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The results of a series of interlaboratory tests using low ionic strength buffer solutions are reported. The test data and other background information are presented as the basis for more realistic quality control materials for pH determination in low ionic strength waters. The effect of atmospheric carbon dioxide on the pH of low ionic strength reference samples is discussed. Several control samples...
A method for the determination of non-ionic surfactants (NS) in the presence of an excess of hydrocarbons is developed. The modified BiAS procedure combined with the indirect tensammetric method (BiAS-ITM) is applied for this purpose. The method consists of extraction of NS into ethyl acetate, precipitation of ethoxylates with modified Dragendorff reagent, removal of adsorbed hydrocarbons by washing...
In the present work the main flow techniques for the analysis and monitoring of several parameters of interest in the quality control of different types of waters are reviewed. Firstly, a review involving the advantages and disadvantages of flow techniques, from those currently out-dated, such as segmented flow analysis (SFA), to the most modern techniques, such as flow injection analysis (FIA), sequential...
An automatic method for the determination of total nitrogen in wastewater by sequential injection analysis and mineralization with UV radiation has been developed. The method is based on the mineralization of the samples with sodium persulphate in basic medium under UV radiation. Small volumes of sample and reagents are firstly aspirated into a single channel and then propelled by flow reversal to...
In the first part of this review [Talanta 60 (2000) 867], flowing-stream methods (namely, segmented flow analysis (SFA), continuous-flow analysis (CFA), flow-injection analysis (FIA), sequential-injection analysis (SIA), multicommuted flow-injection analysis (MCFIA) and multisyringe flow-injection analysis (MSFIA)) were presented as powerful analytical tools for nutrient determination in water samples...
A flow system for the spectrophotometric determination of lead in natural and waste waters is proposed. The determination is based on the colorimetric reaction between malachite green and iodide, followed by the formation of a ternary complex between those reagents and lead cations. The developed flow system includes a lead pre-concentration step in a column packed with a cationic resin (Chelex 100)...
A preconcentration method for silver in environmental waters involving adsorption on a tungsten wire, followed by electrothermal atomic absorption spectrometry with a tungsten tube atomizer is described. The optimal immersing time was 90s. The best pH for the adsorption of silver was 3. Under the optimal conditions, the detection limit for silver by the tungsten wire preconcentration method was 5...
For the first time a new, sensitive, and simple bead injection spectroscopy-flow injection analysis (BIS-FIA) system with spectrofluorimetric detection is described for the sequential determination of two metals. The sensor is based on the alternate use of two carriers and a commercially available flow cell (Hellma 176-QS). The flow cell is filled by injecting in the flow system 500μl of a homogeneous...
A simple, sensitive and selective fluorimetric method for the determination of nitrite ion in waters using a merging zones flow injection system is described. The fluorimetric determination is based on the measurement of the quenching effect produced by nitrite on proflavine (3,6-diaminoacridine) fluorescence (λ ex /λ em =290/519nm).The optimum experimental conditions were...
Accurate simultaneous analysis of different anionic species using ion-selective electrodes (ISEs) can be achieved even for non-specific sensors by resorting to an ordinary least squares multiple regression in the vicinity of the predicted concentrations. In this work the potentialities of this approach are evidenced by the determination of nitrate and chloride in synthetic and real water samples in...
A very sensitive flow injection method with spectrophotometric detection has been developed for the on-line determination of copper in natural waters. The method exhibits a limit of detection three times lower than the most sensitive direct spectrophotometric method previously described and then allows the direct and simple in situ determination of copper in most natural waters.The method was based...
In this paper, an automatic method for the screening of water samples containing Cu(II) was proposed, based on peryoxalate chemiluminescence reaction using coproporphyrin I as fluorophor compound to provide selectivity and a simple flow injection (FI) chemiluminescence detector (CLD). FI system conditions were chosen in order to distinguish samples over or under legislation limit established (50μgl...
Nitrate determination in waters is generally carried out with cadmium filings and carcinogenic reagents or by reaction with phenolic compounds in highly concentrated sulfuric acid medium. In this work, it was developed a green analytical procedure for nitrate determination in natural waters based on direct spectrophotometric measurements in ultraviolet, using a flow-injection system with an anion-exchange...
A sensitive and selective phosphorimetric method for the determination of 1-naphthaleneacetic acid (1-NAA) based on a flow-injection system connected to a flow cell packed with a solid support and placed in the sample compartment of a conventional luminescence spectrometer is described. A non-ionic solid polymeric resin Amberlite XAD-7 is used for the packing. After injection of the sample, 1-NAA...
The speciation measurements of trace metals by the diffusive gradients in thin-films technique (DGT) using a poly(4-styrenesulfonate) (PSS) aqueous solution as a binding phase and a cellulose dialysis membrane (CDM) as a diffusive layer, CDM-PSS DGT, were investigated and showed good agreement with computer modelling calculations. The diffusion coefficients of ethylenediaminetetraacetic acid (EDTA)...
A 100-fold preconcentration procedure based on rare-earth elements (REEs) separation from water samples with an extraction chromatographic column has been developed. The separation of REEs from matrix elements (mainly Fe, alkaline and alkaline-earth elements) in water samples was performed loading the samples, previously acidified to pH 2.0 with HNO 3 , in a 2ml column preconditioned with...
An automatic multisyringe flow injection analysis (MSFIA) system coupling a flow-through optical fiber diffuse reflectance sensor with in-line gas-diffusion (GD) separation is proposed for the isolation, preconcentration and determination of traces of volatile and gas-evolving compounds in samples containing suspended solids, with no need for any preliminary batch sample treatment. The flowing methodology...
A flow injection on-line sorption system was developed for the separation and preconcentration of traces of Ag, Cd, Co, Ni, Pb, U and Y from natural water samples with subsequent detection by ICP TOF MS. Simultaneous preconcentration of the analytes was achieved by complexation with the chelating reagent 1-phenyl-3-methyl-4-benzoylpyrazol-5-one immobilized on the inner walls of a (200cm×0.5mm) PTFE...
A sequential injection (SI) method was developed for the spectrophotometric determination of chlorine based on the reaction between tetramethylbenzidine (TMB) and free chlorine. The advantages resulting from the use of TMB are considerable: TMB is highly selective for chlorine, it enables a fairly low quantification limit and represents a less toxic alternative to reagents such as tolidine. The use...
This paper describes the development of a sequential injection analysis method to automate the determination of picloram by square wave voltammetry exploiting the concept of monosegmented flow analysis to perform in-line sample conditioning and standard addition. To perform these tasks, an 800μL monosegment is formed, composed by 400μL of sample and 400μL of conditioning/standard solution, in medium...
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