Accelerator mass spectrometry (AMS) in plutonium analysis

The paper summarizes the results of the ²⁴⁰Pu/²³⁹Pu atomic ratio studies in atmospheric fallout samples collected in 1986 over Gdynia (Poland) as well as three Baltic fish species collected in 1997 using the accelerator mass spectrometry. A new generation of AMS has been developed during last years and this method is an efficient and good technique to measure long-lived radioisotopes in the environment and provides the most accurate determination of the atomic ratios between ²⁴⁰Pu and ²³⁹Pu. The nuclide compositions of plutonium in filter samples correspond to their means of production. AMS measurements of atmospheric fallout collected in April showed sufficient increase of the ²⁴⁰Pu/²³⁹Pu atomic ratio from 0.28 from March to 0.47. Also such high increase of ²⁴⁰Pu/²³⁹Pu atomic ratio, close to reactor core ²⁴⁰Pu/²³⁹Pu atomic ratio, was observed in September and equaled 0.47.     

Simultaneous quantitation of six major quassinoids in Tongkat Ali dietary supplements by liquid chromatography with tandem mass spectrometry

Tongkat Ali (Eurycoma longifolia) is one of the most popular traditional herbs in Southeast Asia and generally consumed as forms of dietary supplements, tea, or drink additives for coffee or energy beverages. In this study, the liquid chromatography with tandem mass spectrometry method for the simultaneous quantitation of six major quassinoids of Tongkat Ali (eurycomanone, 13,21‐dihydroeurycomanone, 13α(21)‐epoxyeurycomanone, 14,15β‐dihydroxyklaineanone, eurycomalactone, and longilactone) was developed and validated. Using the developed method, the content of the six quassinoids was measured in Tongkat Ali containing dietary supplement tablets or capsules, and the resulting data were used to confirm the presence of Tongkat Ali in those products. Among the six quassinoids, eurycomanone was the most abundant quassinoid in all samples tested. The developed method would be useful for the quality assessment of Tongkat Ali containing dietary supplements.     

The effect of ruthenium(III) chloride on the formation of protonated parent ions in electrospray mass spectrometry

We report the use of RuCl3 as an "alkali metal sponge". This is a general and highly efficient method for generating protonated parent ions for a variety of compounds that usually do not show this ion in electrospray mass spectrometry. This technique is demonstrated to be highly useful in "cleaning up" spectra from multiply metallated ions, thereby substantially improving the signal-to-noise ratio.     

Tyrosinase inhibitory constituents from the bark of Peltophorum dasyrachis (yellow batai)

Tyrosinase inhibitory activity-guided fractionation of the bark of Peltophorum dasyrachis (yellow batai) led to the isolation of the six active compounds which were characterised as six flavonoids: apigenin (1), (+)-2,3-trans-dihydrokaempferol (2), (+)-2,3-trans-dihydrokaempferol-3-O-α-L-rhamnoside (3), (+)-4',7-dimethoxy-2,3-trans-dihydroquercetin (4), (+)-2,3-trans-dihydroquercetin (5) and (-)-2,3-trans-dihydroquercetin-3-O-α-L-rhamnoside (6). All compounds were isolated for the first time from the bark of P. dasyrachis. Moreover, all compounds were evaluated for tyrosinase activities towards L-DOPA as the substrate. We observed that compounds 2 and 5 showed potent inhibitory effects (IC?? values were 126?±?3.2 and 210?±?5.8?μM, respectively). In general, for flavonoids the 3',4'-dihydroxy group's substituent is a more potent inhibitor than the 4'-hydroxy group substituent, i.e. quercetin?>?kaempferol. Interestingly, our result in the oxidation of L-DOPA showed that the 4'-hydroxy group substituent (compound 2) is a more potent inhibitor than the 3',4'-dihydroxy group substituent (compound 5). This result showed a new relationship between tyrosinase inhibitory activities and flavonoids. The kinetic analyses by Lineweaver-Burk plots showed that both the compounds 2 and 5 behaved as competitive inhibitors of L-DOPA oxidation.     

Effects of acidic peptide size and sequence on trivalent praseodymium adduction and electron transfer dissociation mass spectrometry

