Superheated water extraction, steam distillation and Soxhlet extraction of essential oils of Origanum onites

Superheated water extraction (SWE) at various temperatures (100, 125, 150 and 175°C), steam distillation, and Soxhlet extraction were compared in the extraction of essential oils from two samples of the plant Origanum onites, one cultivated, the other wild. C18 solid-phase extraction was used to elute the essential oils from the SWE aqueous extract. The compositions of the extracted essential oils obtained from all three methods were then characterized by comprehensive GC×GC/time-of-flight mass spectrometry (TOF/MS). The highest essential oil yields were obtained by using SWE at 150°C with a flow rate of 2 mL min^–1 and a pressure of 60 bar for 30 min: these were 3.76 and 4.11% for wild and cultivated O. onites samples, respectively, expressed as a percentage of 100 g of dry (leaf) matter. The yields obtained using SWE at 150°C were slightly higher than those from conventional methods. Steam distillation was performed for 3 h, and Soxhlet extraction was completed in 12 h. The major compounds found were borneol, terpinen-4-ol and carvacrol.     

High yield synthesis and characterization of isotopically enriched monoethylmercury chloride (C2H5201HgCl)

An important but commercially unavailable compound isotopically enriched monoethylmercury chloride (C₂H₅²⁰¹HgCl), has been synthesized from commercially available ²⁰¹HgO (98.11% enriched isotopic purity) and tetraethyltin. The required synthesis time is 1 h at 90 °C, and the product is the single product of monoethylmercury chloride, yielding more than 95% as ²⁰¹Hg in C₂H₅²⁰¹Hg⁺ (98.19 ± 0.22% enriched isotopic purity). The synthesized product was analyzed with high‐performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC‐ICP‐MS) to determine its concentration, isotopic composition and purity. The synthetic isotopically enriched monoethylmercury synthesized can be used in speciated isotope dilution mass spectrometry (SIDMS) and isotope dilution mass spectrometry (IDMS) analyses as a standard. Copyright © 2005 John Wiley & Sons, Ltd.     

Metabolomic comparison between wild Ophiocordyceps sinensis and artificial cultured Cordyceps militaris

A systematic study on the metabolome differences between wild Ophiocordyceps sinensis and artificial cultured Cordyceps militaris was conducted using liquid chromatography−mass spectrometry. Principal component analysis and orthogonal projection on latent structure‐discriminant analysis results showed that C. militaris grown on solid rice medium (R‐CM) and C. militaris grown on tussah pupa (T‐CM) evidently separated and individually separated from wild O. sinensis, indicating metabolome difference among wild O. sinensis, R‐CM and T‐CM. The metabolome differences between R‐CM and T‐CM indicated that C. militaris could accommodate to culture medium by differential metabolic regulation. Hierarchical clustering analysis was further performed to cluster the differential metabolites and samples based on their metabolic similarity. The higher content of amino acids (pyroglutamic acid, glutamic acid, histidine, phenylalanine and arginine), unsaturated fatty acid (linolenic acid and linoleic acid), peptides, mannitol, adenosine and succinoadenosine in O. sinensis make it as an excellent choice as a traditional Chinese medicine for invigoration or nutritional supplementation. Similar compositions with O. sinensis and easy cultivation make artificially cultured C. militaris a possible alternative to O. sinensis.     

Rapid fingerprinting of red wines by MALDI mass spectrometry

Here we report a simple and fast method for wine fingerprinting based on direct matrix-assisted laser desorption/ionization (MALDI) mass spectrometry analysis of different red wine samples, useful for batch-to-batch analysis and for the detection of key compounds even in trace amounts which may vary from vintage to vintage, and from one treatment to another one. A series of 20 samples from different wines were subjected to MALDI mass spectrometry. We found that 2,5-dihydroxybenzoic acid is far superior with respect to all the matrices tested To the best of our knowledge this is the first application of an effective wine profiling not limited to detection of anthocyanins. More than 80 molecular species were detected. Moreover, qualitative and quantitative differences were observed, owing to the nature and relative abundance of different chemical compounds among the wines.     

