Selected Reaction Monitoring Mode Research Articles

Infusion Mass Spectrometric Analysis of Sphingomyelin Species in Dairy With Lithium-Mediated Fragmentation

ObjectivesBovine milk is rich in sphingomyelin (SM), a class of polar lipids which may affect the gut microbiome and have anti-inflammatory properties. Infusion mass spectrometry rapidly yields valuable information about the structure of SM, but quantitation is confounded by isobaric phosphatidylcholine (PC) lipids. Using previously established Li-induced fragmentation chemistry, we developed a quantitative method for analysis of SM species using selective multiple reaction monitoring (MRM) transitions.MethodsPolar lipids were extracted from milk samples using organic solvents followed by silicic acid solid phase extraction (SPE) to remove triacylglycerol (TAG). Extracts were dissolved in methanol with 0.2 mM lithium acetate and analyzed on an AB Sciex 5500 QTRAP hybrid mass spectrometer in an infusion-based manner. SM species were identified by a characteristic 207 Da loss, representing the loss of [Li + H2O + (CH3)3NC2H4PO4] allowing for separation from PC species. Commercially available SM standards were used where possible to verify identity. A total SM profile was determined through neutral loss (NL) 207 Da scans, SM fine structure with MS3 scans, and individual SM species were quantified utilizing MRM.ResultsUse of the Li- mediated fragmentation and the NL 207 Da scans allowed for selective quantitation of SM, but not PC species, with limits of detection >1 nM and limits of quantitation >10 nM for individual SM species. Milk matrix TAG suppressed MRM intensities by 10-fold requiring SPE removal of TAG. In bovine milk, 30 individual SM species were detected ranging from SM 28:1 to SM 44:2. SM were predominately 16:1 and 18:1 sphingoid bases with fatty acid tails ranging from 10 to 26 carbons. Utilizing this method, we determined the SM content of fluid dairy products including whole bovine milk (37 μM), half and half (70 μM), whipping cream (130 μM), and goat milk (56 μM).ConclusionsA rapid, infusion-based MS approach was developed to selectivity identify and quantify SM species that avoids isobaric overlap with PC. This method is robust and could potentially be applied to other SM-containing samples.Funding SourcesThis work was funded by USDA-ARS Projects 3062-53,000-001-00D and supported by the USDA-ARS Grand Challenge Synergy project “Dairy Agriculture for People and Planet”.

Effect of Baicalein on the Pharmacokinetics of Cilostazol and Its Two Metabolites in Rat Plasma Using UPLC-MS/MS Method.

This study aimed to explore the effect of baicalein on the pharmacokinetics of cilostazol (CLZ) and its two metabolites 3,4-dehydro cilostazol (3,4-CLZ) and 4′-trans-hydroxy cilostazol (4′-CLZ) in rats using a newly established ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method. Ticagrelor was used as an internal standard (IS), then cilostazol and its two metabolites were separated by means of a UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm) using gradient elution method with 0.4 ml/min of flow rate. Acetonitrile as organic phase and water with 0.1% formic acid as aqueous phase constructed the mobile phase. Selective reaction monitoring (SRM) mode and positive ion mode were preferentially chosen to detect the analytes. Twelve SD rats were divided into two groups (n = 6) when CLZ was administered orally (10 mg/kg) with or without oral baicalein (80 mg/kg). The selectivity, linearity, recovery, accuracy, precision, matrix effect and stability of UPLC-MS/MS assay were satisfied with the standards of United States Food and Drug Administration guidelines. In control group, AUC0-∞ and Cmax of CLZ were 2,169.5 ± 363.1 ng/ml*h and 258.9 ± 82.6 ng/ml, respectively. The corresponding results were 3,767.6 ± 1,049.8 ng/ml*h and 308.6 ± 87.9 ng/ml for 3, 4-CLZ, 728.8 ± 189.9 ng/ml*h and 100.3 ± 51.3 ng/ml for 4′-CLZ, respectively. After combination with baicalein, AUC0-∞ and Cmax of CLZ were 1.48, 1.38 times higher than the controls. Additionally, AUC0-∞ and Cmax were separately decreased by 36.12 and 19.54% for 3,4-CLZ, 13.11 and 44.37% for 4′-CLZ. Baicalein obviously alters the pharmacokinetic parameters of CLZ, 3,4-CLZ and 4′-CLZ in rats. These results suggested that there was a potential drug-drug interaction between baicalein and CLZ. Therefore, it must raise the awareness when concomitant use of CLZ with baicalein, the dosage regimen of CLZ should be taken into consideration, if this result is confirmed in clinical studies.

