Determination of Pesticide Residues in Fruit and Vegetables by High-Performance Liquid Chromatography–Tandem Mass Spectrometry with Multivariate Response Surface Methodology

Multivariate response surface methodology optimization using Placket–Burman and Box–Behnken designs were respectively used for the screening and optimization of significant factors for liquid chromatography–tandem mass spectrometry. Consequently, the optimized instrument successfully improved the sample preparation protocol and the method was validated. However, modified QuEChERS dispersive solid phase extraction coupled with ionic liquid-based dispersive liquid–liquid microextraction were used for the determination of multi-pesticide residues in fruit and vegetable samples. The analysed samples were jackfruit, strawberries, cucumber, pears, and carrots. The resulting linearity range (5–400?µg/kg) and regression coefficient (>0.99) results were satisfactory. The 94.2 and 95.8% accuracy (89–138%) and precision (0–25%) results were satisfactory and within the recommended ranges (≤20%) and (70–120%), respectively. The limits of detection (0.01–0.54?µg/kg) and quantitation (0.03–1.79?µg/kg) were excellent. The matrix effects (≤?87%) for all analysed samples were not significant. The estimated measurement uncertainties (≤27%) were within the acceptable range (≤50%). Justifiably, the response surface methodology optimized instrument and sample treatment techniques were reliable and convenient for multi-pesticide residue determination in various fruits and vegetables.     

Initial study on the structure and photoluminescence properties of SiC films doped with Al

SiC films doped with aluminum (Al) were prepared by the rf-magnetron sputtering technique on p-Si substrates with a composite target of a single crystalline SiC containing several Al pieces on the surface. The as-deposited films were annealed in the temperature range of 400-800 °C under nitrogen ambient. The thin films have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the introduction of Al into films hinders crystalline formation process. And with the increase of annealing temperature, more Si particles are formed in the films, which strongly affect the optical absorption properties. The photoluminescence (PL) spectra of the samples show two peaks at 370 nm and 412 nm. The intensities of the PL peaks are evidently improved after Al doped. We attribute the origin of the two PL peaks to a kind of Si-related defect centres. The obtained results are expected to have important applications in modern optoelectronic devices.     

Design,Synthesis and Herbicidal Activity of Novel Sulfonylureas Containing Tetrahydrophthalimide Substructure

To develop novel sulfonylurea herbicides, a series of chlorsulfuron derivatives was designed and synthesized through introducing tetrahydrophthalimide substructure taken from protoporphyrinogen IX oxidase(PPO) inhibitors onto the critical 5-position of the classical benzene ring. The structures of title compounds were confirmed by infrared spectroscopy, ultraviolet spectroscopy, ¹H and ¹³C NMR spectrometry, mass spectrometry and elemental analysis. In addition, the crystal structure of compound II-5 was further determined by X-ray diffraction analysis. Bioassay results showed that individual compounds exhibited good herbicidal activities, especially compound II-8, which displayed 100% inhibition rate against Echinochloa crusgalli at 150 g/ha(1 ha=10⁴ m²) with the method of foliage spray in the pot experiment.     

Practical Security Analysis of Self-Referenced CV-QKD System in the Presence of Polarization Aberration

How to remove local oscillator (LO) side channel attacks has been a notoriously hard problem in continuous-variable quantum key distribution (CV-QKD). In the self-referenced CV-QKD schemes, the LO signal is locally generated at the receiver by an independent laser so that it is not co-transmitted with the quantum signal. This simple solution removes all LO side channels. However it also introduces some other practical vulnerabilities. Especially the polarization states of the quantum signal and LO signal may not be identical across the detector because of the presence of the polarization aberrations. Thus, the detection efficiency which is arguably the most critical experiment parameter of the practical implementation will be impaired. In this paper, we analyze the impact of polarization aberrations on the detection efficiency for CV-QKD and propose a self-referenced CV-QKD scheme in the presence of polarization aberrations by using an off-axis optical system. In the proposed scheme, the polarization states of the quantum signal would change with the off-axis optical system, thus impairing the heterodyne efficiency. Our security analysis shows a gap between the theory and practice of CV-QKD.