Separation and Quantification of Water-Soluble Cellular Metabolites in Clostridium thermocellum using Liquid Chromatography-Isotope Dilution Tandem Mass Spectrometry

A new protocol for metabolomic studies was developed by combining liquid chromatography-tandem mass spectrometry and isotope dilution mass spectrometry with universal ¹³C labeled internal standards from Escherichia Coli. The multiple reaction monitoring mode of mass spectrometry was used for quantification. Forty-five water-soluble intracellular metabolites, including 20 amino acids, 16 organic acids (primarily from the tricarboxylic acid cycle), and 9 cofactors, were measured and 34 of them were successfully quantified using the ¹³C-labeled internal standards. The limit of detection, limit of quantification, precision, and linearity of the methods were evaluated. The methods were applied to the quantitative analysis of intracellular metabolites extracted from wild-type and ethanol-adapted strains of Clostridium thermocellum cultivated with and without ethanol stress, and all 34 metabolites including all 9 cofactors were successfully quantified. Further multivariate data analyses of the metabolic differences between wild-type and ethanol-adapted strains were performed on the quantitative data, which can help elucidate the metabolic mechanism behind ethanol adaptation in C. thermocellum.

Supplemental materials are available for this article. Go to the publisher's online edition of Analytical Letters to view the supplemental file.     

Geographical Discrimination of Honeysuckle (Lonicera japonica Thunb.) from China by Characterization of the Stable Isotope Ratio and Multielemental Analysis

A total of 117 honeysuckle (Lonicera japonica Thunb.) samples from four major regions of production in China, including Fengqiu in Henan, Pingyi in Shandong, Julu in Hebei, and Xiushan in Chongqing, were analyzed to determine their geographical origin. δ¹³C, δ¹⁵N, and δ¹⁸O values were determined by isotope ratio mass spectrometry (IRMS), and the contents of 18 elements (Fe, Mn, Cu, Zn, K, Ca, Mg, Pb, Cd, Cr, As, Hg, Se, Sr, Ni, Co, B, and Mo) were measured by inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). Multivariate statistical analysis by analysis of variance (ANOVA), principal component analysis (PCA), and linear discriminant analysis (LDA) were performed. The results showed that there were very significant differences in the stable isotope ratios and elemental concentrations in honeysuckle based on geographical origin, with plants from each region having a unique fingerprint. Discriminant functions were established to distinguish the origin of honeysuckle using suitable indicators including Cd, Cr, As, Hg, Se, Co, Ni, Sr, Fe, δ¹³C, δ¹⁵N, and δ¹⁸O. Cross-validated cases of 95.7% were correctly classified.     

Increasing the accuracy of mass isotopomer analysis through calibration curves constructed using biologically synthesized compounds

Mass isotopomer analysis is an important technique to measure the production and flow of metabolites in living cells, tissues, and organisms. This technique depends on accurate quantifications of different mass isotopomers using mass spectrometry. Constructing calibration curves using standard samples is the most universal approach to convert raw mass spectrometry measurements into quantitative distributions of mass isotopomers. Calibration curve approach has been, however, of very limited use in comprehensive analyses of biological systems, mainly suffering from the lack of extensive range of standard samples with accurately known isotopic enrichment. Here, we present a biological method capable of synthesizing specifically labeled amino acids. These amino acids have well‐determined and estimable mass isotopomer distributions and thus can serve as standard samples. In this method, the bacterium strain Methylobacterium salsuginis sp. nov. was cultivated with partially ¹³C‐labeled methanol as the only carbon source to produce ¹³C‐enriched compounds. We show that the mass isotopomer distributions of the various biosynthesized amino acids are well determined and can be reasonably estimated based on proposed binomial approximation if the labeling state of the biomass reached an isotopic steady state. The interference of intramolecular inhomogeneity of ¹³C isotope abundances caused by biological isotope fractionation was eliminated by estimating average ¹³C isotope abundance. Further, the predictions are tested experimentally by mass spectrometry (MS) spectra of the labeled glycine, alanine, and aspartic acid. Most of the error in mass spectrometry measurements was less than 0.74 mol% in the test case, significantly reduced as compared with uncalibrated results, and this error is expected to be less than 0.4 mol% in real experiment as revealed by theoretical analysis. Copyright © 2009 John Wiley & Sons, Ltd.     

