environmental stresses. The protein set of the psychrophilic bacterium Shewanella hanedai was studied by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Gel patterns from control and heat-treated bacteria were evaluated by PDQUEST software. The differentially expressed proteins were excised from the gel and digested by trypsin. The tryptic peptides were analysed by nanoflow LC-MS/MS. On the basis of amino acid sequences obtained by this method, the proteins were identified by similarity searching in the protein database. Using this proteomic approach a heat shock and a 50S ribosomal protein were identified as the major heat induced proteins in Shewanella hanedai.

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A fast, reliable, inexpensive, and practical method with a low determination limit and high recovery has been developed for the determination of the marijuana metabolite in routine analysis. THC-COOH in urine was validated using liquid chromatography—tandem mass spectrometry (LC—MS/MS). Before an easy single-step extraction with Toxi-Tubes, basic hydrolysis was performed at 60 °C for 30 min. LC—MS/MS analysis takes 2.5 min for each sample, and the retention time of the analyte is 1.75 min. Specificity, linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, repeatability, and intermediate precision (inter-day) system suitability parameters were determined in the validation study. The recovery of the extraction method was 88.67 (±5.91). LOD and LOQ values were 1.41 and 5.00 ng mL−1, respectively. The method showed linear response between the values 5.00 and 500.00 ng mL−1. The repeatability was 9.64% (relative standard deviation, RSD%), and the intermediate precisions (RSDR%) were 10.73%, 13.74%, and 8.11% at 10.00, 100.00, and 200.00 ng mL−1 concentration levels, respectively. No statistically significant difference was found in ANOVA analysis, between three consecutive days in intermediate precision study, for 90% confidence level. HorRat values were between 0.34 and 0.61. The method was applied to CEDIA positive samples, obtained from the Trabzon Group Presidency of Turkish Council of Forensic Medicine, successfully.

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In the present study, the degradation behavior of Fenofibrate under different International Conference on Harmonization (ICH) suggested conditions was studied. Characterization of degradation products by liquid chromatography–tandem mass spectrometry (LC–MS/MS) studies in solution form was done, and the possible mechanism for the formation of degradants is discussed. Fenofibrate was subjected to different hydrolytic stress conditions and thermal stress condition (in solid form). Successful separation of drug from degradants was achieved on a C18 column using water–acetonitrile (25:75 v/v) as the mobile phase. Other high-performance liquid chromatography (HPLC) parameters were: flow rate, 1 mL min−1; detection wavelength, 286 nm; column temperature, 25 °C; and injection volume, 20 μL. The method was validated for linearity, precision, accuracy, robustness, and specificity and was stability-indicating one, based on the specificity studies. The drug degraded under acidic, basic, and oxidative hydrolytic stress while it was relatively stable towards neutral hydrolysis and thermal stress. The stressed samples were subjected to LC–MS/MS analysis. On the basis of spectral data, the structures of four degradation products and one interaction product were suggested. Degradation products were characterized to be isopropyl acetate, 2-[4-(4-chlorobenzoyl)phenoxy]-2-methyl propanoic acid, 4-hydroxy benzoic acid, and benzoic acid. The structure of one interaction product was proposed as methyl 2-[4-(4-chlorobenzoyl)phenoxy]-2-methylpropanoate.

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. Activity guided fractionation of Arum italicum Miller Tubers and the LC/MS-MS profiles . Rec. Nat. Prod. 2018 , 12 ( 1 ), 64 – 75 . 10.25135/rnp.06.17.05.089 28

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Summary

A simple, sensitive, and highly specific method has been developed for determination of valacyclovir (VL) in human plasma. The analytical procedure involves a solid-phase extraction method using Valacyclovir-D8 (VLD8) as an internal standard. Chromatographic separation was carried out on a reversed phase Zorbax, SB C18, 4.6 × 75 mm, 3.5μm column. Valacyclovir and Valacyclovir-D8 were detected with proton adducts at m/z 325.2 → 152.0 and 333.3 → 152.0 in multiple reaction monitoring (MRM) positive mode. The method was linear over the concentration range of 0.5–700.0 ng mL−1. The limit of detection (LOD) and limit of quantification (LOQ) for valacyclovir were 0.2 pg mL−1 and 0.5 ng mL−1, respectively. The method was shown to be precise with the average within-run and between-run variations of 0.7 to 3.5% and 3.1 to 4.7%, respectively. The average within-run and between-run accuracies of the method throughout its linear range were 96.7 to 97.9 and 94.7 to 97.3%, respectively. The mean recoveries of valacyclovir and Valacyclovir-D8 from human plasma by the developed method were 99.17 ± 10.78% and 110.84 ± 8.74%, respectively. The method was successfully applied in bioequivalence study with 20 healthy male volunteers under fasting condition.