A quantitative method for the simultaneous detection of SR9009 and SR9011 in equine plasma using liquid chromatography-electrospray ionization-tandem mass spectrometry.

SR9009 and SR9011 are metabolic modulators pharmacologically targeting REV-ERB receptors as synthetic agonists. A liquid chromatography-tandem mass spectrometry method for the detection of SR9009 and SR9011 in equine plasma was developed and validated. Plasma samples were pretreated by protein precipitation with methanol and were loaded onto an ACQUITY ultra performance liquid chromatography high-strength silica C18 column (2.1 × 150 mm, 1.8 μm) for chromatographic separation. The mobile phase consisted of 5-mM ammonium formate (pH 3.0) in distilled water and 0.1% formic acid in acetonitrile, and a gradient elution was used at a flow rate of 0.25 ml/min. For the mass spectrometry detection, the selected reaction monitoring mode was used with transitions of 438.2 → 124.9 for SR9009, 479.2 → 125.1 for SR9011, and 292.2 → 109.1 for the internal standard (testosterone-d3) in the positive ionization mode. The linearity, lower limit of quantification, intra- and inter-day precision, accuracy, matrix effect, recovery, and stability were evaluated. The method was found to be accurate and reproducible for the quantitation of SR9009 and SR9011. The developed method was successfully applied to plasma samples of thoroughbreds injected intramuscularly with SR9009.

Alkylated glutamic acid and histidine derived from protein-adducts indicate exposure to sulfur mustard in avian serum.

Sulfur mustard (SM, bis[2-chloroethyl]-sulfide) is a banned chemical warfare agent deployed in the violent conflict in the Middle East poisoning humans and animals. For legal reasons, bioanalytical methods are mandatory proving exposure to SM. Reaction products (adducts) of SM with endogenous proteins, for example, serum albumin (SA), are valuable long-lived targets for analysis. Whereas nearly all methods known so far focus on human proteins, we address for the first time neat chicken SA and avian serum from chicken, duck, and ostrich. After proteolysis, protein precipitation, evaporation of the supernatant, and re-dissolution analysis were performed by micro-liquid chromatography-electrospray ionization tandem-mass spectrometry in the selected reaction monitoring mode, μLC-ESI MS/MS (SRM), for detection of the hydroxyethylthioethyl product ion [HETE]+ at m/z 105.0. After in vitro incubation with SM and pronase-catalyzed proteolysis, the alkylated amino acids Glu(-HETE) and His(-HETE) were detected. Both borne the SM-characteristic HETE-moiety bound to their side chain. The eightfold deuterated SM analog (d8-SM) was also applied to support adduct identification. Proteolysis conditions were optimized with respect to pH (8.0), temperature (50°C), and time to maximize the yield of Glu(-HETE) (30 min) and His(-HETE) (180 min). Amino acid adducts were stable in the autosampler for at least 24 h. Protein-adducts were stable in serum at -30°C for at least 33 days and for three freeze-and-thaw cycles. At the body temperature of chicken (+40°C), Glu(-HETE) was degraded in serum (period of half-change 3 days), whereas His(-HETE) remained stable. The presented method broadens the toolbox of procedures to document poisoning with SM.

