Determination of Anionic Surfactants in Water

The use of ternary complexes in the determination of anionic surfactants has been investigated and an analytical method using linear alkyl sulfonates as a test substance has been developed. The method involves the formation of the chloroform-extractable bisphenanthroline Cu(II)-linear alkyl sulfonate (LAS) complex and the subsequent equilibration of the extract with erythrosine to form the extractable bisphenanthroline Cu(II)-erythrosine complex. In the equilibration step erythrosine displaces LAS quantitatively, allowing the determination of the LAS originally present by measuring the absorbance of the extracted bisphenanthroline-Cu(II)-erythrosine complex. Results are reported of studies made to determine the optimum analytical conditions, the sensitivity, and the precision for the method described.     

Dispersive liquid–liquid microextraction followed by high-performance liquid chromatography for the determination of three carbamate pesticides in water samples

A simple, rapid and efficient method, dispersive liquid–liquid microextraction (DLLME) in conjunction with high-performance liquid chromatography (HPLC), has been developed for the determination of three carbamate pesticides (methomyl, carbofuran and carbaryl) in water samples. In this extraction process, a mixture of 35 µL chlorobenzene (extraction solvent) and 1.0 mL acetonitrile (disperser solvent) was rapidly injected into the 5.0 mL aqueous sample containing the analytes. After centrifuging (5 min at 4000 rpm), the fine droplets of chlorobenzene were sedimented in the bottom of the conical test tube. Sedimented phase (20 µL) was injected into the HPLC for analysis. Some important parameters, such as kind and volume of extraction and disperser solvent, extraction time and salt addition were investigated and optimised. Under the optimum extraction condition, the enrichment factors and extraction recoveries ranged from 148% to 189% and 74.2% to 94.4%, respectively. The methods yielded a linear range in the concentration from 1 to 1000 µg L^?1 for carbofuran and carbaryl, 5 to 1000 µg L^?1 for methomyl, and the limits of detection were 0.5, 0.9 and 0.1 µg L^?1, respectively. The relative standard deviations (RSD) for the extraction of 500 µg L^?1 carbamate pesticides were in the range of 1.8–4.6% (n = 6). This method could be successfully applied for the determination of carbamate pesticides in tap water, river water and rain water.     

Determination of Some Transition Metals by Atomic Absorption Spectroscopy after Extraction with Pyridine-2-aldehyde-2-quinolylhydrazone

The extraction of pyridine-2-aldehyde-2-quinolylhydrazone chelates of cadmium, cobalt, copper, nickel, and zinc into isoamyl alcohol (IAOL) and methylisobutyl ketone (MIBK) has been investigated as a basis for the determination of these metals. Below pH 6 the extraction is enhanced by the addition of perchlorate, suggesting that charged complexes are being extracted by ion-pair formation. Sensitivities (1% absorption) are reported for IAOL and MIBK solutions of the metals sprayed into an air-acetylene flame. A procedure for the determination of the above metals by atomic absorption spectroscopy after extraction is given. The procedure is applied to the analysis of tap water for cadmium, copper, and zinc.     

Determination of 13C/12C-ratios of anthropogenic organic contaminants in river water samples by GC-irmMS

This study describes the application of a common analytical procedure adapted for compound-specific stable carbon isotope analyses of riverine contaminants. To evaluate the sensitivity of the analytical method and the precision of the isotopic data obtained, a set of numerous substances at different concentration levels were measured. For most of the anthropogenic contaminants investigated (including chlorinated aliphatics and aromatics, musk fragrances, phthalate-based plasticizers and tetrabutyl tin) acceptable carbon isotope analyses could be obtained down to amounts of approximately 5?ng absolutely applied to the gas chromatograph. These amounts correspond to concentrations in water samples at a natural abundance level of approximately 50–200?ng?L^?1 (low to medium contaminated river systems). However, it has to be considered that the precision and the sensitivity of the analytical method depend partially on the chemical properties of the substances measured. Five recovery experiments were conducted to assess changes in carbon isotope ratios during sample preparation and measurement. The compounds selected for these experiments are known riverine contaminants. Isotopic shifts or higher variations of the isotope ratios as a result of the analytical procedures applied were observed only for a couple of contaminants. Furthermore, compound-specific carbon isotope analyses were performed on eight water extracts of the Rhine river. By comparing the variation of the data of several individual compounds with the deviations obtained from the recovery experiments, it was possible to differentiate contaminants with unaffected isotope ratios and substances with significant alterations of the δ¹³C-values.     

