Preparation of a highly sensitive enzyme electrode using gold nanoparticles for measurement of pesticides at the ppt level

A highly sensitive enzyme electrode was prepared based on gold nanoparticles for measurement of pesticides. Gold nanoparticles of 25-30 nm were synthesized on a glassy carbon electrode by double-pulse technique while the coverage was controlled by applied potential and time. The gold nanoparticles were modified to form a self-assembled monolayer, followed by covalent binding of tyrosinase. The TYR-AuNP-GC electrode was compared with bare GC, AuNP-GC, and modified AuNP-GC and TYR-Au (plate type) electrodes in terms of cyclic voltammetry. The voltammograms well represent the sensitivity of enzymatic oxidation of catechol, substrates for the enzyme activity. The prepared electrode integrated into a continuous flow system and was tested to detect pesticides, such as 2,4-D, atrazine, and ziram. Under the optimized conditions of the flow system, the electrode performed reasonably according to the inhibition mechanism in the concentration range of 0.001-0.5 ng mL(-1). The enhanced performance was attributed to the favored microenvironment for the enzyme activity provided by SAM on gold nanoparticles.     

Nanocomposites (conducting polymer and nanoparticles) based electrochemical biosensor for the detection of environment pollutant: Its issues and challenges

Currently, there is an urgent need to develop an electro-analytical technique that can detect and monitor environmental pollutants in a sensitive, specific, and selective manner. Traditional environment pollutant detection techniques suffer from different drawbacks like calibration, sample preparation, blank determination, skilled operator, lengthy time-consuming procedure, costly and no universal approach. The objective of this review article is to provide details regarding the fabrication of conducting polymer-nanoparticles (nanocomposites) based electrochemical biosensors for continuous environmental monitoring. Emphasis has been placed on the principles, development, classification, and use of electrochemical biosensors comprising of nanocomposites of conducting polymer (CP) and metal oxide nanoparticles for the estimation of environmental pollutants present in the air, water, food, and soil.     

Analysis of Pesticides Using a Polyppyrole Modified Electrode

Electrochemical methods can provide fast, sensitive and sometimes real time detection of pesticides. In the course of this work, a dispersed mercury electrode has been used to detect pesticides electrochemically. The electrode was prepared by depositing a thin mercury film on a glassy carbon disc and then coating a layer of polypyrrole on the disc. The effect of coating thickness on detection sensitivity was studied. A thin mercury film of 0.34 µm dispersed by one cycle polymerization of pyrrole was preferred. The influence of electrolyte, pH and organic solvent content on pesticide response was also investigated. The polypyrrole dispersed mercury electrode (Hg-PPy/GC) was not suitable for a pH above 6 but it can tolerate acetonitrile up to 10% at which concentration the mercury film coated glassy carbon electrode (Hg/GC) failed to response. Methyl parathion, methyl azinphos, parathion and fenitrothion were detected. The sensitivity of the dispersed mercury electrode was similar to a normal thin mercury film electrode in this case. A good response can be obtained for 1 ppm pesticides using fast linear sweeping voltammetry.     

Maize tassel-modified carbon paste electrode for voltammetric determination of Cu(II)

The preparation and application of a practical electrochemical sensor for environmental monitoring and assessment of heavy metal ions in samples is a subject of considerable interest. In this paper, a carbon paste electrode modified with maize tassel for the determination of Cu(II) has been proposed. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to study morphology and identify the functional groups on the modified electrode, respectively. First, Cu(II) was adsorbed on the carbon paste electrode surface at open circuit and voltammetric techniques were used to investigate the electrochemical performances of the sensor. The electrochemical sensor showed an excellent electrocatalytic activity towards Cu(II) at pH 5.0 and by increasing the amount of maize tassel biomass, a maximum response at 1:2.5 (maize tassel:carbon paste; w/w) was obtained. The electrocatalytic redox current of Cu(II) showed a linear response in the range (1.23 μM to 0.4 mM) with the correlation coefficient of 0.9980. The limit of detection and current–concentration sensitivity were calculated to be 0.13 (±0.01) μM and 0.012 (±0.001) μA/μM, respectively. The sensor gave good recovery of Cu(II) in the range from 96.0 to 98.0 % when applied to water samples.     

