Methods based on flow injection analysis (FIA) and high-performance liquid chromatography (HPLC) have been developed for the determination of ciprofloxacin (CIP) and norfloxacin (NOR) in pharmaceutical dosage forms. The FIA method is based on the measurement of absorbances of the red complexes formed between iron (III) and the studied drugs at 440 nm. Optimization of chemical and FI variables has been made. Under the optimized conditions, the sampling rate was over 80 h^-1. For the chromatographic method, a reverse phase Suplico LC₈ column (7.5 cm * 4.6 mm i.d, 3μm dp) was used at ambient temperature. The mobile phase finally selected was prepared by using ACN: 0.005 M H₃PO₄ (30:70) adjusted to pH = 4.98 by TEA. The developed methods have been successfully applied for the determination of ciprofloxacin and norfloxacin in pharmaceutical formulations. The common excipients and additives did not interfere in their determinations. The results obtained by the proposed methods have been statistically compared by means of Student t-test and by the variance ratio F-test.

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In this work, mathematical modelling of flow injection analysis is presented. The flow injection analysis (FIA) and sequential flow injection analysis (SIA) manifolds are studied. The mathematical model comprises a system of partial differential equations: i) the Navier-Stokes equation for incompressible fluid flow and ii) the diffusion-convection equation. This system is solved numerically and the resulting profiles of fluid velocity and the concentrations of the species of interest in space and time are obtained. This in turn enables us to obtain signal vs. time curves. The influence of different parameters, such as fluid velocity, diffusion coefficients and the geometry of the system, on the shape of the signal vs. time curves is analyzed. The numerical simulation results are compared with the experimental data.

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A flow injection analysis (FIA) system with turbidimetric determination for cell counting was developed. Similar to the McFarland’s method, the present work is based on the proportionality between the turbidimetric signals obtained for barium sulfate suspension and cell suspension. In spite of differences in physical properties, it was possible to establish a correlation between the two systems. The analytical curves for both species presented the following equations: S = 0.0087C_sulfate + 0.0005 for sulfate calibration and S = 4.8 x 10^-11 C_S.cerevisiae - 0.0018 for Saccharomyces cerevisiae, thus, the correlation between the two systems was: C_S.cerevisiae = 1.0875 C_sulfate + 0.0023. The results obtained, using the proposed procedure, were compared with results obtained in the Neubauer Chamber and there was no significant difference at confidence level of 95% (paired t-test). The proposed technique presented a limit of detection equal to 2.37 x 10⁸ cell L^-1. The main advantages of the FIA system were high sample throughput and good precision; both parameters proved to be better than conventional counting system into Neubauer Chamber. The method was also tested to monitor the cells growth and showed satisfactory results.

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A triply-synchronized automated on-line pretreatment system coupled with ICP-AES, Multi-Auto-Pret AES system, was developed for the rapid determination of trace metals in water samples. The Multi-Auto-Pret AES system consists of three sets of a single Auto-Pret system, one more selection valve and a switching valve. Each single Auto-Pret system has one mini-column (40 mm length x 2 mm i.d.), which was filled with a commercially available resin, Muromac A-1. The Multi-Auto-Pret AES system proposed here consists of 3 mini-columns that could be used for the preconcentration of trace metals sequentially, and can reduce analysis time and running cost. Under the optimum conditions, the repeatability in the same mini-column and the different mini-columns gave similar results, in which were less than 10% the relative standard deviations (RSD). When 5 mL of sample solution was used, the sample throughput was about 30 h^-1. The proposed system was very useful for analyzing a number of samples and applied to the rapid determination of 11 trace metals in river water samples.

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Flow immunoassay methods for the determination of several environmental pollutants, such as 2,4-dichlorophenol, bisphenol A, trinitrophenol, pesticides and allergy related compounds, such as histamine and immunoglobulin E (IgE) based on a surface plasmon resonance (SPR) sensor are reviewed from the view point of methodology of immunoassay. In this review, two types of immobilization methods for an antibody or an antigen conjugate for the target molecule on the sensor chip are proposed. One is the immobilization method for the antibody of the target molecule, where the antibody is immobilized on the sensor chip through a gold binding polypeptide and Protein G by taking into account of high orientation of the antibody for an immunoreaction on the sensor chip. The other method is the immobilization of the antigen conjugate in two way, where an antigen conjugate with protein such as bovine serum albumin is immobilized by physical adsorption and an antigen conjugate is immobilized by amino-coupling with an alkane thiol compound, which is preliminary immobilized on the sensor chip as a self-assembled monolayer. In order to enhance the sensitivity of the SPR sensor by increasing the change in the mass on the sensor chip after the immunoreaction, a competitive immunoreactions is adopted for the both immobilization methods, where the antibody or the antigen conjugate is immobilized on the sensor chip. A sandwich immunoassay method for the allergy related compound, IgE, was demonstrated as a sensitive method for enhancement of the SPR sensor signal. In the present flow immunoassay, a sequential injection technique is utilized in order to automate the immunoassay protocol, which consists of many procedures.

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