Flow techniques in water analysis

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 injection analysis (SIA) and multi-commutation techniques (MCFA), is carried out. On the other hand, a new technique, the multi-syringe flow analysis (MSFA) is hereby described for the first time as both a fast and robust alternative. Its possibilities, limitations and potential advantages when using this technique either on its own or coupled to SIA, which carries out a previous sample handling, are outlined.     

Advancement of flow-based analysis with alternative chemical reactions and new devices for environmental and biological samples.

This review includes our researches and other methodologies related to flow-based techniques, such as flow injection analysis (FIA) and sequential injection analysis (SIA). The methods will demonstrate semi-and full automated FIA and SIA, including liquid-liquid and liquid-solid extraction. FIA using alternative chemical reactions in the aqueous solution was applied to the trace analysis of metals in biological and environmental samples. For durable liquid-liquid extraction, several phase separators were designed. Moreover, multi-channel FIA with newly designed flow cells and SIA with lab-on-valve devices have been used for the simultaneous and successive determination of metals and organic compounds. On-line solid phase extraction (SPE) has also been proposed for highly sensitive analysis of organic and inorganic compounds.     

Comparison of APPI, APCI and ESI for the LC-MS/MS analysis of bezafibrate, cyclophosphamide, enalapril, methotrexate and orlistat in municipal wastewater

The applicability of three different ionization techniques: atmospheric pressure photoionization (APPI), atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) was tested for the liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of five target pharmaceuticals (cyclophosphamide, methotrexate, bezafibrate, enalapril and orlistat) in wastewater samples. Performance was compared both by flow injection analysis (FIA) and on-column analysis in deionized water and wastewater samples. A column switching technique for the on-line extraction and analysis of water samples was used. For both FIA and on-column analysis, signal intensity and signal-to-noise (S/N) ratio of the target analytes in the three sources were studied. Limits of detection and matrix effects during the analysis of wastewater samples were also investigated. ESI generated significantly larger peak areas and higher S/N ratios than APCI and APPI in FIA and in on-column analysis. ESI was proved to be the most suitable ionization method as it enabled the detection of the five target compounds, whereas APCI and APPI ionized only four compounds.     

New approaches to molecular spectroscopic detection in flow-injection analysis

A state-of-the-art overview of molecular spectroscopy as applied in flow injection analysis (FIA) is presented. It deals chiefly with the most interesting FIA approaches aimed at improving detector performance, innovations in the detection system itself and the coupling of FIA with unusual detectors for this technique. The most salient trends in relation to this association are also commented upon.     

Development of an automated on-line analysis system using flow injection, ultrasound filtration and CCD detection

The design and construction of an automated on-line analysis system is described with reference to applications in bioprocess control, clinical, and environmental analysis. The new system is built around three main elements: ultrasound filtration, a micro flow injection analysis (FIA) system, and direct readout spectrophotometry. The advantages of three on-line ultrasound filtration devices, developed for clarification of water, human blood and mammalian cell culture samples, are described. The filters avoid off-line centrifugation and do not suffer from the blockage problems associated with conventional filters. The separation efficiency of the ultrasound filters is also discussed. The delivery system is based on a gas driven FIA technique, using helium to avoid bubble formation, with the carrier and reagent flow being controlled by computer switched solenoid valves. Direct readout spectrometers are used, based on charge coupled devices (CCDs) covering the wavelength range 200-900 nm. These detectors provide near instantaneous capture of full spectra, allowing several analytes to be monitored simultaneously, and are much smaller than conventional spectrophotometers. Optical fibres are used to link the light source to the detector via a flow cell in the FIA system. Software to run the entire system was developed using the LabVIEWtrade mark graphical programming environment, enabling rapid development of the control system and user interface. The integration of these components has shown significant improvement in the application of FIA techniques to on-line analysis.     

Stopped-flow injection analysis. The influence of diffusion on dispersion of normal and reverse flow injection

A relationship is derived to enable the comparison of the dispersion heights of normal and reverse flow injection analysis (FIA). A single channel flow system is employed in the absence of a chemical reaction. The stopped-flow injection method is used to probe the influence of molecular diffusion on the overall dispersion of normal and reverse FIA, which appeared to demonstrate fundamentally different diffusion behaviors. Small discrepancies are observed between the dispersion heights, which are enhanced by the stopped-flow period, especially when unmatched matrix ionic compositions of the indicator and counter solutions were involved. For these conditions, the diffusion flux rate is enhanced considerably, displaying a peak, in addition to the transient, for both methods. The influence of diffusion on the dispersion characteristics of normal and reverse FIA is discussed theoretically. Diffusion in the proposed model is postulated to oppose dispersion by convection. The latter initiates concentration gradients in the injection zone and propagates it with flow time over the dispersion zone profile. The diffusion flux then reacts in order to confine the indicator dispersion for normal FIA and to enhance it for reverse FIA. This model is consistent with the experimental results and accounts for most of the phenomena encountered. Probably owing to the influence of secondary flow phenomena, the use of coiled tubes has suppressed the effects of diffusion on the overall dispersion behavior.Part of the experimental work was performed at IMI Institute for Research and Development, Haifa, Israel.     