Using the lanthanide ion praseodymium, Pr(III), metallated ion formation and electron transfer dissociation (ETD) were studied for 25 biological and model acidic peptides. For chain lengths of seven or more residues, even highly acidic peptides that can be difficult to protonate by electrospray ionization will metallate and undergo abundant ETD fragmentation. Peptides composed of predominantly acidic residues form only the deprotonated ion, [M + Pr ‐ H]²⁺; this ion yields near complete ETD sequence coverage for larger peptides. Peptides with a mixture of acidic and neutral residues generate [M + Pr]³⁺, which cleaves between every residue for many peptides. Acidic peptides that contain at least one residue with a basic side chain also produce the protonated ion, [M + Pr + H]⁴⁺; this ion undergoes the most extensive sequence coverage by ETD. Primarily metallated and non‐metallated c‐ and z‐ions form for all peptides investigated. Metal adducted product ions are only present when at least half of the peptide sequence can be incorporated into the ion; this suggests that the metal ion simultaneously attaches to more than one acidic site. The only site consistently lacking dissociation is at the N‐terminal side of a proline residue. Increasing peptide chain length generates more backbone cleavage for metal‐peptide complexes with the same charge state. For acidic peptides with the same length, increasing the precursor ion charge state from 2+ to 3+ also leads to more cleavage. The results of this study indicate that highly acidic peptides can be sequenced by ETD of complexes formed with Pr(III). Copyright © 2017 John Wiley & Sons, Ltd.     

HPLC-MS/MS检测猪肉中六种大环内酯类抗生素

建立了以高效液相色谱-质谱(HPLC-MS/MS)检测猪肉中替米考星(TILM)、红霉素(ERY)、泰乐菌素(TYL)、吉他霉素(KIT)、罗红菌素(ROX)及交沙霉素(JOS)等6种大环内酯类抗生素的多残留分析方法.样品用乙腈提取后,经正己烷脱脂,过C18 柱净化,4%氨甲醇洗脱后经氮气吹干,采用多反应监测,对6种大环内酯类药物作定性和定量分析.在10～1000μg/L的范围内,6种药物线性良好(R>0.998).在50、100、200μg/Kg添加水平下,6种药物的回收率在62.2%～102%,相对标准偏差为2.7%～16%.替米考星和吉他霉素的检出限(S/N=3)为0.1μg/Kg,其它药物为0.05μg/kg.     

Accelerator mass spectrometry 14C determination in CO2 produced from laser decomposition of aragonite

The determination of (14)C in aragonite (CaCO(3)) decomposed thermally to CO(2) using an yttrium-aluminum-garnet doped neodymium laser is reported. Laser decomposition accelerator mass spectrometry (LD-AMS) measurements reproduce AMS determinations of (14)C from the conventional reaction of aragonite with concentrated phosphoric acid. The lack of significant differences between these sets of measurements indicates that LD-AMS radiocarbon dating can overcome the significant fractionation that has been observed during stable isotope (C and O) laser decomposition analysis of different carbonate minerals. The laser regularly converted nearly 30% of material removed into CO(2) despite it being optimized for ablation, where laser energy breaks material apart rather than chemically altering it. These results illustrate promise for using laser decomposition on the front-end of AMS systems that directly measure CO(2) gas. The feasibility of such measurements depends on (1) the improvement of material removal and/or CO(2) generation efficiency of the laser decomposition system and (2) the ionization efficiency of AMS systems measuring continuously flowing CO(2).     

Double cation adduction in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of electron deficient anthraquinone derivatives

Six anthraquinone derivatives were analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS). Clear (pseudo) molecular ions were observed for all the compounds. Interestingly, for some derivatives, strong ions with double cation adduction were also recorded in the positive mode. It is remarkable that all these ions are singly charged. In this work, possible mechanisms for the double cation adduction were investigated and discussed. It appears that the double cation adduction was due to the electron deficient nature of the derivatives, and formed by taking up two singly charged cations and one electron. Substituents on the anthraquinone ring were found to have a significant effect on the double cation adduction. In contrast, no considerable influence of the acidity of MALDI matrix/solution was observed, even on the double proton adduction. Furthermore, it was demonstrated that double cation adduction might occur in the MALDI gas-phase plume. In addition to the anthraquinones, three more electron deficient compounds of different types, i.e. a perylene bisimide derivative (PB), 3,7-decanoylamino-4,8-dihydrobenzo[1,2-b:4,5-b']dithiophene-4,8-dione (TQ) and 6,6-phenyl C61-butyric acid methyl ester (PCBM), were also analyzed with MALDI TOF MS. The results indicate that the 'abnormal' double cation adduction might be a 'normal' phenomenon in the MALDI TOF MS analysis of many electron deficient compounds.     

Influence of cation adduction on the separation characteristics of flavonoid diglycoside isomers using dual gate-ion mobility-quadrupole ion trap mass spectrometry

An electrospray ionization-dual gate-ion mobility-quadrupole ion trap mass spectrometer was used to evaluate the separation characteristics of isomeric flavonoid diglycosides adducted with sodium, potassium, and silver. This instrumental configuration allows ions to be selectively accumulated within the ion trap on the basis of their gas phase conformation prior to mass analysis. For the metal cations examined, silver produced the most compact adducts with flavonoid diglycosides. Listed in order of increasing size, the trend of flavonoid diglycoside ion-neutral cross sections adducted with Na+, K+, and Ag+ was narirutin < naringin < hesperidin < neohesperidin < rutin. To examine the separation contribution of the carbohydrate group, hesperetin, the aglycone of hesperidin, and neohesperin were compared to quercetin, the aglycone of rutin. Separation of the flavonoid diglycosides indicated that quercetin-derived diglycosides drifted longer than their hesperetin-derived isomers. Combined with the observed collision assisted dissociation (CAD) data, these findings suggest that carbohydrate moiety plays a significant role in both the separation and metal chelating characteristics of flavonoid diglycosides.     