Analysis of Polar Thermally Labile Pesticides using Different Solid-Phase Extraction (SPE) Materials with GC and HPLC Techniques

Abstract

In the present study, an efficient method for extraction, separation and determination of a limited number (30) of polar pesticides in aqueous matrices has been developed. Pesticides were extracted with high recoveries (usually >85%) from 1 L water samples, using the solid-phase extraction (SPE) technique. Affinities to different SPE materials (C-18 and XAD resins) have been studied for all pesticides. Special attention has been paid to the following 5 pesticides (which have classified by the EC as compounds which are particularly difficult to analyse): benazolia, bromofenoxim, ethofumesate, fenamiphos and phenmediphain. Thermally labile compounds have been determined with high pressure liquid chromatography (HPLC) and UV detection in comparison to TSP-LC-MS. Absolute limits of detection (LODs) for the HPLC technique are usually below 1 ng at 220 nm. Thermospray LC-MS determination shows usually limits of detection of 1-10 ng (SCAN) and 60-800 pg (SIM). All pesticides, which are amenable to GC have been detected in a comparative study with the following detectors: flame ionization detector (FID), nitrogen-phosphorus detector (NPD), electron capture detector (ECD) and atomic emission detector (AED). Element-specific detection of various functional groups of these pesticides has been achieved using GC-AED. Thus, while the FID has the lowest specificity, the AED is the most specific detector. LODs are usually < 300 pg (FID < 20 pg, NPD < 1 pg, ECD < 1 pg, AED < 300 pg). Spiked river water samples (from the River Leine and River Weser in Lower Saxony, Germany) have been used to test the employed method. With the spiked surface water samples recoveries were usually >80%.     

Artificial Neural Networks in water analysis: Theory and applications

Artificial Neural Networks (ANNs) have seen an explosion of interest over the last two decades and have been successfully applied in all fields of chemistry and particularly in analytical chemistry. Inspired from biological systems and originated from the perceptron, i.e. a program unit that learns concepts, ANNs are capable of gradual learning over time and modelling extremely complex functions. In addition to the traditional multivariate chemometric techniques, ANNs are often applied for prediction, clustering, classification, modelling of a property, process control, procedural optimisation and/or regression of the obtained data. This paper aims at presenting the most common network architectures such as Multi-layer Perceptrons (MLPs), Radial Basis Function (RBF) and Kohonen's self-organisations maps (SOM). Moreover, back-propagation (BP), the most widespread algorithm used today and its modifications, such as quick-propagation (QP) and Delta-bar-Delta, are also discussed. All architectures correlate input variables to output variables through non-linear, weighted, parameterised functions, called neurons. In addition, various training algorithms have been developed in order to minimise the prediction error made by the network. The applications of ANNs in water analysis and water quality assessment are also reviewed. Most of the ANNs works are focused on modelling and parameters prediction. In the case of water quality assessment, extended predictive models are constructed and optimised, while variables correlation and significance is usually estimated in the framework of the predictive or classifier models. On the contrary, ANNs models are not frequently used for clustering/classification purposes, although they seem to be an effective tool. ANNs proved to be a powerful, yet often complementary, tool for water quality assessment, prediction and classification.     

