Multielemental characterisation of cobalt by glow discharge quadrupole mass spectrometry

Multielemental determination and the assessment of purity of cobalt metal used in the preparation of Ni-based super-alloys have been carried out by glow discharge quadrupole mass spectrometry (GD-QMS). Relative sensitivity factors (RSF) generated from certified iron matrix reference samples (NIST 663 and 664 low alloy steel pin standards) could be used for the determination of different trace element constituents of the sample. Different wet chemical procedures were also carried out for the determination of the trace constituents in the sample. The GD-QMS results are in reasonably good agreement with those obtained from wet chemical procedures, validating the use of the RSF values generated on low alloy steel standards for the computation of trace element concentrations in cobalt metal. A variety of molecular ions formed through the reaction of cobalt (matrix) with the discharge gas (argon) were also detected.     

Accuracy and long-term reproducibility of lead isotopic measurements by multiple-collector inductively coupled plasma mass spectrometry using an external method for correction of mass discrimination

The precision of isotopic measurements of Pb by thermal ionization mass spectrometry (TIMS) is limited by the fact that this element does not possess an invariant isotope ratio that can be used for the correction of mass fractionation by internal normalization. Multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) can overcome this limitation, because with plasma ionization, elements with overlapping mass ranges are thought to display identical mass discrimination. With respect to Pb, this can be exploited by the addition of Tl to the sample solutions; the mass discrimination factor obtained for Tl can then be used for the correction of the measured Pb isotope ratios. In this article we present the results of a detailed study that investigates the accuracy and precision of such an external correction technique for mass discrimination based upon the results of multiple analyses of a mixed standard solution of NIST SRM-981 Pb and SRM-997 Tl. Our data indicate that normalization of the Pb isotope ratios to the certified isotopic composition of SRM-997 Tl produces Pb isotopic results that are significantly lower than recently published reference values by TIMS. This systematic offset can be eliminated by renormalization of the Pb data to a different Tl isotopic composition to obtain an empirically determined mass discrimination factor for Pb that generates accurate results. It is furthermore shown that a linear law is least suited for the correction of mass discrimination, whereas a power or exponential law function provide significantly more accurate and precise results. In detail, it appears that a power law may provide the most appropriate correction procedure, because the corrected Pb isotope ratios display less residual correlations with mass discrimination compared to the exponentially corrected data. Using an exponential or power law correction our results, obtained over a period of over seven months, display a precision (2σ) of better than 60 parts per million (ppm) for ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁷Pb/²⁰⁶Pb and of better than 350 ppm for ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb. This represents a significant improvement compared to conventional TIMS techniques and demonstrates the potential of MC-ICPMS for routine, high-precision measurements of Pb isotopic compositions.     

有机镓配合物的合成及其质谱

本文通过三环戊基镓与取代苯酚, 有机酸, 氨基酸反应合成了八个新的有机镓配合物, 这些配合物经过元素分析、质谱、核磁共振或红外光谱鉴定; 质谱研究表明这些配合物均以二聚体的形式存在。     

亲和标记-基质辅助激光解吸电离飞行时间质谱用于蛋白质相对定量方法的研究

将亲和标记技术和基质辅助激光解吸电离飞行时间串联质谱联用,建立了蛋白质相对定量方法,以牛血清白蛋白为实验对象,考察了该方法的准确度、重现性等指标;又以数种标准蛋白混合物为研究对象,考察了该方法的动态范围及相应的标准偏差,为实际生物样品中差异蛋白质分析奠定了基础。     

Thermal Stability Of Folic Acid in the solid-state

This study attempts to identify the degradative process which folic acid undergoes in the solid-state under thermal stress. In order to facilitate the process, the various pieces of the chemical structure, namely, p-amino benzoic acid, pterin and glutamic acid as both its d- and l-isomers were investigated as separate entities. These structured solid-state pieces were then compared to the composite solid state folic acid degradative curves in order to identify the peaks seen and provide direction for the interpolation of the degradative mechanism. It was observed that none of the structural pieces could be superimposed as assumed earlier and hence an attempt was made to identify the decomposition products using various analytical techniques such as infrared spectroscopy, mass spectroscopy and X-ray diffraction which suggested that the glutamic acid fragment is lost first as evidenced by acid loss and amide enhancement in the IR spectra. The vitamin was ultimately degrading to carbon fragments and that further identification was not necessary. This revised version was published online in August 2006 with corrections to the Cover Date.     