在线净化液相色谱-串联质谱法快速测定牛奶中的6种孕激素

建立了在线净化液相色谱-串联质谱同时测定牛奶中炔诺酮、17α-羟基孕酮、甲羟孕酮、乙酸甲地孕酮、孕酮和醋酸美伦孕酮6种孕激素的方法。本方法采用乙腈为提取溶剂提取目标化合物。提取液经在线净化柱Cyclone-P净化,经Phenyl-Hexyl色谱柱分离,流动相采用0.5%（v/v）甲酸水溶液-乙腈,在电喷雾正离子模式下以多反应监测（MRM）方式测定,内标法定量。方法在0.1~50 μg/L范围内呈线性关系,线性相关系数均大于0.999。6种分析物的测定低限为0.5 μg/kg,在牛奶中3个水平的添加回收率在90.8%~107.5%之间,相对标准偏差在6.3%~11.8%之间。该方法快速简便,灵敏度高,选择性好,可用于牛奶样品中孕激素的快速定性定量分析。     

Determination of anabolic steroids in dietary supplements by liquid chromatography-tandem mass spectrometry

Nineteen different dietary supplements, ordered through the internet and intercepted by the Belgian pharmaceutical inspection at the post office, were analyzed by means of liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the presence of anabolic steroids. After a methanolic extraction the samples were screened for the presence of 49 compounds. This resulted in almost 60% of the samples being suspected of containing one of these 49 anabolic compounds and being subjected to a confirmatory product ion scan. In all of these suspected samples we were able to confirm at least one anabolic steroid with concentrations between 0.01 and 2.5 mg unit(-1) (unit: one capsule or tablet or for liquids: the prescribed dose). The anabolic steroids that was mostly encountered was testosterone (50%) followed by beta-boldenone (25%). These results once more confirm the dubious reputation of over-the-counter dietary supplements.     

Current mass spectrometry strategies for selenium speciation in dietary sources of high-selenium

This document reviews the most relevant mass spectrometry approaches to selenium (Se) speciation in high-Se food supplements in terms of qualitative and quantitative Se speciation and Se-containing species identification, with special reference to high-Se yeast, garlic, onions and Brazil nuts. Important topics such as complexity of Se speciation in these materials and the importance of combining Se-specific detection and molecule-specific determination of the particular species of this element in parallel with chromatography, to understand their nutritional role and cancer preventive properties are critically discussed throughout. The versatility and potential of mass spectrometric detection in this field are clearly demonstrated. Although great advances have been achieved, further developments are required, especially if speciatedcertified reference materials (CRMs) are to be produced for validation of measurements of target Se-containing species in Se-food supplements.     

Nitric oxide (NO) production inhibitory constituents of Tabebuia avellanedae from Brazil

From the water extract of Brazilian Tabebuia avellanedae, two new iridoids (1, 2) and a new phenylethanoid glycoside (3) have been isolated together with twelve known compounds (4-15). Their structures were determined based on the spectroscopic data. The isolated compounds inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-activated macrophage-like J774.1 cells. Compounds 1, 3, 10, 11, and 12 showed inhibitory activities more potent (IC50, 13.8-26.1 microg/ml) than a positive control N(G)-monomethyl-L-arginine (L-NMMA; IC50, 27.4 microg/ml).     

Simultaneous determination of the inhibitory potency of herbal extracts on the activity of six major cytochrome P450 enzymes using liquid chromatography/mass spectrometry and automated online extraction

Here we describe a liquid chromatography/mass spectrometry (LC/MS) method with automated online extraction (LC/LC/MS) to simultaneously determine the in vitro inhibitory potency of herbal extracts on six major human drug-metabolising cytochrome P450 enzymes. Substrates were incubated with a commercially available mixture of CYP1A2/2C8/2C9/2C19/2D6 and 3A4 from baculovirus-infected insect cells and the resulting metabolites were quantified with LC/LC/MS using electrospray ionisation in the selected ion monitoring mode. Consistent inhibitory activities were obtained for known inhibitors and plant extracts using the enzyme/substrate cocktail and the individual enzymes/substrates. Popular herbal remedies including devil's claw root (Harpagophytum procumbens), feverfew herb (Tanacetum parthenium), fo-ti root (Polygonum multiflorum), kava-kava root (Piper methysticum), peppermint oil (Mentha piperita), eucalyptus oil (Eucalyptus globulus), red clover blossom (Trifolium pratense) and grapefruit juice (GJ; Citrus paradisi) could be identified as inhibitors of the applied CYP enzymes with IC(50) values between 20 and 1000 microg/mL.     

