Positive Ion Electrospray Ionization Research Articles

A validated HPTLC method for the simultaneous quantifications of three phenolic acids and three withanolides from Withania somnifera plants and its herbal products

A simple, rapid and selective high-performance thin-layer chromatographic (HPTLC) method has been developed and validated for simultaneous determination of three withanolides (withaferin A, withanone and withanolide A) and three phenolic acids (caffeic acid, ferulic acid and benzoic acid) from different parts (root, stem and leaf) of Withania somnifera and its two commercially available polyherbal formulations. The extraction efficiency of withanolides and phenolic acids were tested using two solvents, chloroform and methanol, respectively. HPTLC separation was performed on silica coated aluminium plates Si 60F254; using toluene, ethyl acetate and acetic acid (60:40:4). The samples were quantitated at 231 nm. The purity and identity of peaks of all the six analytes were confirmed by matching Rf values and UV-spectrum with authentic standards. The identity of three withanolides was further confirmed by positive ion electrospray ionization mass spectrometry (ESI-MS/MS) analyses. The developed method was validated for sensitivity, linearity, reproducibility, accuracy, the limit of detection (LOD) and limit of quantification (LOQ) following the guidelines of the International Conference on Harmonization (ICH). The method was found to be linear (r > 0.99) in the range of 50–2000 ng/band for benzoic acid and 50–1000 ng/band for the other five studied metabolites. This simple and accurate HPTLC method provided enhanced resolution of studied analytes as compared to other phytoconstituents present in W. somnifera extracts. It has also been successfully applied in the analysis and quantification of two polyherbal formulations containing W. somnifera plant parts.

A UHPLC–MS/MS method for the quantitation of olmutinib in rat plasma

Olmutinib (Olita™) is an oral third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) which is used to treat non-small cell lung cancer (NSCLC). A simple, rapid, and sensitive method based on ultra-performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS) has been developed for the determination of olmutinib. Sample preparation was performed following simple one-step protein precipitation with acetonitrile. Olmutinib and internal standard (dasatinib) were separated on an Eclipse Plus C18 RRHD (2.1 × 50 mm, 1.8 μm) column. The mobile phase consisted of acetonitrile–0.1% formic acid in water with gradient elution. A total run time of 1.7 min was achieved. Detection was performed on a positive-ion electrospray ionization mass spectrometer in multiple reaction monitoring (MRM) mode, using transitions of m/z 487.2 → 402.1 for olmutinib and m/z 488.2 → 401 for dasatinib (IS), respectively. The calibration curve (R2 = 0.999) was linear over the range of 1–500 ng/mL. The recovery of olmutinib ranged from 85.8% to 95.5%. This method can be applied to pharmacokinetic studies of olmutinib.

Development and validation of a highly sensitive LC–MS/MS method for in vitro measurement of histamine concentration

The basophil histamine release test (HRT) is an important in vitro diagnostic assay to evaluate immunoglobin E (IgE)-mediated allergic responses. In this study, a bioanalytical LC–MS/MS method was developed and validated to quantify histamine in the leukocyte suspension from human peripheral blood. The method used pre-column derivatization with phenylisothiocyanate (PITC) and the resulting phenylthiocarbamyl (PTC) histamine was analyzed by positive-ion electrospray ionization using the multiple reaction monitoring mode. Chromatographic separation was achieved using an Imtakt-HT C18 column (2.1 mm × 50 mm, 3.0 μm), with a flow rate of 0.35 mL/min, 2 μL injection, and gradient elution with a mixture of acetonitrile-2 mM ammonium acetate buffer (both containing 0.1% formic acid). The total runtime of the method was 3.0 min including equilibration time. The method had a lower limit of detection of 0.1 ng/mL, and the quantifiable range was 0.1–100 ng/mL in the leukocyte suspension. The intra-day and inter-day precision and accuracy results were within the acceptable limits. It was established that histamine quantification should be performed within 2 h of preparing the leukocyte suspension, and freezing and thawing should be avoided. This method was successfully applied to the diagnosis and evaluation of the pathophysiologic mechanism of respiratory or cutaneous allergic diseases.

