Determination of bakkenolide A in rat plasma using liquid chromatography/tandem mass spectrometry and its application to a pharmacokinetic study

A sensitive rapid analytical method was established and validated to determine the bakkenolide A (BA) in rat plasma. This method was further applied to assess the pharmacokinetics of BA in rats receiving a single dose of BA. Liquid chromatography tandem mass spectrometry in multiple reaction monitoring mode was used in the method, and costundide was used as internal standard. A simple protein precipitation based on methanol was employed. The combination of a simple sample cleanup and short chromatographic running time (2.4?min) increased the throughput of the method substantially. The method was validated over the range of 1-1000?ng/mL with a correlation coefficient?>?0.99. The lower limit of quantification was 1?ng/mL for BA in plasma. Intra- and inter-day accuracies for BA were 93-112% and 103-104%, respectively, and the inter-day precision was less than 15%. After a single oral dose of 20?mg/kg of BA, the mean peak plasma concentration (C(max) ) of BA was 234.7?±?161?ng/mL at 0.25?h. The area under the plasma concentration-time curve (AUC(0-24 h) ) was 535.8?±?223.7?h·ng/mL, and the elimination half-life (T(1/2) ) was 5.0?±?0.36?h. In case of intravenous administration of BA at a dosage of 2?mg/kg, the area under the plasma concentration-time curve (AUC(0-24 h) ) was 342?±?98 h?ng/mL, and the elimination half-life (T(1/2) ) was 5.8?±?0.7?h. Based on the results, the oral bioavailability of BA in rats at 20?mg/kg is 15.7%. Copyright ? 2012 John Wiley & Sons, Ltd.     

Uranium passivation by C implantation: A photoemission and secondary ion mass spectrometry study

Implantation of 33 keV C⁺ ions into polycrystalline U²³⁸ with a dose of 4.3 × 10¹⁷ cm⁻² produces a physically and chemically modified surface layer that prevents further air oxidation and corrosion. X-ray photoelectron spectroscopy and secondary ion mass spectrometry were used to investigate the surface chemistry and electronic structure of this C⁺ ion implanted polycrystalline uranium and a non-implanted region of the sample, both regions exposed to air for more than a year. In addition, scanning electron microscopy was used to examine and compare the surface morphology of the two regions. The U 4f, O 1s and C 1s core-level and valence band spectra clearly indicate carbide formation in the modified surface layer. The time-of-flight secondary ion mass spectrometry depth profiling results reveal an oxy-carbide surface layer over an approximately 200 nm thick UC layer with little or no residual oxidation at the carbide layer/U metal transitional interface.     

A reliable method by ultra-performance liquid chromatography coupled with tandem mass spectrometry to quantify and confirm simultaneously the presence of solvent metabolites in workers' urine

Ultra-performance liquid chromatography coupled with tandem mass spectrometry was used for the biological monitoring of workers occupationally exposed to solvents. The method was developed using a triple quadrupole to investigate the relevant urinary metabolites of styrene, namely mandelic acid and phenylglyoxylic acid. The method provides quantitative and qualitative data to give additional assurance about the nature of the contaminant analyzed in workers' urine. A full scan and a product ion scan were acquired within the chromatographic peak acquired in MRM. For the two metabolites, the repeatability was 96%, the precision ≥97%, and the accuracy ≥93?±?3%. The quantitative performances were not influenced by the inclusion of simultaneous full scan acquisition as compared to a usual quantitative approach. Footprints of each substance of interest were obtained at each injection, and full scan data can be interrogated for the presence of interferences and other contaminants. The method developed has been submitted to random real samples from both non-occupationally and occupationally exposed workers. The urines of non-occupationally exposed workers were all free of mandelic acid, phenylglyoxylic acid and putative interferences showing the high selectivity of the method. However, the urines of occupationally exposed workers were robustly quantified. The levels of mandelic acid and phenylglyoxylic acid ranged between 0.2 and 9?mM, and the footprints of each metabolite and structural information were acquired in parallel with the quantitative results, thus providing unquestionable data about the nature of the contaminant and the levels reported. The combination of qualitative information acquired simultaneously with quantitative results provides the structural information needed in case of questions, without any harmful effect on the robustness and throughput of the quantitative analysis.     

Extent of coverage of surfaces treated with hydrophobizing microemulsions: A mass spectrometry and contact angle study

Glass surfaces were treated with various hydrophobizing microemulsions (HME) containing mineral seal oil or polyisobutylene as hydrophobes emulsified by dimethyl dicoco ammonium chloride (i.e. mimicking commercial car wash practices) and characterized by mass spectrometry (MS) and contact angle measurements. The cationic emulsifier mediates the anchoring of hydrophobes to the polar glass surface. It is demonstrated that by the use of even very low (0.3-3.0 w%) HME concentrations the surfaces become hydrophobic and repel water even after numerous (∼20) rinsing cycles. According to MS evidence, however, the surfaces are not fully saturated with hydrophobes and the unprotected areas remain vulnerable to environmental damage.     

Identification and assay of carbohydrates in olive drupes by cesium attachment electrospray tandem mass spectrometry (ESI-MS/MS)

Identification and assay of sugars in olive drupes during their ripening phase is evaluated by tandem mass spectrometry. Recent achievements have shown that the quality of an extra virgin olive oil can be directly correlated to the ripening degree of the drupes that is likely linked to their saccharides content. An innovation in this peculiar food chain is now proposed that considers a high throughput assessment of the carbohydrate content by a recently introduced protocol based on the gas-phase chemistry of sugar-cesium adducts by ESI-MS/MS. Copyright ? 2012 John Wiley & Sons, Ltd.     