     

同位素稀释结合固相萃取快速测定动物组织中β2-兴奋剂

本文采用同位素稀释结合固相萃取技术,测定动物组织中特布他林、克伦特罗、沙丁胺醇、莱克多巴胺4种β2-兴奋剂。动物组织加同位素内标D3-沙丁胺醇和D9-克伦特罗,经甲醇提取后,正己烷脱脂,过SLS离子交换固相萃取柱净化,用BSTFA 1%(φ)TMCS衍生,采用GC/MS进行测定,内标法定量。实验表明,动物组织中添加2.0~10.0μg/kg浓度水平的β2-兴奋剂,方法回收率在72.5%~97.9%,相对标准偏差1.0%~11.4%,线性范围为12.5~500μg/L,样品中特布他林、克伦特罗、沙丁胺醇、莱克多巴胺最低检出限分别为0.5μg/kg、1.0μg/kg、0.5μg/kg和1.0μg/kg。     

Clifford分析中奇异积分的Poincaré-Bertrand置换公式

借助于多元复分析的思想，本文证明了Ｃｌｉｆｏｒｄ分析中奇异积分的Ｐｏｉｎｃａｒé－Ｂｅｒｔｒａｎｄ置换公式．     

实Clifford分析中六类拟Bochner-Martinelli型高阶奇异积分的几个问题

本文借助于Ｈａｄａｍａｒｄ关于高阶奇异积分有限部分的思想,研究关于实 Ｃｌｉｆｆｏｒｄ分析中六个类型(含一个奇点或二个奇点的)拟Ｂｏｃｈｎｅｒ－Ｍａｒｔｉｎｅｌｌｉ型高阶奇异积分的归纳定义、Ｈａｄａｍａｒｄ主值的存在性、递推公式、计算公式、微分公式、Ｐｏｉｎｃａｒｅ－Ｂｅｒｔｒａｎｄ置换公式以及拟Ｂ－Ｍ型高阶奇异积分的Ｈｏｌｄｅｒ连续性等问题．这些问题是研究单、多元复分析的学者们在研究奇异积分时,通常要涉及到的几个问题．     

Enhanced Enzymatic Synthesis of a Cephalosporin,Cefadroclor, in the Presence of Organic Co-solvents

In this study, we investigated the enzymatic synthesis of a semi-synthetic cephalosporin, cefadroclor, from 7-aminodesacetoxymethyl-3-chlorocephalosporanic acid (7-ACCA) and p-OH-phenylglycine methyl ester (D-HPGM) using immobilized penicillin G acylase (IPA) in organic co-solvents. Ethylene glycol (EG) was employed as a component of the reaction mixture to improve the yield of cefadroclor. EG was found to increase the yield of cefadroclor by 15–45%. An investigation of altered reaction parameters including type and concentration of organic solvents, pH of reaction media, reaction temperature, molar ratio of substrates, enzyme loading, and IPA recycling was carried out in the buffer mixture. The best result was a 76.5% conversion of 7-ACCA, which was obtained from the reaction containing 20% EG (v/v), D-HPGM to 7-ACCA molar ratio of 4:1 and pH 6.2, catalyzed by 16 IU mL^?1 IPA at 20 °C for 10 h. Under the optimum conditions, no significant loss of IPA activity was found after seven repeated reaction cycles. In addition, cefadroclor exhibited strong inhibitory activity against yeast, Bacillus subtilis NX-2, and Escherichia coli and weaker activity against Staphylococcus aureus and Pseudomonas aeruginosa. Cefadroclor is a potential antibiotic with activity against common pathogenic microorganisms.     

Simultaneous determination of phthalates and adipates in human serum using gas chromatography–mass spectrometry with solid‐phase extraction

A gas chromatography–mass spectrometry assay was developed and validated for the simultaneous determination of phthalates and adipates in human serum. The phthalates and adipates studied were dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzylbutyl phthalate, di‐2‐ethylhexyl phthalate, di‐n‐octyl phthalate, diethyl adipate, dibutyl adipate, diisobutyl adipate, bis(2‐butoxyethyl) adipate and di‐2‐ethylhexyl adipate, with diisooctyl phthalate as internal standard. The extraction and cleaning up procedure was carried out with solid‐phase extraction cartridges containing dimethyl butylamine groups, which showed extraction efficiencies over 88% for each analyte and the internal standard. The calibration curves obtained were linear with correlation coefficients greater than 0.98. For all analytes, the assay gave CV% values for intra‐day precision from 4.9 to 13.3% and mean accuracy values from 91.4 to 108.4%, while inter‐day precision was 5.2–13.4% and mean accuracy 91.0–110.2%. The limits of detection for the assay of phthalates and adipates were in the range 0.7–4.5 ng/mL. The method is simple, sensitive and accurate, and allows for simultaneous determination of nanogram levels of phthalates and adipates in human serum. It was successfully applied to an investigation on the level of phthalates and adipates in a non‐occupationally exposed population.