A new method for high-resolution and high-precision analysis of flunitrazepam and 7-aminoflunitrazepam in human body fluids using a Monolithic SPE SpinTip and UPLC–Q-ToF–MS

Forensic toxicological analyses of drugs and their metabolites in human specimens usually require extractive pretreatment for successful analysis of substances from the matrix. In the present study, a high-throughput method was developed to analyze flunitrazepam, 7-aminoflunitrazepam, 7-acetamidoflunitrazepam, 7-acetamido-3-hydroxyflunitrazepam, and 3-hydroxyflunitrazepam in human plasma and urine samples using a new Monolithic C18 gel-packed SpinTip and ultra-performance liquid chromatography (UPLC)–quadrupole time-of-flight (Q-ToF) mass spectrometry (MS). Plasma (20 µL) or urine (100 µL) samples spiked with each component were extracted using a Monolithic C18 SPE SpinTip and quantified by UPLC–Q-Tof–MS with positive-ion electrospray ionization (ESI). Good separation, with clear peak shapes of flunitrazepam and its metabolites, was achieved within an analysis time of 6 min, including the extraction time. Recoveries of flunitrazepam and 7-aminoflunitrazepam for plasma and urine samples were 93.5–118% and 97.7–109%, respectively. The regression equations for flunitrazepam and 7-aminoflunitrazepam showed excellent linearity in the range of 0.5–250 ng/mL for plasma and 0.4–500 ng/mL for urine, with detection limits of 0.2–0.5 ng/mL. Intra- and inter-day coefficients of variations for two drugs are smaller than 13.5%. The accuracy of quantitation was 89–110%. The method was successfully applied to determine the level of flunitrazepam and its metabolites in human plasma and urine, respectively, after oral administration to a volunteer.

Selective Methylation of Sulfides in Petroleum for Electrospray Ionization Mass Spectrometry Analysis

A method for selective methylation of sulfides (particularly aliphatic sulfides) but not thiophenes in petroleum has been developed for positive-ion electrospray ionization (ESI) mass spectrometry. The new method uses only CH3I without AgBF4 to produce methyl sulfonium ions of sulfides for molecular composition analysis. It provides simplicity and saves time compared to a previously developed methylation method using CH3I/AgBF4 to methylate all sulfur compounds into ionic species analyzable by positive-ion ESI. The composition of sulfides by this method agrees with that of the sulfide fraction obtained from CH3I/AgBF4 methylation/demethylation. Hence, the separation of sulfides from thiophenes through elaborate procedures is eliminated. The new method was validated by model compounds and has been successfully applied to the analysis of sulfides in diesel, vacuum gas oil, crude oil, and atmospheric pressure distillation residue. When combined with the previously developed CH3I/AgBF4 method, the new method may have the potential to differentiate reactive sulfur, such as sulfides, from nonreactive sulfur, such as thiophenes. This could provide a means to develop correlations between sulfur types and corrosion, and possibly for other studies.

Molecular characterization of aldehydes and ketones in particle phase of mainstream and sidestream cigarette smoke.

Aldehydes and ketones (AKs) in cigarette smoke are risk to humans and environment. Due to the complexity of itself and the interference of the smoke tar matrix, the aldehydes and ketones in particle phase (AKPs) of mainstream smoke (MSS) and sidestream smoke (SSS) have not been well investigated. In this study, the AKPs of MSS and SSS were derivatized into polar products by reaction with Girard T reagent. The derivatives were isolated rapidly by column chromatography and analysed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Fifteen species of aldehydes and ketones were detected by positive ion electrospray ionization (ESI) FT-ICR MS: O1–6, N1O1–4, N2O1–3 and N3O2–3. The total number of AKPs obtained by ESI FT-ICR MS in MSS and SSS is about 1100 and 970, respectively. After hydrolysis, the original AKPs were obtained and 63 carbonyls were identified and quantified by gas chromatography–mass spectrometry (GCMS). The nitrogen-containing and high-oxygen AKPs were further characterized by Orbitrap mass spectrometry. Structures of compounds with high relative abundance in the mass spectrum were speculated (e.g. a series of degradants of cembrenediol) by comparison with the results of GCMS.

Quantification and pharmacokinetic study of entrectinib in rat plasma using ultra-performance liquid chromatography tandem mass spectrometry.