Application of flowing stream techniques to water analysis Part III. Metal ions: alkaline and alkaline-earth metals, elemental and harmful transition metals, and multielemental analysis

In the earlier parts of this series of reviews [1] and [2], the most relevant flowing stream techniques (namely, segmented flow analysis, continuous flow analysis, flow injection (FI) analysis, sequential injection (SI) analysis, multicommuted flow injection analysis and multisyringe flow injection analysis) applied to the determination of several core inorganic parameters for water quality assessment, such as nutrients and anionic species including nitrogen, sulfur and halogen compounds, were described.In the present paper, flow techniques are presented as powerful analytical tools for the environmental monitoring of metal ions (alkaline and alkaline-earth metals, and elemental and harmful transition metals) as well as to perform both multielemental and speciation analysis in water samples. The potentials of flow techniques for automated sample treatment involving on-line analyte separation and/or pre-concentration are also discussed in the body of the text, and demonstrated for each individual ion with a variety of strategies successfully applied to trace analysis. In this context, the coupling of flow methodologies with atomic spectrometric techniques such as flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma mass spectrometry (ICPMS) or hydride-generation (HG)/cold-vapor (CV) approaches, launching the so-called hyphenated techniques, is specially worth mentioning.     

Advances in On-Line Hydride Generation Atomic Spectrometric Determination of Arsenic

Flow analysis has played a major role in many areas of chemical analysis, making operations more robust and precise. It facilitates experimental studies opening new areas of research. In the field of arsenic research, there are various examples of surveys concerning arsenic determination and its species with the use of flow injection analysis (FIA) and sequential injection analysis (SIA). The increasing concern over the human exposure to arsenic and its species has necessitated the development of rapid, highly sensitive, precise, and accurate analytical methods for its determination in trace levels in environmental and biological samples. This review provides a literature survey on the automatic on-line hydride generation methodologies coupled to atomic spectrometry for determination of inorganic and organic arsenic species, during the last decades. All advances in on-line manifolds are categorized and highlighted. There are several reports of manifolds and setup instrumentation concerning hydride generation including continuous flow analysis (CFA), FIA, SIA, lab-on-valve (LOV), multicommutation flow systems, and hyphenated techniques. On-line preconcentration and pretreatment methodologies coupled with hydride generation such as solid phase extraction, co-precipitation and trapping are also discussed, as they are of particular interest in the development of fully automated methods.     

Flow injection analysis NMR (FIA–NMR): a novel flow NMR technique that complements LC–NMR and direct injection NMR (DI–NMR)

Details of a new flow NMR technique, flow injection analysis NMR (FIA–NMR), are presented for the first time. This method blends some aspects of both liquid chromatography–NMR and direct injection NMR, and complements both. FIA‐NMR is shown to be useful as an analytical technique, especially for repetitive analyses, and may also prove useful in the analysis of combinatorial chemistry libraries. The feasibility of FIA‐NMR is demonstrated by the quantitative analysis of an over‐the‐counter pharmaceutical. Copyright © 2003 John Wiley & Sons, Ltd.     

Polar organic compounds in the river Elbe — Development of optimized concentration methods using substance-specific detection techniques

Different methods for solid phase extraction (SPE) of polar, organic compounds found in Elbe water were compared. Mass-spectrometric detection (MS) after liquid chromatographic separation (LC) or flow injection analysis (FIA) and thermospray ionization (TSP) was used to assess the concentration behaviour as well as the detection techniques. A selected compound was identified using tandem mass spectrometry (MS/MS) carrying out mixture analysis.     

Extraction-chromatographic preconcentration with chromatomembrane separation of extract from aqueous phase for luminescence determination of oil products and phenols in natural water by flow injection analysis

The new method of preconcentration by extraction for flow injection analysis (FIA) with luminescence and photometric detection is proposed. Preconcentration is carried out on extraction-chromatographic column, extract is eluted by extragent with the following separation of extract from aqueous phase in chromatomembrane cell. Possibilities of the proposed method are illustrated in the examples of FIA with luminescence determination of oil products and phenols in natural water.     

Application of flowing-stream techniques to water analysis Part II. General quality parameters and anionic compounds: halogenated, sulphur and metalloid species

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 when coupled to photometric/fluorimetric detection, flow-through ion-selective electrodes or amperometric sensors.In the present paper, relevant flow methods applied to the monitoring of anionic species as well as to the determination of general parameters for water quality evaluation (such as pH, alkalinity, chemical and biochemical oxygen demand, conductivity and total ionic content) are reviewed, and their background, detection technique and noteworthy analytical features are detailed. Furthermore, other techniques, such as flow systems connected to hydride-generation atomic absorption spectrometry, should be highlighted as practical approaches for metalloid determination since a series of speciation schemes are demonstrated to be readily adaptable.     