双道原子荧光同时测定海水中痕量砷和汞

建立了双道原子荧光同时测定海水中痕量砷和汞的方法。在试验条件下,砷和汞测定的相对标准偏差≤4．0％．加标回收率在92．0％～104％之间。方法操作简便,灵敏快速,适用于海水及其他水体中砷和汞的测定。     

Detection and extraction of endosulfan by metal nanoparticles

One of the most common pesticides in the developing world, endosulfan, can be detected in ppm levels using gold nanoparticles. Endosulfan adsorbs on the nanoparticle surface and upon interaction for a long time, the nanoparticles precipitate from the solution. Interaction with silver is weak, yet adsorption occurs leading to removal of endosulfan from the solution. A multilayer assembly of gold nanoparticles prepared on a glass substrate shows excellent spectrophotometric response suggesting potential applications.     

Environmental applications of poly(amic acid)-based nanomaterials

Nanoscale materials offer new possibilities for the development of novel remediation and environmental monitoring technologies. Different nanoscale materials have been exploited for preventing environmental degradation and pollutant transformation. However, the rapid self-aggregation of nanoparticles or their association with suspended solids or sediments where they could bioaccumulate supports the need for polymeric coatings to improve mobility, allows faster site cleanups and reduces remediation cost. The ideal material must be able to coordinate different nanomaterials functionalities and exhibit the potential for reusability. We hereby describe two novel environmental applications of nanostructured poly (amic acid)-based (nPAA) materials. In the first application, nPAA was used as both reductant and stabilizer during the in situ chemical reduction of chromium(vi) to chromium(iii). Results showed that Cr(vi) species were rapidly reduced within the concentration range of 10(-1) to 10(2) mM with efficiency of 99.9% at 40 °C in water samples and 90% at 40 °C in soil samples respectively. Furthermore, the presence of PdNPs on the PAA-Au electrode was found to significantly enhance the rate of reduction. In the second application, nPAA membranes were tested as filters to capture, isolate and detect nanosilver. Preliminary results demonstrate the capability of the nPAA membranes to quantitatively capture nanoparticles from suspension and quantify their abundance on the membranes. Silver nanoparticles detection at concentrations near the toxic threshold of silver was also demonstrated.     

Quantitative detection of nitrate in water and wastewater by surface-enhanced Raman spectroscopy

The presence of inorganic nitrogen species in water can be unsuitable for drinking and detrimental to the environment. In this study, a surface-enhanced Raman spectroscopy (SERS) method coupled with a commercially available gold nanosubstrate (a gold-coated silicon material) was evaluated for the detection of nitrate and nitrite in water and wastewater. Applications of SERS coupled with gold nanosubstrates resulted in an enhancement of Raman signals by a factor of ～10⁴ compared to that from Raman spectroscopy. The new method was able to detect nitrate with linear ranges of 1–10,000 mg NO₃ ^?/L (R ²?=?0.978) and 1–100 mg NO₃ ^?/L (R ²?=?0.919) for water and wastewater samples, respectively. Among the common anions, phosphate appeared to be the major interfering anion affecting nitrate measurement. Nevertheless, the percentage error of nitrate measurement in wastewater by the proposed SERS method was comparable to that by ion chromatography. The nitrate detection limits in water and wastewater samples were about 0.5 mg/L. The SERS method could simultaneously detect sulfate, which may serve as a reference standard in water. These results suggested that the SERS coupled with nanosubstrates is a promising method to determine nitrate concentrations in water and wastewater.     