To characterize the preclinical plasma pharmacokinetics of entrectinib, a reproducible and precise assay is necessary. In this study, we developed and validated a simple ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for the measurement of entrectinib using carbamazepine as the internal standard in rat plasma. Sample preparation was a simple protein precipitation with acetonitrile, then entrectinib was eluted on an Acquity UPLC BEH C18 column (2.1 × 50 mm, 1.7 μm) using a gradient elution with a mobile phase composed of acetonitrile (A) and 0.1% formic acid in water (B). Detection was achieved using multiple-reaction monitoring in positive ion electrospray ionization mode. The method showed good linearity over the concentration range of 1-250 ng/mL (r2 > 0.9951). The intra- and inter-day precision was determined with the values of 6.3-12.9 and 2.6-6.9%, respectively, and accuracy values of 0.5-11.6%. Matrix effect, extraction recovery, and stability data all met the acceptance criteria of US Food and Drug Administration guidelines for bioanalytical method validation. The method was successfully applied to a pharmacokinetic study. In this study, we developed the complete validated method for the quantification of entrectinib in rat plasma.

Determination of phenolic compounds in Chinese poplar propolis, Brazil green propolis, and poplar gum by high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry and preliminary study of the identification of adulteration

High-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (HPLC/Q-TOF MS) was used to analyze 23 phenolic compounds in Chinese poplar propolis, Brazil green propolis, and poplar gum. Propolis and poplar gum samples were dissolved in methanol-water (1:1, v/v) and filtered by 0.45 μm organic phase filtration membrane. The separation was carried out in an Agilent Eclipse Plus C18 column with gradient elution using acetoni-trile and 0.1% (volume percentage) formic acid solution as the mobile phases. The compounds were detected using positive ion electrospray ionization in full scan mode (m/z 100-1000). The quantification analysis was performed by the external standard method. The results showed that all the compounds were linear, with correlation coefficients>0.99, in the range of 10-20 μg/L. The limits of detection and limits of quantification for tangeretin and formononetin were 0.2 and 1 μg/L, respectively, and those for the other compounds were 2 and 10 μg/L, respectively. At the spiked levels of 10, 25, and 50 mg/kg, the recoveries of all the compounds ranged from 70.2% to 122.6%, with relative standard deviations of less than 10%. Salicin, cinnamic acid, caffeic acid, and coumaric acid could be used as markers for detecting adulteration in Chinese poplar propolis, while caffeic acid, ferulic acid, chrysin, caffeic acid phenethyl ester, pinocembrin, galangin, coumaric acid, isorhamnetin, kaempferide, and arte-pillin C could be used as markers for identifying Chinese poplar propolis and Brazil green propolis. The results presented in this paper may be helpful in quality control of propolis products.

Quantitative bioanalytical assay for the human epidermal growth factor receptor (HER) inhibitor dacomitinib in rat plasma by UPLC-MS/MS

Dacomitinib is a highly selective irreversible small-molecule inhibitor of the human epidermal growth factor receptor (HER) family of tyrosine kinases. A simple and quick bioanalytical method was completely developed and validated for the assay and pharmacokinetic investigation of dacomitinib in rat plasma using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Proteins in 0.1 mL plasma samples were prepared by precipitant acetonitrile containing ibrutinib as the internal standard (IS). Separation of the analyte from plasma samples was carried out on an Acquity UPLC BEH C18 column using acetonitrile and 0.1% formic acid in water as mobile phase for gradient elution. The total run time and the elution time of dacomitinib were 3.0 min and 1.07 min, respectively. Positive-ion electrospray ionization (ESI) and multiple reaction monitoring (MRM) on a triple quadrupole tandem mass spectrometer were used for detection at the transitions of m/z 470.1 → 124.1 for dacomitinib and m/z 441.2 → 84.3 for ibrutinib (IS), respectively. In the range of 1–150 ng/mL, the calibration curve of dacomitinib was linear with a lower limit of quantitation (LLOQ) of 1 ng/mL. Mean recovery of dacomitinib in plasma was in the range of 76.9–84.1%. The inter- and intra-day precision (RSD) was in the scope of 1.7–8.7% and the accuracy (RE) ranged from -6.1 to 8.5%. Stability studies under different conditions were indicated to be stable. A pharmacokinetic study after oral administration of 40 mg/kg dacomitinib in rats illustrated the applicability of the new presented determination of dacomitinib.

