GC/MS SIM法快速测定酒中的游离脂肪酸

本文介绍一种简单、快速、灵敏、直接分析酒中游离脂肪酸的测定方法。用涂有OV-17熔融石英毛细管柱。选择游离脂肪酸质谱图中的基峰离子m/z 60进行SIM检测。定量测定了茅台酒、珍酒及鸭溪窖酒中十二种游离脂肪酸。     

Slow Relaxation of the Magnetization in Anilato-Based Dy(III) 2D Lattices

The search for two- and three-dimensional materials with slow relaxation of the magnetization (single-ion magnets, SIM and single-molecule magnets, SMM) has become a very active area in recent years. Here we show how it is possible to prepare two-dimensional SIMs by combining Dy(III) with two different anilato-type ligands (dianions of the 3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone: C₆O₄X₂²⁻, with X = H and Cl) in dimethyl sulfoxide (dmso). The two compounds prepared, formulated as: [Dy₂(C₆O₄H₂)₃(dmso)₂(H₂O)₂]·2dmso·18H₂O (1) and [Dy₂(C₆O₄Cl₂)₃(dmso)₄]·2dmso·2H₂O (2) show distorted hexagonal honeycomb layers with the solvent molecules (dmso and H₂O) located in the interlayer space and in the hexagonal channels that run perpendicular to the layers. The magnetic measurements of compounds 1, 2 and [Dy₂(C₆O₄(CN)Cl)₃(dmso)₆] (3), a recently reported related compound, show that the three compounds present slow relaxation of the magnetization. In compound 1 the SIM behaviour does not need the application of a DC field whereas 2 and 3 are field-induced SIM (FI-SIM) since they show slow relaxation of the magnetization when a DC field is applied. We discuss the differences observed in the crystal structures and magnetic properties based on the X group of the anilato ligands (H, Cl and Cl/CN) in 1–3 and in the recently reported derivative [Dy₂(C₆O₄Br₂)₃(dmso)₄]·2dmso·2H₂O (4) with X = Br, that is also a FI-SIM.     

金属标记结合高效液相色谱-选择离子监测质谱的蛋白质绝对定量新方法

建立了金属标记结合高效液相色谱-选择性离子监测质谱(SIM)的蛋白质绝对定量新方法。实验考察了金属标记效率、金属标记的稳定性、标记后肽段的色谱保留和质谱行为、新定量方法的线性范围和准确度。实验结果表明金属标记具有标记效率高,稳定性好,色谱保留行为一致等优点。另外,金属标记-选择离子监测质谱绝对定量方法灵敏度高,其定量限低至1 fmol,线性范围为1~500 fmol,线性范围内R2值大于0.99,具有良好的线性关系;经过测量,标准肽段的回收率为117.01%,说明该方法具有较高的准确度。将该方法应用于腾冲嗜热菌中烯醇酶蛋白的定量分析,相对标准偏差为5.47%,表明该方法的精密度高。以上结果表明该方法可以用于生物样本中的蛋白质的绝对定量分析,为比较简单的生物样本中蛋白质的绝对定量方法提供了一种新的选择。     

Analysis of microcystins by capillary zone electrophoresis coupling with electrospray ionization mass spectrometry

In this paper, a rapid and effective method based on capillary zone electrophoresis (CZE) coupled with electrospray ionization mass spectrometry (ESI-MS) was established for the trace analysis of microcystin (MC) isomers in crude algae sample. The experimental conditions including the composition, acidity and concentration of buffer, separation voltage, injection time, and MS detection parameters were investigated in detail. A capillary separation system was as follows: a uncoated fused-silica capillary tube (50 μm i.d. × 90 cm), 40 mmol L⁻¹ ammonium acetate solution (pH 9.86) as running buffer, 25 kV as separation voltage, 20 kV × 3 s water first and 20 kV × 20 s for sample injection. Mass analysis was performed in ESI source, with sheath gas temperature 150 °C, sheath gas pressure 10 psi, and sheath gas flow 6 L min⁻¹. And sheath liquid was 7.5 mmol L⁻¹ acetic acid in 50% isopropanol-water (3 μL min⁻¹). Protonation and ammonium adduct molecular ions m/z 506.9 (MC-LR) and 532.0 (MC-YR) were used for the quantification of MCs. Under these conditions, two MCs were baseline separated within 9 min, the calibration curves were obtained in the range of 0.11-10.0 μg mL⁻¹ and 0.16-10.5 μg mL⁻¹ for MC-LR and MC-YR, respectively. Meanwhile, limits of detection were 0.05 and 0.08 μg mL⁻¹ for MC-LR and MC-YR, respectively. The recoveries for the two MCs were in the range of 95.8-108%. The developed approach had been successfully applied to the analysis of MCs in crude algae samples.     

