Use of Al2O3 in an automated on-line pre-concentration system for determination of cadmium(II) by FAAS

This paper presents the development of an on-line pre-concentration system to determine cadmium(II) in aqueous samples. The analyte was trapped in a mini-column filled with Al(2)O(3) in the form of macro-spheres obtained by the mixture of Al(NO(3))(3).9H(2)O(aq) and chitosan dissolved in acetic acid. The mixture was dropped into an NH(4)OH aqueous solution under rigorous agitation using a peristaltic pump, the macro-spheres were separated from alkaline solution and dried, and finally were submitted to thermal treatment. The pre-concentration system was linear between 1.0 and 100 microg L(-1), with a linearity of 0.999, sensitivity of 3.58 x 10(-3)L microg(-1) and enrichment factor of 21.9. The limits of detection and quantification were 0.08 microg L(-1) and 0.28 microg L(-1), respectively. The repeatability was between 2.6 and 5.9%. Recovery tests were carried out with a real aqueous sample.     

Automatic on-line pre-concentration system using a knotted reactor for the FAAS determination of lead in drinking water

An automatic on-line pre-concentration system is proposed for lead determination in drinking water using flame atomic absorption spectrometry (FAAS). Lead(II) ions are retained as the 1-(2-pyridylazo)-2-naphthol (PAN) complex in the walls of a knotted reactor, followed by an elution step using 0.50molL(-1) hydrochloric acid solution. Optimisation involving the sampling flow rate, pH and buffer concentration factors was performed using a Box-Behnken design. Other factors were established considering results of previous experiments. The procedure allows the determination of lead with a 0.43microgL(-1) detection limit (3sigma/S) and precisions (expressed as relative standard deviation) of 4.84% (N=7) and 2.9% (N=7) for lead concentrations of 5 and 25microgL(-1), respectively. The accuracy was confirmed by the determination of lead in the NIST SRM 1643d trace elements in natural water standard reference material. The pre-concentration factor obtained is 26.5 and the sampling frequency is 48h(-1). The recovery achieved for lead determination in the presence of several ions demonstrated that this procedure could be applied to the analysis of drinking water samples. The method was applied for lead determination in drinking water samples collected in Jequié City, Brazil. The lead concentration found in 25 samples were always lower than the permissible maximum levels stipulated by World Health Organization.     

Bi(III)4-methylpiperidinedithiocarbamate coprecipitation procedure for separation--pre-concentration of trace metal ions in water samples by flame atomic absorption spectrometric determination

A pre-concentration method was developed for determination of trace amounts of cadmium, copper and lead in water samples by FAAS after coprecipitation by using potassium 4-methylpiperidinedithiocarbamate (K4-MPDC) as a chelating agent and Bi(III) as a carrier element. This procedure is based on filtration of the solution containing precipitate on a cellulose nitrate membrane filter following Cd(II), Cu(II) and Pb(II) coprecipitation with Bi(III)4-MPDC and then the precipitates together with membrane filter were dissolved in concentrated nitric acid. The metal contents of the final solution were determined by FAAS. Several parameters including pH of sample solution, amount of carrier element and reagent, standing time, sample volume for precipitation and the effects of diverse ions were examined. The accuracy of the method was tested with standard reference material (MBH, C31XB20 and CRM BCR-32) and Cd, Cu and Pb added samples. Determination of Cd, Cu and Pb was carried out in sea water, river water and tap water samples. The recoveries were >95%. The relative standard deviations of determination were less than 10%.     

石墨炉原子吸收法直接测定饮用水中的铍

采用石墨炉原子吸收法,使用热解涂层石墨管,加上硝酸镁作基体改进剂,直接测定水中的铍。     

Preconcentration system for cadmium and lead determination in environmental samples using polyurethane foam/Me-BTANC

In this work, polyurethane foam (PUF) loaded with 2-(6'-methyl-2'-benzothiazolylazo)chromotropic acid (Me-BTANC) was packed in a minicolumn and it was used in an on-line preconcentration system for cadmium and lead determination. Optimum hydrodynamic and chemical conditions for metal sorption were investigated. The effects of several foreign substances on the adsorption of cadmium and lead were also reported. The enrichment factor obtained was 37 (Cd and Pb) for 180 s preconcentration time. The proposed procedures allowed the determination of metals with detection limits (3 sigma) of 0.80 and 3.75 microg L(-1) (0.10 and 0.47 microg g(-1) of solid sample) for cadmium and lead, respectively. The precision of the procedures was also calculated: 3.1 (Cd 10 microg L(-1)) and 4.4% (Pb 100 microg L(-1)). The accuracy of the procedure was checked by analysis of the certified reference materials Spinach Leaves and Fish Tissue. Cadmium and lead contents in environmental samples (black tea, spinach leaves, natural and tap water) were determined by applying the proposed procedure.     