UPLC-MS/MS method for the quantification of ertugliflozin and sitagliptin in rat plasma

In the present study, an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) approach was designed to concurrently measure the levels of ertugliflozin and sitagliptin in rat plasma with diazepam as the internal standard (IS). Acetonitrile-based protein precipitation was applied for sample preparation, then analytes (ertugliflozin and sitagliptin) were subjected to gradient elution chromatography with a mobile phase composed of acetonitrile (A) and 0.1% formic acid in water (B). Ertugliflozin was monitored by m/z 437.2 → 329.0 transition for quantification and m/z 437.2 → 207.5 transition for qualification, and sitagliptin was determined by m/z 408.2 → 235.0 transition for quantification and m/z 408.2 → 174.0 transition for qualification by multiple reaction monitoring (MRM) in positive ion electrospray ionization (ESI) source. When the concentration of ertugliflozin ranged from 1 to 1000 ng/mL and sitagliptin ranged from 2 to 2500 ng/mL, the method exhibited good linearity. For both ertugliflozin and sitagliptin, the intra- and inter-day precision were determined with the values of 1.6–10.9% and 0.8–13.3%, respectively; and the accuracy ranged from −5.7% to 14.6%. Matrix effect, extraction recovery, and stability data were in line with the stipulated FDA guidelines for validating a bioanalytical method. The validity of the designed method was confirmed through the pharmacokinetic experiments.

Combinational Biomarkers for Atrial Fibrillation Derived from Atrial Appendage and Plasma Metabolomics Analysis

Atrial fibrillation (AF) is one of the most common types of arrhythmias and often leads to clinical complications. The objectives of this study were to offer insights into the metabolites of AF and to determine biomarkers for AF diagnosis or prediction. Sixty atrial appendage samples (AF group: 30; non-AF group: 30) and 163 plasma samples (AF group: 48; non-AF group: 115) from 49 AF patients and 116 non-AF patients were subjected to liquid chromatography positive ion electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) metabolomics analysis. Consequently, 24 metabolites in atrial appendage samples and 24 metabolites in plasma samples were found to reflect metabolic differences between AF and non-AF patients (variable importance in projection (VIP) ≥ 1, P ≤ 0.05). Five identical metabolites including creatinine, D-glutamic acid, choline, hypoxanthine, and niacinamide (VIP ≥ 1.5, P < 0.01, FDR < 0.05) in atrial appendage and plasma samples were considered prominent features of AF patients, and the D-glutamine and D-glutamate metabolic pathway was also identified as a feature of AF patients. Finally, in plasma samples, the combination of D-glutamic acid, creatinine, and choline had an AUC value of 0.927 (95% CI: 0.875–0.979, P < 0.001) and displayed 90.5% sensitivity and 83.3% specificity; this group of metabolites was thus defined as a combinational biomarker for the recognition of AF and non-AF patients.

High-throughput doping control analysis of 28 amphetamine-type stimulants in equine plasma using hydrophilic interaction liquid chromatography-tandem mass spectrometry.

A hydrophilic interaction liquid chromatography-tandem mass spectrometry method (HILIC-MS/MS) was developed for the simultaneous determination of 28 amphetamine-type stimulants (ATSs) in equine plasma for doping control analysis. In this method, stimulants were recovered from equine plasma by liquid-liquid extraction (LLE) at pH9.5 using methyl tert-butyl ether and detected on a Thermo Finnigan triple quadrupole mass spectrometer operating in positive-ion mode electrospray ionization. All stimulants were eluted within 7minutes and baseline separation was achieved for isomeric and isobaric compounds using HILIC chromatography. Extraction efficiency was greater than 80% and matrix effect was acceptable for most stimulants. The limit of detection (LOD) was in the range of 10-50pg/mL and the lower limit of quantification (LLOQ) was in the range of 50-100pg/mL. Quadratic regression was employed for quantification and the dynamic range of quantification was 50-10000pg/mL. Confirmatory analysis criteria were established using product ion ratios and retention time. The limit of confirmation (LOC) was in the range of 20-100pg/mL. Stability study results indicated that some stimulants were unstable in equine plasma at room temperature and 4°C. However, all the stimulants studied were stable at -20°C and-80°C for the 6month study period.

