大豆中二硝基苯胺类除草剂多残留的气相色谱法定量检测及质谱确证

建立以凝胶渗透色谱法（GPC）和固相萃取法（SPE）及气相色谱法（GC）联用技术测定大豆中10种二硝基苯胺类除草剂（氟乐灵、乙氟灵、环丙氟、氯乙氟灵、仲丁灵、异乐灵、二甲戊乐灵、二硝胺、氨基丙氟灵和磺乐灵）多残留检测方法。目标农药经正己烷饱和的乙腈提取，凝胶渗透色谱除去大豆中大部分油脂及色素，再经Florisil柱净化和富集，依次用6mL二氯甲烷和6mL二氯甲烷＋丙酮（99＋1）洗脱。目标农药采用电子捕获检测（GC／ECD），外标法定量，并经质谱（MS）确证。两个添加水平重复6次，回收率分别为74％～105％和59％～105％；相对标准偏差〈20％；检出限为1．8～7．6μg／kg；定量限为6～38μg/kg。     

A simple and direct isolation of whey components from raw milk by gel filtration chromatography and structural characterization by Fourier transform Raman spectroscopy

A simple and economical method to isolate whey protein from fresh raw milk is developed by serial defatting, casein eliminating, lactose removing, and separating by gel filtration chromatography. Four major whey components, including immunoglobulin (Ig), bovine serum albumin (BSA), β-lactoglobulin (β-Lg) and -lactalbumin (-Lac), and a non-protein of low molecular mass (1.7 kDa) but strong absorbance at 280 nm, are detected simultaneously. The small non-protein molecule is rich in aromatic amino acids and thiol groups as supported by the structural characterization with near infrared Fourier transform Raman spectroscopy (FT-Raman). FT-Raman results show that the secondary structure of Ig is dominated by anti-parallel β-pleated sheet; BSA is mainly in -helix; both β-form and unordered structure are important in β-Lg; while -Lac is mostly in -helix coupling with random coil. Differences in the Raman profile for each whey component reflect their intrinsic compositional differences and distinct spatial arrangement. The S–S linkages diverging around 510–540 cm⁻¹ indicate that the conformation of disulfide bonds in each whey components is different, which may be responsible for their diversified behaviors in solubility, rheological and functional properties.     

Optical and electrochemical detection techniques for cell-based microfluidic systems

The ability to fabricate microfluidic systems with complex structures and with compatible dimensions between the microfluidics and biological cells have attracted significant attention in the development of microchips for analyzing the biophysical and biochemical functions of cells. Just as cell-based microfluidics have become a versatile tool for biosensing, diagnostics, drug screening and biological research, detector modules for cell-based microfluidics have also undergone major development over the past decade. This review focuses on detection methods commonly used in cell-based microfluidic systems, and provides a general survey and an in-depth look at recent developments in optical and electrochemical detection methods for microfluidic applications for biological systems, particularly cell analysis. Selected examples are used to illustrate applications of these detection systems and their advantages and weaknesses.     

Accurate localization and relative quantification of arginine methylation using nanoflow liquid chromatography coupled to electron transfer dissociation and drbitrap mass spectrometry

Protein arginine (Arg) methylation serves an important functional role in eucaryotic cells, and typically occurs in domains consisting of multiple Arg in close proximity. Localization of methylarginine (MA) within Arg-rich domains poses a challenge for mass spectrometry (MS)-based methods; the peptides are highly charged under electrospray ionization (ESI), which limits the number of sequence-informative products produced by collision induced dissociation (CID), and loss of the labile methylation moieties during CID precludes effective fragmentation of the peptide backbone. Here the fragmentation behavior of Arg-rich peptides was investigated comprehensively using electron-transfer dissociation (ETD) and CID for both methylated and unmodified glycine-/Arg-rich peptides (GAR), derived from residues 679–695 of human nucleolin, which contains methylation motifs that are widely-represented in biological systems. ETD produced abundant information for sequencing and MA localization, whereas CID failed to provide credible identification for any available charge state (z=2–4). Nevertheless, CID produced characteristic neutral losses that can be employed to distinguish among different types of MA, as suggested by previous works and confirmed here with product ion scans of high accuracy/resolution by an LTQ/Orbitrap. To analyze MA-peptides in relatively complex mixtures, a method was developed that employs nano-LC coupled to alternating CID/ETD for peptide sequencing and MA localization/characterization, and an Orbitrap for accurate precursor measurement and relative quantification of MA-peptide stoichiometries. As proof of concept, GAR-peptides methylated in vitro by protein arginine N-methyltransferases PRMT1 and PRMT7 were analyzed. It was observed that PRMT1 generated a number of monomethylated (MMA) and asymmetric-dimethylated peptides, while PRMT7 produced predominantly MMA peptides and some symmetric-dimethylated peptides. This approach and the results may advance understanding of the actions of PRMTs and the functional significance of Arg methylation patterns.     

Separation and identification of compounds in Adinandra nitida by comprehensive two-dimensional liquid chromatography coupled to atmospheric pressure chemical ionization source ion trap tandem mass spectrometry

A comprehensive two-dimensional liquid chromatographic (2D-LC) separation system based on the combination of a CN column and a Merck Chromolith Flash reversed-phase column was developed for the separation of components in Adinandra nitida, one type of traditional Chinese medicine (TCM). The two dimensions were connected by a ten-port, dual-position valve controlled automatically by software written in-house. The effluents were detected by both ultraviolet and atmospheric pressure chemical ionization source ion trap tandem mass spectrometry (MS). The calculated peak capacity of the 2D-LC–MS/MS system was above 1240. More than 57 components were resolved in the methanol extract from Adinandra nitida leaves, and five of these were identified based on their relative retention times, molecular weights and MS/MS spectra.     

