Real-world Water Samples Research Articles

A new solid-phase extraction disk based on a sheet of single-walled carbon nanotubes

A new kind of solid-phase extraction disk based on a sheet of single-walled carbon nanotubes (SWCNTs) is developed in this study. The properties of such disks are tested, and different disks showed satisfactory reproducibility. One liter of aqueous solution can pass through the disk within 10-100 min while still allowing good recoveries. Two disks (DD-disk) can be stacked to enrich phthalate esters, bisphenol A (BPA), 4-n-nonylphenol (4-NP), 4-tert-octylphenol (4-OP) and chlorophenols from various volumes of solution. The results show that SWCNT disks have high extraction ability for all analytes. The SWCNT disk can extract polar chlorophenols more efficiently than a C(18) disk from water solution. Unlike the activated carbon disk, analytes adsorbed by the new disks can be eluted completely with 8-15 mL of methanol or acetonitrile. Finally, the DD-disk system is used to pretreat 1000-mL real-world water samples spiked with BPA, 4-OP and 4-NP. Detection limits of 7, 25, and 38 ng L(-1) for BPA, 4-OP, and 4-NP, respectively, were achieved under optimized conditions. The advantages of this new disk include its strong adsorption ability, its high flow rate and its easy preparation.

Rapid determination of amide herbicides in environmental water samples with dispersive liquid–liquid microextraction prior to gas chromatography–mass spectrometry

This paper describes a novel, simple and environmentally friendly method for rapid determination of the amide herbicides metoalchlor, acetochlor, and butachlor. It is based on dispersive liquid-liquid microextraction and gas chromatography-mass spectrometry. Factors that may influence the enrichment efficiency, such as type and volume of extraction solvent, type and volume of dispersive solvent, extraction time, and content of NaCl, were investigated and optimized in detail. Under the optimum conditions, the limits of detection of metoalchlor, acetochlor, and butachlor were 0.02, 0.04, and 0.003 microg L(-1), respectively. The experimental results indicated that there was linearity over the range 0.1-50 microg L(-1) and good reproducibility with relative standard deviations over the range 1.6-3.0% (n = 5). The proposed method has been applied for the analysis of real-world water samples, and satisfactory results were achieved. Average recoveries of spiked herbicides were in the range 80.3-108.8%. All of these indicated that the developed method would be an efficient method for simultaneous determination of the three herbicides in environmental water samples.

Determination of aniline in environmental water samples by alternating-current oscillopolarographic titration

A new method for the determination of aniline in environmental water based on oscillopolarographic titration was presented in this paper. Several factors including the kind, concentration, and volume of acid, the dosage of potassium bromide, the temperature and concentration of concomitant substances were investigated in detail. The experimental results indicated that this method was simple, rapid, and sensitive. The linear range was 8.367 × 10 −4 to 2.789 × 10 −2 mol L −1, the relative standard deviation (R.S.D.) was lower than 0.96%, and the spiked recoveries of aniline in environmental water samples were in the range of 99.4–106.9% under the optimal conditions. The results indicated that the present method could be used as an alternative method for aniline determination in realworld water samples.

Simultaneous Determination of Cyanazine, Chlorotoluron and Chlorbenzuron in Environmental Water Samples with SPE Multiwalled Carbon Nanotubes and LC

In this paper, a new method based on solid-phase extraction with multiwalled carbon nanotubes as the packed materials for sensitive determination of cyanazine, chlorotoluron and chlorbenzuron in environmental water samples was demonstrated. Related parameters that may influence the enrichment efficiency of multiwalled carbon nanotubes such as the kind and volume of elute, sample flow rate, sample pH, and volume of the water samples were investigated. Under the optimum conditions, the detection limits of cyanazine, chlorbenzuron and chlorotoluron were 0.015, 0.012, 0.034 ng mL−1, respectively. The experimental results indicated a good linearity (R2 > 0.9947) over the concentration range of 0.4–40 ng mL−1 for cyanazine and chlorotoluron, and 0.8–80 ng mL−1 for chlorbenzuron. The relative standard deviations of the three analytes were 3.54, 1.55 and 1.38%, respectively. The established method also was applied to the analysis of the real-world water samples and excellent achievements were obtained with average spiked recoveries from 87.8 to 110.1%. All the results indicated that this procedure could allow the simultaneous determination of these three compounds in environmental water samples at trace levels.