Optimized bio-analytical methods development and comparative pharmacokinetic studies of four antidepressants in Egyptian population based on gender difference

The pharmacokinetics (PK) and pharmacodynamics of many oral antidepressants (OADs) vary substantially among different genders and ethnicities. Likewise is their therapeutic effectiveness, time to response and the incidence of adverse drug events. The aim of this study is to compare the PK of four OADs (desvenlafaxine; DSV, venlafaxine; VLX, escitalopram; ESP, and agomelatine; AGT) among Egyptian males and females.In this study, LC-MS/MS methods were developed and validated for determining the four OADs in human plasma. Samples were prepared by liquid-liquid extraction. Chromatographic separation was performed on reversed-phase C18 columns followed by positive-ion electrospray ionization and MS/MS detection. The assays were applied for the assessment of PK parameters in human volunteers (n = 95).The developed methods were linear, accurate, and precise for the determination of DSV, VLX, ESP and AGT with extraction recovery of 90 ± 2.0, 98 ± 1.0, 90 ± 1.3 and 87 ± 4.3%, respectively. OADs levels were successfully measured in subjects' plasma and PK parameters were calculated.A prevalent inter-individual variation in PK of the studied OAD was observed. The PK profile of DSV, VLX or ESP did not vary significantly between male and female subjects (p = 0.07–0.98; confidence level (CL) = 95) while the PK of AGT exhibited a significant gender-based variation in both the Cmax and the AUC∞ (p = 0.047 and 0.0015; CL = 95).Our results highlight the significance of therapeutic drug monitoring of OADs. Further, it indicates the dose adjustment based on gender difference may not be relevant for DSV, VLX and ESP while it may be considered for AGT.

Analysis of lanthionine ketimine ethyl ester in mouse serum, whole blood and tissues using ultrahigh-pressure liquid chromatography/tandem mass spectrometry.

Preclinical studies in the search for treatments for several neurodegenerative diseases have identified lanthionine ketimine (LK) and its monoethyl ester derivative (LKE) as potential candidates. An ultrahigh-pressure liquid chromatography/tandem mass spectrometry (UHPLC/MS/MS) assay was developed to evaluate bioavailability by measuring these compounds in mouse serum, whole blood and brain tissue. Following administration of LKE to mice for 3 days in chow at 300 ppm, the animals were sacrificed, and LKE was extracted from serum, whole blood and brain tissues through protein precipitation using cold methanol. To enhance chromatographic separation and electrospray ionization, LK was methylated using diazomethane. Separations were carried out using C18 reversed-phase UHPLC, and quantitative measurements were obtained using on-line triple-quadruple mass spectrometry with positive ion electrospray ionization, collision-induced dissociation and selected reaction monitoring. Tolbutamide was used as internal standard. LKE showed good recovery ranging from 77-90% in serum and 82-88% in brain tissue. An eight-point standard curve ranging from 0.005 to 4.6 μM was linear (R2 0.998). The average LKE detected in mouse serum was 277.42 nM, while the concentration in whole blood was 38 nM. Neither LK nor LKE was detected in brain tissues. A rapid quantitative method to measure LKE in mouse serum, whole blood and brain tissues using UHPLC/MS/MS was developed and validated following FDA guidelines. This method is suitable for bioavailability and pharmacokinetic studies.

Capecitabine bioequivalence in healthy volunteers

Capecitabine is a prodrug and is selectively activated by tumor cells to its cytotoxic moiety, 5-fluorouracil, by thymidine phosphorylase, which is generally expressed at high levels in tumors. Clinical and pharmacokinetic studies of capecitabine have been performed in patients with cancer. This study aims to evaluate the bioequivalence of two capecitabine formulations (150-mg tablet) using healthy male subjects under nonfasting conditions. The study was conducted as an open, randomized, three-period, semi-replicated design with three sequences (RRT, RTR, TRR) with a 1-week washout interval. The subjects were selected for the study after having their health status previously assessed by a clinical evaluation and laboratory tests (biochemical and hematological parameters, and urinalysis). A single capecitabine tablet (150mg) was given in each occasion. Plasma capecitabine concentrations were analyzed by liquid chromatography coupled with tandem mass spectrometry (HPLC/MS/MS) with positive ion electrospray ionization using multiple reactions monitoring (MRM). The geometric mean and 90% confidence intervals (CI) of capecitabine/Xeloda® (T/R) percent ratio were 104.34% (98.74 - 110.25%) for AUClast, 103.06% (97.48 - 108.96%) for AUCinf, and 104.07% (88.13 - 122.90%) for Cmax. Since the 90% CI for Cmax, AUClast, and AUCinf ratios were all inside the 80 - 125% interval proposed by the US Food and Drug Administration Agency, it was concluded that the capecitabine formulation elaborated by Eurofarma Laboratórios Ltda. is bioequivalent to Xeloda® formulation for both the rate and the extent of absorption. The drug was well tolerated by the subjects, indicating that it is safe to perform capecitabine bioequivalence studies in healthy male subjects. .