Pharmaceuticals are identified in insects in River Fyris – A study with both tandem quadrupole and quadrupole-time-of-flight mass spectrometry

The internal concentrations of active pharmaceutical compounds in insects/macroinvertebrates in River Fyris, Uppsala, Sweden, have for the first time been investigated. Specimen of backswimmer, caddisfly larva, damselfly larva, mayfly larva and water louse were caught in the river downstream a waste-water treatment plant. After homogenization and extraction, analysis was carried out with Ultra-High Performance Liquid Chromatography – Electrospray – Tandem Mass Spectrometry (UHPLC-ESI-MS/MS) using both a tandem quadrupole (QqQ) and a quadrupole-time-of-flight (qToF) mass spectrometer. A combined qualitative/quantitative screening method for 89 pharmaceutical compounds in the selective reaction monitoring mode was applied to the samples using the QqQ instrument. Thirty-three different drugs were detected and quantified in the macroinvertebrate samples, covering a wide range of pharmacological classes, the most common being antidepressants, psycholeptics and antihistamines. Drug concentrations up to 260 ng/g (for tetracycline) were determined. A subset of thirteen compounds were selected for a complementary qualitative UHPLC-qToF-MS/MS analysis. This way, the confidence in the substance identifications was significantly strengthened by the availability of full scan high-resolution spectra and accurate mass measurements. This is the first study demonstrating the uptake of pharmaceuticals in water-living macroinvertebrates in Sweden. Since these organisms are in the lower part of the food chain, pharmaceuticals might accumulate in predators leading to ecotoxicological effect at higher trophic levels. Macroinvertebrates might be promising indicator organisms for pharmaceutical pollution.

A robust, accurate, sensitive LC-MS/MS method to measure indoxyl sulfate, validated for plasma and kidney cells.

Proximal tubular damage is an important prognostic determinant in various chronic kidney diseases (CKDs). Currently available diagnostic methods do not allow for early disease detection and are neither efficient. Indoxyl sulfate (IS) is an endogenous metabolite and protein‐bound uremic toxin that is eliminated via renal secretion, but accumulates in plasma during tubular dysfunction. Therefore, it may be suitable as a tubular function marker. To evaluate this, a fast bioanalytical method was developed and validated for IS in various species and a kidney cell line using LC–MS/MS. An isotope‐labeled IS potassium salt as an internal standard and acetonitrile (ACN) as a protein precipitant were used for sample pretreatment. The analyte was separated on a Polaris 3 C18‐A column by gradient elution using 0.1% formic acid in water and ACN, and detected by negative electrospray ionization in selected reaction monitoring mode. The within‐day (≤ 4.0%) and between‐day (≤ 4.3%) precisions and accuracies (97.7 to 107.3%) were within the acceptable range. The analyte showed sufficient stability at all conditions investigated. Finally, applying this assay, significantly higher plasma and lower urine concentrations of IS were observed in mice with diabetic nephropathy with tubular damage, which encourages validation toward its use as a biomarker.

Use of liquid chromatography-tandem mass spectrometry for foscarnet quantification in human serum and cerebrospinal fluid.

Foscarnet (FCV) is used to treat cytomegalovirus, human herpesvirus, and human immunodeficiency virus infections. It is a low-molecular-weight compound containing carboxylate and phosphate groups. There are no reports on the use of liquid chromatography-tandem mass spectrometry (LC/MS/MS) to analyze FCV via bioanalysis. In the present study, we developed the ion-pair LC/MS/MS method to analyze FCV in human serum and cerebrospinal fluid (CSF). FCV was extracted from human serum and CSF by weak anion exchange (WAX) solid-phase extraction. The LC/MS/MS systems were coated with 0.1% phosphoric acid in methanol to avoid nonspecific absorption. FCV was detected using ion-pair LC/MS/MS with dibutylammonium acetate. Selected reaction monitoring transition of FCV in the negative ion mode was selected at m/z 125.1 → 62.9. FCV was selectively detected in human serum and CSF, and the liner range was 5-1000 μM (R2 = 0.99). The intraday and interday accuracy and precision were within ±15%. FCV was constantly extracted from human serum and CSF by WAX solid-phase extraction (recovery ratio = 76.0-77.9%). No matrix effect was observed. A robust LC/MS/MS method to analyze FCV was successfully developed. FCV was selectively measured using LC/MS/MS in very low extract volumes (20 μL). The method will be useful in evaluating the FCV level in human serum and CSF.