Differentiation of isomeric dinitrotoluenes and aminodinitrotoluenes using electrospray high resolution mass spectrometry

Explosive detection and identification play an important role in the environmental and forensic sciences. However, accurate identification of isomeric compounds remains a challenging task for current analytical methods. The combination of electrospray multistage mass spectrometry (ESI‐MSⁿ) and high resolution mass spectrometry (HRMS) is a powerful tool for the structure characterization of isomeric compounds. We show herein that resonant ion activation performed in a linear quadrupole ion trap allows the differentiation of dinitrotoluene isomers as well as aminodinitrotoluene isomers. The explosive‐related compounds: 2,4‐dinitrotoluene (2,4‐DNT), 2,6‐dinitrotoluene (2,6‐DNT), 2‐amino‐4,6‐dinitrotoluene (2A‐4,6‐DNT) and 4‐amino‐2,6‐dinitrotoluene (4A‐2,6‐DNT) were analyzed by ESI‐MS in the negative ion mode; they produced mainly deprotonated molecules [M ? H]^?. Subsequent low resolution MSⁿ experiments provided support for fragment ion assignments and determination of consecutive dissociation pathways. Resonant activation of deprotonated dinitrotoluene isomers gave different fragment ions according to the position of the nitro and amino groups on the toluene backbone. Fragment ion identification was bolstered by accurate mass measurements performed using Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR/MS). Notably, unexpected results were found from accurate mass measurements performed at high resolution for 2,6‐DNT where a 30‐Da loss was observed that corresponds to CH₂O departure instead of the expected isobaric NO^? loss. Moreover, 2,4‐DNT showed a diagnostic fragment ion at m/z 116, allowing the unambiguous distinction between 2,4‐ and 2,6‐DNT isomers. Here, CH₂O loss is hindered by the presence of an amino group in both 2A‐4,6‐DNT and 4A‐2,6‐DNT isomers, but nevertheless, these isomers showed significant differences in their fragmentation sequences, thus allowing their differentiation. DFT calculations were also performed to support experimental observations. Copyright © 2014 John Wiley & Sons, Ltd.     

Stable Isotope Fingerprinting for Pharmaceutical Authentication

ABSTRACT

The ¹³C stable isotopic composition of 38 pharmaceutical products was investigated for six medicine analgesics classes ibuprofen, diclofenac, paracetamol, metamizole, ketoprofene, and combinations containing paracetamol to evaluate differences between manufacturers and production batches. Complementary measurements were performed by inductively coupled plasma-mass spectrometry. Linear discriminant analysis was applied on experimental obtained data set for differentiation of three investigated drug types. The carbon isotopic compositions were between ?32.9 and ?22.6‰. The lowest values of ¹³C (mean of ?31.3‰) were obtained for metamizole from all six categories of investigated analgesics. The highest δ¹³C values were obtained for diclofenac (mean of ?25.9‰). The most accurate elemental predictors were V, Al, Sb, As, Pb, and Mn.     

