A methodological approach to the application of a vermiculite modified carbon paste electrode in interaction studies: Influence of some pesticides on the uptake of Cu(II) from a solution to the solid phase

A new methodological approach, for studying metal ion binding interactions with a clay mineral is presented. A carbon paste electrode (CPE) modified with vermiculite clay mineral was used as a model for a soil-like solid phase and Cu(II) ions were chosen as the test ions. The application of this model is demonstrated and explained by investigating the influence of seven pesticides (bromofenoxim, fenamiphos, phenmedipham, atrazine and its three natural degradation products) on the uptake of Cu(II) ions from a solution to the vermiculite, included in a CPE. Different conditions (pH, concentration, exposure time etc.) were considered and the amount of bound copper, accumulated when no potential was applied, was then determined by stripping voltammetry.     

A methodological approach to the application of a vermiculite modified carbon paste electrode in interaction studies: Influence of some pesticides on the uptake of Cu(II) from a solution to the solid phase

A new methodological approach, for studying metal ion binding interactions with a clay mineral is presented. A carbon paste electrode (CPE) modified with vermiculite clay mineral was used as a model for a soil-like solid phase and Cu(II) ions were chosen as the test ions. The application of this model is demonstrated and explained by investigating the influence of seven pesticides (bromofenoxim, fenamiphos, phenmedipham, atrazine and its three natural degradation products) on the uptake of Cu(II) ions from a solution to the vermiculite, included in a CPE. Different conditions (pH, concentration, exposure time etc.) were considered and the amount of bound copper, accumulated when no potential was applied, was then determined by stripping voltammetry.     

A new approach to anodic substitution reaction using acoustic emulsification

We have developed a novel electrolytic system for anodic substitution reactions using acoustic emulsification. This new system involves the generation of a carbocation by anodic oxidation of a substrate, and then its reaction with a nucleophile droplet formed by ultrasonication. In this system, even if the oxidation potential of the nucleophile is lower than that of the substrate, the substrate was predominantly oxidized to give the corresponding cation intermediate because the nucleophile phase, which was insoluble in the electrolytic medium, was electro-inactive. In addition, the overoxidation of the desired products was considerably suppressed by the extraction of products from the electrolyte solution into the nucleophile phase. As a result, the anodic substitution reaction of several carbamates with allyltrimethylsilane was carried out to provide the corresponding products in good to moderate yields.     

Determination of selenium in bread-wheat samples grown under a Se-supplementation regime in actual field conditions

Selenium is an essential micronutrient for humans and animals, yet it is deficient in at least one billion people worldwide. Plants and plant-derived products transfer the soil-uptaken selenium to humans; therefore, the cultivation of plants enriched in selenium can be an effective way to improve the selenium status on humankind. This paper focuses on determining the ability of bread wheat to accumulate selenium after supplementation. One of the methods for supplementing this element in plants is foliar application with selenium solutions. These supplemented crop of wheat samples—bread wheat; Triticum aestivum L.—were used to determine if there is an increase of selenium content in cereal grains by comparing them with cereals cultivated in 2009 and harvested in 2010 with no supplementation. The experiments were done using sodium selenate and sodium selenite at three different selenium concentrations: 4, 20 and 100 g per hectare. Total Se is assessed by cyclic neutron activation analysis (CNAA), through short irradiations on the fast pneumatic system (SIPRA) of the Portuguese Research Reactor (RPI-ITN). The short-lived nuclide ^77mSe, that features a half-lifetime of 17.5 s, was used to determine the Se content in SIPRA. The experiment was successful, since the selenium concentration increased in the cropped grains and reached values up to 35 times the non-supplemented ones.     

The application of activation analysis for the control of bromide accumulation in vegetable

Soil desinfestation with methyl bromide increases the uptake of bromine by plants. According to the tolerance regulations in the FRG only 30–50 ppm Br are allowed. The bromine uptake by plants depends on: (a) the fumigation technique (applied amounts, reaction time, date of cultivation); (b) the growing conditions (soil type, climate and irrigation); (c) the plants (species, rotation, harvesting time etc.). The INAA is a simple and rapid method to analyse bromine in vegetables within a wide range using⁸⁰Br and⁸²Br. Since several years this method was also used to control imported crops.     

camoo4薄膜的恒电位阳极氧化法制备及表征

camoo4薄膜;恒电位;阳极氧化; 制备;表征     

Effect of ultraviolet-B radiation on salt marsh vegetation: Trends of the genus Salicornia along the Americas