Electrochemical behavior and determination of epinephrine at a mercaptoacetic acid self-assembled gold electrode

The electrochemical behavior of epinephrine (EP) at a mercaptoacetic acid (MAA) self-assembled monolayer modified gold electrode was studied. The MAA/Au electrode is demonstrated to promote the electrochemical response of epinephrine by cyclic voltammetry. The possible reaction mechanism is also discussed. The diffusion coefficient D of EP is 6.85 × 10⁻⁶ cm² s⁻¹. In 0.1 mol L⁻¹ phosphate buffer (pH 7.20), a sensitive oxidation peak was observed at 0.177 V, and the peak current is proportional to the concentration of EP in the range of 1.0 × 10⁻⁵–2.0 × 10⁻⁴ mol L⁻¹ and 1.0 × 10⁻⁷–1.0 × 10⁻⁶ mol L⁻¹. The detection limit is 5 × 10⁻⁸ mol L⁻¹. The modified electrode is highly stable and can be applied to the determination of EP in practical injection samples. The method is simple, quick, sensitive and accurate.     

普鲁士兰修饰碳黑微电极同时微分伏安法测定多巴胺和抗坏血酸

将含有1.0%普鲁士蓝的碳黑与固体石蜡按2.5∶1(质量比)混合后装入φ0.2mm的石英毛细管中,在其上端插入一铂丝并抛光后即制成普鲁士蓝修饰碳黑微电极.对多巴胺(DA)及抗坏血酸(VC)在此电极上的电化学行为及应用此电极测定两组分的最佳条件进行了研究,在定量测定中采用二次微分线性扫描伏安法.在最佳条件下,DA与VC的峰电流(i″p)分别与各自的浓度保持如下线性关系DA为4.0×10-6～8.0×10-4mol·L-1,VC为6.0×10-5～1.0×10-3mol·L-1;检出限(3σ)依次为2.0×10-6mol·L-1及1.0×10-5mol·L-1.应用此方法分析了3种含DA及VC的混合溶液,测得结果的相对标准偏差(n=8)依次小于2.0%及3.0%,回收率范围依次为96.5%～101.0%及95.0%～102.5%.     

固相萃取-高效液相色谱法同时检测大米中12种磺酰脲类除草剂的残留

建立了固相萃取前处理净化技术-高效液相色谱（HPLC）同时检测大米中12种磺酰脲类除草剂残留的方法。采用ENVITM-18(C18)硅胶柱和ENVI-Carb(GCB)石墨化碳柱对样品进行净化、萃取,采用C8柱,以乙腈和5 mmol/L 冰乙酸混合溶剂为流动相进行梯度洗脱,在240 nm下进行检测。12种磺酰脲类除草剂在0.01~0.50 μg/g添加范围内的回收率为72.2%~106.5%,相对标准偏差为0.6%~6.4%,检出限为0.01~0.02 μg/g。     

气相色谱-质谱法分析蜂蜜中的多种农药残留

开展了蜂蜜中23种农药残留的气相色谱-电子轰击离子源质谱(GC-EI/MS)分析方法的研究,并对其中3种农药的EI/MS碎片离子的断裂机理与结构进行了初步解析。探讨了蜂蜜试样前处理条件的优化与选择。将蜂蜜试样用乙酸乙酯提取剂超声提取、Florisil硅藻土色谱柱净化和正己烷-乙酸乙酯(体积比为7∶3)混合洗脱剂洗脱后,以PCB103为内标物,采用选择离子监测(SIM)方式下的GC-EI/MS分析。当试样的加标浓度为50,100和200 μg/kg时,加标回收率为82%～120%,相对标准偏差小于11.0%。23种农药的检测限都小于10.0 μg/kg,线性范围为10～500 μg/kg,相关系数都大于0.995。此分析方法已成功地应用于蜂蜜中23种痕量农药残留的分析。     

Pr0.6-xNdxSr0.4FeO3-δ电极材料的光谱及性能研究

以柠檬酸-硝酸盐自蔓延燃烧法合成了ABO₃型钙钛矿结构的Pr_0.6-xNd_xSr_0.4FeO_3-δ(x=0.0～0.6)系列稀土复合氧化物粉体。利用傅立叶变换红外光谱(FTIR)和激光共焦拉曼光谱(LRS)对产物的晶体结构进行了表征。分别采用热膨胀仪测定烧结陶瓷体的热膨胀系数(TEC)；TG-DTA记录材料的热稳定性；XRD研究阴极材料与中温电解质Sm_0.2Ce_0.8O_1.9(SDC)及La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ(LSGM)的化学相容性；SEM观察阴极/电解质复合材料的断口形貌。结果表明，该系列样品在高、低温热循环过程中化学稳定、晶型稳定；在室温至1 100 ℃范围内的平均热膨胀系数为1.16 × 10^-5 K^-1，与SDC及LSGM的热膨胀系数十分接近。阴极/电解质混合粉体1 200 ℃煅烧10 h，XRD未检测到新物质；SEM显示复合层断面界面清晰，没有相互扩散现象。该体系有望成为以SDC或LSGM为电解质的中温固体氧化物燃料电池合适的阴极材料。