Design of two-dimensional biomimetic uranyl optrode and its application to the analysis of natural waters

A two-dimensional biomimetic optrode for the detection and quantification of uranium in natural waters was fabricated. The sensing element was designed by the inclusion of uranyl ion imprinted polymer particles into polymethyl methacrylate followed by casting a thin film on a glass slide without any plasticizer. The ion imprinted polymer material was prepared via covalent immobilization of the newly synthesised ligand 4-vinyl phenylazo-2-naphthol by thermal polymerization. Operational parameters such as pH, response time and the amount of sensing material were optimized. The response characteristics of the imprinted and the corresponding non-imprinted polymer inclusion optrodes of uranium were compared under optimum conditions. The imprinted polymer inclusion optrode responds linearly to uranium in the concentration range 0–1.0 μg mL⁻¹ with a detection limit of 0.18 μg mL⁻¹, which is much better than the solution studies using 4-vinyl phenylazo-2-naphthol (1.5 μg mL⁻¹). Triplicate determinations of 100 μg of uranium(VI) present in 250 mL of solution gave a mean absorbance of 0.018 with a relative standard deviation of 8.33%. The superior sensitivity of imprinted polymer inclusion optrode is exemplified by lower detection limits and broader dynamic range over non-imprinted polymer inclusion optrode. The developed imprinted polymer inclusion optrode was found to give stable and precise response for 3 months and can be used without any loss in sensitivity. The applicability for analysing ground, lake and tap-water samples collected in the vicinity of uranium deposits was successfully demonstrated.     

Trace determination of cobalt ion by using malic acid-malonic acid double substrate oscillating chemical system

A novel kinetic method for determination of trace amounts of cobalt ion was proposed and validated. The method is based on adding malic acid into classical Belousov-Zhabotinskii （B-Z） oscillating chemical system to form a double substrate one. The results showed that when the concentration of cobalt ion was in the range of 5.27× 10^-8 to 5.37 × 10^-12 mol L^-1, the change of the oscillating period was directly proportional to the negative logarithm of cobalt ion concentration. The sensitivity and precision of the developed method were quite satisfactory. The limit of detection was down to 5.20 × 10^-13 mol L^-1 which was a highest sensitivity found for determination of metal ions using oscillating chemical reaction so far. Some factors influencing the determination were also examined. The method has been successfully used to determine cobalt ion in vitamin B12 injection.     

Salicylate-spectrophotometric determination of inorganic monochloramine

On the basis of classical Berthelot reaction, a simple salicylate-spectrophotometric method was developed for quantitative determination of inorganic monochloramine in water samples. With the catalysis of disodium pentacyanonitrosylferrate(III), inorganic monochloramine reacts with salicylate in equimolar to produce indophenol compound which has an intense absorption at 703 nm. Parameters that influence method performance, such as pH, dosage of salicylate and nitroprussiate and reaction time, were modified to enhance the method performance. By using this method, inorganic monochloramine can be distinguished from organic chloramines and other inorganic chlorine species, such as free chlorine, dichloramine, and trichloramine. The molar absorptivities of the final products formed by these compounds are below ±3% of inorganic monochloramine, because of the α-N in them have only one exchangeable hydrogen atom, and cannot react with salicylate to produce the indophenol compound. The upper concentrations of typical ions that do not interfere with the inorganic monochloramine determination are also tested to be much higher than that mostly encountered in actual water treatment. Case study demonstrates that the results obtained from this method are lower than DPD-titrimetric method because the organic chloramines formed by chlorination of organic nitrogenous compounds give no response in the newly established method. And the result measured by salicylate-spectrophotometric method is coincident with theoretical calculation.     