Degradation of the antiviral drug oseltamivir carboxylate in surface water samples

Numerous studies have documented that a wide number of pharmaceuticals used in human and veterinary medicine have the potential to enter the aquatic ecosystem. The antiviral prodrug oseltamivir phosphate has received recent attention with regard to its possible use against the highly pathogenic H5N1 virus. This preliminary laboratory study investigated the persistence of the active antiviral drug, oseltamivir carboxylate (OSC), in water samples taken from an irrigation canal. After an initial rapid decrease, OSC concentrations slowly decreased during the remaining incubation period. Approximately 65% of the initial OSC amount remained in water at the end of the 36-day incubation period. A small amount of OSC was lost both from sterilized water and from sterilized water/sediment samples, suggesting a significant role for microbial degradation. Stimulating microbial processes by the addition of sediments resulted in reduced OSC persistence. Presence of OSC (1.5?µg?mL^?1) did not significantly affect the metabolic potential of the water microbial population, estimated by glyphosate and metolachlor mineralization. In contrast, OSC caused an initial transient decrease in the size of the indigenous microbial population of water samples.     

Simple Device for Isolation of Organic Compounds from Water

Abstract

A simple device for isolation of organic compounds from aqueous samples has been designed and its operating parameters tested during bioth periodic and continuous operation using isolation of organochlorine compounds as an example.

A stream of an aqueous sample is pumped at elevated temperature by a piston pump to an unit for expransion of the liquid phase surface, where the liquid is sprayed on the walls of the unit and flows down freely.

Organochlorine compounds passing to the gaseous phase are purged with a stream of purified air, oxidied and the chlorides formed are determined coulometrically. The designed device, due to its simplicity, can be built and employed in each averagely equipped laboratory.     

Chromatography of Uranium on High-Performance Ion Exchangers

Abstract

The potential of high-performance liquid chromatography (HPLC) for the determination of U(VI) in ground waters and urine has been examined under a variety of HPLC experimental conditions. Conventional cross-linked and bonded-phase ion exchangers, both cation and anion, were studied with aqueous mobile phases containing tartrate, citrate, or α-hydroxyisobutyrate. The best chromatography was obtained on bonded-phase cation exchangers with an α-hydroxyisobutyrate eluent. The metal ions were detected either by visible spectrophotometry after a post-column reaction with a complexing reagent, or with a polarographic detector. Dectection after post-column reaction gave the best sensitivity; the detection limit (2 × baseline noise was 6 ng or 60 ng.ml^?1 for 100 μl samples. In-line trace enrichment was used to decrease detection limits and linear calibration curves were observed in the ranges studied; 0.5 to 50 ng.mL^?1 for ground waters and 25 to 400 ng.mL^?1 for artificial urine.     

Determination of organochlorine pesticides in river water using dispersive liquid–liquid microextraction and gas chromatography–electron capture detection

Dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–electron capture detection (GC–ECD), has been developed for the extraction and determination of 14 organochlorine pesticides (hexachlorocyclohexanes (α-HCH, β-HCH and δ-HCH), Lindane (γ-HCH), Aldrin, Dieldrin, Endrin, Heptachlor, Heptachlor epoxide, α-Chlordane, β-Chlordane and p,p′-DDT, p,p′-DDD, p,p′-DDE) in river water samples. Factors relevant to the microextraction efficiency, such as the kind of extraction and disperser solvent, their volume and the salt effect was investigated and optimised. In this method the appropriate mixture of extraction solvent (13.5 µL carbon disulphide) and disperser solvent (0.50 mL acetone) were rapidly injected into the aqueous sample by syringe. The values of the detection limit of the method were in the range of 0.05–0.001 µg L^?1, while the relative standard deviations for five replicates varied from 2.7 to 9.3%. A good linearity (0.9894 ≤ r ² ≤ 0.9998) and a broad linear range (0.01–200 µg L^?1) were obtained. The method exhibited enrichment factors ranging from 647 to 923, at room temperature. The relative standard deviations varied from 2.7 to 9.3% (n = 5). The relative recoveries of each pesticide from water samples at spiking levels of 2.00 and 10.0 µg L^?1 were 88.0–111.0% and 95.8–104.1%, respectively. Finally, the proposed method was successfully utilised for the preconcentration and determination of the organochlorine pesticides in the Jajrood River water samples.