Flow-injection analysis detection systems

Al-Gailani, B.R.M., G.M. Greenway, and T. McCreedy. 2007. Miniaturized flow-injection-analysis (jiFIA) system with on-hne chemiluminescence detection based on the luminol-hypochlorite reaction for the determination of ammonium in river water. Int. J. Environ. Anal. Chem. 87 425-436. 

An automated flow injection analysis (FIA) system for quantifying ethanol was developed using alcohol oxidase, horseradish peroxidase, 4-amino-phenazone, and phenol. A colorimetric detection method was developed using two different methods of analysis, with free and immobilized enzymes. The system with free enzymes permitted analysis of standard ethanol solution in a range of 0.05-1.0 g of ethanol/L without external dilution, a sampling frequency of 15 analyses/h, and relative SD of 3.5%. 

Fig. 19. Schematic design of a flow injection analysis (FIA) system. A selection valve (top) allows a selection between sample stream and standard(s). The selected specimen is pumped through an injection loop. Repeatedly, the injection valve is switched for a short while so that the contents of the loop are transported by the carrier stream into the dispersion/reaction manifold. In this manifold, any type of chemical or physical reaction can be implemented (e.g. by addition of other chemicals, passing through an enzyme column, dilution by another injection, diffusion through a membrane, liquid-liquid extraction, etc. not shown). On its way through the manifold, the original plug undergoes axial dispersion which results in the typical shape of the finally detected signal peak...

The utilization of a dsDNA matrix to aid enzyme immobilization is also a promising alternative for the development of DNA biosensors and its application in flow injection analysis (FIA) systems. A DNA-tyrosinase carbon paste electrode described by Serrano and co-workers [115] showed excellent performance for the detection of catechol in an FIA system and suggests that other enzymatic biosensors can benefit from the presence of DNA. 

Some authors claim that detection limits (DLs) of 5 mgL are easily obtainable [167] using the batch PCV detection method. However, it has been reported that daily DLs range between 5 and 10 mg L and that personnel who are highly acquainted with the method were needed to achieve DLs down to <10 mg L [168]. This poses a problem when the non-labile or monomeric organic fraction of aluminium to be measured is very small. Errors for Alni can become high, and, because the Driscoll method is a subtraction method, the uncertainty of the calculated Ali fraction (Alim—Alni) can become unacceptable. To increase the precision, sample throughput and practicality of the Driscoll method, several flow injection analysis (FIA) systems have been designed both for the PCV method [169,170] and for detection with a fluorimetric determination of the 8-hydroxyquinoline-5-sulfonic acid (8-HQS) aluminium complex in a micellar medium (cetyltri-methylammonium bromide, CTAB) [168,171]. 

ABEI produces ECL when oxidized at 1.0 V versus Ag/AgCl in alkaline aqueous solution. In contrast to luminol, ABEI labels do not markedly lose their CL efficiency when conjugated with proteins. ECL immunoassays with a flow injection analysis (FIA) system using ABEl-isothiocyanate as a label were proposed, which have a better performance than either single-radial immunodiffusion or nephelometric immunoassays. ABEI can also be used as an oligonucleotide marker to label a DNA probe. The intensity of the ABEI ECL was linearly related to the concentration of the complementary sequence in the range 96-96 nM, and the detection limit was down to 30 pM. 

Various programs have been developed for the automation of flow injection analysis (FIA) systems and many of these are already employed for industrial applications [1]. None of these automation systems consider the complexity of FIA systems with its increased potential of faults. Until now only few investigations have been published, concerning fault detection in flow injection analysis. Gine et al. [2] investigated possible faults of a certain FIA system, the influence of the faults on the... 

Figure 5.17 shows an SIA system for the AAS determination of iron by preconcentration of the metal on a Chelex 100 column and elution with nitric acid [5]. The system uses a Crison Compact titrator to operate both burettes in such a way that the nebulizer will continuously receive liquid at a constant flow-rate. Another interesting example of coupling ASS detection and flow techniques is a multisyringe flow injection analysis (MSFIA) system with cold-vapor AAS developed to determine mercury [6]. 

FIGURE 1.5 Schematic diagram of flow injection analysis (FIA) system with immunoassay detection RIANA (abbreviation from River ANAlyser ) based on total internal reflection fluorescence with immobilized fluorescently labeled antibodies. The source of the excitation light is a He-Ne laser, and the collected fluorescent light is filtered and detected by photodiodes (PD). (Adapted from Rodriguez-Mozaz, S. et al. 2004. Biosens. Bioelectron. 19 633-640.)... 

Direct, sensitive, selective, and rapid biosensors have been developed based on OPH, organophosphoms acid hydrolase (OPAA), and parathion hydrolase (PH). Schoning and co-workers developed a silicon-based capacitive field-effect pH sensor, which can detect 2 pM of paraoxon. " The same group prepared ampero-metric and potentiometric biosensor chips by thin-film techniques and integrated them in a flow-injection analysis (ElA) system, which can detect different OP pesticides at the low pM concentration range.Recently, mesoporous carbon and carbon black-modified electrodes have been used to develop an amperometric biosensor based on OPH. With increased sensitivity, the biosensor can detect as low as 0.12 pM (36 ppb) paraoxon. ... 