Simple LC-MS/MS Methods Using Core-Shell Octadecylsilyl Microparticulate for the Quantitation of Total and Free Daptomycin in Human Plasma.

Daptomycin, a cyclic lipopeptide antibiotic, displays high plasma protein binding. This study developed the simple method of liquid chromatographic separation using a core-shell octadecylsilyl microparticulate coupled to tandem mass spectrometry for the quantitation of total and free daptomycin in human plasma. Free daptomycin in plasma was obtained by centrifugal ultrafiltration. Deproteinized plasma specimens were directly separated using a core-shell octadecylsilyl microparticulate with isocratic elution. The mass spectrometer was run in positive-ion electrospray ionization mode. This method was applied to the quantitation of plasma samples in patients treated with intravenous daptomycin. Daptomycin and diazepam as an internal standard were eluted with a total run time of 10 minutes. The calibration curves of total and free daptomycin in human plasma were linear over the concentration ranges of 1-100 and 0.1-10 mcg/mL, respectively. The lower limits of quantitation of the total and free daptomycin in human plasma were 1.0 and 0.1 mcg/mL, respectively. Their extraction recovery rates in nonfiltrated and ultrafiltrated plasma samples were 106.1% and 98.2%, respectively. Total and free daptomycin did not exhibit any matrix effects in human plasma. The intraday and interday accuracies and imprecisions of total daptomycin were 88.7%-106.0% and 98.7%-105.9%, and within 4.1% and 10.4%, whereas those of free daptomycin were 86.8%-101.6% and 103.0%-107.8%, and within 14.6% and 14.6%, respectively. The plasma concentration ranges of total and free daptomycin in 15 infected patients were 3.01-34.1 and 0.39-3.64 mcg/mL, respectively. The plasma protein binding rate of daptomycin ranged from 80.8% to 94.9%. The present simple method with an acceptable analytical performance can be helpful for monitoring the pharmacokinetics of daptomycin in infected patients observed in clinical settings.

Simultaneous Detection of Vanadyl, Nickel, Iron, and Gallium Porphyrins in Marine Shales from the Eagle Ford Formation, South Texas

Metalloporphyrins in immature shales of the Late Cretaceous Eagle Ford Formation from South Texas were analyzed by positive-ion electrospray ionization (ESI) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Vanadyl, nickel, iron, and gallium porphyrins were detected in a single mass spectrum. The iron porphyrins were most abundant, followed by vanadyl, nickel, and gallium porphyrins, consistent with the metal contents determined by elemental analysis. The distribution of porphyrins shows that deoxophylloerythroetio (DPEP) porphyrins, dicyclic-deoxophylloerythroetio (di-DPEP) porphyrins, and porphyrins containing oxygen functional groups are the main components. The detection of oxygen-containing porphyrins, such as iron porphyrins with formulas of CnHmN4FeO, CnHmN4FeO2, and CnHmN5FeO2, would offer new clues of petroporphyrins formation mechanism from biological sources, such as chlorophylls and hemes. To our knowledge, this reports for the first time the presence of oxygen-containing iron porphyrins and gallium porphyrins in geological samples other than coals and lignites. The discovery of these petroporphyrins could provide additional insights into the diagenetic pathway of petroporphyrins and novel applications in petroleum geochemistry/exploration and oil refining. The composition of metalloporphyrins may potentially provide clues to decipher the redox conditions during deposition in the Eagle Ford Formation and provide better understanding of the Oceanic Anoxic Event 2 (OAE-2).

