The impact of insecticides containing deltamethrin and cyfluthrin on the composition of surface compounds in the larvae,females and males of Tenebrio molitor

This paper presents the effect of insecticides on the composition of the surface compounds of one of the most harmful insects, Tenebrio molitor, by analysis using GC–MS. As a result of the use of insecticides, the composition of the chemical compounds on the surface of insects changes, depending on the insecticides used. The most numerous groups of the marked compounds were fatty acids, alkanes, esters and sterols. The content of the identified compounds in the larvae increased at both 24 and 48 h after the application of insecticides, in comparison with the control samples. The content of identified compounds in the samples taken from the females increased 24, 48 and 72 h after the application of insecticides in comparison with the control samples. By contrast, in samples prepared from males, the content of identified compounds decreased 24 h after the application of insecticides, compared with the control samples. The highest content of chemical compounds was for fatty acids and alkanes after the use of insecticides. The content of fatty acids after the application of the insecticide with deltamethrin was 62.1 ± 3.3–466.9 ± 5.9 μg/g, and after the application of the insecticide with cyfluthrin was 49.9 ± 1.9–458.3 ± 4.2 μg/g. However, the content of alkanes after the use of deltamethrin was 115.6 ± 4.2–4672.0 ± 32.1 μg/g, and after the use of cyfluthrin was 189.4 ± 3.8–3975.0 ± 10.2 μg/g.     

Validation of a robust and rapid liquid chromatography tandem mass spectrometric method for the quantitative analysis of navitoclax

The Bcl-2 family small molecule inhibitor navitoclax is being clinically evaluated to treat multiple cancers including lymphoid malignancies and small cell lung cancer. A sensitive and reliable method was developed to quantitate navitoclax in human plasma using liquid chromatography with tandem mass spectrometry with which to perform detailed pharmacokinetic studies. Sample preparation involved protein precipitation using acetonitrile. Separation of navitoclax and the internal standard, navitoclax-d8, was achieved with a Waters Acquity UPLC BEH C₁₈ column using isocratic flow over a 3 min total analytical run time. A SCIEX 4500 triple quadrupole mass spectrometer operated in positive electrospray ionization mode was used for the detection of navitoclax. The assay range was 5–5,000 ng/ml and proved to be accurate (89.5–104.9%) and precise (CV ≤ 11%). Long-term frozen plasma stability for navitoclax at −70°C was at least 43 months. The method was applied for the measurement of total plasma concentration of navitoclax in a patient receiving a 250 mg daily oral dose.     

湿法消解-原子荧光法测定全血中硒

以全血样品为原料,探讨湿法消解-原子荧光法测定全血中的硒含量。血样经硝酸-高氯酸消解后,用硼氢化钠将硒还原成硒化氢,由氩气载入原子化器,产生的原子荧光强度与试液中硒元素含量在一定范围内呈正比,外标法定量。以消解效率为指标,优化样品的消解条件,测定血中硒在0-10μg/L范围内线性情况良好,相关系数为0.9992,最低检出限为0.143μg/L,相对标准偏差为1.51%-1.58%,平均加标回收率为90.86%-104.62%。血中硒的原子荧光测定法灵敏度高,精密度和稳定性好,可应用于血中硒的生物监测。     

Sample preparation,instrumental analysis,and natural distribution of complex organic pollutants in the wastewater from unconventional gas production

Large amounts of flowback and produced water (FPW) have been generated from hydraulic fracturing process for the production of unconventional gas such as shale gas. Complex organic pollutants are abundantly present in FPW with revealed toxicity to aquatic organisms and these contaminants may transfer into surrounding aquatic environment. Characterization and determination of complicated organic pollutants in FPW remains a challenge due to its complex composition and high salinity matrix. This review article covers the progress of recent 5 years regarding the sample preparation and instrumental analysis methods and thus summarizes the advantages and disadvantages of these methods for critical analysis of organic contaminants in FPW samples. Furthermore, the natural distribution of detected organic compounds and their transformation were reviewed and discussed to enhance the understanding of spatial and temporal behaviors of these organic pollutants in natural environment, paving the way for future development of pollution control policies and strategies. Enlightened by the studies of FPW contamination in the US, the investigations of FPW contamination in China continued to grow due to rapidly growing production of shale gas in China and resulted pollution.     

Developing the Low-Temperature Oxidation Mechanism of Cyclopentane: An Experimental and Theoretical Study

At present, the reactivity of cyclic alkanes is estimated by comparison with acyclic hydrocarbons. Due to the difference in the structure of cycloalkanes and acycloalkanes, the thermodynamic data obtained by analogy are not applicable. In this study, a molecular beam sampling vacuum ultraviolet photoionization time-of-flight mass spectrometer (MB-VUV-PI-TOFMS) was applied to study the low-temperature oxidation of cyclopentane (CPT) at a total pressure range from 1–3 atm and low-temperature range between 500 and 800 K. Low-temperature reaction products including cyclic olefins, cyclic ethers, and highly oxygenated intermediates (e. g., ketohydroperoxide KHP, keto-dihydroperoxide KDHP, olefinic hydroperoxides OHP and ketone structure products) were observed. Further investigation of the oxidation of CPT – electronic structure calculations – were carried out at the UCCSD(T)-F12a/aug-cc-pVDZ//B3LYP/6-31+ G(d,p) level to explore the reactivity of O₂ molecules adding sequentially to cyclopentyl radicals. Experimental and theoretical observations showed that the dominant product channel in the reaction of CPT radicals with O₂ is HO₂ elimination yielding cyclopentene. The pathways of second and third O₂ addition – the dissociation of hydroperoxide – were further confirmed. The results of this study will develop the low-temperature oxidation mechanism of CPT, which can be used for future research on accurately simulating the combustion process of CPT.     