Simultaneous detection of 93 anabolic androgenic steroids in dietary supplements using gas chromatography tandem mass spectrometry

In recent years, anabolic androgenic steroids (AASs) have been frequently detected as undeclared ingredients in dietary supplements, where the adverse analytical findings (AAFs) were obtained from analysis of athletes’ urine samples after ingestion. In our present study, a GC-MS/MS method for simultaneous detection of 93 anabolic steroids was developed. The chromatographic and mass spectrometric conditions were optimized, and selective reaction monitoring (SRM) mode was adopted to obtain the necessary sensitivity. The whole sample analysis process was completed within 23 min, and the limit of detection (LOD) was 0.5–4 ng.g−1 for solid samples and 0.1–0.8 ng.mL−1 for liquid samples. This method was verified according to World Anti-Doping Agency (WADA) regulations. In addition, the method was found to be specific, accurate. The developed method was then applied to a routine analysis of more than 300 liquid and solid dietary supplements, and one testosterone-positive sample was found. Three suspected drugs, (4-hydroxyandrostenedione, DHEA, and 6-Br androstenedione) were found in three dietary supplements obtained from the Internet through the pretreatment method of this study. This study provides a high-throughput method for screening and monitoring the ingredients of supplements and their subsequent harm to public health.

A selective and accurate liquid chromatography-tandem mass spectrometry method for the quantitation of the novel 5-HT4 receptor partial agonist SUVN-D4010 (Usmarapride) in human plasma and urine

Liquid chromatography and the tandem mass spectrometry method to quantitate SUVN-D4010 (Usmarapride) in human plasma and urine have been developed and fully validated in compliance with regulatory guidelines. The sample preparation technique is simple and rapid consisting of acetonitrile precipitation followed by dilution of supernatant with a compatible solvent. Chromatographic separation was achieved on an X-Bridge C18 (2.1×50 mm, 3.5 µm) column using 0.1% v/v ammonium hydroxide and acetonitrile as mobile phase components, delivered at a flow rate of 0.75 mL min−1. Electrospray Ionization technique in positive mode was used for mass spectrometric detection. Selective reaction monitoring (SRM) transitions of m/z 384.2 → 352.1 for SUVN-D4010 and m/z 388.2 → 356.1 for SUVN-D4010-d4 were used for quantitation. Calibration curves for SUVN-D4010 were linear across the concentration range of 0.3–300 ng mL−1 in human plasma and 5.00–5000 ng mL−1 in human urine. The method generated results with acceptable accuracy (± 9.0%), precision (%CV, ≤8.7), and mean extraction recovery (≥93.4%) with negligible matrix effect in both plasma and urine. SUVN-D4010 was found to be stable in human plasma and urine at the defined storage conditions. The validated method was successfully applied to quantitate SUVN-D4010 in human plasma and urine from a clinical first-in-human study conducted to evaluate its safety, tolerability, and pharmacokinetics in healthy adults.

Development and Validation of a Bioanalytical UHPLC-MS/MS Method Applied to Murine Liver Tissue for the Determination of Indocyanine Green Loaded in H-Ferritin Nanoparticles.

Indocyanine green (ICG) is one of the most commonly used fluorophores in near-infrared fluorescence-guided techniques. However, the molecule is prone to form aggregates in saline solution with a limited photostability and a moderate fluorescence yield. ICG was thus formulated using protein-based nanoparticles of H-ferritin (HFn) in order to generate a new nanostructure, HFn-ICG. In this study, an ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) system was employed to develop and validate the quantitative analysis of ICG in liver tissue samples from HFn-ICG-treated mice. To precipitate HFn, cold acetone in acidic solution at pH 5.0 was used. The processed liver samples were injected into the UHPLC-MS/MS system for analysis using the positive electrospray ionization mode. Chromatographic separation was achieved on a Waters Acquity UPLC® HSS T3 Column (1.8 μm, 2.1 × 100 mm) with 0.1% formic acid and acetonitrile as the mobile phase with gradient elution. The selected reaction monitoring transitions of 753 330 and 827 330 were applied for ICG and IR-820 (the internal standard, IS), respectively. The method was selective and linear over a concentration range of 50–1,500 ng/ml. The method was validated for sensitivity, accuracy, precision, extraction recovery, matrix effect, and stability in liver tissue homogenates. ICG extraction recoveries ranged between 85 and 108%. The intra- and inter-day precisions were less than 6.28%. The method was applied to a bio-distribution study to compare the amount of ICG levels from mice treated with HFn-ICG and free ICG. The analyses of the homogenate samples from the two types of treatment showed that the concentration levels of ICG is approximately six-fold higher than those of free ICG (1,411 ± 7.62 ng/ml vs. 235 ± 26.0 ng/ml) at 2 h post injection.

