Concentration from environmental water samples

Pu has been concentrated from environmental water samples by chemi-... 

A Comparison of Seven Methods for Concentrating Organic Chemicals from Environmental Water Samples... 

Two independent analytical methods—LC-MS-MS and 19F-NMR— for the determination of perfluorinated anionic surfactants in environmental water samples were presented. Perfluorinated alkanesulfonates and perfluorocarboxylates were determined qualitatively and quantitatively because of an accidental release of perfluorosurfactant contaminated fire-fighting foam [55]. Ci8-SPE was applied for concentration of the compounds from water samples. Methanol was used for elution prior to ESI-LC-MS(—) analysis. The negatively recorded LC-MS-MS TIC for the determination of PFOS, PFHxS, PFOA, perfluor-oheptanoic acid (PFHpA), perfluorododecanoic acid (PFDoA internal standard) in water samples was presented [55]. 

Solutions must be concentrated or the constituents must be isolated before trace amounts of the various organics present as complex mixtures in environmental water samples can be chemically analyzed or tested for toxicity. A major objective is to concentrate or isolate the constituents with minimum chemical alteration to optimize the generation of useful information. Factors to be considered in selecting a concentration technique include the nature of the constituents (e.g., volatile, nonvolatile), volume of the sample, and analytical or test system to be used. The principal methods currently in use involve (1) concentration processes to remove water from the samples (e.g., lyophilization, vacuum distillation, and passage through a membrane) and (2) isolation processes to separate the chemicals from the water (e.g., solvent extraction and resin adsorption). Selected methods are reviewed and evaluated. 

A modified reduction-aeration method to analyse mercury in environmental water samples is described. After aeration of the sample, the mercury is pre-concentrated on gold-coated sand which is then analysed by thermal desorption and cold vapour atomic absorption spectrometry (CVAAS). When applying reduction-cells of volumes up to 1 1, limits of detection as low as 1 ng.r are obtained. The method avoids matrix-effects caused by complexing agents such as Cl and 1, which interfere in the direct measurement of mercury by common CVAAS-techniques. The method was applied to dty drinking-water. Mercury levels ranging from less than 1 ng.l" to 10 ng.T were found. 

Ding et al. described an automated on-line SPE-LC-MS/MS method for the determination of macrolide antibiotics, including erythromycin, roxithromycin, tylosin, and tilmicosin in environmental water samples. A Capcell Pak ME Ph-1 packed-column RAM was used as SPE column for the concentration of the analytes and clean-up of the sample. One millilitre of a water sample was injected into the conditioned SPE column, and the matrix was washed out with 3 ml high-purity water. By rotation of the switching valve (see Fig. 4.2), macrolides were eluted in the back-flush mode and transferred to the analytical column. The limits of detection and quantification obtained were 2-6 and 7-20 ng/1, respectively, which is suitable for trace analysis of macrolides. The intra- and inter-day precisions ranged within 2.9-12% and 3.3-8.9%, respectively. At the three fortification concentrations tested (20, 200, and 2000 ng/1), recoveries of macrolides ranged from 86.5% to 98.3%. 

MIP for diclofenac [DEC] was synthesized by precipitation polymerization [Dai et al., 2011]. The MIP showed high affinity toward DEC in aqueous solution and was used as SPE material for the quantitative enrichment of DEC in environmental water samples. The parameters such as washing solvent, elution solvent and breakthrough volume, which affects the extraction efficiency of the MIPS were evaluated to achieve the selective pre-concentration of DEC from water samples and to reduce non-specific interactions. Recoveries of DEC extracted from tap water, river water and wastewater samples were higher than 95%. The MIPs were found to be highly reusable as the stability of the MIP did not vary even after 30 adsorption and desorption cycles. 

For the separation and determination of inorganics in some biological samples (115,180), textile materials (118), environmental water samples (55,81,129,204,206), plants and food stuffs (112,206), alloys (51,84,128,182,207), and geological samples (89,94,127,207), specific standard methods are followed. Relatively pure real samples or their concentrated extracts can be spotted directly for TLC analysis. However, if the analyte concentration in a complex sample (biological, plant, environmental, food etc.) is low, extraction of the analyte from the sample matrix, cleanup of the extract and concentration of the analyte usually precede TLC. Below are given some examples for the preparation of solutions of real samples ... 

Two examples from the analysis of water samples illustrate how a separation and preconcentration can be accomplished simultaneously. In the gas chromatographic analysis for organophosphorous pesticides in environmental waters, the analytes in a 1000-mL sample may be separated from their aqueous matrix by a solid-phase extraction using 15 mb of ethyl acetate. After the extraction, the analytes are present in the ethyl acetate at a concentration that is 67 times greater than that in... 

Due to the predicted and previously detected low concentrations of pesticides in environmental samples (usually around the nanogram per liter level), a preconcentration step of the water samples is necessary prior to measurement. In this way, a preconcentration factor of several orders of magnitude (200-1,000-fold) is mandatory to reach the low detection limits necessary for the identification of pesticides, especially in complex wastewater samples. Also, the use of surrogate standards (e.g., triphenyl phosphate) added before the extraction step is a common practice in order to account for possible errors during the extraction process and for quantitative purposes. The commonly used extraction methods for polar compounds from water matrices involve isolation using liquid-liquid extraction (LLE) and solid-phase extraction (SPE), which are commented on below. Other methods such as semipermeable membrane devices (SPMD) are also mentioned. 

Environmental detections of benzalkonium chlorides BAC homologue concentrations in wastewater samples collected from various WWTPs across the US were determined by on-line SPE-LC-ESI-MS (Table 2.12.4) [23,41], Concentration levels of BAC detected in effluents of WWTPs reached maximum levels of 36.6 xgL 1 and in surface-water samples collected downstream from different WWTP discharges detected concentrations ranged from 1.2 to 2.4 pig L 1, thus indicating its input and persistence through the wastewater treatment process. 

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