热解吸反压低温等离子体电离源质谱检测食品中的邻苯二甲酸酯EI北大核心CSCD

基于低温等离子体设计并实现了一套热解吸反压低温等离子体电离(TD-iLTPI)装置。TD-iLTPI装置由热解吸模块和电离源模块集成在一个π型四通管上组成,进样探针取得样品后插入热解吸模块使其气化,之后随载气进入电离区域被电离。iLTPI内部的针电极接交流电,外部的环形电极接地,电极连接方式与LTP相反。该文对热解吸反压低温等离子体电离源进行了参数的优化,并与三重四极杆质谱联用检测了12种代表性的邻苯二甲酸酯,同时考察了TD-iLTPI-MS的分析性能,并对含有邻苯二甲酸酯的实际样品进行了检测。结果表明,邻苯二甲酸丁苄酯(BBP)的标准曲线具有良好的线性相关系数(R;=0.9958),加标回收率为89.7%~116.8%,相对标准偏差为4.5%~8.2%,对邻苯二甲酸酯的检出限也远低于其他敞开式离子源。对白酒、果汁、面包、奶酪和黄油中的邻苯二甲酸酯进行了快速筛查,并定量检测了果汁中的邻苯二甲酸丁苄酯。     

Dielectric loss and electromagnetic absorption performance study of 1T/2H-MoS2/Mo2S3 nanocomposites with different ratios

High dielectric loss materials have an important application in electromagnetic (EM) absorption fields. In this paper, the ternary nanocomposites: 1T/2H-MoS₂/Mo₂S₃ with heterogeneous interfaces are synthesized by hydrothermal method. XRD, XPS, FTIR, SEM, and TEM measurements are applied to study the structure, morphology, and composition. The frequency spectra of complex permittivity (ε_r-f) are measured in 2–18 GHz by vector network analyzer. The results show that the nanocomposites have higher dielectric loss angle tangents than the reported 2H-MoS₂ absorbers. Based on the ε_r-f spectra, the reflection loss-frequency curves ($RL-f$) are simulated at given thicknesses. An effective absorption bandwidth of 5.2 GHz (12.8–18 GHz) and a $RL$ peak of −29.49 dB are achieved in a thin thickness of 1.62 mm, which are comparable to the reported 2H-MoS₂ absorbers with complex composition, showing that the 1T/2H-MoS₂/Mo₂S₃ nanocomposites have great application potential as an EM wave absorber in the K_u band.     

A simple,rapid and sensitive method based on modified multiwalled carbon nanotube for preconcentration and determination of lead ions in aqueous media in natural pHs

In this study, multiwalled carbon nanotube (MWCNT) was modified by the pyridine group using a silane agent and characterized by infrared spectroscopy (IR), thermal analysis (TG/DTA), and elemental analysis (CHN) and scanning electron microscopy (SEM). The application of this sorbent was investigated in determination of lead ions in aqueous samples, using flame atomic absorption spectrometry (FAAS). Through this study, different parameters such as pH and sample flow rate on adsorption process and eluent concentration, volume and flow rate were optimized. The limit of detection (LOD), the relative standard deviation and the recovery of the method were 2 ng mL^?1, 1.3% and 99.7%, respectively. Two standard reference materials (NIST 1571 and NIST 1572) were used to verify accuracy of this method. Finally, the sorbent was successfully applied for extraction and determination of low levels of Pb(II) ions in aqueous samples.     

Mass spectrometry combined with affinity probes for the identification of CP4 EPSPS in genetically modified soybeans

Sample preparation methods used for genetically modified organisms (GMOs) analysis are often time consuming, require extensive manual manipulation, and result in limited amounts of purified protein, which may complicate the detection of low‐abundance GM protein. A robust sample pretreatment method prior to mass spectrometry (MS) detection of the transgenic protein (5‐enolpyruvylshikimate‐3‐phosphate synthase [CP4 EPSPS]) present in Roundup Ready soya is investigated. Liquid chromatography‐multiple reaction monitoring tandem MS (nano LC‐MS/MS‐MRM) was used for the detection and quantification of CP4 EPSPS. Gold nanoparticles (AuNPs) and concanavalin A (Con A)‐immobilized Sepharose 4B were used as selective probes for the separation of the major storage proteins in soybeans. AuNPs that enable the capture of cysteine‐containing proteins were used to reduce the complexity of the crude extract of GM soya. Con A‐sepharose was used for the affinity capture of β‐conglycinin and other glycoproteins of soya prior to enzymatic digestion. The methods enabled the detection of unique peptides of CP4 EPSPS at a level as low as 0.5% of GM soya in MRM mode. Stable‐isotope dimethyl labeling was further applied to the quantification of GM soya. Both probes exhibited high selectivity and efficiency for the affinity capture of storage proteins, leading to the quantitative detection at 0.5% GM soya, which is a level below the current European Union's threshold for food labeling. The square correlation coefficients were greater than 0.99. The approach for sample preparation is very simple without the need for time‐consuming protein prefractionation or separation procedures and thus presents a significant improvement over existing methods for the analysis of the GM soya protein.