A potentiometric biosensor based on acetyleholinesterase inhibition was developed for the determination of neurotoxic insecticides. The enzyme was mixed with bovine serum albumine (BSA) and immobilized by cross-linking with glutaraldehyde on a cellulose ester membrane with pore diameters of 0.45 or 0.22 mu m. Then, the biosensor was assembled by attaching this membrane to the sensitive end of a flat pH glass electrode. The enzyme activity was estimated before and after the inhibition by measuring the pH decrease at the surface of glass electrode on substrate addition in the buffer solution. The optimum working parameters were as follows: cellulose ester membrane pore 0.45 mu m, 17mU ACHE/electrode membrane, final substrate concentration in the cell of 1 mM, phosphate buffer solution of 0.002 M pH=8, and a 20 min incubation time with the pesticide. The inhibited enzyme activity was restored with pyridine 2-aldoxime methiodide, allowing the repeated use of the biosensor The ethylparaoxon, methylparathion and dichlorvos insecticides were determined within a detection limit of 0.1 mu M (0.027 ppm)for etkyl paraoxon, 0.5 mu M (0.11 ppm) for dichlorvos and 1 mu M (0.26 ppm) for methyl parathion. The method was applied on tap water samples.

A flow injection (FI) device with spectrophotometric detection-based on utilization of a peristaltic pump, four solenoid valves with three ways and a spectrophotometric flow cell were designed and optimized for the chlorine determination in drinking waters. The FI device was entirely conducted by a computer and data acquisition and processing were performed using VISUAL-LAB software. Two-analytical methods based on the N,N-diethyl-p-phenylenediamine (method, I) and o-tolidine (method II) enhanced reactions with chlorine Method I allowed the chlorine determination in the range 0.1 - 10 mg/mL and method H in the range 0.05 - 8 mg/mL. The sampling rates were: 120 samples/h and 90 samples/h, respectively. In order to minimize-the-consumption of reagents, a new flow methodology based on the tandem injection of samples and reagents was-tested.

A flow injection system (FIA) for the mercaptoacetic acid (MAAc) determination was carried out and optimized. The analytical method is based on a new chemiluminescence (CL) reaction between luminol and mercaptoacetic acid in the presence of a co-oxidant and in alkaline medium without hydrogen peroxide. After the instrumental and chemical parameters optimisation, the proposed FIA-CL method allowed the determination of MAAc over the range of concentration 0.01-1 mg/mL with a detection limit of 0.005 mg/mL. Moreover, the method is also characterized by a good reproducibility, RSD = 2.37% (n=10) for 0.1 mg mercaptoacetic acid/mL and a higher throughput, 60 samples/hour.

This work presents a FIA system for pesticide analysis in water based on irreversible inhibition of acetylcholine esterase by organophosphoric insecticides with spectrometric determination of thiocholine with Ellman's reagent. The enzyme was immobilized on amminated glass pearls kept into a reactor and reactivated with 2-PAM after each inhibition step. The total toxic substances of real sample is expressed as equivalent paraoxon and calculated based on relative inhibition of the enzyme measuring the FIA peaks high before and after inhibition. The calibration graph was linear between 2 and 70 ppb paraoxon at an incubation time of 20 min. The LOD was 1.3 mug/L. A complete analysis lasted 35 min. The method was used for analysis of real water samples.

A new flow injection system (FIA) is described for the spectrophotometric determination of free chlorine in waters. Analytical method is based on reaction between N,N-diethyl-p-phenylendiamine and free chlorine. Absorbance of resulted colored complex at 520 nm was measured. After FIA system parameters optimization the free chlorine determination was carried out over the range of concentration 0, 1-10 mug mL(-1), with an excellent reproducibility (RSD = 1.06% n = 10) and without interferences from chloramines or other chemical species normally present in waters.

A flow injection system and method for the ClO- chemiliminescent determination in various water samples are described The oxidation of indole dissolved in i-propanol with hydrogen peroxide in presence of ClO- was used as chemiluminescence reaction. Following the operational parameters optimization, ClO- was determined over the concentration range between 5 (detection limit) -500 mu g mL(-1) with a very good reproductibility (RSD = 1,0%, n = 15), sample throughout is of the order of 50 h(-1) and the results obtained through both FIA method and conventional one with o-tolidine were the same.