New interface for coupling flow-injection and capillary electrophoresis

A flow injection analysis (FIA) system for evaluation of the antioxidant activity of a compound capable of scavenging a hypochlorite anion (OCl⁻), one of the reactive oxygen species (ROS), was developed. Aminophenyl fluorescein (APF), a fluorescence indicator of ROS, was mixed manually with the test compounds and the mixed solution was injected into the FIA system. The injected solution was reacted in-line with OCl⁻, that was produced by using sodium dichloroisocyanurate in the presence of 0.1 M CH3CO2Na in H2O. The fluorescence intensity of fluorescein generated from non-fluorescent APF was significantly attenuated in compounds that had a scavenging effect on OCl⁻. The precision obtained by the FIA system was satisfactory (relative standard deviation < 5.0%) and a rapid assay within 0.5 min per sample was achieved. The proposed FIA system was used to demonstrate that reduced glutathione, dithiothreitol, and 3-methyl-1-phenyl-5-pyrazolone (edaravone) showed a significant scavenging effect on OCl⁻. Therefore, the proposed FIA system can be used as a screening assay for OCl⁻-scavenging compounds.

On-line determination of intracellular β-galactosidase activity in recombinant Escherichia coli using flow injection analysis (FIA)

Much has been written about the theoretical background of Flow Injection Analysis (FIA) systems. Until now the prediction of the dispersion in a FIA system was restricted to the use of simple formulae or two-dimensional numerical models. Through recent developments in computer hardware and, at the same time, the development of efficient computational fluid dynamics software it is possible, with the use of a three dimensional model (based on the Navier-Stokes equations), to make a 1 to 1 translation between experimental systems and systems based on numerical calculations. A 1 to 1 translation means that only (fundamental) parameters are necessary in the numerical description without the need for fit or match factors. All the known phenomena, such as convection and diffusion, are incorporated in this description. The fundamental parameters in this thesis are: the concentrations, the diffusion coefficients, the geometry, the flow rates and in case of a reaction, the reaction constant, the reaction equation and reaction order. Next to these macro FIA systems the micro FIA systems are emerging. These systems have many advantages compared to the traditional macro systems. Two examples are: a considerable reduction in analyte consumption and the development of portable systems. One disadvantage of the current microsystems, is the expensive development. It would be very helpful, money wise, if numerical calculations could be used for the development of an optimal microsystem. In this thesis the results of a three dimensional numerical model, based on the Navier-Stokes equations, are compared with experimental results. This has been done for channels of different geometries, different flow rates and a simple reaction.

A bacterial biosensor integrated within a flow injection analysis (FIA) system has been developed for the detection of benzene, based on its aerobic catabolism by Pseudomonas putida ML2. P. putida ML2 cells were immobilised between two cellulose acetate membranes and fixed onto a Clark dissolved oxygen electrode. Biosensor responses were investigated with the FIA system, resulting in a linear detection range between 0.01–0.1 mM benzene. A response and baseline recovery time of 6 and 10–15 min, respectively, was obtained. A stable and reproducible sensor response has been found up to 28 days of use based on the same bacterial membrane, and the sensor has shown a high specificity to benzene, with a negligible response to other benzene‐related compounds. Its ease of operation, rapid and sensitive response, and cost‐effective production, demonstrate that the P. putida ML2 biosensor has potential applications for the analysis of samples containing benzene. The optimisation of the biosensor‐flow injection system is described.

A flow injection analysis (FIA) system is presented which is able to monitor simultaneously and on-line the concentrations of glucose and total malto sugars during fermentation or hydrolysis processes. The system consists of glucoamylase (GA), glucose oxidase (GOD) EC 1.1.3.4 and mutarotase (MUT) EC 5.1.3.3 immobilized on synthetic polymer beads contained in cartridges serving as reactors. A high degree of selectivity towards non-malto sugars and carbohydrates, amino acids, and other possible components in the fermentation medium was exhibited by the system. The measurements delivered by the system during the monitoring of Bacillus licheniformis fermentation for protease production in complex media described the actual progress of the process. A correlation of the on-line measurements with the off-line enzymatic and off-line colorimetric measurements rendered correlation coefficients (r 2 ) of 0.997 and 0.995, respectively. The enzyme reactors could be used on a long-term basis at 30°C and a pH of 5.5.

