仪器分析综合实验:固相微萃取纤维的制备及在有机氯农药富集和分析中的应用*

设计了一个综合性仪器分析实验:固相微萃取纤维的制备及应用。实验内容包括微孔有机聚合物固相微萃取纤维的制备、红外光谱表征、固相微萃取实验条件优化和气相色谱测定有机氯农药含量等4个部分。通过综合运用多种仪器分析实验手段,加深了学生对分离富集技术的了解,巩固了学生对仪器分析课程中的气相色谱法、红外光谱法相关内容的掌握,培养学生构建一个完整、科学的仪器分析操作流程,形成综合性思维能力。     

Determination of Anthelmintic and Antiprotozoal Drug Residues in Fish Using Liquid Chromatography-Tandem Mass Spectrometry

The objective of this study is to develop a comprehensive and simple method for the simultaneous determination of anthelmintic and antiprotozoal drug residues in fish. For sample preparation, we used the “quick, easy, cheap, effective, rugged, and safe” (QuEChERS) method with a simple modification. The sample was extracted with water and 1% formic acid in acetonitrile/methanol (MeCN/MeOH) (95:5, v/v), followed by phase separation (salting out) with MgSO₄ and NaCl (4:1, w/w). After centrifugation, an aliquot of the extract was purified by dispersive solid-phase extraction (d-SPE) prior to liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The method was validated at three concentration levels for all matrices, in accordance with the Codex guidelines (CAC/GL-71). Quantitative analysis was performed using the method of matrix-matched calibration. The recoveries were between 60.6% and 119.9%, with coefficients of variation (CV) <30% for all matrices. The limit of quantitation (LOQ) of the method ranged from 0.02 μg kg⁻¹ to 4.8 μg kg⁻¹ for all matrices. This comprehensive method can be used for the investigation of both anthelmintic and antiprotozoal drugs belonging to different chemical families in fishery products.     

Strategies in protein sequencing and characterization: Multi-enzyme digestion coupled with alternate CID/ETD tandem mass spectrometry

A strategy based on a simultaneous multi-enzyme digestion coupled with electron transfer dissociation (ETD) and collision-induced dissociation (CID) was developed for protein sequencing and characterization, as a valid alternative platform in ion-trap based proteomics. The effect of different proteolytic procedures using chymotrypsin, trypsin, a combination of both, and Lys-C, was carefully evaluated in terms of number of identified peptides, protein coverage, and score distribution. A systematic comparison between CID and ETD is shown for the analysis of peptides originating from the in-solution digestion of standard caseins. The best results were achieved with a trypsin/chymotrypsin mix combined with CID and ETD operating in alternating mode. A post-database search validation of MS/MS dataset was performed, then, the matched peptides were cross checked by the evaluation of ion scores, rank, number of experimental product ions, and their relative abundances in the MS/MS spectrum. By integrated CID/ETD experiments, high quality-spectra have been obtained, thus allowing a confirmation of spectral information and an increase of accuracy in peptide sequence assignments. Overlapping peptides, produced throughout the proteins, reduce the ambiguity in mapping modifications between natural variants and animal species, and allow the characterization of post translational modifications. The advantages of using the enzymatic mix trypsin/chymotrypsin were confirmed by the nanoLC and CID/ETD tandem mass spectrometry of goat milk proteins, previously separated by two-dimensional gel electrophoresis.     