The effects of natural UV-B radiation on growth, photosynthetic and photoprotective pigment composition of different Salicornia species were analyzed in salt marshes at three different sites along the Americas (Puerto Rico, southern Brazil and Patagonia, Argentina). Plants were exposed to different levels of UV-B radiation for 1-2 years in situ as well as in outdoor garden UV-B exclusion experiments. Different UV-B levels were obtained by covering plants with UV-B opaque (blocked 93-100% of ambient UV-B) and UV-B attenuating (near-ambient) filters (reduced 20-25% of UV-B). Unfiltered plants were exposed to natural irradiance. UV-B filters had significant effects on temperature and photosynthetic pigments (due to changes in PAR; 400-700 nm). The growth of Salicornia species was inhibited after 35 to 88 days of exposure to mean UV-B radiation dosages between 3.6 and 4.1 kJ m(-2) day(-1). The highest number of branches on the main shoot (S. bigelovii and S. gaudichaudiana) and longest total length of the branches (S. gaudichaudiana) were observed in the UV-B opaque treatment. Salicornia species responded to increasing levels of UV-B radiation by increasing the amount of UV-B absorbing pigments up to 330%. Chromatographic analyses of seedlings and adult S. bigelovii plants found seven different UV-B absorbing flavonoids that are likely to serve as UV-B filtering pigments. No evidence of differential sensitivity or resilience to UV-B radiation was found between Salicornia species from low-mid latitudes and a previously published study of a high-latitude population.     

Determination of amlodipine besylate by adsorptive square-wave anodic stripping voltammetry on glassy carbon electrode in tablets and biological fluids

The adsorptive and electrochemical behavior of amlodipine besylate on a glassy carbon electrode were explored in Britton-Robinson buffer solution by using cyclic and square-wave voltammetry. Cyclic voltammetric studies indicated the oxidation of amlodipine besylate at the electrode surface through a single two-electron irreversible step and fundamentally controlled by adsorption. The solution conditions and instrumental parameters were optimized for the determination of the authentic drug by adsorptive square-wave stripping voltammetry. Amlodipine besylate gave a sensitive adsorptive oxidation peak at 0.510 V (versus Ag/AgCl). The oxidation peak was used to determine amlodipine besylate in range 4.0×10⁻⁸ to 2.0×10⁻⁶ with a detection limit of 1.4×10⁻⁸ M. The procedure was successfully applied for the assay of amlodipine besylate in tablets (Norvasc)^®. The percentage recoveries were in agreement with those obtained by the reference method. Applicability to assay the drug in urine and serum samples was illustrated. The mean percentage recoveries were 96.31±1.18 and 96.98±1.17, respectively. The proposd method used for monotoring clinically relevant concntrations of drug in human urine and serum.     

Sensitive and specific post-column fluorimetric determination of diethylstilboestrol residues in extracts of urine and animal tissues at the 1-ppb level

A rapid method for the selective detection and quantitation of diethylstilboestrol (DES) residues at the 1 ppb level in extracts of urine and animal tissues is described. After selective extraction of the oestrogens, DES is analysed by high-performance liquid chromatography using an in-line specific photochemical reactor followed by oxidation to highly fluorescent products. The reaction products of DES were investigated by thin-layer chromatography (TLC). The specificity of the proposed method was compared with that of a reference TLC method on different extracts of animal origin.     

Online monitoring of chemical reactions by polarization-induced electrospray ionization

Polarization-induced electrospray ionization (PI-ESI) is a simple technique for instant generation of gas-phase ions directly from a microliter-sized droplet for mass spectrometric analysis. A sample droplet was placed over a dielectric substrate and in proximity (2–3 mm) to the inlet of a mass spectrometer. Owing to the polarization effect induced by the high electric field provided by the mass spectrometer, the droplet was polarized and the electrospray was generated from the apex of the droplet. The polarization-induced electrospray could last for tens of seconds, which was sufficiently long to monitor fast reactions occurring within few seconds. Thus, we demonstrated the feasibility of using the droplet-based PI-ESI MS for the online monitoring of fast reactions by simply mixing two droplets (5–10 μL) containing reactants on a dielectric substrate placed in front of a mass spectrometer applied with a high voltage (−4500 V). Schiff base reactions and oxidation reactions that can generate intermediates/products within a few seconds were selected as the model reactions. The ionic reaction species generated from intermediates and products can be simultaneously monitored by PI-ESI MS in real time. We also used this approach to selectively detect acetone from a urine sample, in which acetone was derivatized in situ. In addition, the possibility of using this approach for quantitative analysis of acetone from urine samples was examined.     

