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The state of the art and prospects for the combined use of continuous sample treatment systems and custom-made and commercially available capillary electrophoresis equipment is presented and discussed. Sample treatment in this separation technique is of great practical relevance by virtue of its inherent shortcomings, which include low sensitivity, small sample volumes, and a marked influence of matrix components. The main technical types of coupling (in-line, on-line, and mixed) are dealt with systematically and compared to manually implemented approaches in order to derive practical conclusions with a view to developing new technical applications and facilitate use by routine laboratories.

The use of a suitable sampling or sample-processing unit connected to a flow injection system can significantly expand the scope of application of the flow injection technique by enabling the direct introduction and treatment of solid and other complex samples in a single automated system. In recent years various sample pretreatment techniques, including electrolytic dissolution, on-line leaching, continuous microwave digestion, on-line sterilizable membrane dialysis/filtration, pervaporation, dynamic gas-extraction, and flow-reversal liquid-liquid extraction, among others, have proven useful for solving a variety of analytical problems in conjunction with flow injection systems. The principles behind these techniques and their applications in fast assay and on-line process monitoring are reviewed and discussed. Selected major advances in this research field are outlined.

A flow system integrating a soil sample pretreatment unit and a flow manifold was developed for the sequential determination of nitrate and nitrite. The pretreatment unit comprises a probe where filtration and dialysis are performed in order to clean-up aqueous soil suspensions. The flow manifold is a straightforward configuration including a copperized cadmium minicolumn in a bifurcated channel for the sequential determination of nitrate and nitrite. The analytes were determined at the microgram per gram level in soils with relative standard deviations between ±3 and ±5%.

An optical flow-through biosensor based on the transient retention of p-nitrophenol on an ion-exchange support packed in the flow cell is presented. The approach was applied to the determination of the activity of some enzymes which catalyze the conversion of p-nitrophenyl-derivatives into p-nitrophenol. The method was first developed for determination of p-nitrophenol yielding a linear range between 0.1–5 μg/mL (r2 = 0.9922, r.s.d.% less than 2.5), then, it was also applied to the determination of β-D-glucuronidase activity in serum, with a linear range between 0.1–20 U/L (r2 = 0.9976, r.s.d.% less than 3.0), and a sampling frequency of 20 h−1. The application of the method to the determination of the enzyme activity in serum samples provided results consistent with those obtained by a conventional method and recoveries within 95–104%.

A sensor for the determination of cadmium based on retention of the CdI4 − complex on a QAE Sephadex resin located in the flow-cell of a conventional photometric detector and on subsequent complex displacement reaction with 4-(2-pyridylazo)-resorcinol is proposed. Formation of the colored chelate and detection take place simultaneously. The method features a determination range between 30 and 500 ng/ml of Cd(II) with relative standard deviations of 1.8% and 3.4% for 200 and 50 ng/ml of Cd(II), respectively. The selectivity involved in the use of the proposed sensor is shown in the study of interference.

An integrated-sensor method for the determination of formaldehyde based on retention of the reaction product of the analyte with p-rosaniline and sulfite in a flow-cell packed with Dowex 1-X-8 anion exchange resin was developed. The method has a good selectivity with a detection limit of 0.3 μg ml−1 (1 ml sample) or 75 ng ml−1 (2 ml sample), and a linear range between 1–30 μg ml−1. The relative standard deviations (n = 11) were 2.8 and 1.3% for 2 and 20 μg ml−1 formaldehyde, respectively. Depending on the working conditions, the sampling frenquency ranged between 10 and 18 h−1. The method was applied to the determination of formaldehyde in well water.

An overview of the state of the art in Flow Injection Analysis for environmental control is presented The contributions to single- and multi-parameter determinations and potential of this technique for speciation are considered. Improvements resulting from the on-line use of separation techniques, of easy implementation, make an excellent feature which allows the user to address problems arising from complex matrices and/or low analyte concentration

Two flow injection analysis catalytic-fluorimetric methods for the determination of titanium are suggested, based on the measurement of the peak height and of the peak width, respectively. Both methods allow the determination of titanium at the ng.mL−1 level with good selectivity. A comparison between both method is also established.

A new spectrofluorimetric method for the determination of zinc using pyridoxal nicotinylhydrazone as the reagent has been developed. This system forms a ternary complex with ammonia, ethylenediamine or pyridine with a stoichiometry ratio of 1:1:1. The interferences of foreign ions have been determined.

The nitrite ion oxidizes pyridoxal-5-phosphate-2-pyridyl-hydrazone in acid medium giving a fluorescent product (λex 325 nm, λem 420 nm). This redox reaction is used to developed a spectrofluorimetric method for the determination of nitrite. The calibration graph is liner in the 0.1 − 1.0 μg mL−1 range. The interference levels, stoichiometry and nature of the reaction have been studied. The method is applied to determine nitrite in water and soil samples

A kinetic fluorimetric method is developed for the determination of microamounts of copper(II) on the basis of its catalytic activity on the hydrolysis of 2-hydroxybenzaldehyde azine. To monitor the reaction, the appearance rate of fluorescence in the hydrolysis reaction product, the 2-hydroxy benzaldehyde hydrazone (λexe = 355 nm., λem = 465 nm.), is measured. The determination of copper at the 100–500 ng/ml level suffers very few interferences. The mechanism of this catalyzed reaction is proposed.

The synthesis, characteristics and analytical applications of the three pyridylazines are described. The ortho isomer reacts with Fe(II) to produce a bidentate 1:3 red complex (λmax = 475 nm), which undergoes a rearrangement by a “in situ” reaction into tridentate 1:2 blue complex (λmax, = 660 nm, ∊ = 2.9.103 1.mol−1.cm−1). The optimal conditions for max formation of the blue complex are determined. A spectrophotometric method for the determination of iron is also proposed. The interferences of tile foreign ions arc determined.