Fluoride in drinking water and its removal

Excessive fluoride concentrations have been reported in groundwaters of more than 20 developed and developing countries including India where 19 states are facing acute fluorosis problems. Various technologies are being used to remove fluoride from water but still the problem has not been rooted out. In this paper, a broad overview of the available technologies for fluoride removal and advantages and limitations of each one have been presented based on literature survey and the experiments conducted in the laboratory with several processes. It has been concluded that the selection of treatment process should be site specific as per local needs and prevailing conditions as each technology has some limitations and no one process can serve the purpose in diverse conditions.     

离子色谱法测定饮用水中常见阴离子

本文主要介绍离子色谱法检测饮用水中常见阴离子的方法。本方法采用瑞士万通的761型离子色谱仪。分离柱为METROSEPAnionDual2,淋洗液为2.0mmol/LNaHCO3和1.3mmol/LNa2CO3抑制液为20mmol/LH2SO4在测定范围内,F-、Cl-、NO2-、NO32-;-SO42-的峰面积和质量浓度呈线性关系,相关系数均大于0.999。回收率F-为101.5%,CL-O101.6%,NO2-为108.0%.NO32-为97.7%,SO42-为103.3%。相对标准偏差在0.7%-4.3%之间。     

Flow injection preconcentration system using a new functionalized resin for determination of cadmium and nickel in tobacco samples

A solid-phase extraction method combined with flow injection (FI) on-line flame atomic absorption spectrometry (FAAS) for the determination of cadmium and nickel in tobacco samples is presented. The 2-aminothiophenol functionalized Amberlite XAD-4 (AT-XAD) resin was synthesized by covalent coupling of the ligand with the copolymer through a methylene group. A minicolumn packed with AT-XAD was connected into the automated on-line preconcentration system. Elution of metal ions from minicolumn can be made with 0.50 mol L⁻¹ hydrochloric acid solution. With a consumption of 21.0 mL of sample solution, detection limits (3 s) of 0.3 (Cd) and 0.8 μg L⁻¹ (Ni) were achieved at a sample throughput of 18 h⁻¹. Enrichment factors (EF) of 99 (cadmium) and 43 (nickel) were obtained compared with the slope of the linear portion of the calibration curves before and after preconcentration. The contents of Cd and Ni in a certified reference material (NIST 1570a, spinach leaves) determined by the present method was in good agreement with the certified value. The developed procedure was also successfully applied to the determination of Cd and Ni in local tobacco samples.     

Analysis of steel structure corrosion of drinking water distribution system in family indoor environment

In this paper, corrosion investigation and analysis of steel structure of drinking water distribution system in a family kitchen have been carried out. Results indicate that galvanized corrosion and condensation corrosion under thin water layer have been found the main corrosion type. XRD analysis shows that the rust layer is composed of α‐FeOOH, γ‐FeOOH and Fe₃O₄. For preventing galvanic corrosion, using non‐conductive materials between metals of different electropotential, i.e. electrically insulating the two metals from each other has been recommended. For preventing condensation corrosion under thin water layer, cleaning the pipe external surface to minimize the condensation corrosion is necessary and a good epoxy coating on the pipe external surface may also work. The selection of PVC pipe with better quality and no leaching of inorganic pollutants into water is also a good choice, however, in this condition strong hitting to the PVC pipe should be avoided.     

气相色谱法测定饮用水源中四氯化碳

基于FYGC-2000(C)气相色谱仪气相色谱法测定了饮用水源中四氯化碳含量,所得的回归方程为=79477X-6097.8相关系数r=0.9998,2μg/L和10μg/L两个浓度电位的精密度试验中的所得标准偏差分别为3.3778％和0.742％.在加标回收率测试中加标量分别为2 ug/L和5 ug/L时,回收率在99...     