Sensitive determination of thiamethoxam, imidacloprid and acetamiprid in environmental water samples with solid-phase extraction packed with multiwalled carbon nanotubes prior to high-performance liquid chromatography

This paper describes a novel method for sensitive determination of thiamethoxam, imidacloprid and acetamiprid based on solid-phase extraction with multiwalled carbon nanotubes as the packed materials. Factors that maybe influence the enrichment efficiency, such as sample flow rate, sample pH, and sample volume, were investigated in detail. Under the optimized conditions, the detection limits of thiamethoxam, imidacloprid and acetamiprid were 6.1, 5.4 and 6.7 ng L(-1), respectively. The experimental results indicated that there was good linearity (R2>0.9993) over the range of 0.08 approximately 100 ng mL(-1) and good reproducibility with the relative standard deviations over the range of 0.7 approximately 1.1% (n=6). The proposed method has been applied to the analysis of real-world water samples, and satisfactory achievements were obtained. The average spiked recoveries were in the range of 87.5 approximately 109.8%. All the results indicated that the proposed method could be used for the simultaneous determination of the three pesticides in environmental water samples at trace levels.

Using multi-walled carbon nanotubes as solid phase extraction adsorbents to determine dichlorodiphenyltrichloroethane and its metabolites at trace level in water samples by high performance liquid chromatography with UV detection

Carbon nanotubes (CNTs) are a kind of new carbon-based nano-materials which have drawn great attention in many application fields. The potential of multi-walled carbon nanotubes (MWNTs) as solid-phase extraction (SPE) adsorbents for the preconcentration of environmental pollutants has been investigated in recent years. The goal of this work was to investigate the feasibility of MWNTs used as SPE adsorbents to enrich dichlorodiphenyltrichloroethane (DDT) and its metabolites including 1,1-dichloro-2,2-bis-(4′-chlorophenyl)ethane (DDD) and 1,1-dichloro-2,2-bis-(4′-chlorophenyl)ethane (DDE) at trace level which are typical persistent organic pollutants in environment. Parameters that maybe influence the extraction efficiency such as the eluent volume, sample flow rate, sample pH and the sample volume were optimized in detail. The experimental results showed the excellent linear relationship between peak area and the concentration of DDT and its metabolites over the range of 0.2–60 μg L −1, and the precisions (RSD) were 2.3–2.5% under the optimal conditions. The detection limits of proposed method could reach 4–13 ng L −1 based on the ratio of chromatographic signal to base line noise (S/N = 3). Satisfied results were achieved when the proposed method was applied to determine the four target compounds in realworld water samples with spiked recoveries over the range of 89.7–115.5%. All these facts indicated that MWCNTs as SPE packing materials coupled to HPLC was an excellent alternative for the routine analysis of DDT and its metabolites at trace level in environment.

Determination of atrazine and simazine in environmental water samples using multiwalled carbon nanotubes as the adsorbents for preconcentration prior to high performance liquid chromatography with diode array detector

Multiwalled carbon nanotubes, a new nanoscale material, has been gained many interests for use in various fields, and has exhibited exceptional merit as SPE absorbents for enrichment of environmental pollutants. This paper focused on the enriching power of atrazine and simazine, two important widely used triazine herbicides and described a novel and sensitive method for determination of these two herbicides based on SPE using multiwalled carbon nanotubes as solid phase absorbents followed by high performance liquid chromatography with diode array detector. Factors that maybe affect the enrichment efficiency of multiwalled carbon nanotubes such as the volume of eluent, sample flow rate, sample pH, and volume of the water samples were optimized. Under the optimal procedures, multiwalled carbon nanotubes as the absorbents have obtained excellent enrichment efficiency for atrazine and simazine. The detection limits of the atrazine and simazine were 33 and 9 ng l −1, respectively. The spiked recoveries of the two analytes were over the range of 82.6–103.7% in most cases. Good analytical performance was achieved from real-world water samples such as river water, reservoir water, tap water and wastewater after primary pretreatment with proposed method. All these experimental results indicated that the developed method could be used as an alternative for the routine analysis of atrazine and simazine in many real water samples.

Electrospray ionization-ion mobility spectrometry: a rapid analytical method for aqueous nitrate and nitrite analysis

This paper reports the first example of electrospray ionization (ESI) for the separation and detection of anions in aqueous solutions by ion mobility spectrometry (IMS). Standard solutions of arsenate, phosphate, sulfate, nitrate, nitrite, chloride, formate, and acetate were analyzed using ESI-IMS and distinct peak patterns and reduced mobility constants (K(0)) were observed for respective anions. Real world water samples were analyzed for nitrate and nitrite to determine the feasibility of using ESI-IMS as a rapid analytical method for monitoring nitrate and nitrite in water systems. The data showed satisfactory correlation between the measured value ([similar]0.16 ppm) and the reported maximum nitrate-nitrogen concentration (0.2 ppm) found in a local drinking water system. For on-site measurement applications, direct sample introduction and air as an alternate drift gas to nitrogen were evaluated. The identities of the nitrite and nitrate mobility peaks were verified by comparison of reduced mobility constants with mass identified nitrate and nitrite ions reported in literature. In the mixing ratio, a linear dynamic range of 3 orders of magnitude and instrument detection limits of 10 ppb for nitrate and 40 ppb for nitrite were obtained. The calibration curves showed r(2) value of 0.98 and slope of 0.06 for nitrate and r(2) value of 0.99 and slope of 0.11 for nitrite.