Simultaneous and Rapid Determination of Six Tyrosine Kinase Inhibitors in Patients with Non-Small Cell Lung Cancer Using HPLC-MS/MS.

Objective To develop a new method for quantitatively analyzing six tyrosine kinase inhibitors (gefitinib, erlotinib, icotinib, afatinib, osimertinib, and crizotinib) used in the treatment of non-small cell lung cancer (NSCLC) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Methods The analytes were detected in the selected reaction monitoring mode on a triple quadrupole mass spectrometer with the positive ionization mode. Carbamazepine was utilized as the internal standard. The pretreatment of the plasma sample was completed based on protein precipitation with acetonitrile, and the analytes were separated on an Agilent Zorbax SB-C18 reversed-phase column (2.1 mm × 100 mm, 3.5 μm, Agilent, USA) using gradient elution. The mobile phase consisted of 0.1% formic acid in water (phase A) and 0.1% formic acid in acetonitrile (phase B). The flow rate was 0.3 mL/min, and the injection volume was 5 μL. The column temperature was set and maintained at 35°C. Results The calibration curves were linear over the range from 5.0 to 1000.0 ng/mL for gefitinib, crizotinib, and osimertinib; from 50.0 to 4000.0 ng/mL for icotinib and erlotinib; and from 5.0 to 400.0 ng/mL for afatinib. Linear correlation coefficients were >0.990 for all regression curves. The intra- and interday accuracy and precision of the method were within ±15.0% and not more than 15.0%, respectively. The mean recovery of all the analytes ranged from 70.18% to 110.76%, the matrix effect was from 88.85% to 127.58%, and stability was within ±15.0%. Conclusion This newly developed method was sensitive, simple, and robust and could be used in therapeutic drug monitoring of six tyrosine kinase inhibitors in NSCLC patients.

Determination of veterinary drugs in microalgae biomass from photobioreactors fed with piggery wastewater

Concentration data of veterinary drugs in microalgae biomass collected from photobioreactors fed with piggery wastewaters are presented for the first time in this work. To this aim, a QuEChERS methodology and an ultrasound-assisted solid-liquid extraction have been assessed as sample preparation procedures with the purpose of determining 20 veterinary drugs, mainly antibiotics of different physico-chemical properties in addition to dexamethasone, fenbendazole and progesterone. Some critical operation parameters of the QuEChERS procedure were optimized by an experimental design but tetracycline, oxytetracycline, doxycycline, marbofloxacin and ciprofloxacin were not detected by the QuEChERS sample preparation. The use of a longer and thorough approach, a solid-liquid extraction with water/methanol in presence of primary secondary amine as a clean-up agent followed by solid-phase extraction on Oasis HLB cartridges, is recommended to monitor all intended analytes. The determination in extracts is carried out by ultra-high performance liquid chromatography–tandem mass spectrometry in selected reaction monitoring mode. Limits of detection about 0.2–42 ng per g of lyophilized microalgae sample, and repeatabilities about 6–46% (n = 5, RSDs) are reached. The solid-liquid extraction method was applied to microalgae biomass samples collected from a photobioreactor. Nine drugs were detected in the samples at relatively low concentration and a proportional relationship between the found concentrations and the octanol/water partition coefficients of the drugs has been outlined. Moreover, a linear ratio between the concentrations measured in biomass and effluent has been observed for most of the drugs.