Since 1970, new analytical techniques, eg, ion chromatography, have been developed, and others, eg, atomic absorption and emission, have been improved (1—5). Detection limits for many chemicals have been dramatically lowered. Many wet chemical methods have been automated and are controlled by microprocessors which allow greater data output in a shorter time. Perhaps the best known continuous-flow analy2er for water analysis is the Autoanaly2er system manufactured by Technicon Instmments Corp. (Tarrytown, N.Y.) (6). Isolation of samples is maintained by pumping air bubbles into the flow line. Recently, flow-injection analysis has also become popular, and a theoretical comparison of it with the segmented flow analy2er has been made (7—9). 

The ion pair extraction by flow injection analysis (FIA) has been used to analyze sodium dodecyl sulfate and sodium dodecyl ether (3 EO) sulfate among other anionic surfactants. The solvating agent was methanol and the phase-separating system was designed with a PTFE porous membrane permeable to chloroform but impermeable to the aqueous solution. The method is applicable to concentrations up to 1.25 mM with a detection limit of 15 pM [304]. 

Sample preparation, injection, calibration, and data collection, must be automated for process analysis. Methods used for flow injection analysis (FLA) are also useful for reliable sampling for process LC systems.1 Dynamic dilution is a technique that is used extensively in FIA.13 In this technique, sample from a loop or slot of a valve is diluted as it is transferred to a HPLC injection valve for analysis. As the diluted sample plug passes through the HPLC valve it is switched and the sample is injected onto the HPLC column for separation. The sample transfer time typically is determined with a refractive index detector and valve switching, which can be controlled by an integrator or computer. The transfer time is very reproducible. Calibration is typically done by external standardization using normalization by response factor. Internal standardization has also been used. To detect upsets or for process optimization, absolute numbers are not always needed. An alternative to... 

Simultaneous determination of both cations and anions in acid rain has been achieved using a portable conductimetric ion-exclusion cation-exchange chromatographic analyzer.14 This system utilized the poly(meth-ylmethacrylate)-based weak acid cation exchange resin TSK-Gel OA-PAK-A, (Tosoh , Tokyo, Japan) with an eluent of tartaric acid-methanol-water. All of the desired species, 3 anions and 5 cations, were separated in less than 30 minutes detection limits were on the order of 10 ppb. Simultaneous determination of nitrate, phosphate, and ammonium ions in wastewater has been reported utilizing isocratic IEC followed by sequential flow injection analysis.9 The ammonium cations were detected by colorimetry, while the anions were measured by conductivity. These determinations could be done with a single injection and the run time was under 9 minutes. 

Vinas et al. [46] also determined penicillamine by chemiluminescence - flow injection analysis. The sample was dissolved in water, and a portion of resulting solution was introduced into an FIA system consisting of 5 mM luminol in 0.1 M KOH-boric acid buffer (pH 10.4), 50 pM Cu(II), and 10 mM H202 eluted at 7.2 mL/min. Chemiluminescent detection was used, the calibration graphs were linear from 0.1 to 10 mM of penicillamine, and the coefficients of variation were from 1.2% and 2.1%i. 

Methods for determination of thiol drugs (i.e., captopril [21-25], penicillamine [26-28], hydrochlorothiazide [24, 25, 29, 30], and tiopronin [31, 32]) have been developed. These methods are based on CL from a cerium (IV) oxidation system sensitized by adequate fluorophores such as quinine and rhodamine B. By using HPLC-coupled CL-flow-injection analysis method, tiopronin and its metabolite 2-mercaptopropionic acid in human urine were sensitively determined with the detection limits of 0.8 and 1 pM, respectively [32],... 

Three methods for trace metal preconcentration were examined liquid-liquid extraction aided by a chelating agent, concentration on a synthetic chelating resin and reductive precipitation with NaBTLt. The latter method gave 1000-fold preconcentration factors with total recovery of Pb and other elements17. Preconcentration of nanogram amounts of lead can be carried out with a resin incorporating quinolin-8-ol (3)18. Enhancement factors of 50-100 can be achieved by such preconcentration procedures followed by determination in a FLA (flow injection analysis) system limits of detection are a few pg Pb/L19. 

There is increasing interest in the use of specific sensor or biosensor detection systems with the FIA technique (Galensa, 1998). Tsafack et al. (2000) described an electrochemiluminescence-based fibre optic biosensor for choline with flow-injection analysis and Su et al. (1998) reported a flow-injection determination of sulphite in wines and fruit juices using a bulk acoustic wave impedance sensor coupled to a membrane separation technique. Prodromidis et al. (1997) also coupled a biosensor with an FIA system for analysis of citric acid in juices, fruits and sports beverages and Okawa et al. (1998) reported a procedure for the simultaneous determination of ascorbic acid and glucose in soft drinks with an electrochemical filter/biosensor FIA system. 

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