DPIS-RFQ系统的高频参数测试及功率锻炼

中国科学院近代物理研究所于2007年开始进行等离子体直接注入项目的预研。详细介绍了RFQ系统的高频参数测试的方法及结果,并针对高脉冲功率的测试提出通过标定定向耦合器来测试脉冲功率的方法。介绍了系统锻炼的情况,包括针对功率源末级和腔内电极的打火问题提出了理论的分析和改善的方法。高频参数的测试和载束实验证实整套系统满足加速器的设计要求。     

二维半导体中电子能谷研究新进展

物质材料伴随着体系维度的降低往往会衍生出新的特性,展现丰富的物理现象,并带来新奇可观测及可操控的量子态。作为新兴超薄半导体出现的二维六族过渡金属硫化物,除了具有区别于块体材料的直接能隙,在其第一布里渊区里还存在着简并但不等价的分立能谷。由于体系中空间反演对称性的破缺,在这些能谷里,电子及空穴具有非零且相反的轨道磁矩以及贝里曲率,从而提供了利用外场对能谷自由度进行量子调控的前提。文章对二维六族过渡金属硫化物中能谷电子学的发展进行了介绍,并对未来的潜在发展方向做出一些展望。     

Comprehensive gas chromatography coupled to mass spectrometry for the separation of pesticides in a very complex matrix

The present research is focused on the development of a comprehensive two-dimensional gas chromatography–rapid scanning quadrupole mass spectrometric (GC x GC-qMS) methodology for the analysis of trace-amount pesticides contained in a complex real-world sample. Reliable peak assignment was carried out by using a recently developed, dedicated pesticide MS library (for comprehensive GC analysis), characterized by a twin-filter search procedure, the first based on a minimum degree of spectral similarity and the second on the interactive use of linear retention indices (LRI). The library was constructed by subjecting mixtures of commonly used pesticides to GC x GC-qMS analysis and then deriving their pure mass spectra and LRI values. In order to verify the effectiveness of the approach, a pesticide-contaminated red grapefruit extract was analysed. The certainty of peak assignment was attained by exploiting both the enhanced separation power of dual-oven GC x GC and the highly effective search procedure.     

基质固相分散-气相色谱串联质谱法测定孕妇血清中22种持久性有机污染物

建立了基质固相分散技术-气相色谱串联质谱法(MSPD-GC-QQQ-MS/MS)同时测定孕妇血清中22种持久性有机污染物(艾氏剂、狄氏剂、七氯、灭蚁灵、六六六、多氯联苯和滴滴涕)的方法.血清样品与C18吸附剂混合净化,正己烷溶液洗脱,GC-QQQ-MS/MS测定.采用Agilent J&W DB-35ms (30 m×0.25 mm×0.25 μm)分离,正电子离子源(EI+)模式电离,多反应监测模式(MRM)下进行测定,外标法定量.结果表明,在1.0～1000.0 ng/mL的范围内,22种持久性有机污染物的相关系数均大于0.99;在2.0和20.0 ng/mL的添加水平下,所有持久性有机污染物回收率均在75％～ 115％之间,方法定量限均≤0.15 ng/mL.在比较基质固相分散(MSPD)、液液萃取(LLE)和固相萃取(SPE)提取和净化实际加标血清样品时,MSPD方法的结果中位数更接近真实值,且离散程度最小.本方法适用于人类血清中多种持久性有机物的定性和定量分析.     

Application of a highly sensitive magnetic solid phase extraction for phytochemical compounds in medicinal plant and biological fluids by ultra‐high performance liquid chromatography coupled with quadrupole time‐of‐flight tandem mass spectrometry

A highly sensitive method using reduced graphene oxide with iron oxide (rGO/Fe₃O₄) as the sorbent in magnetic SPE has been developed for the purification of five anthraquinones (emodin, rhein, aloeemodin, physcion, and chrysophanol) in rhubarb and rat urine by ultra‐HPLC coupled with quadrupole TOF/MS. The extraction was accomplished by adding trace amount rGO/Fe₃O₄ suspension to 200 mL of aqueous mixture, and the excellent adsorption capacity of the nanoparticles was fully demonstrated in this procedure. Under the optimized conditions, the calibration curves were linear in the concentration range of 0.05–27.77 ng/mL with correlation coefficients varying from 0.9902 to 0.9978. The LODs ranged from 0.28 to 58.99 pg/mL. The experimental results indicated that the proposed method was feasible for the analysis of anthraquinones in rhubarb and urine samples.     

Metabolic profiling of β-cryptoxanthin and its fatty acid esters by supercritical fluid chromatography coupled with triple quadrupole mass spectrometry

In this study, a high-throughput and high-sensitivity profiling system for β-cryptoxanthin (βCX) and β-cryptoxanthin fatty acid ester (βCXFA) was constructed by supercritical fluid chromatography (SFC) coupled with triple quadrupole mass spectrometry (QqQMS). βCX and nine βCXFAs were successfully separated within 20 min using a column packed with octadecylsilyl-bonded silica particles. The limit of detection was 540 fmol for the free form and 32-130 fmol for the esterified forms. These results demonstrate that both the throughput and the sensitivity of this SFC-QqQMS system are considerably higher than those of conventional methods. When this system was applied for the analysis of Citrus unshiu, βCX and five βCXFAs were directly detected with much simpler sample pre-preparation. The analysis of other citrus fruits indicated that the βCXFA profiles varied with their breed variety. Furthermore, gas chromatography-mass spectrometry was used to analyze total fatty acid profiles in C. unshiu, and the results revealed that the profiles of fatty acids located in βCXFA were distinct. This is the first report on the analysis of βCX and its fatty acid derivatives by SFC-QqQMS. The profiling system developed in this study will be a powerful tool for investigating xanthophyll fatty acid esters.     