基于抗原包被的微孔板式化学发光酶免疫分析法测定人尿中的雌三醇

将雌三醇-6-(O-羧甲基)肟(E3-6-CMO)与牛血清白蛋白(BSA)形成的偶联物E3-6-CMO-BSA物理吸附于聚苯乙烯微孔板孔内作为固相抗原,与雌三醇(E3)标准溶液或者水解尿样中待测E3通过竞争法进行免疫反应.以对碘苯酚增强的辣根过氧化物酶(HRP)催化鲁米诺-过氧化氢化学发光体系作为信号检测系统,建立了一种高通量、简便快速、灵敏稳定的化学发光酶免疫分析方法用于测定人尿中E3的含量.考察和优化了包被液的酸碱性、抗原包被浓度、酶标抗体稀释比例及用量、温育时间、化学发光底物用量及化学发光反应时间的影响.在最优实验条件下,方法的灵敏度为0.20ng/mL,批内和批间变异系数均在15%之内,低、中、高浓度加标水解尿样的平均回收率分别为107.9%、100.9%和91.2%.使用抗原包被法和抗体包被法同时对10份水解尿样进行测定,结果显示相关性良好,相关系数为0.9984,表明本方法可以满足临床检测的要求.     

Gas chromatographic-mass spectrometric method for polycyclic aromatic hydrocarbon analysis in plant biota

Using gas chromatography-mass spectrometry, a new method was developed for the identification and the quantification of polycyclic aromatic hydrocarbons (PAHs) in plants. This method was particularly optimised for PAH analyses in marine plants such as the halophytic species, Salicornia fragilis Ball et Tutin. The saponification of samples and their clean up by Florisil solid-phase extraction succeeded in eliminating pigments and natural compounds, which may interfere with GC-MS analysis. Moreover, a good recovery of the PAHs studied was obtained with percentages ranging from 88 to 116%. Application to the determination of PAH in a wide range of coastal halophytic plants is presented and validated the efficiency, the accuracy and the reproducibility of this method.     

Analysis of dyestuff degradation products by capillary electrophoresis.

Capillary electrophoresis (CE) with two different detection methods, mass spectrometry (MS) and UV absorption spectroscopy with photodiode array detection (UV/DAD), was used for the analysis of the degradation products of dyestuffs. We have studied wet oxidation with solid catalyst as the treatment method of wastewaters containing dyestuffs. When the Orange II (C.I. Acid Orange 7) solution was used as the model wastewater, treated solution contained unknown highly polar degradation products. We were able to determine the molecular masses of some products by CE-MS. From this clue, we tried to identify these products by CE-UV/DAD. By means of the comparison of the migration time and UV spectra of standard samples, three degradation products were identified. The separation of degradation products was successful within 15 min.     

食品及生物样品中痕量草酸的荧光动力学法测定

拟定了一个荧光动力学测定痕量草酸根的新方法。在硫酸介质中，草酸催化重铬酸钾氧化罗丹明６Ｇ使其荧光猝灭。方法线性范围为０．８－１４．０ｍｇ／Ｌ，直接用于菠菜，人尿中草酸根的测定，获得满意结果。     

Separation and determination of 11 marker pteridines in human urine by liquid chromatography and fluorimetric detection

A simple liquid chromatographic method has been developed to achieve the complete separation and determination of a wide range of pteridinic compounds and creatinine (CREA) in urine samples, in just one run. The influences of mobile phase composition and buffer pH have been studied. The optimized mobile phase was composed of a Tris-HCl buffer (15 mmol/L) at pH 6.10 solution (eluent A) and a Tris-HCl buffer (15 mmol/L) at pH 6.40 solution (eluent B), in gradient mode. Analytes were determined by fluorimetric detection, exciting at 272 nm, and measuring the fluorescence emission at three wavelengths, 410, 445 and 465 nm. CREA, as a reference of metabolites excretion in urine, was determined by photometric detection at 230 nm. Pteridines detection limits varied from 0.2 to 6.1 ng/mL, and 0.2 g/mL for CREA. Calculated precision values expressed as RSD (%) varied from 1.1 to 5.9. Two different oxidation procedures for urine samples were optimized. The neopterin/biopterin ratios found were 0.98 and 0.86 for adults and children, respectively, by means of the alkaline iodide/iodine oxidation and 0.45 and 0.57 using neutral KMnO(4) oxidation.     