On-line determination of glucose and lactate concentrations in animal cell culture based on fibre optic detection of oxygen in flow-injection analysis

Simultaneous and direct determination of urea and creatinine in human urine using a cost-effective flow injection system equipped with in-house contactless conductivity detector and LED colorimeter

The implementation of flow injection analysis (FIA) systems and correlated techniques in the laboratory routine provides an increase of analytical throughput and the reduction of risks of analyte losses and contamination. Naturally, it contributes to the reduction of reagent consumption and minimization of waste generation. This paper presents and discusses an overview of the main strategies adopted to make methods based on FIA systems more environmentally friendly, and offers a review of these methods that covers the period from January 2002 to December 2019. Strategies based on reagent management (adoption of procedures without reagents, replacement of toxic reagents, recycling and reuse of reagents and, use of immobilized reagents), the online waste treatment, and the improvements of FIA systems (flow system configurations that avoid reagent wastage, use of green detectors, automation, and miniaturization) are approached in this perspective.

Closed-loop peristaltic micro-pump for flow-through sample injection in capillary electrophoresis.

Simultaneous separation of up to 22 inorganic and organic anions, alkali, alkaline earth and transition metal cations was achieved in less than 3 min in the capillary electrophoresis system with contactless conductometric detector. The sample was injected from both capillary ends (dual opposite end injection) and anionic and cationic species were detected in the center of the separation capillary. The parameters of the separation electrolyte, such as pH, concentration of the electrolyte, concentration of complexing agents and concentration of 18-crown-6 were studied. Best results were achieved with electrolytes consisting of 8 mM L-histidine, 2.8 mM 2-hydroxyisobutyric acid, 0.32 mM 18-crown-6 at pH 4.25 or 9 mM L-histidine, 4.6 mM lactic acid, 0.38 mM 18-crown-6 at pH 4.25. Other electrolytes containing complexing agents such as malic or tartaric acid at various concentrations could also be used. The detection limits achieved for most cations and anions were 7.5 - 62 micro gL(-1) except for Ba2+ (90 micro gL(-1)), Cd 2+, Cr 3+ and F- (125 micro gL(-1)), and fumarate (250 micro gL(-1)). The repeatability of migration times and peak areas was better than 0.4% and 5.9%, respectively. The developed method was applied for analysis of real samples, such as tap, rain, drainage and surface water samples, plant exudates, plant extracts and ore leachates.

Amperometric method for rapid detection of Escherichia coli by flow injection analysis using a bismuth nano-film modified glassy carbon electrode

Determination of free catecholamines in urine by tandem affinity/ion-pair chromatography and flow injection analysis

A novel method based on flow injection analysis (FIA) and flame atomic emission spectrometry (FAES) is presented. It was developed for direct determination of barium in drinking water, in natural water, in digested samples of bone and liver, in saline water and in a standard reference material (NIST SRM 1640). It was found that digestion of bone by an incineration procedure was required, in order to extract most of the barium. In the FIA manifold, barium was pre-concentrated by co-precipitation with lead chromate leading to a crystalline deposit that adhered well to the inner walls of a nylon knotted reactor (KR). The method documents a novel example of formation of a crystalline compound during the pre-concentration step. The method comprises filterless pre-concentration by co-precipitation that proceeds successfully in a FIA system. An enrichment factor (EF) of 24 was achieved under normal working conditions at a sampling frequency of 50 h−1. The detection limit (LOD, 3σ) was determined as 0.8 µg L−1 and species of iron(II) and iron(III) constituted the main species of interference.

A measurement system for food nutrient with flow injection analysis (FIA) system was constructed. The sensing system consisted of a peristaltic pump, a glucose oxidase (GOD) reactor and a photodiode. GOD was immobilized on a polytetrafluoroethylene (PTFE) membrane by crosslinking using glutaraldehyde. H2O2 generated by the GOD reaction oxidized luminol to produce chemiluminescence in the presence of horseradish peroxide. The chemiluminescence was detected using a photodiode. The calibration range of the nutrient sensor for glucose was from 2.0 to 100.0 mmol/1. The glucose concentration of tomato extraction measured with the glucose FIA system and the spectroscopy measurement were 78.4 mmol/1 and 94.4 mmol/1, respectively.

2.50 - Development of FIA Biosensor System for the Determination of Starch in Flour