Zirconium silicate assisted removal of residual proteins after organic solvent deproteinization of human plasma,enhancing the stability of the LC–ESI-MS response for the bioanalysis of small molecules

An efficient blood plasma clean-up method was developed, where methanol protein precipitation was applied, followed by zirconium silicate assisted exclusion of residual proteins. A strong binding of zirconium (IV) silicate to the proteins enabled the elimination of remaining proteins after solvent deproteinization through a rapid solid-phase extraction (SPE) procedure. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF MS) was used for monitoring the proteins during clean-up practice applied to human plasma samples. The proteins were quantified by colorimetric detection using the bicinchoninic acid (BCA) assay. The presented analytical strategy resulted in the depletion of >99.6% proteins from human plasma samples. Furthermore, high-performance liquid chromatography hyphenated to diode-array and electrospray ionization mass spectrometric detection (HPLC–DAD/ESI MS) was applied for qualitative and quantitative analysis of the caffeoylquinic acids (CQAs) and their metabolites in human plasma. The procedure demonstrated high recoveries for the standard compounds spiked at different concentrations. Cynarin and chlorogenic acid were recovered in the range of 81–86% and 78–83%, respectively. Caffeic acid was extracted in the excess of 89–92%, while ferulic acid and dihydroxyhydrocinnamic acid showed a recovery of 87–91% and 92–95%, respectively. The method was partially validated in accordance with FDA-Industry Guidelines for Bioanalytical Method Validation (2001). The presented scheme improves the clean-up efficacy of the methanol deproteinization, significantly reduces the matrix effects and provides a great analytical tool for the isolation of small molecules from human plasma.     

Cylindrospermopsin determination using 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) as the internal standard

Cylindrospermopsin (CYN) was determined by liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS) using 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) as the internal standard. In the selected ion monitoring of LC/ESI-MS, m/z 414 for CYN and 237 for HEPES were monitored using the negative mode; the retention times of CYN and HEPES were 12.41 and 14.21 min, respectively. CYN was determined from peak area ratios of m/z 414/237. By the treatment of an anion exchange cartridge using a buffer at pH 10.5, CYN was isolated and condensed. No interfering peak was observed. Linearity of this method was observed at the range of 0.10-31.12 ng. Total coefficients of variation were 5.1 and 2.9% at 104 and 1038 μg CYN L⁻¹. The quantitative limit at a signal-to-noise (S/N) ratio of 10 was 0.16 ng.CYN concentration in natural waters is low. CYN in waters should be condensed for determination. This method including the treatment for isolation and condensation of CYN is useful for determination of CYN in environmental and/or drinking waters.     

SIM(2)-invariant modifications of electrodynamic theory

In the Cohen–Glashow Very Special Relativity we exhibit possible modifications to the Maxwell theory and to the quantum electrodynamics Lagrangian in some generality, and discuss characteristic features depending on the modifications. Modified gauge transformations in SIM(2)-invariant theories are introduced and the related gauge fields, with two polarization states, can have nonzero mass. Also considered are SIM(2)-covariant modifications to the Proca-type field equations for a massive spin-1 particle.     

An overview of analytical methodologies for the determination of antibiotics in environmental waters

The widespread occurrence of antibiotics as contaminants in the aquatic environment has increased attention in the last years. The concern over the release of antibiotics into the environment is related primarily to the potential for the development of antimicrobial resistance among microorganisms. This article presents an overview of analytical methodologies for the determination of quinolone (Qs) and fluoroquinolone (FQs), macrolide (MLs), tetracycline (TCs), sulfonamide (SAs) antibiotics and trimethoprim (TMP) in different environmental waters. The analysis of these antibiotics has usually been carried out by high-performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) or tandem mass spectrometry (MS/MS) and to a lesser extent by ultraviolet (UV) or fluorescence detection (FD). A very important step before LC analysis is sample preparation and extraction leading to elimination of interferences and prevention of matrix effect and preconcentration of target analytes.     

气相色谱/质谱测定皮革及其制品中乙二醇醚类有机溶剂的残留量

建立了同时测定皮革及其制品中12种乙二醇醚类有机溶剂残留量的气相色谱/质谱-选择离子监测方法。以乙酸乙酯为萃取溶剂,在45℃下超声萃取皮革及其制品中的乙二醇醚类有机溶剂,萃取液经固相萃取柱净化后进行气相色谱/质谱-选择离子监测法测定,外标法定量。在信噪比（S/N）=3的条件下,乙二醇单乙醚（EGEE）的检出限为0.10 mg/kg,其余11种乙二醇醚类有机溶剂的检出限均小于0.05 mg/kg。在3个加标水平下,该方法的平均加标回收率为81.2%~95.5%,相对标准偏差（RSD）为1.4%~6.6%（n=9）。该方法简便快捷,灵敏度高,检出限远远低于欧盟法规《化学品的注册、评估、授权和限制》（REACH）的限量要求,适用于皮革及其制品中乙二醇醚类有机溶剂残留量的测定,为制定相关检测标准提供了参考。