Reversed flow injection and sandwich sequential injection methods for the spectrophotometric determination of copper(II) with cuprizone

Two new flow methods, flow injection analysis (FIA) and sequential injection analysis (SIA), for the spectrophotometric determination of Cu(II) in water at trace levels have been developed and optimised. Both methods are based on the reaction with oxalic acid bis(cyclohexylidene hydrazide) (cuprizone) in alkaline media. The two procedures have been developed for the final aim to compare their performances and to offer new rapid heavy metals analysis tools, avoiding the use of extraction steps. A detailed study of the physico-chemical parameters affecting the systems performances has been carried out. The reversed FIA and sandwich SIA approaches offered the best sensitivity. In both cases, an extremely good linearity has been obtained within the range 0.06-4 μg ml⁻¹ (correlation coefficient r=0.9999), whereas the observed detection limits were 0.013 and 0.004 μg ml⁻¹, for FIA and SIA, respectively. Furthermore, due to the great similarity of the diffusion zones in the reaction slugs, our approach offers the opportunity to compare the two methods in analogous conditions. This SIA method, besides keeping its typical reagent saving features, offered analytical performances equivalent to those of FIA. To obtain these results, an original “stop-flow like” method was successfully employed in the SIA approach. Both methods were validated by analysis of real water samples, after copper addition, and certified reference samples of fortified and waste waters.     

双光束流动注射光度法测定生活用水中氯离子

将流动注射分析技术应用到双光束分光光度法中，对其理论和实验技术进行了研究，采用自行组装的流动注射系统进行了生活用水中氯离子的测定，获得满意结果。     

Some aspects of analytical instrumentation: models, techniques, instruments

Summary The paper gives a review of investigations aimed at the development of instruments and techniques for analytical chemistry performed by the Institute for Analytical Instrumentation of the USSR Academy of Sciences. Advances in mass spectrometry of non-volatile labile compounds, determination of amino acid sequence in peptides, multidimensional Mössbauer spectroscopy, EPR recording optical techniques, microcolumn chromatography, field flow fractionation (FFF), and flow injection analysis (FIA) are considered.

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Einige Aspekte des analytischen Gerätebaus: Modelle, Verfahren, Instrumente

     

The impact of flow injection on modern chemical analysis: has it fulfilled our expectations? And where are we going?

Presenting a condensation of the opening lecture of the 12th ICFIA conference, this communication presents a view of the impact that flow injection analysis (FIA) has had on modern analytical chemistry, evaluated both within the academic community and outside it, i.e. in “industry”. The ensuing developments of FIA, encompassing sequential injection analysis (SIA) and bead injection lab-on-valve (BI-LOV), are described and their individual features discussed. Finally, some recent results of the activities from the author’s own research group are briefly mentioned.     

Increasing the scope and power of flow-injection analysis through chemometric approaches

The objective of this paper is to illustrate how chemometrics can enhance the scope and power of flow injection analysis (FIA) by considering a few simple but representative cases where the ability of chemometrics to improve performance is not readily apparent. In principle, there are two phases when chemometrics can be usefully combined with FIA: first when developing an FIA method and, second, when treating raw data acquired from an FIA detection system. The most obvious application of chemometrics for the FIA practitioner is to use experimental design to replace the obsolete, but too often used one-variable-at-a-time approach when optimising an FIA method. Therefore, methods for screening variables and system optimisation are discussed. Raw data acquired from most FIA systems are first-order data, containing information about the dispersed sample plug. However, the information that is extracted when using FIA for routine purposes is of zero-order: predominantly peak height values. It is shown by a simple example that a chemometric approach in such cases can again provide additional useful information about the sample. First-order spectral data and second-order data more or less require a chemometrics approach for successful analysis, and examples of such applications are briefly discussed.     

On the mathematical model of flow injection analysis-II. The second order chemical reaction in a straight tube

The mathematical model of flow injection analysis (FIA) for fast second-order chemical reaction in a straight tube is presented. The sample and reagent are initially premixed and the analytical solution for the detection output, i.e. the integral of the product of reaction concentration over the tube cross-section is given. The optimization of FIA is discussed. It is proposed to put the detector in the real FIA systems immediately after the point where the sample and reagent are satisfactorily mixed.     

平头pH电极-流动注射联用技术快速滴定食醋中醋酸的方法研究

采用一种具有平头结构的pH电极作为流动注射分析(FIA)的检测器,构建了流动注射自动化酸度滴定系统.优化了样品进样量、流速、载液浓度和反应管长度等参数.用NaOH溶液作为载液,在4.639×10-4～0.212 mol·L-1范围内醋酸浓度的对数与FIA峰的峰面积成正比,该方法的相对标准偏差(RSD)小于0.5%.采用...