Simultaneous determination of ten neonicotinoid insecticides and two metabolites in honey and Royal-jelly by solid−phase extraction and liquid chromatography−tandem mass spectrometry

An analytical method based on liquid chromatography-tandem mass spectrometry (LC–MS/MS) method was developed for the first simultaneous determination of ten neonicotinoid insecticides (pymetrozine, dinotefuran, nitenpyram, thiamethoxam, flonicamid, imidacloprid, clothianidin, imidaclothiz, acetamiprid, thiacloprid) and two metabolites (4-trifluoromethylnicotinamide and N-desmethylacetamiprid) in honey and royal-jelly. The quantitative detection was performed by LC–MS/MS on multiple reaction monitoring (MRM) mode under positive-ion electrospray ionization. The isotope dilution internal standard method or external standard method was used for quantitation analysis. The limits of quantification (LOQs), calculated as 10 times the standard deviation, were 0.25–5.0 µg kg−1 for ten neonicotinoid insecticides and two metabolites. The average recoveries were in the range of 72.8–106.5%, with relative standard deviations (RSDs) below 13.8%, measured at three concentration levels. The developed method exhibits a high sensitivity and suitable for the simultaneous determination of neonicotinoid insecticides and metabolites in honey and royal-jelly.

Development, validation and application of a novel HPLC-MS/MS method for the quantification of atorvastatin, bisoprolol and clopidogrel in a large cardiovascular patient cohort

Cardiovascular disease is a leading cause of morbidity, mortality, and healthcare expenditure worldwide. Importantly, there is interindividual variation in response to cardiovascular medications, leading to variable efficacy and adverse events. Therefore a rapid, selective, sensitive and reproducible multi-analyte HPLC-MS/MS assay for the quantification in human plasma of atorvastatin, its major metabolites 2-hydroxyatorvastatin, atorvastatin lactone and 2-hydroxyatorvastatin lactone, plus bisoprolol and clopidogrel-carboxylic acid has been developed, fully validated, and applied to a large patient study. Fifty microliter plasma samples were extracted with a simple protein precipitation procedure involving acetonitrile with acetic acid (0.1%, v/v). Chromatographic separation was via a 2.7 μm Halo C18 (50 × 2.1 mm ID, 90 Å) column and gradient elution at a flow rate of 500 μL/min consisting of a mobile phase of water (A) and acetonitrile (B), each containing 0.1% formic acid (v/v), over a 6.0 min run time. The six analytes and their corresponding six deuterated internal standards underwent positive ion electrospray ionisation and were detected with multiple reaction monitoring. The developed method was fully validated with acceptable selectivity, carryover, dilution integrity, and within-run and between-run accuracy and precision. Mean extraction recovery for the analytes was 92.7–108.5%, and internal standard-normalised matrix effects had acceptable precision (coefficients of variation 2.2–12.3%). Moreover, all analytes were stable under the tested conditions. Atorvastatin lactone to acid interconversion was assessed and recommendations for its minimisation are made. The validated assay was successfully applied to analyse 1279 samples from 1024 patients recruited to a cardiovascular secondary prevention prospective study.

Simultaneous Determination and Pharmacokinetics of Peimine and Peiminine in Beagle Dog Plasma by UPLC-MS/MS after the Oral Administration of Fritillariae ussuriensis Maxim and Fritillariae thunbergii Miq Powder.

A simple and high sensitive ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the simultaneous determination of peimine and peiminine in beagle dog plasma after the oral administration of Fritillariae ussuriensis Maxim and Fritillariae thunbergii Miq powder. Chromatographic separation was achieved on an ACQUIT UPLC® BEH C18 column (1.7 μm, 2.1 × 100 mm) in a gradient elution way with a mobile phase consisting of acetonitrile and water containing 0.1% formic acid at a flow rate of 0.4 mL/min. The plasma samples were prepared by a liquid–liquid extraction (LLE) method with ethyl acetate. The analytes were detected with a triple quadrupole tandem mass spectrometry (MS) in multiple reaction monitoring (MRM) mode and a positive ion electrospray ionization (ESI) of the transitions at m/z 432.4→414.4 for peimine and m/z 430.3→412.3 for peiminine. The method was linear for two analytes over the investigated range with all determined correlation coefficients exceeding 0.9900. The lower limit of quantification (LLOQ) was 0.988 ng/mL for peimine and 0.980 ng/mL for peiminine. The mean extraction recoveries of peimine and peiminine at three quality control samples (QC) levels were ranged from 82.56 to 88.71%, and matrix effects ranged from 92.06 to 101.2%. The intra-day and inter-day precision and accuracy were within the acceptable limits at LLOQ and QC levels. The method was effectively and successfully applied to the pharmacokinetics of peimine and peiminine after oral administration of powder to beagle dogs. The obtained results may be help to guide the clinical application of Fritillaria ussuriensis Maxim and Fritillaria thunbergii Miq.