Practical Water Samples Research Articles

Direct determination of polyacrylamide in water samples by its enhancement effect on the resonance Rayleigh scattering of some basic diphenyl naphthylmethane dyes

Interaction of partially hydrolyzed polyacrylamide (HPAM) with basic diphenyl naphthylmethane dyes including victoria blue 4R (VB4R), victoria blue B (VBB) and night blue (NB), was characterized by resonance Rayleigh scattering (RRS) spectra. Accordingly a RRS method for the direct determination of HPAM at nanogram levels has been developed. The maximum RRS wavelengths (λmax) appear at 276 nm, 284 nm, and 374 nm for VB4R, VBB, and NB systems, respectively. The RRS spectral characteristics, the influencing factors, and the optimum conditions have been investigated. The RRS intensity was directly proportional to the concentration of HPAM in the range of 0.054∼3.5 µg mL−1 for VB4R system, 0.10∼5.0 µg mL−1for VBB system, and 0.10∼1.5 µg mL−1 for NB system. The methods exhibited high sensitivities. The detection limits were 16.5 ng mL−1 (VB4R system), and 31.0 ng mL−1 (VBB and NB systems). The selectivity of the method was investigated by using VB4R system owing to the highest sensitivity. Concentrations of HPAM in tap water, synthetic water and practical waste water samples were analyzed satisfactorily. The reaction mechanism and RRS enhancement reasons were discussed.

Electrochemical sensoring of 2,4-dinitrophenol by using composites of graphene oxide with surface molecular imprinted polymer

A simple surface molecular imprinted approach was developed to synthesize composites of molecular imprinted polymer (MIP) with graphene oxide (GO) in aqueous solution, where 2,4-dinitrophenol (DNP) was used as the template. The GO-MIP composites were characterized with, FT-IR, Raman spectroscopy, SEM and EDAX. The composites were demonstrated to have high adsorption capacity, excellent selectivity and site accessibility for the target pollutant DNP under optimal conditions. The composites were used to fabricate sensor for the determination of DNP, and the electrochemical behaviors of the sensor in the presence of DNP were investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and differential pulse voltammetry (DPV). Under optimal conditions by the DPV, there was a good linear correlation between the current of the cathodic peak at about −0.35 V (vs. saturated calomel electrode) and the concentration of DNP in the range of 1.0–150.0 μM. The electrochemical sensor was satisfactorily applied to determine DNP in practical water samples.

Simultaneous detection of enteroviruses from surface waters by real-time RT-PCR with universal primers

In order to realize simultaneous quantitative detection of various enteroviruses from water samples, a real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) method was developed with universal primer pairs designed based on the highly conserved non-coding region sequences of genome targeting poliovirus, coxsackievirus and enterovirus 71. The recombinant plasmid was constructed as enterovirus DNA standard by cloning poliovirus cDNA into a pMD18-T vector. The real-time RT-PCR method utilizing SYBR Green I was optimized. As a result of a series of examinations, the detection limit of the method was found to be 2.31 genome equivalent copy (GEC)/μL, the intra- and inter-assay variations were lower than 2% and 5%, respectively, and enteroviruses were well distinguished from other microorganisms. There was a good linear relationship ( r 2 = 0.997) between the logarithm of viral density and cycle threshold in a wide range of 2.31 × 10 0 to 2.31 × 10 9 GEC/μL. The validity of the method was further proved by its application for the detection of enteroviruses from various practical water samples.

Determination of Triazines by Ultrasonic‐Assisted Ionic Liquid Microextraction Coupled with High Performance Liquid Chromatography

AbstractThe determination of triazine herbicides by ultrasonic‐assisted ionic liquid microextraction coupled with high‐performance liquid chromatography was described. 1‐Hexyl‐3‐methylimidazolium hexafluorophosphate ([C6MIm][PF6]) was used as the extraction solvent and some extraction parameters, including volume of [C6MIm][PF6], extraction temperature and time, salt concentration and pH values of sample solution, were examined and optimized. The isolation of the target compounds from the matrix was found to be efficient when triazines in 10 mL of sample solution was extracted with 100 µL of [C6MIm][PF6] for 40 min at 50°C. The detection limits for the triazine range from 0.36 to 1.41 µg·L−1. The satisfactory recoveries (82.3% –120.3%) with relative standard deviations ≦10.1% were obtained for the four triazine herbicides from six kinds of practical water samples.

