- Email: [email protected]
FLOW INJECTION ANALYSIS | Detection Techniques
48
FLOW INJECTION ANALYSIS / Detection Techniques
electrothermal atomic-absorption spectrometry. Spectrochimica Acta, Part B 53(10): 1371–1379. Hansen EH (1992) Exploiting kinetic-based flow-injection methods for quantitative chemical assays. Analytica Chimica Acta 261(1–2): 125–136. Luque de Castro MD and Tena MT (1995) Hyphenated flow injection systems and high discrimination instruments. Talanta 42: 151–169. Prados-Rosales RC, Luque Garcı´a JL, and Luque de Castro MD (2002) Propelling devices: the heart of flow injection approaches. Analytica Chimica Acta 461: 169–180.
Prados-Rosales RC, Luque-Garcı´a JL, and Luque de Castro MD (2003) Valves and flow injection manifolds: an excellent marriage with unlimited versatility. Analytica Chimica Acta 480: 181–192. Ruzicka J and Hansen EH (1988) Flow Injection Analysis. New York: Wiley Interscience. Valca´rcel M and Luque de Castro MD (1987) Flow Injection Analysis: Principles and Applications. Chichester: Ellis Horwood. Wang JH and Hansen EH (2003) Sequential injectionlabon-valve: the third generation of flow-injection analysis. Trends in Analytical Chemistry 22(4): 225–231.
Detection Techniques M Miro´, University of the Balearic Islands, Palma de Mallorca, Spain W Frenzel, Technische Universita¨t Berlin, Berlin, Germany & 2005, Elsevier Ltd. All Rights Reserved.
Introduction Flow injection analysis (FIA) is a popular methodology with widespread use largely because it can employ any detection system that is capable of accepting a flowing stream. In many instances, the flow pattern of a liquid stream passing through a particular detector is not disrupted, so that additional detection systems can be arranged in series for multiparametric measurements in a single sample zone injected. In recent years, daughter flow techniques such as sequential injection analysis (SIA), multicommuted flow injection analysis, and multisyringe flow injection analysis have emerged as competitive methodologies of the former, especially in terms of versatility and online coupling to different detection instruments for sequential monitoring of key analytes. Moreover, the discontinuous operation of these novel techniques has expanded the applicability of flow systems, so that discrete, non-flow-through detection principles can also be hyphenated. In general, detectors can be classified according to the way in which the analyte or reaction product is probed, i.e., whether it is done by bulk or surface sensing. It is also possible to draw a distinction between flow-through detectors measuring an intrinsic property of the analyte and those requiring prior online derivatization. From the point of view of instrumental requirements, it is more appropriate to
make the classification according to the underlying detection principle as presented in this article. An ideal detector integrated in a flow manifold should possess several attributes, which in many respects are identical to those demanded for liquid chromatography. Accordingly, fast response, small dead volumes, wide dynamic ranges, high sensitivity, low noise level, reproducible and stable response, independence of the signal with fluctuations in flow velocity, simplicity of design, miniaturized size, robustness, and moderate cost are desirable. No existing detector fulfils the entire set of aforementioned requirements, and therefore a compromise between the various factors should be considered. This article provides some general remarks on detection requirements for FIA and related techniques and outlines the basic features of the most commonly used detection principles, including optical methods (namely, ultraviolet (UV)–visible spectrophotometry, spectrofluorimetry, chemiluminescence (CL), infrared (IR) spectroscopy, and atomic absorption/emission spectrometry) and electrochemical techniques such as potentiometry, amperometry, voltammetry, and stripping analysis methods. Very few flowing stream applications involve other detection techniques. In this respect, measurement of physical properties such as the refractive index, surface tension, and optical rotation, as well as the a-, b-, or g-emission of radionuclides, should be underlined. Piezoelectric quartz crystal detectors, thermal lens spectroscopy, photoacoustic spectroscopy, surface-enhanced Raman spectroscopy, and conductometric detection have also been coupled to flow systems, with notable advantages in terms of automation, precision, and sampling rate in comparison with the manual counterparts. Special emphasis is given in the bulk of the text to the design criteria for both flow-through cells and
FLOW INJECTION ANALYSIS / Detection Techniques
electrothermal atomic-absorption spectrometry. Spectrochimica Acta, Part B 53(10): 1371–1379. Hansen EH (1992) Exploiting kinetic-based flow-injection methods for quantitative chemical assays. Analytica Chimica Acta 261(1–2): 125–136. Luque de Castro MD and Tena MT (1995) Hyphenated flow injection systems and high discrimination instruments. Talanta 42: 151–169. Prados-Rosales RC, Luque Garcı´a JL, and Luque de Castro MD (2002) Propelling devices: the heart of flow injection approaches. Analytica Chimica Acta 461: 169–180.