New and versatile optical-immunoassay instrumentation for water monitoring.

This article is a review of new and versatile optical-immunoassay instrumentation for water monitoring developed through two European Union projects, RIver ANAlyser (RIANA) and Automated Water Analyser Computer Supported System (AWACSS). Both projects utilise immunoassay techniques to isolate the analytes and Total Internal Reflection Fluorescence (TIRF) to quantify them. Completed in 1999, the RIANA project developed a sensitive and cost-effective analytical system capable of simultaneous detection of multiple-analytes in real-world water samples. The AWACSS project has been in progress since 2001 and is developing rugged-but-sensitive instrumentation that will detect up to 30 analytes simultaneously, will operate unattended, and will have networking capability.

Micro-porous membrane liquid–liquid extraction as an enrichment step prior to nonaqueous capillary electrophoresis determination of sulfonylurea herbicides

A method based on micro-porous membrane liquid–liquid extraction (MMLLE) enrichment and nonaqueous capillary electrophoresis (CE) separation, was established for the analysis of sulfonylurea herbicides in water samples. After MMLLE, the analyte trapped in the chloroform was treated mildly with nitrogen flow to dryness and then dissolved in 200 μl of 4 mM Tris methanol solution for CE analysis. Five sulfonylurea herbicides were separated by nonaqueous CE with Tris/acetate of methanol solution as the run buffer. MMLLE related parameters such as organic solvent used as acceptor, sample flow rate, sample pH, enrichment time, and salt effect were investigated with tribenuron methyl (TBM) as a model compound. Results showed that with a sample flow rate of 3.0 ml min −1 and an enrichment time of 20 min, the proposed method has good linear relationship over the scope of 1–15 ng ml −1 with related coefficient of R 2=0.9911, and a detection limit of 0.4 ng ml −1. This method was applied to determine TBM in realworld water samples with recoveries over the range of 89–97%.

ELISA Determination of the Sulfonylurea Herbicide Metsulfuron-Methyl in Different Water Types

Sulfonylurea herbicides efficiently control broad-leafed weeds and some grasses in cereals. They are typically applied at rates of <100 g/ha. The application of a recently developed competitive enzyme-linked immunosorbent assay (ELISA) for metsulfuron-methyl to spiked real-world water samples such as tap water, surface water from lakes and rivers, municipal wastewater, and landfill leachate is described. With pure water samples the IC50 value for the target analyte is 1.4 μg/L with the LOD being 40 ng/L. Determination of tap water and surface water was possible without any sample preparation such as filtration, extraction, pH adjustment, or dilution. On the contrary, with wastewater and leachate strong matrix interferences were observed, and, therefore, filtration and dilution of these samples prior to the immunochemical determination was necessary. Whereas with wastewater a 100-fold dilution was sufficient to ensure accurate herbicide quantification, even with a 500-fold dilution of leachate a positive b...

Sample preparation system for ion-selective electrodes

The sample preparation of real world water samples for potentiometric determinations is often time and labor consuming. Therefore sample preparation systems were developed for the determination of water hardness and nitrate concentrations in drinking water and well water. The systems allow the adjustment of the ionic strength and removal of interfering ions. The sample preparation agents required are fixed by using a disposable sample preparation disk. The system was tested by analyzing real water samples and the results were compared to those obtained by using reference methods.

Determination of BTEX Compounds in Water by Solid-Phase Microextraction and Raman Spectroscopy

A new method is described for determining benzene, toluene, ethylbenzene, and xylenes (BTEX) in water that combines solid-phase microextraction and spontaneous Raman spectroscopy. In this method, the BTEX analytes are extracted from the water solution into a solid phase before direct detection by Raman spectroscopy. The solid phase consists of a small volume (ca. 55 μL) of poly(dimethylsiloxane) itch has optical windows in the 750-1300- and 1410-2800-cm -1 Raman shift regions. The time required for each BTEX compound to reach equilibrium between the solid phase and the aqueous phase is in the rye of 16-30 min and affords preconcentration enhancements of 2-3 orders of magnitude. Limits of detection using the most intense Raman bands are in the 1-4-ppm range and produce relative standard deviations of 3-9%. Preliminary application of this new method to the detection of BTEX compounds in real-world water samples shows no significant interferences from river and well water matrices