电化学传感法测定水中亚硝酸盐

借助于简单可控的在线电聚合方法,溴酚蓝被修饰到玻碳电极表面,制备了聚溴酚蓝修饰玻碳电极。实验表明,聚溴酚蓝薄膜对于亚硝酸盐的电化学氧化具有很好的催化作用。经实验优化,聚溴酚蓝膜的最佳厚度为聚合20圈,最佳的检测底液为pH=4.0的0.01 mol/L磷酸盐缓冲溶液。亚硝酸盐在传感器上的电化学氧化是一个双电子双质子参与的过程。在最佳检测条件下,亚硝酸盐的氧化峰电流与其浓度在0.02~109.1μmol/L范围内有良好的线性关系,检测限低至5 nmol/L(S/N=3),所制备的亚硝酸盐传感器线性范围宽、检出限低、稳定性和重现性好、抗干扰能力强,将传感器应用于东湖水样中亚硝酸盐含量的测定,结果令人满意。     

Two-year monitoring of Cryptosporidium parvum and Giardia lamblia occurrence in a recreational and drinking water reservoir using standard microscopic and molecular biology techniques

Starting in 2006, a monitoring of Giardia lamblia and Cryptosporidium parvum occurrence was conducted for 2 years in the largest drinking water reservoir of Luxembourg (Esch-sur-S?re reservoir) using microscopy and qPCR techniques. Parasite analyses were performed on water samples collected from three sites: site A located at the inlet of the reservoir, site B located 18 km downstream site A, at the inlet of the drinking water treatment plant near the dam of the reservoir and site C where the finished drinking water is injected in the distribution network. Results show that both parasites are present in the reservoir throughout the year with a higher occurrence of G. lamblia cysts compared to C. parvum oocysts. According to our results, only 25% of the samples positive by microscopy were confirmed by qPCR. (Oo)cyst concentrations were 10 to 100 times higher at site A compared to site B and they were positively correlated to the water turbidity and negatively correlated to the temperature. Highest (oo)cyst concentrations were observed in winter. In contrast, no relationship between the concentrations of (oo)cysts in the reservoir and rain events could be established. Though a correlation has been observed between both parasites and faecal indicators in the reservoir, some discrepancies highlight that the latter do not represent a reliable tool to predict the presence/absence of these pathogenic protozoa. In summer 2007, the maximal risk of parasite infection per exposure event for swimmers in the reservoir was estimated to be 0.0015% for C. parvum and 0.56% for G. lamblia. Finally, no (oo)cysts could be detected in large volumes of finished drinking water.     

Voltammetric determination of platinum at a lead film electrode in environmental water samples

The paper presents the first report on the application of a lead film electrode for the determination of ultratrace concentrations of platinum. The procedure is based on preconcentration of the Pt(IV)-formaldehyde complexes at an in situ plated lead film electrode held at ?0.9 V (vs. Ag/AgCl), followed by a negatively sweeping differential pulse voltammetric scan. The composition of the supporting electrolyte, the influence of accumulation potential and time on the sensitivity of platinum responses are discussed. The detection limit of Pt(IV) with the accumulation time of 60 was equal to 9.2?×?10^?12 mol L^?1. The application of this method was tested by recovery of Pt(IV) from spiked environmental water samples.     

Sensitive immunoassay detection of multiple environmental chemicals on protein microarrays using DNA/dye conjugate as a fluorescent label

Indirect competitive immunoassays were developed on protein microarrays for the sensitive and simultaneous detection of multiple environmental chemicals in one sample. In this assay, a DNA/SYTOX Orange conjugate was employed as an antibody label to increase the fluorescence signal and sensitivity of the immunoassays. Epoxy-modified glass slides were selected as the substrate for the production of 4 × 4 coating antigen microarrays. With this signal-enhancing system, competition curves for 17β-estradiol (E2), benzo[a]pyrene (BaP) and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) were obtained individually on the protein microarray. The IC(50) and calculated limit of detection (LOD) are 0.32 μg L(-1) and 0.022 μg L(-1) for E2, 37.2 μg L(-1) and 24.5 μg L(-1) for BaP, and 31.6 μg L(-1) and 2.8 μg L(-1) for BDE-47, respectively. LOD of E2 is 14-fold lower than the value reported in a previous study using Cy3 labeled antibody (Du et al., Clin. Chem, 2005, 51, 368-375). The results of the microarray immunoassay were within 15% of chromatographic analysis for all three pollutants in spiked river water samples, thus verifying the immunoassay. Simultaneous detection of E2, BaP and BDE-47 in one sample was demonstrated. There was no cross-reaction in the immunoassay between these three environmental chemicals. These results suggest that microarray-based immunoassays with DNA/dye conjugate labels are useful tools for the rapid, sensitive, and high throughput screening of multiple environmental contaminants.     