两种β-环糊精单臂键合固定相液相色谱法拆分三唑类手性农药

以有序介孔材料SBA-15为基质,β-环糊精和氨基β-环糊精为配体,通过环糊精端口的羟基和氨基与3-异氰酸丙基三乙氧基硅烷偶联剂上活泼的异氰酸酯基之间的加成反应,制备了2种不同单键合臂的β-环糊精修饰SBA-15手性固定相(CDSP和NCDSP),它们分别含有稳定的氨基甲酸酯基和脲基键合臂.在反相高效液相色谱模式下,以灭菌唑、烯唑醇、己唑醇和戊唑醇等10种常见的三唑类手性农药为探针,考察了CDSP和NCDSP的基本手性色谱性能.研究结果表明,2种新固定相对三唑类农药对映体均有较好的快速拆分能力,所需分离时间较短(30 min),其中灭菌唑和烯唑醇的选择性因子(α)分别为1.29和1.28,分离度分别达到3.84和3.23.采用甲醇、乙腈和水组成的简单流动相,室温下在CDSP和NCDSP上分别拆分了9种和8种三唑类手性农药对映体.研究发现拥有适当大小和手性碳连接羟基的三唑类农药在上述2种新固定相上有较好的拆分效果,说明固定相上的环糊精配体对溶质的包结、氢键和空间位阻等协同作用对空间手性识别有重要贡献.不同批次CDSP和NCDSP的键合量分别为0.139~0.156和0.120~0.137μmol/m2,表明2种固定相的制备方法有较好的重现性.与涂覆型纤维素商品柱相比,新的脲基环糊精固定相性能更稳定,反相色谱实用性更强,且制备方法简便,成本较低,在三唑类手性农药对映体残留量检测中具有良好的应用前景.     

An efficient and fast microwave-assisted extraction method developed for the simultaneous determination of 18 organochlorine pesticides in sediment

An efficient and fast microwave-assisted extraction (MAE) method followed by gas chromatographic separation with mass spectrometric detection (GC–MS) was developed for the extraction of 18 organochlorine pesticides (OCPs) from sediment. Parameters affecting the MAE procedure such as the type and volume of the extraction solvent, irradiation power, temperature and irradiation time were successfully optimised. Under the optimal conditions, extraction efficiencies in the range of 73.4–119% were obtained with THF–HEX (9:1, v/v) for all OCPs studied. The method was linear over the range of 2.9–5000 ng g^?1 with determination coefficients (r²) higher than 0.992 for all analytes. The limits of detection, LODs (S/N = 3), obtained varied from 1.0 to 2.2 ng g^?1 and limits of quantification, LOQs (S/N = 10) were between 2.9 and 6.8 ng g^?1. The proposed method was successfully applied to the analysis of real sediment samples and acceptable recoveries from 70.1 to 124% with RSDs ≤14.8% were obtained. 10 OCPs were determined below their LOQ and 8 OCPs in the range of 124–2830 ng g^?1. The MAE method was compared with Soxhlet, shake flask and ultrasonic solvent extraction techniques. Thus, the MAE–GC–MS method could efficiently be used for selective extraction and quantification of the target analytes from the complex sediment matrices.     

适体及其在分析检测中的应用

适体的出现使人们认识到核酸不仅可以作为遗传信息存储和转运的载体,还可以作为一种具有识别功能的分子。适体对目标物的识别具有高选择性和高亲和力,还有很多其它传统识别分子所不具备的优点,这使得其在分析检测领域得到关注和广泛应用。对适体的筛选过程、特点以及其在分析检测方面的主要应用进行综述。     

Determination of multi‐pesticide residue in tobacco using multi‐walled carbon nanotubes as a reversed‐dispersive solid‐phase extraction sorbent

A multi‐pesticide residue determination method based on a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method using multiwalled carbon nanotubes as reversed‐dispersive solid‐phase extraction material was validated in 37 representative pesticides in tobacco. Determination was performed using liquid chromatography with tandem mass spectrometry in multiple reaction monitoring mode. Three major types of tobacco leaf samples, namely, flue‐cured, burley, and oriental tobacco were studied and compared. Three factors (extraction time, external diameter, and amount of extraction material used) that could affect the performance of multi‐walled carbon nanotubes were investigated. Optimization of sample preparation and determination allowed recoveries between 70.8 and 114.8% for all 37 pesticides with < 20.0% relative standard deviations at three spiking levels of 20, 50, and 200 μg/kg. The limits of quantification and limits of detection for the 37 pesticides ranged within 0.46–28.57 and 0.14–8.57 μg/kg at a signal‐to‐noise ratio of 10 and 3, respectively.     