河口水体中痕量稀土元素的共沉淀预富集-电感耦合等离子体质谱法测定研究

建立了氢氧化铟共沉淀预富集 -电感耦合等离子体质谱法测定河口水体中痕量稀土元素的方法。实验结果表明 ,在80mg·L -1的In3 +和pH9.5的实验条件下 ,在1.0L水样中添加5.0～200.0ng的混合稀土标准溶液 ,均能定量回收 ,回收率在82.2 %～106.9 %之间。方法的分析流程空白为0.04(Tb)～10.17(La)ng·L -1,检出限在0.17(Yb)～1.46(La)ng·L-1之间 ,精密度 (RSD ,n=3)小于11.7 % ,可满足河口淡水和海水样品中的痕量稀土元素定量分析的要求     

LC-MS/MS method for the confirmatory determination of aromatic amines and its application in textile analysis

A confirmation method for the determination of 18 aromatic amines originating from azo dyes after reductive cleavage was developed. The method is based on the use of high-performance liquid chromatography/tandem mass spectrometry with atmospheric-pressure chemical ionization. For the identification of the analytes one precursor ion and two daughter ions (multi-reaction monitoring, MRM) were selected and the LC-MS/MS parameters optimized to obtain high sensitivity and selectivity. The linear ranges varied from 0.1–1 to 30–50 g mL^–1 with correlation coefficients of 0.99 or better. The applicability of the method to determine o-tolidine (3,3-dimethylbenzidine) and 3,3-dimethoxybenzidine in textiles following reductive cleavage of acid red 114, trypan blue, and Chicago sky blue 6B was demonstrated.     

Headspace Solid-phase Microextraction–Gas Chromatographic–Mass Spectrometric Analysis of the Essential Oils of Two Traditional Chinese Medicines, Angelica pubescens and Angelica sinensis

Angelica pubescens and Angelica sinensis belong to the Umbelliferae family and both are used as traditional Chinese medicines. In the present study, headspace solid-phase microextraction (HS-SPME) with gas chromatography-mass spectrometry (GC-MS) was used for the analysis of the volatile constituents present in their roots. Eighty-seven compounds in Angelica pubescens and thirty-six compounds in Angelica sinensis were identified by GC-MS. Their relative contents were calculated by the peak area ratio. HS-SPME was compared to steam distillation (SD) by analyzing the volatile constituents of Angelica sinensis root. A good agreement between results obtained with both techniques was found. As a conclusion, HS-SPME is a powerful tool for determining the volatile constituents present in the TCMs.     

N-取代苯并咪唑和N-取代-2-硫代噻唑烷酮类化合物的质谱研究

本文所研究的7种N-取代苯并咪唑和硫代噻唑烷酮类化合物是一类新合成的具有较高杀菌活性的化合物。本文利用电子轰击质谱技术对表中所列的化合物进行了研究。在高分辨精确质量测量和亚稳离子测定的基础上着重讨论了分子内3、4位C—C键的断裂和与杂环     

苯基重氮盐-冠醚分子嵌合物的FAB-MS及其准分子离子生成机理的研究

Fast atom bombardment mass spectra of a series of arenediazonium salts with various substituents complexed with 18-crown-6 and dibenzo-24-crown-8 ethers were examined. The correlation between quasi-molecular ion abundance of various complexes and the properties, coordination ability of donor-acceptor linkages in the complexes were studied. By using molecular orbital calculation we have successfully demonstrated that the correlation cited is related to the electron cloud densities on the heteroatoms α-N and β-N of arenediazonium salts.