A simple fluorescent probe for the determination of dissolved oxygen based on the catalytic activation of oxygen by iron(II) chelates

This work aims at establishing a simple fluorescent probe for the determination of dissolved oxygen. It is found that iron(II) ions activate oxygen to produce reactive species being capable of oxidizing non-fluorescent coumarin to fluorescent 7-hydroxycoumarin. However, this process is not effective because the yield of the reactive species is very low in the presence of simple iron(II) salts alone. The addition of organic ligands such as oxalate results in the formation of complexes between iron(II) ions, which leads to considerable increase in the yield of reactive species (such as hydroxyl radicals) and then increase in the fluorescence intensity of 7-hydroxycoumarin to a significant level. It has been observed that in the mixture solution of iron(II) ions, ligand, coumarin, and dissolved oxygen, there is an excellent linear response between the fluorescence and dissolved oxygen. Therefore, a new spectrofluorimetric method has been proposed for the determination of dissolved oxygen by using catalytic activation of O 2 by iron(II) chelates. Under optimized conditions, a linear correlation ( r = 0.995) has been observed between the fluorescence intensity of 7-hydroxycoumarin at 456 nm and the concentration of dissolved oxygen over the range of 0.96–9.22 mg L −1. The limit of detection for dissolved oxygen at a signal-to-noise ratio of 3 has been estimated to be 0.35 mg L −1. The proposed method has been applied to determine the concentration of dissolved oxygen in practical water samples with results as satisfactory as that obtained by the standard iodometric method.

Application of liquid–liquid–liquid microextraction and high-performance liquid-chromatography for the determination of sulfonamides in water

This work presents a novel liquid–liquid–liquid microextraction (LLLME) technique for the extraction of sulfonamides from aqueous systems; it combines with high-performance liquid-chromatography-ultraviolet absorbance detection (HPLC/UV). In this experiment the sulfonamides were successively extracted from a donor phase (i.e., a water sample) into several microliters of an organic phase and then from the organic phase into an acceptor phase (i.e., an aqueous extract) by LLLME. The following separation and quantitative analyses were performed using HPLC/UV with 265 nm detection. Extraction condition such as solvent identity, agitation, extraction time, acceptor phase NaOH concentration, donor phase pH, and salt addition were optimized. Relative standard deviation (RSD, 2.6–5.3%), coefficient of estimation ( R 2, 0.9972–0.9999), and method detection limit (MDL, 0.11–0.77 ng mL −1) were achieved under the selected conditions. The proposed method was successfully applied to the analyses of three practical water samples and the relative recoveries of sulfonamides from the spiked water samples were in the range of 86.2–108.7%. The proposed method also confirms microextraction to be robust to monitoring trace levels of sulfacetamide, sulfadiazine, sulfathiazole, sulfamerazine, sulfadimidine, sulfamonomethoxine, sulfamethoxazole, and sulfaquinoxaline in aqueous samples.