衍生化-气相色谱-三重四极杆质谱法同时测定粮食作物中三氯甲基吡啶及其代谢物残留

建立了粮食作物中三氯甲基吡啶及其代谢物6-氯吡啶甲酸的衍生化-气相色谱-三重四极杆质谱(GC-MS/MS)检测方法。选取高粱、小麦、玉米及爆谷等典型的粮食作物,采用酸性乙腈提取,以浓硫酸作为三氯甲基吡啶代谢物的衍生化试剂,优化了衍生化反应的最佳反应条件,并使用GC-MS/MS分析,以内标法对三氯甲基吡啶及其代谢物进行定量检测。结果表明,在0.025～0.4 mg/L范围内,线性关系良好,相关系数(r²)均大于0.995,在3个不同添加水平下的平均回收率在80.4%～98.4%之间,相对标准偏差(RSD)在1.0%～10.1%之间。该方法操作简单、高效,灵敏度高,抗干扰能力强,回收率和重复性良好,能够满足粮食作物中三氯甲基吡啶及其代谢产物残留量的检测要求。     

高效液相色谱-串联质谱法同时测定贝类中22种农药残留

建立了高效液相色谱-三重四极杆质谱（HPLC-MS/MS）同时测定贝类中22种农药残留的分析方法。样品经含0.1%（v/v）甲酸的乙腈提取，N-丙基乙二胺（PSA）和石墨化碳黑（GCB）净化，然后采用ACE UltraCore 2.5 SuperC18柱（100 mm×2.1 mm，2.5 μm）分离，以甲醇-0.1%（v/v）甲酸水溶液为流动相梯度洗脱，流速为0.4 mL/min，柱温为35 ℃，然后以电喷雾电离（ESI）源，在多反应监测（MRM）、正离子模式下，采用三重四极杆质谱检测。22种农药在各自的线性范围内线性关系良好，相关系数均大于0.997，检出限为0.1~0.3 μg/kg，定量限为0.3~1.0 μg/kg。在3个添加水平下，22种农药的平均回收率为65.2%~109.4%，相对标准偏差为1.3%~15.2%（n=6）。该方法操作简单，快速，准确度高，灵敏度高，可用于贝类中22种农药残留的同时检测。     

Positive chemical ionization triple‐quadrupole mass spectrometry and ab initio computational studies of the multi‐pathway fragmentation of phthalates

We report the first positive chemical ionization (PCI) fragmentation mechanisms of phthalates using triple‐quadrupole mass spectrometry and ab initio computational studies using density functional theories (DFT). Methane PCI spectra showed abundant [M + H]⁺, together with [M + C₂H₅]⁺ and [M + C₃H₅]⁺. Fragmentation of [M + H]⁺, [M + C₂H₅]⁺ and [M + C₃H₅]⁺ involved characteristic ions at m/z 149, 177 and 189, assigned as protonated phthalic anhydride and an adduct of phthalic anhydride with C₂H₅⁺ and C₃H₅⁺, respectively. Fragmentation of these ions provided more structural information from the PCI spectra. A multi‐pathway fragmentation was proposed for these ions leading to the protonated phthalic anhydride. DFT methods were used to calculate relative free energies and to determine structures of intermediate ions for these pathways. The first step of the fragmentation of [M + C₂H₅]⁺ and [M + C₃H₅]⁺ is the elimination of [R? H] from an ester group. The second ester group undergoes either a McLafferty rearrangement route or a neutral loss elimination of ROH. DFT calculations (B3LYP, B3PW91 and BPW91) using 6‐311G(d,p) basis sets showed that McLafferty rearrangement of dibutyl, di(‐n‐octyl) and di(2‐ethyl‐n‐hexyl) phthalates is an energetically more favorable pathway than loss of an alcohol moiety. Prominent ions in these pathways were confirmed with deuterium labeled phthalates. Copyright © 2010 John Wiley & Sons, Ltd.     

固相萃取-大体积程序升温进样气相色谱-三重四极杆串联质谱测定饮用水中3种挥发性N-亚硝胺

建立了固相萃取大体积程序升温进样气相色谱-三重四极杆质谱联用（GC-QqQ-MS/MS）同时测定饮用水中N-亚硝基二甲胺、N-亚硝基甲基乙基胺及N-亚硝基二乙基胺的分析方法。用椰壳活性炭固相萃取小柱萃取水样中待测物组分，少量二氯甲烷洗脱、无水硫酸钠脱水，大体积程序升温进样，气相色谱-三重四极杆质谱联用仪进行多反应监测（MRM）模式检测，外标法定量。3种N-亚硝胺在1~50 ng/L范围内线性关系良好，相关系数（r²）均大于0.999，在饮用水中进行10、20和50 ng/L水平的添加，3种待测物平均加标回收率为94.8%~109%，相对标准偏差（RSD）为4.44%~8.10%（n=5），定量限（LOQ）为0.08~0.7 ng/L。该法灵敏、准确、简单、可靠，适用于饮用水中3种N-亚硝胺组分的痕量检测。