The misuse of anabolic androgenic steroids is of particular concern in sports and society. Thus, it is of great importance todiscriminate endogenous steroids such as testosterone or testosterone prohormones from their chemically identical syntheticcopies. In this study, gas chromatography-combustion/isotope ratio mass spectrometric (GC−C/IRMS) method has been developedand validated for discriminating the origin of anabolic androgenic steroids. The method involves the solid-phase extraction,enzymatic hydrolysis with β-glucuronidase, HPLC-fractionation for the cleanup and analysis by GC−C/IRMS. The difference(Δ13C) of urinary δ13C values between synthetic analogues and endogenous reference compounds (ERC) by GC−C/IRMS wasused to elucidate the origin of steroids, and intra- and inter-day precision, specificity and isotope fractionation were evaluated. The present GC−C/IRMS method combined with HPLC cleanup was accurate and reproducible enough to be successfullyapplied to the test of urine sample from suspected anabolic steroid abusers.
Saccharin is a commonly used artificial sweetener in foodstuffs. However, for its carcinogenic dispute, it has beenregulated by government bodies. In this study, isotope dilution mass spectrometry (ID-MS) was introduced for the accuratequantification of saccharin. To employ ID-LC/MS, we obtained its isotope analogue, 13C1−sodium saccharin, by customized synthesis. Samples were spiked with 13C1-sodium saccharin and analyzed with LC/MS in negative mode. Chromatographic conditionswere optimized for the adequate chromatographic retention and separation of saccharin with a C18 column. MS was operatedwith electrospray ionization by the selected ion monitoring (SIM) mode of [M − H]− for saccharin (m/z 182) and [M − Na]− forits isotope analogue (m/z 183). To validate the ID-LC/MS method for accurate measurement, we prepared a batch of a candidatematerial by sortifying quasi−tea−drinks with saccharin and analyzed samples gravimetrically fortified in various levels of concentration. The repeatability and reproducibility of this method was tested by analyzing the reference material. Result show thatID-LC/MS is a reliable method for the quantitative analysis of saccharin.
Molecular compositions of two types of heavy oil were studied using positive atmospheric pressure photoionization(APPI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Vacuum gas oil (VGO) was generated fromvacuum distillation of atmospheric residual oil (AR), and slurry oil (SLO) was generated from catalytic cracking of AR. Theseheavy oils have similar boiling point ranges in the range of 210-650oC, but they showed different mass ranges and double-bondequivalent (DBE) distributions. Using DBE and carbon number distributions, aromatic ring distributions, and the extent of alkylside chains were estimated. In addition to the main aromatic hydrocarbon compounds, those containing sulfur, nitrogen, andoxygen heteroatoms were identified using simple sample preparation and ultra-high mass resolution FT-ICR MS analysis. VGOis primarily composed of mono- and di-aromatic hydrocarbons as well as sulfur-containing hydrocarbons, whereas SLO containedmainly polyaromatic hydrocarbons and sulfur-containing hydrocarbons. Both heavy oils contain polyaromatic nitrogen components. SLO inludes shorter aromatic alkyl side chains than VGO. This study demonstrates that APPI FT-ICR MS is useful formolecular composition characterization of petroleum heavy oils obtained from different refining processes.
The authors describe a method for monitoring dicyclanil levels in lamb and chicken muscle tissues. The devised procedureinvolves dicyclanyl extraction by SPE and its detection HPLC-UV/Vis and LC/MS/MS. The method was found to haveLOD and LOQ values of 0.02 mg kg−1 and 0.05~0.06 mg kg−1, respectively. The intraday precision and an accuracy of spikedsamples were found to have 2.3~10.4 RSD% and 80.9~105.7%, respectively.
Competitive binding of C60 and C70 to meso-substituted porphyrins was studied by mass spectrometry (MS). Electrosprayionization MS was employed to acquire the mass spectra of 1 : 1 porphyrin–fullerene complexes formed in a mixture of mesosubstitutedporphyrin and fullerite to determine the ratio of complexes between C60 and C70. Matrix-free laser desorption ionizationMS was used to obtain the mass spectra of fullerite to measure the mole fraction of C60 and C70. The binding constant ratio (K70/K60)was determined from the mass spectral data. The difference in standard Gibbs free energy change, Δ(ΔGo)70–60, for the competitivebinding of C60 and C70 was calculated from K70/K60. Of the five porphyrins, tetraphenyl, tetra(4-pyridyl), tetra(4-carboxyphenyl),tetra(3,5-di-tert-butylphenyl), and tetra(pentafluorophenyl) porphyrins, the first three non-bulky porphyrins yield negative valuesof Δ(ΔGo)70−60, whereas the other two bulky porphyrins result in positive values of Δ(ΔGo)70−60. This result indicates that C70binding to porphyrin is thermodynamically favored over C60 binding in non-bulky porphyrins, but disfavored in bulky ones. Italso suggests that the binding mode of C70 is different between non-bulky and bulky porphyrins, which is in line with previousexperimental findings of the “side-on” binding to non-bulky porphyrins and the C60-like “end-on” binding to bulky porphyrins.
C8-functionalized magnetic nanoparticles were synthesized by coating magnetic Fe3O4 nanoparticles with silica–amine groups using 3-aminopropyltriethoxysilane and by subsequently modifying the amine groups with chloro(dimethyl)octylsilaneto produce octyl groups on the surface of the MNPs. The C8-functionalized MNPs were used to enrich peptides from trypticprotein digests of myoglobin and α-casein. The enriched peptides were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI−ΤΟF−MS). MALDI-MS was also used to investigate desalting of the C8-functionalized MNPs. Sample solutions were prepared in 1.0 M NaCl, and the successful removal of salt was observed. Enrichmentwith C8-functionalized MNPs was very effective for separating and concentrating tryptic peptides.
As background significantly affects measurement accuracy and a detection limit in determination of the traceamounts of uranium, it is necessary to determine the impurities in the Lexan detector film for single particle measurements bythermal ionization mass spectrometry coupled with fission track technique (FT-TIMS). We have prepared various micro sizes ofthe blank Lexan detector film using a micromanipulation technique for uranium measurements by TIMS. Few tens of fg of uraniumbackground with no remarkable dependency on the film sizes were observed in the blank Lexan films with the sizes from50 × 50 μm2 to 300 × 300 μm2. Based on the determination of the uranium background in the Lexan film, any background correctionis necessary in the isotopic analysis of a uranium single particle with micron sizes when the particle bearing Lexan film is dissectedwith less than 300 × 300 μm2 size. The isotopic analysis of a uranium particle in U030 standard material using TIMS was carriedout to verify the applicability of the Lexan film to the single particle analysis with high accuracy and precision.