Adsorption and removal of As(V) and As(III) using Zr-loaded lysine diacetic acid chelating resin

An adsorption process for the removal of As(V) and As(III) was evaluated under various conditions using zirconium(IV) loaded chelating resin (Zr-LDA) with lysine- N α, N α diacetic acid functional groups. Arsenate ions strongly adsorbed in the pH range from 2 to 5, while arsenite was adsorbed between pH 7 and 10.5. The sorption mechanism is an additional complexation between arsenate or arsenite and Zr complex of LDA. Adsorption isotherm data could be well interpreted by Langmuir equation for As(V) at pH 4 and As(III) at pH 9 with a binding constant 227.93 and 270.47 dm 3 mol −1 and capacity constant 0.656 and 1.1843 mmol g −1, respectively. Regeneration of the resin was carried out for As(V) using 1 M NaOH. Six adsorption/desorption cycles were performed without significant decrease in the uptake performance. Column adsorption studies showed that the adsorption of As(V) is more favorable compared to As(III), due to the faster kinetics of As(V) compared to As(III). Influence of the coexisting ions on the adsorption of As(V) and As(III) was studied. The applicability of the method for practical water samples was studied.

Computer Simulation of the Speciation of Aluminum in Acidic Natural Waters in Equil ibria with the Mineral Phase Kaolinite

基于热力学平衡计算,用计算机模拟研究了与高岭石固相平衡的酸性天然地表水中铝的形态分布,讨论了影响铝形态分布的各种因素.同三水铝石固相平衡相比,与高岭石固相平衡的酸性天然地表水中,铝的形态分布与溶解硅酸的浓度密切相关,聚合态铝浓度较低,总溶解铝浓度明显减小约 2个数量级.模型被用于实际水样的分析,所得结果与实验值符合较好.最后用MonteCarlo模拟考察了由于平衡常数的选择而带来的不确定性.;This paper presents a computer simulation to invest ig ate the speciation of aluminum in acidic natural waters equilibria with mineral kaolinite based on the chemical equilibrium calculation. Various factors affect ing the dist ribution and concent rations of aluminum complexes are discussed. Compared with the case of equilibria with gibbsite, some unique characterist ics are discovered. This simulation has been verified by analyzing practical water samples and found in near-perfect ag reement with the experimental result s.The uncertainties in thermodynamic constant s are evaluated by the Monte Carlo simulation.

Capillary zone electrophoresis of nitrophenols with off-line isotachophoretic sample pretreatment.

Preparative capillary isotachophoresis (ITP) operating in a discontinuous fractionation mode was studied as a sample pretreatment technique for capillary zone electrophoresis (CZE) trace analysis of a group of ten nitrophenols. Different separation mechanisms employed by these capillary electrophoresis techniques made possible a group isolation of the studied analytes by ITP while their CZE resolutions based on differences in the interactions with polyvinylpyrrolidone (PVP) provided suitable conditions for a final analytical evaluation. Experiments with model and practical water samples revealed high and reproducible recovery rates of the ITP pretreatment of nitrophenols when sample loadability limits of the preparative ITP equipment were met. A main disadvantage of the studied ITP-CZE combination was an inefficient use of the pretreated sample as only 0.5% of the fraction containing nitrophenols was used in the final CZE step. Despite these limitations associated with the CZE sample injection, the concentration limit of detection (LOD) for nitrophenols in practical water samples could be reduced to 2-8 ppb concentrations (photometric absorbance detector operating at a 254 nm wavelength) when 200 microL sample volumes were taken for the ITP pretreatment. This was accompanied by an efficient sample clean-up as no other trace ionic constituents originating from the samples were detected on CZE.

Flow-Injection Spectrophotometric Determination of Micro Amounts of Sulfate Ion in Surface- and Sea-Water Samples with a Barium Chromate Reaction Column

A rapid and simple flow-injection method using a reaction column packed with barium chromate powder is described for the determination of micro amounts of sulfate ion in surface- and sea-water samples. An aqueous solution containing 4.5mM sodium acetate and 4% ethanol was used as a carrier solution at a flow rate of 0.8ml/min. The absorbance of the chromate ion (which corresponds to the sulfate ion concentration) in the carrier solution from the reaction column was measured using a photometric detector at 370nm. Interference from some cations was eliminated by the use of a cation-exchange resin column installed in front of the reaction column; interference from some anions was reduced by using the carrier solution mentioned above. The concentration range from 0.5 to 5ppm of the sulfate ion in practical water samples can be determined by the proposed method with good reproducibility.