氧化铑电致变色薄膜的制备、结构及性能

采用溶胶_凝胶方法在ITO导电基底上制备氧化铑电致变色薄膜 .当在碱性溶液中对薄膜分别施加阴极和阳极电位时 ,薄膜即呈现由亮黄到深绿的可逆变化 .采用原位XRD、TG_DTA、IR、XPS等方法对薄膜的结晶态、热处理过程以及膜的化学组成进行分析 .应用交流阻抗法计算了薄膜变色过程的扩散系数 ,结果表明该膜基本可以用于变色器件     

Stationary Kinetics of Light Olefin Oxidation by Hydrogen Peroxide in Aqueous Alkali Solutions in the Presence of Fe(III) Oxide

The steady-state kinetics of ethylene and propylene oxidation by hydrogen peroxide in the presence of Fe(III) oxide in aqueous solutions with the permanent adding of H₂O₂ to the reaction medium was studied. The use of an original method for the study of the steady-state reaction kinetics with gas chromatographic detection of substrate consumption from the gas phase made it possible to estimate the apparent rate constants of ethylene oxidation, the ratio of the rate constants of propylene and ethylene oxidation, the reaction orders with respect to the substrate and oxidant concentration, the dependence of the apparent rate constant of ethylene oxidation on the catalyst weight and on the pH of solution, and the apparent activation energy of the process under condition of substrate distribution between the gas and liquid phases. It was found that the kinetic isotope effect in ethylene oxidation is almost absent when completely deuterated ethylene is used.     

Microfluidic tool based on the antibody-modified paramagnetic particles for detection of 8-hydroxy-2'-deoxyguanosine in urine of prostate cancer patients

Guanosine derivatives are important for diagnosis of oxidative DNA damage including 8-hydroxy-2'-deoxyguanosine (8-OHdG) as one of the most abundant products of DNA oxidation. This compound is commonly determined in urine, which makes 8-OHdG a good non-invasive marker of oxidation stress. In this study, we optimized and tested the isolation of 8-OHdG from biological matrix by using paramagnetic particles with an antibody-modified surface. 8-OHdG was determined using 1-naphthol generated by alkaline phosphatase conjugated with the secondary antibody. 1-Naphthol was determined by stopped flow injection analysis (SFIA) with electrochemical detector using a glassy carbon working electrode and by stationary electrochemical detection using linear sweep voltammetry. A special modular electrochemical SFIA system which needs only 10 μL of sample including working buffer for one analysis was completely designed and successfully verified. The recoveries in different matrices and analyte concentration were estimated. Detection limit (3 S/N) was estimated as 5 pg/mL of 8-OHdG. This method promises to be very easily modified to microfluidic systems as "lab on valve". The optimized method had sufficient selectivity and thus could be used for determination of 8-OHDG in human urine and therefore for estimation of oxidative DNA damage as a result of oxidation stress in prostate cancer patients.     

Measurement of alpha-amylase activity in white wheat flour,milled malt,and microbial enzyme preparations,using the Ceralpha assay: collaborative study

This study was conducted to evaluate the method performance of a rapid procedure for the measurement of alpha-amylase activity in flours and microbial enzyme preparations. Samples were milled (if necessary) to pass a 0.5 mm sieve and then extracted with a buffer/salt solution, and the extracts were clarified and diluted. Aliquots of diluted extract (containing alpha-amylase) were incubated with substrate mixture under defined conditions of pH, temperature, and time. The substrate used was nonreducing end-blocked p-nitrophenyl maltoheptaoside (BPNPG7) in the presence of excess quantities of thermostable alpha-glucosidase. The blocking group in BPNPG7 prevents hydrolysis of this substrate by exo-acting enzymes such as amyloglucosidase, alpha-glucosidase, and beta-amylase. When the substrate is cleaved by endo-acting alpha-amylase, the nitrophenyl oligosaccharide is immediately and completely hydrolyzed to p-nitrophenol and free glucose by the excess quantities of alpha-glucosidase present in the substrate mixture. The reaction is terminated, and the phenolate color developed by the addition of an alkaline solution is measured at 400 nm. Amylase activity is expressed in terms of Ceralpha units; 1 unit is defined as the amount of enzyme required to release 1 micromol p-nitrophenyl (in the presence of excess quantities of alpha-glucosidase) in 1 min at 40 degrees C. In the present study, 15 laboratories analyzed 16 samples as blind duplicates. The analyzed samples were white wheat flour, white wheat flour to which fungal alpha-amylase had been added, milled malt, and fungal and bacterial enzyme preparations. Repeatability relative standard deviations ranged from 1.4 to 14.4%, and reproducibility relative standard deviations ranged from 5.0 to 16.7%.     

Head-space chromatography in determination of enzymatic activity: microdetermination of the urinary kallikrein as arginine esterases

Many enzymatic reactions yield volatile products either directly or by cascade sequences, so it seems possible that head-space chromatography might be used to determine enzymatic activity. The activity of urinary kallikrein, as arginine esterase, has been determined in this way by using the N(alpha)-acetyl-L-phenylalanyl-L-arginine ethyl ester as substrate and measuring the ethanol yielded on incubation for 10 min at 30 degrees, followed by quenching of the reaction. The method has been applied to aqueous solutions and urine.