Prados-Rosales RC, Luque-Garcı´a JL, and Luque de Castro MD (2003) Valves and flow injection manifolds: an excellent marriage with unlimited versatility. Analytica Chimica Acta 480: 181–192. Ruzicka J and Hansen EH (1988) Flow Injection Analysis. New York: Wiley Interscience. Valca´rcel M and Luque de Castro MD (1987) Flow Injection Analysis: Principles and Applications. Chichester: Ellis Horwood. Wang JH and Hansen EH (2003) Sequential injectionlabon-valve: the third generation of flow-injection analysis. Trends in Analytical Chemistry 22(4): 225–231.
Detection Techniques M Miro´, University of the Balearic Islands, Palma de Mallorca, Spain W Frenzel, Technische Universita¨t Berlin, Berlin, Germany & 2005, Elsevier Ltd. All Rights Reserved.
Introduction Flow injection analysis (FIA) is a popular methodology with widespread use largely because it can employ any detection system that is capable of accepting a flowing stream. In many instances, the flow pattern of a liquid stream passing through a particular detector is not disrupted, so that additional detection systems can be arranged in series for multiparametric measurements in a single sample zone injected. In recent years, daughter flow techniques such as sequential injection analysis (SIA), multicommuted flow injection analysis, and multisyringe flow injection analysis have emerged as competitive methodologies of the former, especially in terms of versatility and online coupling to different detection instruments for sequential monitoring of key analytes. Moreover, the discontinuous operation of these novel techniques has expanded the applicability of flow systems, so that discrete, non-flow-through detection principles can also be hyphenated. In general, detectors can be classified according to the way in which the analyte or reaction product is probed, i.e., whether it is done by bulk or surface sensing. It is also possible to draw a distinction between flow-through detectors measuring an intrinsic property of the analyte and those requiring prior online derivatization. From the point of view of instrumental requirements, it is more appropriate to
make the classification according to the underlying detection principle as presented in this article. An ideal detector integrated in a flow manifold should possess several attributes, which in many respects are identical to those demanded for liquid chromatography. Accordingly, fast response, small dead volumes, wide dynamic ranges, high sensitivity, low noise level, reproducible and stable response, independence of the signal with fluctuations in flow velocity, simplicity of design, miniaturized size, robustness, and moderate cost are desirable. No existing detector fulfils the entire set of aforementioned requirements, and therefore a compromise between the various factors should be considered. This article provides some general remarks on detection requirements for FIA and related techniques and outlines the basic features of the most commonly used detection principles, including optical methods (namely, ultraviolet (UV)–visible spectrophotometry, spectrofluorimetry, chemiluminescence (CL), infrared (IR) spectroscopy, and atomic absorption/emission spectrometry) and electrochemical techniques such as potentiometry, amperometry, voltammetry, and stripping analysis methods. Very few flowing stream applications involve other detection techniques. In this respect, measurement of physical properties such as the refractive index, surface tension, and optical rotation, as well as the a-, b-, or g-emission of radionuclides, should be underlined. Piezoelectric quartz crystal detectors, thermal lens spectroscopy, photoacoustic spectroscopy, surface-enhanced Raman spectroscopy, and conductometric detection have also been coupled to flow systems, with notable advantages in terms of automation, precision, and sampling rate in comparison with the manual counterparts. Special emphasis is given in the bulk of the text to the design criteria for both flow-through cells and