Riboflavin as a green sorbent in dispersive micro-solid-phase extraction of several pesticides from fruit juices combined with dispersive liquid–liquid microextraction

A vortex-assisted dispersive micro-solid-phase extraction procedure using a new and green sorbent was developed as a simple, fast, and efficient sample preparation method for the extracting five pesticides in several fruit juice samples. In this study, for the first time, riboflavin was used as an efficient sorbent. A few milligrams of riboflavin was directly added into the aqueous solution containing the analytes to adsorb them. After adsorption the analytes, they were desorbed and more concentrated by a dispersive liquid–liquid microextraction procedure. The influence of several effective parameters such as amount of riboflavin, pH, vortex time, eluent nature and volume, and extraction solvent type and volume on the extraction efficiency was investigated. In optimal conditions, linear ranges of the calibration curves were broad. The limits of detection and quantification were attained in the ranges of 0.56–1.5  and 1.9–0.52 ng mL⁻¹, respectively. The proposed method demonstrated to be suitable for concurrent extraction of the studied pesticides in various fruit juice samples with high enrichment factors (320–360) and precision (relative standard deviation ≤7.8% for intra- [n = 6] and interday [n = 4] precisions at a concentration of 25 ng mL⁻¹ of each pesticide).     

PKI域间互操作性研究

Internet作为电子商务和数字通信的基础平台面临着很多安全威胁.PKI技术为安全电子交易提供了保障.电子商务中.在不同的PKI域之间需要实现互操作.本文提出了一种不使用交叉证书的情况下连接多个独立的PKI域的新方法.该方法是将多个PKl域整合成一个PKI域来实现PKl域之间的互操作.本文采用形式化的方法来描述合并过程.     

Efficient regeneration of aldehydes from their corresponding 1,3-oxathiolanes in the absence of solvent

A mild and efficient method for the oxidative deprotection of 1,3-oxathiolanes with Fe（NO₃）₃·9H₂O and Cu（NO₃）₂·3H₂O in the absence of solvent is reported.     

墨水书写时间的鉴定

介绍了墨水书写时间的鉴定,其中包括墨水书写时间鉴定的依据,取样以及样品制备技术,墨水书写时间鉴定的方法,包括化学分析方法、光度法、薄层色谱法、气相色谱法、高效液相色谱法、质谱法、毛细管电泳法及色谱质谱联用法。     

甲基丙烯酸丁酯接枝纤维素的制备

为开发纤维素基吸油材料,以棉浆粕为基材、甲基丙烯酸丁酯(BMA)为单体、乙二醇二甲基丙烯酸酯为交联剂,采用悬浮接枝聚合法合成了BMA接枝纤维素的聚合物。采用红外光谱(FT-IR)、X射线衍射(XRD)、扫描电镜(SEM)、热重(TG)、差热(DSC)等手段对所得吸油材料结构进行了表征。考察了引发剂的种类及用量、接枝单体及交联剂用量、反应温度、反应时间等因素对BMA接枝纤维素聚合物的接枝聚合反应性能及吸油性能的影响。结果表明:当m(棉浆粕)∶m(K2S2O8)∶m(BMA)∶m(乙二醇二甲基丙烯酸酯)=1∶0.025∶1.5∶0.005,75℃下恒温反应6 h,合成的BMA接枝纤维素的接枝率最高(36.2%),均聚物含量相对较低(5.8%),且吸油性能优良。     

少数民族地区大学物理化学教学方法探索

根据长期从事物理化学教学的经验,分析了物理化学教材和物理化学课程教学内容,根据教材和课程的教学要求以及物理化学课程的特点,就如何在少数民族地区大学做好物理化学课程的教学,进行宽、精、细的教育教学,为培养基础知识扎实,素质全面,思维宽阔、广泛,作风认真、细致、负责的基础型和创新型少数民族人才进行了探讨。     

基于数字证书的校园网安全通信模型的实现

用户名＋口令的简单身份认证方式以及在Intranet内基于B／S模式的信息以明文交换的方式已经无法满足校园网内部通信的安全性需求．本文在对相关理论知识进行介绍的基础上提出了基于数字证书的校园网安全通信模型，分析了模型的逻辑结构和工作流程，并具体实现了该模型．     

思维导图法在大学化学教学中的应用——以化学平衡为例

以化学平衡相关内容为例阐述了一种有效归纳大学化学内容的方法——思维导图法。该方法有助于大学生自主梳理学习内容,尽快整理和掌握学过的内容,激发学生的学习积极性,通过知识点归类和条理化培养学生的实践能力。     

V(HSO_4)_3 promoted oxidation of alcohols and trimethylsilyl,tetrahyropyranyl and methoxymethyl ethers with Cu(NO_3)_2·3H_2O in the absence of solvent

V(HSO_4)_3 has been found to be an efficient reagent for the promotion of the oxidation of alcohols and trimethylsilyl, tetrahydropyranyl and methoxymethyl ethers to their corresponding carbonyl compounds with Cu(NO_3)_2·3H_2O in the absence of solvent.