Determination of cadmium at ultra-trace levels by CPE–molecular fluorescence combined methodology

A highly sensitive micelle-mediated extraction methodology for the preconcentration and determination of trace levels of cadmium by molecular fluorescence has been developed. Metal was complexed with o-phenanthroline (o-phen) and eosin (eo) at pH 7.6 in buffer Tris medium and quantitatively extracted into a small volume of surfactant-rich phase of PONPE 7.5 after centrifugating. The chemical variables affecting cloud point extraction (CPE) were evaluated and optimized. The RSD for six replicates of cadmium determinations at 0.84 μg L⁻¹ level was 1.17%. The linearity range using the preconcentration system was between 2.79 × 10⁻³ μg L⁻¹ and 2.81 μg L⁻¹ with a correlation coefficient of 0.99. Under the optimal conditions, it obtained a LOD of 8.38 × 10⁻⁴ μg L⁻¹ and LOQ of 2.79 × 10⁻³ μg L⁻¹. The method presented good sensitivity and selectivity and was applied to the determination of trace amounts of cadmium in commercially bottled mineral water, tap water and water well samples with satisfactory results. The proposed method is an innovative application of CPE-luminescence to metal analysis comparable in sensitivity and accuracy with atomic spectroscopies.     

Novel oxidative electrophilic coupling reactions of phenoxazine derivatives with MBTH and their applications to spectrophotometric determination of residual chlorine in drinking water and environmental water samples

Novel, sensitive and rapid spectrophotometric methods, using phenoxazine (PNZ), 2-chlorophe-noxazine (CPN) and 2-trifluoromethylphenoxazine (TPN) as chromogenic reagents for the determination of residual chlorine are proposed. The methods are based on the reduction of chlorine by an electrophilic coupling reagent, 3-methyl-2-benzothiazoline hydrazono hydrochloride hydrate (MBTH) in mild hydrochloric acid medium and subsequent coupling with PNZ, CPN or TPN. The blue color formed in the reaction showed maximum absorbance at 680–690 nm and obeyed Beer's law over the range 0.1–2.2 μg ml⁻¹. The molar absorptivity values with PNZ, CPN and TPN were 2.80 × 10⁴, 2.67 × 10⁴ and 1.91 × 10⁴ l mol⁻¹ cm⁻¹ and Sandell's sensitivity values were 0.028, 0.027 and 0.028 μg cm⁻² respectively. The proposed methods were successfully applied in the determination of residual chlorine in drinking water and environmental water samples. The performance of proposed methods was evaluated in terms of Student's t-test and variance ratio F-test which indicated the significance of proposed methods over the standard spectrophotometric method.     

Flame atomic absorption spectrometric determination of trace quantities of cadmium in water samples after cloud point extraction in Triton X-114 without added chelating agents

A new micell-mediated phase separation method for preconcentration of ultra-trace quantities of cadmium as a prior step to its determination by flame atomic absorption spectrometry has been developed. The method is based on the cloud point extraction (CPE) of cadmium in iodide media with Triton X-114 in the absence of any chelating agent. The optimal extraction and reaction conditions (e.g., acid concentration, iodide concentration, effect of time) were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 3-300 ng mL(-1) of cadmium. The detection limit of the method is 1.0 ng mL(-1) of cadmium. The interference effect of some anions and cations was also tested. The method was applied to the determination of cadmium in tap water, waste water, and sea water samples.     

Photosensitized oxidation by dioxygen as the base for drinking water disinfection

Efficiencies of the series water-soluble anionic and cationic sensitizers have been studied in photodynamic natural water disinfection. It was found that only cationic sensitizers are efficient in photooxidative bacteria killing during photodynamic water treatment. The difference in photodynamic action towards different groups of microorganisms has been observed. The most vulnerable are enterococcus and enterococcus faecalis. Spores of sulfite-reducing clostridium are resistant to photodynamic action but, to provide drinking water, clostridium may be removed by sedimentation and filtration. The dependence of photodisinfection on treatment conditions was studied. It was found that sunlight along with artificial visible light sources may be used for photodynamic water treatment. The photodynamic step, arranged with artificial visible light source, was included in a process of conventional water purification instead of chlorine disinfection. Preliminary pilot testing have shown that photodynamic water disinfection in combination with coagulation, sedimentation, sand and carbon filtrations (latter-to remove sensitizer and products of its photolysis) provides water of high quality, free of bacteria and chemicals as well.     