Critical comparison of radiometric and mass spectrometric methods for the determination of radionuclides in environmental, biological and nuclear waste samples

The radiometric methods, alpha (α)-, beta (β)-, gamma (γ)-spectrometry, and mass spectrometric methods, inductively coupled plasma mass spectrometry, accelerator mass spectrometry, thermal ionization mass spectrometry, resonance ionization mass spectrometry, secondary ion mass spectrometry, and glow discharge mass spectrometry are reviewed for the determination of radionuclides. These methods are critically compared for the determination of long-lived radionuclides important for radiation protection, decommissioning of nuclear facilities, repository of nuclear waste, tracer application in the environmental and biological researches, these radionuclides include ³H, ¹⁴C, ³⁶Cl, ⁴¹Ca, ^59,63Ni, ^89,90Sr, ⁹⁹Tc, ¹²⁹I, ^135,137Cs, ²¹⁰Pb, ^226,228Ra, ²³⁷Np, ²⁴¹Am, and isotopes of thorium, uranium and plutonium. The application of on-line methods (flow injection/sequential injection) for separation of radionuclides and automated determination of radionuclides is also discussed.     

Identification of C-21 steroidal glycosides from the roots of Cynanchum chekiangense by high-performance liquid chromatography/tandem mass spectrometry

High-performance liquid chromatography coupled with electrospray tandem mass spectrometry (HPLC/ESI-MS/MS) was used to identify C-21 steroidal glycosides with immunological activities in roots of Cynanchum chekiangense. In the MS/MS spectra, fragmentation reactions of the [M + Na]⁺ were recorded to provide structural information about the glycosyl and aglycone moieties. To further confirm the fragments structures, off-line Fourier transform ion cyclotron resonance tandem mass spectrometry (FT-ICR-MS/MS) was also performed. In the study, four known steroidal glycosides cynascyroside C, chekiangensosides A and B, glaucoside H, and four novel steroidal glycosides chekiangensosides C, D, E and chekiangensoside A isomer were identified based on mass spectral data, NMR spectral data and standards. This is the first report on identifying steroidal glycosides in roots of C. chekiangense by HPLC/ESI-MS/MS directly, which could save time and material consuming efforts in traditional phytochemistry analysis.     

Mass spectrometric analysis of the 13C/12C abundance ratios in vine plants and wines depending on regional climate factors (Krasnodar krai and Rostov oblast, Russia)

Distribution of ¹³C/¹²C isotopes in vegetative (roots, grapevine, leaves) and generative (berries) parts of vine plants of the West European genetically different varieties Cabernet Sauvignon and Aligoté growing on soils of Krasnodar krai and Rostov oblast, as well as autochthonous varieties Sibirkovy and Krasnostop Zolotovsky growing in Rostov oblast, has been studied using isotopic mass spectrometry methods. It has been shown that the variations of δ¹³C values in plant tissues and berries are related to the climatic conditions of plant growth: moisture (a sum of annual precipitation) and temperature (a sum of annual effective temperatures). The carbon isotope ratios of vegetative and generative parts of vine plants have been found to be noticeably affected by vine varieties. The different ¹³C contents in ethanol produced from wine of the Aligoté and Cabernet Sauvignon varieties grown in two Russian vineyard regions are due to vine growth conditions, variety attribution and wine production techniques. An analytically significant parameter determined as exemplified by the Aligoté and Cabernet Sauvignon varieties in fermentation of vine harvested in different seasons and in both vineyard regions was an increased ¹³C content in ethanol with respect to dry (non-volatile) residue in wine after distillation of ethanol. This characteristic has been determined by a systematic difference of about 1–2‰ between the δ¹³C value of ethanol and the dry residue. A relative constancy in the carbon isotope composition of ethanol and of the dry residue in the final product is the basis for determining the authenticity of grape wines by means of isotopic mass spectrometry irrespective of natural factors.     