Pharmacokinetic and tissue distribution study of eight volatile constituents in rats orally administrated with the essential oil of Artemisiae argyi Folium by GC–MS/MS

Artemisia argyi is commonly used as a remedy for gynecological and respiratory disease in traditional Chinese medicine. The essential oil is considered as the major active ingredients of A. argyi, mainly composed of eucalyptol, α-thujone, camphor, borneol, bornyl acetate, eugenol, β-caryophyllene, and caryophyllene oxide, while limited study addresses the in vivo disposition of these volatile ingredients. In present study, a rapid, sensitive and selective GC–MS/MS method has been developed and validated for the quantification of the eight volatile constituents in rat plasma and tissues after orally dosing with the essential oil of Artemisiae Argyi Folium (AAEO) using naphthalene as an internal standard (IS). The analytes were extracted from biosamples by liquid–liquid extraction with hexane/ethyl acetate. The GC separation was achieved on a TG-5SILMS column (30 m × 0.25 mm, 0.25 μm film thickness) and MS detection was performed on selective reaction monitoring (SRM) mode. The assay had a lower limit of quantification (LLOQ) less than 2 ng/ml for the analytes with good linearity (r ≥ 0.9907). Their disposition profile in rat plasma and tissues was characterized after orally giving AAEO, and the data revealed the analytes underwent rapid absorption from GI tract and were mainly transferred to the liver, heart, kidney, lung, and spleen with prompt elimination. The results provided a meaningful basis for guiding the pharmacodynamic study and clinical applications of this herbal medicine.

UPLC-MS/MS assay for the simultaneous determination of pyrotinib and its oxidative metabolite in rat plasma: Application to a pharmacokinetic study.

Pyrotinib is an irreversible EGFR/HER2 inhibitor that has been approved for the treatment of breast cancer. The aim of this work was to establish a quantification method for the simultaneous determination of pyrotinib and its metabolite pyrotinib-lactam in rat plasma using UPLC-MS/MS. After simple protein precipitation with acetonitrile, the analytes and internal standard (neratinib) were separated on an ACQUITY BEH C18 column (2.1× 50 mm, 1.7μm) using a mobile phase of water containing 0.1% formic acid and acetonitrile. The detection was performed using selected reaction monitoring mode with precursor-to-product ion transitions at m/z 583.2> 138.1 for pyrotinib, m/z 597.2> 152.1 for pyrotinib-lactam, and m/z 557.2> 112.1 for internal standard. The assay exhibited excellent linearity in the concentration range of 0.5-1000 ng/mL for pyrotinib and pyrotinib-lactam. The assay met the criteria of the United States Food and Drug Administration-validated bioanalytical methods and was successfully applied to a pharmacokinetic study of pyrotinib and its metabolite for the first time. Our results demonstrated that pyrotinib rapidly converted into pyrotinib-lactam, whose in vivo exposure was 21% that of pyrotinib.

Rapid quantification of fatty acids in plant oils and biological samples by LC-MS

Analysis of fatty acids (FA) in food and biological samples such as blood is indispensable in modern life sciences. We developed a rapid, sensitive and comprehensive method for the quantification of 41 saturated and unsaturated fatty acids by means of LC-MS. Optimized chromatographic separation of isobaric analytes was carried out on a C8 reversed phase analytical column (100 × 2.1 mm, 2.6 μm core–shell particle) with a total run time of 15 min with back pressure lower than 300 bar. On an old triple quadrupole instrument (3200, AB Sciex), pseudo selected reaction monitoring mode was used for quantification of the poorly fragmenting FA, yielding limits of detection of 5–100 nM. Sample preparation was carried out by removal of phospholipids and triglycerides by solid-phase extraction (non-esterified fatty acids in oils) or saponification in iso-propanol (fatty acyls). This is not only a rapid strategy for quantification of fatty acyls, but allows the direct combination with the LC-MS-based analysis of fatty acid oxidation products (eicosanoids and other oxylipins) from the same sample. The concentrations of fatty acyls determined by means of LC-MS were consistent with those from GC-FID analysis demonstrating the accuracy of the developed method. Moreover, the method shows high precisions with a low intra-day (≤ 10% for almost all fatty acids in plasma and ≤ 15% in oils) and inter-day as well as inter-operator variability (< 20%). The method was successfully applied on human plasma and edible oils. The possibility to quantify non-esterified fatty acids in samples containing an excess of triacylglycerols and phospholipids is a major strength of the described approach allowing to gain new insights in the composition of biological samples.Graphical abstract