Development of a simple combining apparatus to perform a magnetic stirring-assisted dispersive liquid–liquid microextraction and its application for the analysis of carbamate and organophosphorus pesticides in tea drinks

This study introduced a simple combining apparatus for performing a magnetic stirring-assisted dispersive liquid–liquid microextraction (MSA-DLLME) for the detection of trace carbamate and organophosphorus pesticides in tea drinks coupled with high performance liquid chromatography. The simple combining apparatus was made up of a sample vial and a cut plastic dropper. The bulb end of the cut plastic dropper was inserted into the neck of the sample vial and the open tip end of the plastic dropper was then cut to an appropriate length. The combining apparatus made was then used to perform the MSA-DLLME. In this experiment, 1-octanol was injected into the tea drink sample solution and the extraction process accelerated by magnetic agitation. The sample solution turned clear and separated into two layers after leaving it alone for several minutes. The cut plastic dropper was gently put down into the sample vial, and then the liquid level of the sample solution elevated up to the tip of the plastic dropper for the collection of low-density extractant. Finally, the collected extractant was drawn out by a microsyringe and injected into the high performance liquid chromatography-diode-array detector for analysis. A series of extraction parameters were investigated and optimized. Under the most favorable conditions, high enrichment factors were obtained for carbofuran, carbaryl and isocarbophos (between 130 and 185). The limits of detection (S/N = 3) were in the range of 0.13–0.61 μg L⁻¹, and the relative standard deviation varied below 7.8% (n = 5). Additionally, good recoveries were obtained between 79.4% and 114.4% in the three tea drinks. The simple combining apparatus utilized in this MSA-DLLME method was shown to be economical, fast, and convenient for the collection of low density extractant.     

Analytical chemistry of the persistent organic pollutants identified in the Stockholm Convention: A review

Persistent organic pollutants (POPs) are major environmental concern due to their persistence, long-range transportability, bio-accumulation and potentially adverse effects on living organisms. Analytical chemistry plays an essential role in the measurement of POPs and provides important information on their distribution and environmental transformations. Much effort has been devoted during the last two decades to the development of faster, safer, more reliable and more sensitive analytical techniques for these pollutants. Since the Stockholm Convention (SC) on POPs was adopted 12 years ago, analytical methods have been extensively developed. This review article introduces recent analytical techniques and applications for the determination of POPs in environmental and biota samples, and summarizes the extraction, separation and instrumental analyses of the halogenated POPs. Also, this review covers important aspects for the analyses of SC POPs (e.g. lipid determination and quality assurance/quality control (QA/QC)), and finally discusses future trends for improving the POPs analyses and for potential new POPs.     

An Adsorption Procedure for Determining the Level of Organophosphorus Pesticide Residues in Pond Water

Abstract

A procedure for the accumulation of phosphorus-containing degradation products of organophosphorus pesticides from water by elution of ion-associates of dialkylphosphorus anions with tetraphenylarsonium cation adsorbed onto an activated carbon micro-column is described.

Using a 50cm³ sample volume at a concentration of 1 μcm^?3 the average accumulation recoveries (%±S.D.) were 81±11 and 91±8 for diethyl and dimethyl phosphorodithioates, 69±10 and 66±10 for the corresponding phosphorothioates and 33±13 and 13±6 for the analogous phosphates. A decrease in these values was caused by the presence of common inorganic anions and at lower concentrations of the analysed species. At a detection limit of 20 ng cm^?3 the recovery was 20–30%. Despite of low accumulation recoveries the minimum detectable concentration of these anions was decreased below 0.1 ng cm^?3 by handling 1 dm³ sample volumes.

The procedure was applied for the analysis of dialkyl phosphorothioates and dialkyl phosphorodithioates in the water from, three ponds located in an apple orchard before and after seasonal application of organophosphorus pesticides.