有序介孔碳固相微萃取涂层测定水中氯苯类有机污染物

采用溶剂挥发自组装结合提拉法,在石墨纤维表面制备有序介孔碳(Ordered mesoporous cabon,OMC)涂层,并开展其对水中氯苯类有机污染物的固相微萃取(SPME)测定.扫描电镜(SEM)结果显示,制备的OMC涂层完整,与基体结合紧密,厚度约为7μm.透射电镜(TEM)、X射线衍射(XRD)和氮吸附脱附结果证实,OMC涂层具有规整二维六方特征,比表面积和孔容分别为369.7 m2/g和0.28 cm3/g.以氯苯类污染物为分析对象,采用顶空固相微萃取与氢火焰气相色谱联用法对OMC涂层的萃取性能进行全面的评价,优化萃取时间和温度、解吸时间、搅拌速率、离子强度及顶空体积等萃取条件,并与商品化涂层进行比对.结果表明,最佳萃取条件为:萃取时间30 min,萃取温度50℃,脱附时间2 min,盐浓度0.35 g/mL,顶空体积15 mL.在最佳萃取条件下,检出限在0.05～0.15 μg/L之间;在1～1000 μg/L线性范围内,线性关系良好;7次平行样测定的相对标准偏差为4.1％ ～6.4％.制备的OMC涂层的峰面积是商用聚二甲基硅氧烷/二乙烯基苯(Polydimethylsiloxane/divinylbenzene,PDMS/DVB)涂层的2倍,商用聚丙烯酸酯(Polyacrylate,PA)涂层的18倍.将此涂层应用于两种实际水样中,4种氯苯均未检出,添加浓度为20 μg/L时,样品回收率分别为99.4％～114.5％和92.3％～ 97.0％.     

利用芯片式高场非对称波形离子迁移谱技术快速检测苯丙氨酸

采用金属扩散管-芯片式高场非对称波形离子迁移谱(FAIMS)技术对苯丙氨酸进行了快速检测,设定测试压强为250 kPa,金属扩散管温度为190℃,在优化的最佳分析条件下,即:载气流速为2000 mL/min,分离电压为152.8 V时,在正模式下获得了苯丙氨酸的离子特征谱图和补偿电压特征值-0.62 V.另外,利用FAIMS对不同浓度的苯丙氨酸样品气进行了检测,确定了FAIMS检测的定量线性范围为6～20 mg/L和检出限为5.9 mg/L.本实验为FAIMS应用于苯丙氨酸的快速检测提供了重要参考.     

新型3D纸基微流控分析器件的研制及应用

基于棉涤线进样通道、过滤区、检测区和"开关元件",研制了一种新型3D纸基微流控分析器件,并应用于食盐中IO-3的测定。实验探讨并优化了该器件的制备和测定条件。在优化的测定条件下,显色测定灰度值与IO-3浓度在5~250μmol/L范围内呈线性关系,检出限为2.3μmol/L。该方法可应用于实际样品中IO-3的测定。     

Rapid and Sensitive Determination of Dinotefuran Residue Based on Electrochemical Enhancement of β‐cyclodextrin‐Graphene Composite

A rapid method for sensitive voltammetric determination of dinotefuran residue was reported. The proposed method was based on the electrocatalytic reduction of dinotefuran on β‐cyclodextrin‐graphene composite modified glassy carbon electrode (β‐CD‐rGO/GCE), giving rise to a higher reduction signal to dinotefuran relative to the bare (GCE) and graphene modified electrode (rGO/GCE). Moreover, a further signal enhancement was observed when the modified electrode incubated in solution at low temperature (0 °C) for a short time. The reduction mechanism and binding affinity were also discussed. The external standard calibration curve was obtained from linear sweep voltammetry in the range of 0.5 to 16.0 μM with a detection limit of 0.10 μM. In addition to optimization of pretreatment, this electrochemical method has been applied to the dinotefuran residue determination in millet samples with the detection limit of 0.01 mg kg^?1 and compared with an high performance liquid chromatography method. The proposed electrode and analysis methods were proven to be sensitive, accurate and rapid under the used conditions.     