Development and validation of a multi-pollutant method for the analysis of polycyclic aromatic hydrocarbons, synthetic musk compounds and plasticizers in atmospheric particulate matter (PM2.5)

Exposure to atmospheric particulate matter (PM) associated pollutants is a global concern due to the risk posed in human health after inhalation. In this study, a simple and sensitive multi-residue method is developed for the analysis of 50 organic pollutants, comprising 18 polycyclic aromatic hydrocarbons (PAHs), 12 phthalate esters (PAEs), 12 organophosphorus flame retardants (OPFRs), 6 synthetic musk compounds (SMCs) and 2 bisphenols in PM2.5 samples. The method consists of three cycles of ultrasonic assisted solvent extraction and vortex (UASE + vortex), followed by a vortex-assisted dispersive solid phase extraction (d-SPE) clean-up and a final determination step by using programmed temperature vaporization-gas chromatography-tandem mass spectrometry (PTV-GC-MS/MS). Experimental conditions concerning clean-up adsorbents (alumina, silica gel and Florisil®) and filters (glass fibre, PTFE and nylon), as well as PTV-GC-MS/MS conditions were studied. In addition, the use of SRM (selected reaction monitoring) mode in MS-MS, as well as matrix-matched calibration together with labelled subrogate standards, resulted in successfully validation results for most of the compounds due to the high sensitivity, minimization of matrix effects and recovering losses compensation. The proposed method was validated in terms of linearity, limits of detection and quantification (LODs and LOQs), analytical recoveries by analysing a spiked composite sample (PM2.5) at three spiking levels and intra-day and inter-day precision. Moreover, an urban particulate matter standard reference material (SRM 1648a) was analysed to assess PAHs determination accuracy. Furthermore, applicability of the method was proved by analysing 12 PM2.5 samples from an industrial area. Among all studied pollutants, bisphenol A (BPA) was the most predominant with an average concentration of 5000 pg m−3, followed by bis(2-ethylhexyl) phthalate (DEHP) and diisobutyl phthtalate (DiBP) with 1990 pg m−3 and 632 pg m-3, respectively. Concerning OPFRs, average concentrations between 345 – 253 pg m−3 were found for triphenyl phosphine oxide (TPPO), tris(chloropropyl) phosphate (TCPP), tri-iso-butyl phosphate (TiBP) and tris(2-butoxyethyl) phosphate (TBOEP). Finally, the highest PAHs levels were found for 5-6 ring-number PAHs (Σ5-6 rings PAHs) with an average concentration of 2680 pg m−3, while only 2 SMCs were quantitated accounting for 17.5 pg m−3 by average.

Simultaneous determination of 3-n-butylphthalide and its metabolite 10-hydroxy-butylphthalide in rat plasma using liquid chromatography-tandem mass spectrometry and application to a pharmacokinetic study.

3-n-Butylphthalide (NBP) is a potent drug for the treatment of ischemic stroke. The aim of this study was to develop a simple and sensitive ultra-high-performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method for the simultaneous determination of NBP and its circulating metabolite 10-hydroxy-NBP in rat plasma using senkyunolide I as the internal standard (IS). The analytes and IS were extracted from the plasma by ethyl acetate-ethyl ether (1:5, v/v) and then separated on an ACQUITY BEH C18 column (2.1 × 50 mm, 1.7 μm). The mobile phase consisted of water containing 0.1% formic acid and acetonitrile containing 0.1% formic acid, which was delivered at a flow rate of 0.3 mL/min with gradient elution. MS detection was achieved under selective reaction monitoring mode with precursor-to-product transitions at m/z 191.1 > 145.1 for NBP, m/z 207.1 > 171.1 for 10-hydroxy-NBP and m/z 207.1 > 161.1 for IS, respectively. The assay showed excellent linearity over the concentration range of 0.5-1000 ng/mL for both analytes, with correlation coefficient greater than 0.998. The other validation parameters were all within the required limits. The validated UPLC-MS/MS method has been further applied to the pharmacokinetic study of NBP and 10-hydroxy-NBP in rats after they were orally administered with NBP (30 mg/kg).