Isotopic Determination of Silicon by Mass Spectrometry in Plants and Soils Labeled with 30Si

Abstract

A method for isotopic determination of silicon by mass spectrometry in plants and soils labeled with ³⁰Si is reported. The development of this method is for use with studies involving the physiological process of absorption, transport, and redistribution of Si in the soil-plant system by use of the stable isotope ³⁰Si as a tracer. The procedure leads to SiF₄ formation, and the isotopic determination of Si was based on the measurements of the ²⁸SiF₃ ⁺, ²⁹SiF₃ ⁺, and ³⁰SiF₃ ⁺ signals. Relative standard deviation of ³⁰Si abundance measurements (n = 6) were lower than 0.1%, and the detection limit was 0.5 mg Si (dry mass).     

H NMR and C-IRMS analyses of acetic acid from vinegar, O-IRMS analysis of water in vinegar: International collaborative study report

An international collaborative study of isotopic methods applied to control the authenticity of vinegar was organized in order to support the recognition of these procedures as official methods. The determination of the ²H/¹H ratio of the methyl site of acetic acid by SNIF-NMR (site-specific natural isotopic fractionation-nuclear magnetic resonance) and the determination of the ¹³C/¹²C ratio, by IRMS (isotope ratio mass spectrometry) provide complementary information to characterize the botanical origin of acetic acid and to detect adulterations of vinegar using synthetic acetic acid. Both methods use the same initial steps to recover pure acetic acid from vinegar. In the case of wine vinegar, the determination of the ¹⁸O/¹⁶O ratio of water by IRMS allows to differentiate wine vinegar from vinegars made from dried grapes. The same set of vinegar samples was used to validate these three determinations.The precision parameters of the method for measuring δ¹³C (carbon isotopic deviation) were found to be similar to the values previously obtained for similar methods applied to wine ethanol or sugars extracted from fruit juices: the average repeatability (r) was 0.45 ‰, and the average reproducibility (R) was 0.91‰. As expected from previous in-house study of the uncertainties, the precision parameters of the method for measuring the ²H/¹H ratio of the methyl site were found to be slightly higher than the values previously obtained for similar methods applied to wine ethanol or fermentation ethanol in fruit juices: the average repeatability was 1.34 ppm, and the average reproducibility was 1.62 ppm. This precision is still significantly smaller than the differences between various acetic acid sources (δ¹³C and δ¹⁸O) and allows a satisfactory discrimination of vinegar types. The precision parameters of the method for measuring δ¹⁸O were found to be similar to the values previously obtained for other methods applied to wine and fruit juices: the average repeatability was 0.15‰, and the average reproducibility was 0.59‰. The above values are proposed as repeatability and reproducibility limits in the current state of the art.On the basis of this satisfactory inter-laboratory precision and on the accuracy demonstrated by a spiking experiment, the authors recommend the adoption of the three isotopic determinations included in this study as official methods for controlling the authenticity of vinegar.     

Gas‐phase copper and silver complexes with phosphorothioate and phosphorodithioate pesticides investigated using electrospray ionization mass spectrometry

Efforts to improve agricultural productivity have led to a growing dependency on organophosphorus pesticides. Phosphorothioate and phosphorodithioate pesticides are organophosphorus pesticide subclasses with widespread application for the control of insects feeding on vegetables and fruits. However, even low doses of these pesticides can cause neurological problems in humans; thus, their determination and monitoring in agricultural foodstuffs is important for human health. Phosphorothioate and phosphorodithioate pesticides may be poorly ionized during electrospray, adversely affecting limits of detection. These pesticides can form complexes with Cu²⁺ and Ag⁺, however, potentially improving ionization. In the present work, we used electrospray ionization/mass spectrometry (ESI/MS) to study fenitrothion, parathion, diazinon, and malathion coordination complexes with silver and copper ions. Stable 1 : 1 and 1 : 2 metal/pesticide complexes were detected. Mass spectra acquired from pesticide solutions containing Ag⁺ or Cu²⁺ showed a significant increase in signal‐to‐background ratio over those acquired from solutions containing only the pesticides, with Ag⁺ improving detection more effectively than Cu²⁺. Addition of Ag⁺ to a pesticide solution improved the limit of detection by ten times. The relative affinity of each pesticide for Ag⁺ was related to complex stability, following the order diazinon > malathion > fenitrothion > parathion. The formation of Ag⁺–pesticide complexes can significantly improve the detection of phosphorothioate and phosphorodithioate pesticides using ESI/MS. The technique could potentially be used in reactive desorption electrospray ionization/mass spectrometry to detect phosphorothioate and phosphorodithioate pesticides on fruit and vegetable skins. Copyright © 2015 John Wiley & Sons, Ltd.     