QuEChERS-气相色谱-串联质谱法快速检测茶叶中6种禁用香精成分

建立了QuEChERS净化作为样品前处理，结合气相色谱-串联质谱（GC-MS/MS）同时检测茶叶中6种禁用香精成分（香豆素、侧柏酮、2-己基噻吩、反式-β-金合欢烯、p-薄荷-1，8（10）-二烯-9-乙酸乙酯和肉桂酸丁酯）的分析方法。茶叶样品用乙酸乙酯溶液萃取，涡旋振荡，离心后上清液中加入无水硫酸镁、十八烷基键合硅胶（C18）和乙二胺-N-丙基甲硅烷（PSA），涡旋，低温离心后过滤膜，以DB-5MS色谱柱分离，MS/MS于MRM模式下测定，基质曲线外标法定量。实验结果表明，6种禁用香精成分在1~200 μg/L线性范围内呈良好线性，线性相关系数（R²）均大于0.999。方法检出限0.005~1 μg/kg，定量限0.02~2 μg/kg，平均回收率82.3%~93.1%，日内、日间精密度均小于10%。该方法处理简单、快速，准确度和灵敏度高，可用于茶叶中6种禁用香精成分的检测。     

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) of polyisoprenes

Polyisoprenes (PIPs) with average molecular weights from 650 to 800,000 Da have been studied by time-of-flight secondary ion mass Spectrometry (TOF-SIMS) in the static mode. Polymer samples were bombarded by argon primary ions, and positive SIMS spectra were collected. Effects of branching and unsaturation in the polymer structure on ion formation were studied. The pendant methyl group showed little tendency to fracture as a cation. In the low mass region, C_nH _2n–1 ⁺ appeared to be more intense than C_nH _2n+1 ⁺ , attributed to the double bond structure of polyisoprene. Additionally, ion formation varied as a function of polymer molecular weight. Cationized intact oligomers and fragments dominate the high mass region. Oligomer distributions were used to calculate average molecular weights for polyisoprenes. A statistical chain scission mechanism was used to qualitatively explain the formation of five clusters within a unique fragmentation pattern. Detailed studies of the cluster structure pointed out that each cluster contained several species having varied degrees of unsaturation. It is believed that double bond rearrangements occur.     

Triboelectric nanogenerator (TENG) mass spectrometry of falsified antimalarials

Rationale

An epidemic of low‐quality medicines continues to endanger patients worldwide. Detection of such ‘medicines’ requires low cost, ambient ionization sources coupled to fieldable mass spectrometers for optimum sensitivity and specificity. With the use of triboelectric nanogenerators (TENGs), the charge required to produce gas‐phase ions for mass analysis can be obtained without the need for high‐voltage electrical circuitry, simplifying and lowering the cost of next‐generation mass spectrometry instruments.

Methods

A sliding freestanding (SF) TENG was coupled to a toothpick electrospray setup for the purposes of testing if falsified medicines could be fingerprinted by this approach. Extracts from both genuine and falsified medicines were deposited on the toothpick and the SF TENG actuated to generate electrical charges, resulting in gas‐phase ions for both active pharmaceutical ingredients and excipients.

Results

Our previous work had shown that direct analysis in real time (DART) ambient mass spectrometry can identify the components of multiple classes of falsified antimalarial medicines. Experiments performed in this study show that a simple extraction into methanol along with the use of a SF TENG‐powered toothpick electrospray can provide similar detection capabilities, but with much simpler and rugged instrumentation, and without the need for compressed gases or high‐voltage ion source power supplies.

Conclusions

TENG toothpick MS allows for rapid analyte ion detection in a safe and low‐cost manner, providing robust sampling and ionization capabilities.

     

Electrospray mass spectrometry determination of poly(oxazolidine acetal)

The polycondensation of terephthalaldehyde with 2-amino-2-hydroxymethyl-1,3-propanediol (TRIS), or of terephthaldehyde with 2,2'-(1,4-phenylene)-bis-1,3-(4,4-dihydroxymethyl)oxazolidine (bis-oxazolidine), using acidic catalysts, leads to the formation of linear polymers and macrocyclic compounds. The structure of the polymer was determined by (1)H-, (13)C-NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS) analysis. ESI-MS measurements were used to study the details of the polymer structure and support the alternating nature of equimolar amounts of oxazolidine and the cyclic acetal of terephthaldehyde in these macromolecules.