Evidence of sulfur mustard poisoning by detection of the albumin-derived dipeptide biomarker C(-HETE)P after nicotinylation.

Sulfur mustard (SM, bis[2-chloroethyl]-sulfide) is a banned chemical warfare agent that was frequently used in recent years and led to numerous poisoned victims who developed painful erythema and blisters. Post-exposure analysis of SM incorporation can be performed by the detection of human serum albumin (HSA)-derived peptides. HSA alkylated by SM contains a hydroxyethylthioethyl (HETE)-moiety bound to the cysteine residue C34 yielding the dipeptide biomarker C(-HETE)P after pronase-catalyzed proteolysis. We herein present a novel procedure for the selective precolumn nicotinylation of its N-terminus using 1-nicotinoyloxy-succinimide. The reaction was carried out for 2 h at ambient temperature with a yield of 81%. The derivative NA-C(-HETE)P was analyzed by micro liquid chromatography-electrospray ionization tandem-mass spectrometry working in the selected reaction monitoring mode (μLC-ESI MS/MS SRM). The derivative was shown to be stable in the autosampler at 15°C for at least 24 h. The single protonated precursor ion (m/z 428.1) was subjected to collision-induced dissociation yielding product ions at m/z 116.1, m/z 137.0, and m/z 105.0 used for selective monitoring without any plasma-derived interferences. NA-C(-HETE)P showed a mass spectrometric response superior to the non-derivatized dipeptide thus yielding larger peak areas (factor 1.3 ± 0.2). The lower limit of identification corresponded to 80 nM SM spiked to plasma in vitro. The presented procedure was applied to real case plasma samples from 2015 collected in the Middle East confirming SM poisoning.

Pharmacokinetics and tissue distribution of cantharidin after oral administration of aqueous extracts from Mylabris in rats.

A sensitive gas chromatography-mass spectroscopy method was established for the determination of cantharidin (CTD) in rat plasma and liver homogenates. During the experiment, rats were randomly divided into two groups (low, high) and were administered aqueous extract of Mylabris compound for 7days. Then, plasma and tissue samples were taken at different time points to study the pharmacokinetics and tissue distribution of CTD in rats. The selected reaction monitoring transitions for CTD and clofibrate (internal standard) were m/z 128 → 85 and m/z 169 → 141, respectively. The calibration curve ranged from 10.26 to 3,078 ng/ml for plasma and from 10.26 to 246.24 ng/ml for liver homogenates. The lower limits of quantification were 10.26 ng/ml for both plasma and liver. The intra- and inter-day precision and accuracy were <20% for both plasma and liver homogenates. Extraction recovery ranged from 89.21 to 103.61% for CTD in rat plasma and liver and from 83.79 to 102.74% for IS in rat plasma and liver. Matrix effects ranged from 93.06 to 110.44% for CTD and from 91.65 to 110.80% for IS.

Bioanalysis of selinexor in mouse plasma micro-samples utilizing UPLC-MS/MS

Selinexor, a first-in-class inhibitor of the nuclear export protein Exportin-1 (XPO1), was recently approved for the treatment of multiple myeloma in combination with dexamethasone, and as monotherapy for diffuse large B-cell lymphoma. To enable investigations of selinexor in mice, we established and validated an ultrahigh-performance liquid chromatography – tandem mass spectrometry (UPLC-MS/MS) assay in the plasma concentration range of 1–1000 ng/mL using plasma microsamples of 5 µL. Protein depletion with acetonitrile was used for efficient isolation of selinexor which was followed by a dilution step, resulting in a scalable sample processing. Quantification was performed with positive electrospray ionization tandem mass spectrometry in the selected reaction monitoring mode. Due to the high sensitivity of the quantification and the scalable sample processing procedure, the assay can be used for different concentration ranges to either further decrease the achievable lower limit of quantification or to reduce the amount of plasma used. The assay showed interday and intraday accuracy of 89.0–109.0% with a corresponding precision ≤ 14.1%. Suitability for investigations of selinexor in small animal experiments was demonstrated by determination of plasma selinexor in mice after oral administration.