Strategies to Make Methods Based on Flow Injection Analysis Greener

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.

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.

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

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.

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

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

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.

A single-line flow injection analysis (FIA) system for simultaneous determination of hydrolyzable metals and free acid has been developed. As a model for hydrolyzable metals iron was chosen. The setup allows determination of 0.5-6 M acid and 0.1-1.6 M iron. The resulting prediction error is 7% for acid and 3.8% for iron. Data were obtained by using a diode array detector. The calibration models were developed by using partial least-squares (PLS) regression. These results were compared with results obtained by traditional univariate calibration. The project aimed at developing a simple and robust FIA system to be applicable in an industrial process setting. Necessary modifications of present FIA instrumentation to fit such an environment are discussed.

Cobalt(III) oxidation was applied to an on-line pretreatment of organic phosphorus compounds in a system of flow injection analysis (FIA). An FIA manifold, comprised parts for cobalt(III) oxidation and subsequent Molybdenum Blue spectrophotometric measurement, was assembled and the analytical conditions of the system were optimized. A platinum wire (0.2 mm×3 m) was inserted in a pretreatment coil (1 mm i.d.×5 m) for accelerating the digestion of organic phosphorus compounds by cobalt(III) ions. Cobalt(III) ions could completely convert organic phosphorus (<1 mg dm-3) to phosphate ions with the aid of the platinum catalyst at room temperature and in a relatively short time (average residence time in the coil: ca. 7 min). The detection limit for phosphorus by the subsequent spectrophotometry was 0.005 mgdnr3 (S/N=3) and the relative standard deviation of repeated measurements (n=10) was below 3% for 1 mg dm-3 (as P) disodium phenylphosphate. The present method reduced the amounts of the pretreatment and coloration reagents required and the time for analysis (10-12 samples could be determined per 1 h), compared to the amounts and time needed for the batchwise pretreatment method.

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

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

Modified screen-printed electrode for the FIA-amperometric determination of 2-nitro-p-phenylenediamine

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.

New interface for coupling flow-injection and capillary electrophoresis