Possible way to substantial improvement of early warning system in the International Odra (Oder) River Basin

Water ecosystems are threatened by accidental spills of pollution. Rapidity and trueness of information gathering the biological impact of accidental pollution is crucial for the efficiency of the minimisation of possible deterioration of ecosystems and for success in detecting the source of pollution. Due to the randomised occurrence of accidental spills the only way to quickly detect hazardous situations is to perform continuous monitoring of surface water quality. The current situation in the field of early warning in the International Odra (Oder) River basin is not satisfactory. The actual number of monitoring stations and list of routinely continuously monitored parameters are not able to meet the needs of sensitive and rapid detection of biological impact of accidental pollution spills. An effort to change this unfavourable situation was the reason for the offer survey, selection and a model operation of a commercially produced biological monitoring device. This apparatus was located on the border-line profile on the territory of the Czech Republic and represented the first and only one tool of continual biological monitoring of surface water quality in the International Odra (Oder) River Basin. The selected apparatus was the Daphnia Toximeter produced by the firm bbe Moldaenke (Kiel, Germany). This device exploited for rapid detection of changes of biological quality of surface water evaluation of behavioural response of monitoring organisms??daphnids. Five years of model operation proved its suitability for early warning purposes. The apparatus was reliable in function and sensitive enough to detect the deterioration of the biological quality of the river water. The given examples document its applicability not only for detection of accidental spills but also of illegal emissions of pollution, which are very often toxic.     

Determination of Nitrobenzene in Wastewater Using a Hanging Mercury Drop Electrode

The determination of trace amount nitrobenzene in wastewater on a hanging mercury drop electrode was studied. The determination conditions of pH, supporting electrolyte, accumulation potential, accumulation time, and voltammetric response were optimized. The sharp peak of the nitrobenzene was appeared at 0.05 V. The peak electric current was proportional to the concentration of nitrobenzene in the range of 1.47 × 10⁻⁵ ∼ 1.0 × 10⁻³ mol/l with relative standard deviations of 3.99 ∼ 8.94%. The detection limit of the nitrobenzene in water was 5 × 10⁻⁶ mol/l. The proposed method offered low limit of determination, easy operation, the use of simple instrumentation, high sensitivity and good reproducibility. It was applied to the determination of nitrobenzene in wastewater with an average recovery of 94.0% ∼ 105%. The proposed method provided fast, sensitive and sometimes real time detection of nitrobenzene.     

A new nanosilver-based spectrophotometric method for monitoring Eriochrome black T in river water

In this paper, a new spectrophotometric method is reported for the determination of nanomolar levels of Eriochrome black T in environmental samples. The method is based on the catalytic effect of silver nanoparticles on the oxidation of Eriochrome black T by hexacyanoferrate (III) in acetate–acetic acid medium and at 25 °C. The absorbance is measured at 512 nm with the fixed-time method. It relies on the linear relationship between the absorbance difference (?A) and Eriochrome black T amounts in the range of 40–1,250 nM. Under optimum conditions, the sensitivity of the proposed method, i.e., the detection limit corresponding to 80 s, is about 25 nM. The method is featured with good accuracy and reproducibility for Eriochrome black T determination in river water samples without any pre-concentration and separation step.     

填埋场衬层渗漏的电学法检测研究进展

综述了几种常用的填埋场渗漏检测方法,指出电学法已成为填埋场不同运行阶段（施工期和运营期）渗漏检测的主流方法。分析了各阶段电学检测方法的适用条件和优缺点,在防渗膜铺设阶段,常利用双电极法或电极-偶极子法进行施工完整性检测;在填埋场运营期间,根据场地实际情况可以选择电极格栅法、基于物联网的监测预警云平台、阵列式偶极子法或高密度电法进行膜渗漏检测及长期监测。     

Identification and quantification of bisphenol A by gas chromatography and mass spectrometry in a lab-scale dual membrane system