Detection and quantitation of a pheomelanin component in melanin pigments using pyrolysis-gas chromatography/tandem mass spectrometry system with multiple reaction monitoring mode

Here, we describe the reliable method for the detection and quantitation of a pheomelanin component in melanin pigments. Synthetic melanins with various contents of pheomelanin-type structural units were thermally degraded, and the multiple reaction monitoring mode was applied to detect the pheomelanin markers in the pyrolysates by GC/MS/MS. The method allowed the specific detection and quantitation of a pheomelanin component in melanin with the incorporation of pheomelanin-type units as low as 0.05%. Considering highly universal character of the pheomelanin markers, the method could be applied for structural studies of natural melanin pigments being mixtures of eumelanin and pheomelanin.     

Competition between counterions and active protein sites to bind bisquaternary ammonium groups. A combined mass spectrometry and quantum chemistry model study

A model study of the interaction between biologically active bisquaternary ammonium salts and their molecular targets in living systems is urgently needed to elucidate the molecular mechanisms involved in the interactions between these compounds. To address this need a combined experimental-computational study of the interaction of two tetramethylammonium cations (modeling two quaternary groups) with the chlorine anion and with the deprotonated 2,5-dihydroxybenzoic acid (modeling a carboxylic group and an aromatic ring of side radicals of proteins) has been performed. Fast atom bombardment mass spectrometry method and DFT/B3LYP/6-31++G^** and MP2/6-31++G^** calculations have been employed in the study. Stable noncovalent complexes with different ratios of the tetramethylammonium cations and chlorine anions or deprotonated 2,5-dihydroxybenzoic acid anions were registered in the mass spectra of tetramethylammonium chloride and 2,5-dihydroxybenzoic acid mixture. This finding shows that the organic and inorganic anions compete to bind tetramethylammonium in the studied system. The theoretically determined stabilities of the noncovalent complexes were compared with the relative stabilities evaluated from the mass spectrometric measurements. The results of the study allow us to elucidate the competing interactions that exist between quaternary groups with inorganic counterions or with active groups of molecular protein targets.     

Screening of glycoside isomers in P. scrophulariiflora using ionic liquid-based ultrasonic-assisted extraction and ultra-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry

A powerful ionic liquid-based ultrasonic-assisted extraction (ILUAE) method combined with ultra-performance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC/ESI-QTOFMS(n) ) was employed in the rapid simultaneous screening of iridoid glycosides, phenylethanoid glycosides, and cucurbitacin glycosides from P. scrophulariiflora. The ILUAE procedure was optimized over several ultrasonic parameters, including the ultrasonic power, concentration of the ionic liquid, and solid-liquid ratio. A comparison with conventional heat-reflux extraction and regular UAE demonstrated that the optimized approach yielded a high extraction efficiency (Picroside I, 2.84%; Picroside II, 3.57%; 6-O-E-feruloyl catalpol, 2.20%) within a short extraction time of 30?min. Negative ion mode ESI-QTOFMS(2) analysis of the fragmentation reactions of the [M-H](-) ions was conducted to characterize the diagnostic ions related to the glycosyl moieties, aglycone units, and the type and substituted position of the ester groups. Interestingly, the positional isomers of the iridoid glycosides could be easily discriminated based on the characteristic ions. A total of 15 glycosides, including three groups of iridoid glycoside isomers and two groups of phenylethanoid glycoside isomers, were conveniently identified within 13.5?min. Moreover, 6'-O-vanilloyl catalpol was identified in P. scrophulariiflora for the first time. The method developed here was further validated by measuring the recovery, correlation coefficient (R(2) ), and reproducibility (RSD, n?=?5) of three iridoid glycosides: 89.60%-109.02%, 0.9991-0.9998, and 0.93%-1.44%, respectively. This study demonstrated the capabilities of ILUAE combined with UPLC/ESI-QTOFMS(n) for the rapid screening of glycosides in P. scrophulariiflora. This method offers an approach to similar studies on other natural plants.     

Simultaneous analysis of several synthetic cannabinoids, THC, CBD and CBN, in hair by ultra-high performance liquid chromatography tandem mass spectrometry. Method validation and application to real samples

A simple procedure for the quantitative detection of JWH-018, JWH-073, JWH 200, JWH-250, HU-210, Δ(9)-tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN) in hair has been developed and fully validated. After digestion with NaOH and liquid-liquid extraction, the separation was performed with an ultra-high performance liquid chromatography system coupled to a triple quadrupole mass spectrometer operating in the selected reaction monitoring mode. The absence of matrix interferents, together with excellent repeatability of both retention times and relative abundances of diagnostic transitions, allowed the correct identification of all analytes tested. The method was linear in two different intervals at low and high concentration, with correlation coefficient values between 0.9933 and 0.9991. Quantitation limits ranged from 0.07 pg/mg for JWH-200 up to 18 pg/mg for CBD The present method for the determination of several cannabinoids in hair proved to be simple, fast, specific and sensitive. The method was successfully applied to the analysis of 179 real samples collected from proven consumers of Cannabis, among which 14 were found positive to at least one synthetic cannabinoid.     

A57Fe Mössbauer study of iron assimilation inN. crassa mediated by siderophores

The siderophore coprogen is tansported in N. crassa as an entity. Neither ligand exchange nor reduction is a rate limiting step for intracellular accumulation. Metabolized iron was found predominantly to exist as fast relaxing Fe(II) high-spin (σ=1.32 mm/s, ΔE_Q=2.95 mm/s) and Fe(III) high-spin species (δ=0.35−0.42 mm/s ΔE_Q=0.5−0.58 mm/s). Within 27 hours, no measurable amounts of iron are transferred to ferritin like storage forms. Rather, coprogen itself serves as an intermediate iron storage compound.