Distribution of polycyclic aromatic hydrocarbons in water, sediment and soil in drinking water resource of Zhejiang Province, China

The spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was investigated in Qiantang River, the most important drinking water resource in Zhejiang Province, China. A total of 270 water samples, 64 sediment samples and 21 soil samples near riverbank were collected during January 2005-July 2006. The total concentrations of PAHs in water, sediments and soils ranged from 70.3 to 1844.4 ng/L, from 91.3 to 1835.2 ng/g and from 85.2 to 676.2 ng/g, respectively. The concentrations of PAHs in rural areas were lower than those in city zones. The concentrations of PAHs in July were the lowest while those in January were the highest during four seasons. The concentrations of PAHs in 2006 were compared with those in 2003 and 2005. The result showed PAHs pollution in this drinking water resource was increasing with time. The relationship between log K(oc) and log K(ow) of PAHs for field data on sediments and predicted values indicated that Qiantang River was mainly contaminated by petrogenic PAHs. The same result was obtained by the ratios of AN/(AN + Phen) and Flur/(Flur + Pye). Ratios of K(oc) for PAHs on sediments to that on corresponding soils indicated that PAHs in Qiantang River were mainly obtained from soil runoff.     

Review of procedures involving separation and preconcentration for the determination of cadmium using spectrometric techniques

Spectrometric techniques for the analysis of trace cadmium have developed rapidly due to the increasing need for accurate measurements at extremely low levels of this element in diverse matrices. This review covers separation and preconcentration procedures, such as electrochemical deposition, precipitation, coprecipitation, solid phase extraction, liquid-liquid extraction (LLE) and cloud point extraction (CPE), and consider the features of the their application with several spectrometric techniques.     

Direct photolysis of polycyclic aromatic hydrocarbons in drinking water sources

The widely used low pressure lamps were tested in terms of their efficiency to degrade polycyclic aromatic hydrocarbons listed as priority pollutants by the European Water Framework Directive and the U.S. Environmental Protection Agency, in water matrices with very different compositions (laboratory grade water, groundwater, and surface water). Using a UV fluence of 1500 mJ/cm², anthracene and benzo(a)pyrene were efficiently degraded, with much higher percent removals obtained when present in groundwater (83-93%) compared to surface water (36-48%). The removal percentages obtained for fluoranthene were lower and ranged from 13 to 54% in the different water matrices tested. Several parameters that influence the direct photolysis of polycyclic aromatic hydrocarbons were determined and their photolysis by-products were identified by mass spectrometry. The formation of photolysis by-products was found to be highly dependent on the source waters tested.     

Optimization models for operative planning in drinking water networks

The topic of this paper is minimum cost operative planning of pressurized water supply networks over a finite horizon and under reliable demand forecast. Since this is a very hard problem, it is desirable to employ sophisticated mathematical algorithms, which in turn calls for carefully designed models with suitable properties. The paper develops a nonlinear mixed integer model and a nonlinear programming model with favorable properties for gradient-based optimization methods, based on smooth component models for the network elements. In combination with further nonlinear programming techniques (Burgschweiger et al. in ZIB Report ZR-05-31, Zuse Institute Berlin, 2005), practically satisfactory near-optimum solutions even for large networks can be generated in acceptable time using standard optimization software on a PC workstation. Such an optimization system is in operation at Berliner Wasserbetriebe.     

电感耦合等离子体质谱法测定饮用水中微量元素

采用电感耦合等离子体质谱法快速测定饮用水中的微量元素 ,样品处理简便 ,检出限低 ,重现性好 ,分析速度快。方法检出限为 (0 0 0 7～ 0 911) μg L ,精密度达到 0 73%～ 4 87%。     

新型野外饮水净化系统

针对石油、地矿等野外作业或边防驻军的饮水净化问题，采用ＤＯＷ公司反渗透膜，通过苦咸水水质调整，工艺以及预处理工艺研究，研制出结构合理、性能可靠的装置，在某边防部队应用状态良好，该设备在反渗透与预处理工艺的结合上有独到之处。引进的反渗透专用多级离心泵在节能和提高回收率方面有明显效果。