Endocrine disruptor contamination is an emerging issue of concern in the field of water quality engineering. In this study, a lab-scale microfiltration (MF) and reverse osmosis (RO) based water reclamation system was set up to monitor and evaluate the removal of bisphenol A (BPA), which is a known oestrogenic compound. The identification and quantification of BPA were performed by using gas chromatography coupled with mass spectrometry. It was noted that the detection method used in this study was able to achieve an average recovery ranging from 88.2 to 94.1% of BPA with standard deviations of less than 10% in different spiked samples. The detection limit of the analytical protocol was determined at 20 ng L(-1). Based on the analytical protocol, it was noted that a low level of BPA (1.18-3.04 microg L(-1)) could be detected in feed water (effluent of an activated sludge treatment system) to the dual membrane water reclamation system. The results obtained suggested that BPA could be easily chlorinated by sodium hypochlorite with a dosage of 4 to 5 mg L(-1) and a contact time of 1 to 2 min. In this lab-scale study, a satisfactory removal of BPA was readily obtained by RO and BPA was abated to an undetectable level in the product water. It was noted that the RO rejection characteristic of BPA was not sensitive to the variations in raw feed water characteristics experienced in this study. In addition, it was noted that BPA concentration present in raw feed water did not exert any significant impact on RO performance in terms of BPA rejection. The results of this study demonstrated that membrane technology could be effectively used for BPA removal.     

Voltammetric trace determination of mercury using plant refuse modified carbon paste electrodes

Citrus limon peel (kitchen waste) and Leucaena leucocephala seeds (agricultural waste) were used as a modifier for fabrication of modified carbon paste electrode for determination of mercury in aqueous sample using differential pulse anodic stripping voltammetry. Mercury was adsorbed on electrode surface at open circuit and anodic stripping voltammetric scan was run from ?0.5 to 0.5 V. Various electrochemical parameters including amount of modifier, supporting electrolyte, accumulating solvent, pH of the accumulating solvent, and accumulation time were investigated. The effect of presence of other metal ions and surfactants was also studied. In comparison C. limon peel proved to be a better modifier than L. leucocephala seed biomass. This was justified by electrode characterization using cyclic voltammetry that indicated decrease in resistance of electrode when C. limon peel was used as modifier and increase when modifier was L. leucocephala seeds. Maximum current response was obtained using 5 % C. limon peel biomass, hydrochloric acid as supporting electrolyte, acetate buffer of pH 6 as an accumulating solvent, 10-min accumulation time, and scan rate of 50 mV/s. Linear calibration curves were obtained in the concentration range 100 to 1,000 μg L^?1 of mercury for accumulation time of 10 min with limit of detection of 57.75 μg L^?1 and limit of quantification of 192.48 μg L^?1. This technique does not use mercury as electrode material and, therefore, has a positive environmental benefit.     

基于亨利定律的水中臭氧浓度检测方法研究

为提高水中臭氧(O_3)浓度检测方法的普适性、准确性和便捷性,提出了一种新的非接触式的水中O_3浓度检测方法。基于亨利定律(Henry’s Law),采用电化学方法,建立空气中O_3浓度与水中O_3浓度的回归方程,从而推导出水中O_3浓度。实验结果显示,水体O_3传感器的检出限为0.02 mg/L,检测上限为0.40 mg/L,可决系数R~2为0.998 9,相对误差最大值为7.05%,相对标准偏差最大值为2.82%。实际样品检测显示,水体O_3检测传感器的检测结果与O_3快速测定试剂盒(DPD法)的检测结果完全吻合。该方法不但综合了智能传感器的小型化、网络化、实时测量等特性,而且结构简单、成本低、响应快,适用于水体中O_3浓度的快速检测。     

Simultaneous determination of hydroxylamine and phenol using a nanostructure-based electrochemical sensor

The electrochemical oxidation of hydroxylamine on the surface of a carbon paste electrode modified with carbon nanotubes and 2,7-bis(ferrocenyl ethyl)fluoren-9-one is studied. The electrochemical response characteristics of the modified electrode toward hydroxylamine and phenol were investigated. The results showed an efficient catalytic activity of the electrode for the electro-oxidation of hydroxylamine, which leads to lowering its overpotential. The modified electrode exhibits an efficient electron-mediating behavior together with well-separated oxidation peaks for hydroxylamine and phenol. Also, the modified electrode was used for determination of hydroxylamine and phenol in some real samples.