Enhancement of the effective resolution of mass spectra of high-mass biomolecules by maximum entropy-based deconvolution to eliminate the isotopic natural abundance distribution

Although high-resolution Fourier transform ion cyclotron resonance mass spectrometry can resolve individual isotopic masses for biomolecules of more than 100 ku, its effective mass accuracy is limited by the distribution of naturally occurring rare isotopes (¹³C, ¹⁵N, ¹⁸O, ³⁴S, etc.). In this article, we compare least-squares and maximum entropy methods for deconvolution of the isotopic natural abundance distribution to narrow the mass spectral isotopic abundance envelope for greatly enhanced effective mass resolution. We apply both methods to yield deconvolved high-resolution deuterium distributions for peptides and proteins subjected to H/D exchange prior to electrospray Fourier transform ion cyclotron resonance mass analysis. In addition, we show that even unresolved isotopic envelopes from a quadrupole mass spectrometer can be narrowed for considerably improved resolution there as well.     

Differentiation of 18O‐ and 16O‐rich layers in anodic alumina films by glow discharge time‐of‐flight mass spectroscopy

The performance of glow discharge time‐of‐flight mass spectrometry in isotopic differentiation is revealed using the distribution of oxygen isotopes ¹⁶O and ¹⁸O in barrier‐type anodic alumina films as a focus. Anodic alumina films comprising ¹⁸O‐rich layers of controlled thickness were formed by the appropriate combination of anodising of superpure aluminium in electrolytes enriched with ¹⁸O isotopes and of natural abundance of ¹⁸O isotopes. Analysis of the elemental depth profiles of selected ionic species, i.e. ¹⁶O¹⁸O, allowed determination of the locations of the ¹⁸O‐rich layers and the ¹⁸O/¹⁶O interface. Copyright © 2010 John Wiley & Sons, Ltd.     

带羟乙基侧臂三脚架多胺Cu(Ⅱ)配合物切割肌红蛋白所得片断的质谱指认

采用电喷雾质谱和串联质谱以及聚丙烯酰胺凝胶电泳技术研究了[CuL(H₂O)](BF₄)₂(L为2-[二(2-氨乙酸)氨基]乙醇)与马心肌红蛋白的键合作用和水解切割。聚丙烯酰胺凝胶电泳研究显示在中性及60 ℃条件下，切割效率与[CuL(H₂O)]²⁺的浓度和温育时间密切相关。电喷雾质谱和串联质谱分析显示，[CuL(H₂O)]²⁺通过与肌红蛋白的氨基酸His36，His93，His116和Arg139侧链的结合，并在羟乙基侧臂的促进下，选择性地水解了肽键Phe33-Thr34，Gln91-Ser92，Ala94-Thr95，His116-Ser117和Asn140-Asp141。     

Application of the total evaporation technique to chromium isotope ratio measurement by thermal ionization mass spectrometry

The total evaporation technique of thermal ionization mass spectrometry was applied to the isotopic analysis of chromium. High measurement reproducibility of the chromium isotope ratios was verified (2 S.E. < 0.05% (⁵³Cr/⁵²Cr)), while a clear mass fractionation effect was observed by using conventional measurement technique. The chromium isotope ratios analyzed by the total evaporation method were not affected by the sample amount on the rhenium filament (50-500 ng Cr). The isotopic analysis under the coexistence of zinc was also performed, and its effect to the chromium isotope ratios was confirmed.