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A rapid, selective, sensitive, and simple method for simultaneous determination of tigecycline and its epimer in human plasma samples was developed and validated by liquid chromatography–tandem mass spectrometry (LC–MS/MS). Sample preparation involved one-step protein precipitation by adding 0.1% formic acid–methanol and phosphate buffer (PB) solution to the plasma. Chromatographic separation was obtained with XBridge BEH C18 column (3.5 μm, 50 × 4.6 mm) through a 9.5-min gradient mobile phase at the flow rate of 0.6 mL min−1 at 4 °C. The calibration curves were linear over concentration 5.00–2000 ng mL−1 with correlation coefficient greater than 0.998. Intra-batch and inter-batch accuracy of the assay were in the ranges of −2.90% to 3.00%, and the corresponding precision was less than 6.97%. The extraction recovery of tigecycline and its epimer with the current method were 87.2% and 76.9%, respectively. The applied LC–MS/MS method was shown to be sufficiently sensitive and will be suitable for pharmacokinetic studies.

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Summary

The objective of the present study was to report the stability of novel antiviral drug, valganciclovir based on the information obtained from forced degradation studies. Valganciclovir was subjected to forced hydrolytic (acidic, alkaline and neutral), oxidative, photolytic and thermal stress in accordance with the ICH guideline Q1A (R2). The drug showed labiality under only acidic and photoacidic conditions while it was stable to other stress conditions. Resolution of the drug and degradation products was achieved on a Hypersil Gold C-18 column (4.6 × 250 mm, 5 μm) utilizing acetonitrile (A) and potassium dihydrogen ortho phosphate buffer (pH 5.0; 0.01M) in the ratio of 5:95 (v/v) at a flow rate of 0.6 ml/min and at the detection wavelength 252 nm. The major acidic stress degradation product was characterized by LC-MS/MS and its fragmentation pathway was proposed. Validation of the LC-DAD method was carried out in accordance with ICH guideline. The method met all required criteria and was applied for analysis of commercially available tablets.

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Abstract

Venetoclax is the first oral Bcl-2 inhibitor with high affinity targeting tumor cell apoptosis mechanism. In this study we developed a simple, sensitive and reliable LC–MS/MS method to determine venetoclax in children's hemolytic or lipemic samples. The method utilized an electrospray ion source and operated in multiple reaction monitoring mode. Venetoclax-d8 was used as an internal standard. Plasma samples were precipitated by acetonitrile containing 10% dimethyl sulfoxide and were separated by a Hypersil GOLD column (2.1 mm × 150 mm, 5 μm). The mobile phase consisted of acetonitrile-2 mM ammonium acetate (30:70, v/v) containing 0.4% formic acid. The quantification for venetoclax and venetoclax-d8 were m/z 868.1 → 636.1, m/z 876.1 → 644.1, respectively. The linear range was 10–2,000 ng mL−1 for venetoclax. The matrix in normal plasma, hemolytic or lipemic plasma had no significant effect on the detection results. The specificity, recovery and stability also met the acceptance criteria of guiding principles for the validation of biological sample quantitative analysis presented in the Chinese Pharmacopoeia (2015). As a result, this method is particularly suitable for determining venetoclax in hemolytic or lipemic samples from children with acute myeloid leukemia. The method, with the application of monitoring drug concentrations in pediatric patients, was successful.

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nanomaterials followed with LC-MS/MS to determine GLM in beagle dog plasma showed extraction recovery (71.2–85.7%) [ 13 ]. Also, protein precipitation with acetonitrile has been used for the extraction of GLM from plasma with lower sensitivity (limit of

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