Flow injection visible diffuse reflectance quantitative analysis of nickel

Flow injection (FI) methodology, using diffuse reflectance in the visible region of the spectrum, for the analysis of nickel, precipitated in the form of dimethylglyoximate, is presented. A reflectance cell, constructed in polytetrafluoroethylene, using a LED (light emitting diode) as light source and a LDR (light dependent resistor) as detector, is described. The analytical signal (S) correlates with nickel concentration (C) between 1.6 × 10⁻⁴ and 6.6 × 10⁻⁴ mol L⁻¹. This correlation is described by the equation S = −1.108 + 3.314 × 10⁴C − 2.081 × 10⁷C² (r = 0.9996). The experimentally observed limit of detection is about 1.3 × 10⁻⁴ mol L⁻¹, as in lower concentrations the formation of precipitate is not observed. The experimental quantitation limit is about 1.6 × 10⁻⁴ mol L⁻¹. The mean R.S.D. (relative standard deviation) is about 2.7%. Samples containing nickel were analyzed and the results obtained in this method were compared with those of other methods using the statistical Student's t-test.     

Bioanalytical procedures for determination of drugs of abuse in blood

Determination of drugs of abuse in blood is of great importance in clinical and forensic toxicology. This review describes procedures for detection of the following drugs of abuse and their metabolites in whole blood, plasma or serum: Δ9-tetrahydrocannabinol, 11-hydroxy-Δ9-tetrahydrocannabinol, 11-nor-9-carboxy-Δ9-tetrahydrocannabinol, 11-nor-9-carboxy-Δ9-tetrahydrocannabinol glucuronide, heroin, 6-monoacetylmorphine, morphine, morphine-6-glucuronide, morphine-3-glucuronide, codeine, amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine, N-ethyl-3,4-methylenedioxyamphetamine, 3,4-methylenedioxyamphetamine, cocaine, benzoylecgonine, ecgonine methyl ester, cocaethylene, other cocaine metabolites or pyrolysis products (norcocaine, norcocaethylene, norbenzoylecgonine, m-hydroxycocaine, p-hydroxycocaine, m-hydroxybenzoylecgonine, p-hydroxybenzoylecgonine, ethyl ecgonine, ecgonine, anhydroecgonine methyl ester, anhydroecgonine ethyl ester, anhydroecgonine, noranhydroecgonine, N-hydroxynorcocaine, cocaine N-oxide, anhydroecgonine methyl ester N-oxide). Metabolites and degradation products which are recommended to be monitored for assessment in clinical or forensic toxicology are mentioned. Papers written in English between 2002 and the beginning of 2007 are reviewed. Analytical methods are assessed for their suitability in forensic toxicology, where special requirements have to be met. For many of the analytes sensitive immunological methods for screening are available. Screening and confirmation is mostly done by gas chromatography (GC)–mass spectrometry (MS) or liquid chromatography (LC)–MS(/MS) procedures. Basic information about the biosample assayed, internal standard, workup, GC or LC column and mobile phase, detection mode, and validation data for each procedure is summarized in two tables to facilitate the selection of a method suitable for a specific analytic problem.     

Determination of ascorbic acid in pharmaceutical dosage forms and urine by means of an oscillatory reaction system using the pulse perturbation technique

A simple and reliable method for the determination of ascorbic acid (AA) is proposed and validated. It is based on potentiometric monitoring of the concentration perturbations of an oscillatory reaction system in a stable nonequilibrium stationary state close to the bifurcation point. The response of the Bray–Liebhafsky (BL) oscillatory reaction as a matrix, to the perturbation by different concentrations of AA, is followed by a Pt electrode. The linear relationship between maximal potential shift and the logarithm of the amount of AA is obtained between 0.01 and 1.0 μmol. The sensitivity of the proposed method (as the limit of detection) is 0.009 μmol and the method has excellent sample throughput (30 samples per hour). The procedure was used for AA determination in pharmaceutical formulations and urine. The results are in agreement with those obtained using the official method. Some aspects of the possible mechanism of AA action on the BL oscillating chemical system are discussed.