Abstract: A new highly sensitive, simple and low-cost methodology for the direct determination of Pb (II) with 2-(5-bromo-2- pyridylazo)-5-dimethylaminophenol in ethanolic medium has been developed. The absorption spectroscopy of the complex has been examined in detail, and the chemical variables affecting the sensitivity of procedure studied. optimized and applied to the determination of trace amounts of lead in human saliva. Under the optimal experimental conditions, a precision of 1.61 x 10^-4 µg cm was achieved, the molar absorptivity being (i:) 5.6 x 10^-4 l mol-1 cm-1. An FI technique is proposed, and it is possible to determine trace levels of lead by injection into a steam buffered at pH 7.15, containing 70%, ethanol: 30% Tris buffer 3.5 x 10^-3 mol L-1 (pH = 7.2), 1 x 10^-4 mol-1 5-BrDMPAP. The FIA configuration allows the analysis of 45 samples per hour. The lower limit of detection (LOD) was 1 x 10^-7 mol L-1. The calibration plot was linear at least within two orders of magnitude of lead concentration. The use of an HPLC pump for the FI analysis led to a substantial improvement in the analytical performance of the method, which clearly satisfies the typical requirements for control processes. (C) 2001 Elsevier Science B.V. All rights reserved.

Abstract: The analytical procedure for the determination of lead in tap water has been described. The method comprises an enrichment step (cloud point extraction without chelating agents), and FI-ICP-OES detection. In the initial aqueous solution the analyte was pre-concentrated and introduced into the surfactant rich phase of polyethyleneglycolmono-p-nonylphenylether. After the phase separation at the increased temperature, a satisfactory pre-concentration factor (>300) has been achieved. Hydrochloric acid was used for the dilution of the surfactant-rich phase. Several parameters influencing the efficiency and performance of the method were evaluated, i.e. pH of the extraction, extractant volume, composition of the diluent. Recoveries of the spiked (3-20 ?g L -1) doubly distilled water samples were quantitative. Under the optimum conditions, E was higher than 99.9%, and the sensitivity of 0.077 ?g L-1 has been achieved. The results of the analysis of the certified reference material (QC METAL LL2) were consistent with the certified values. The proposed method was successfully applied to the determination of lead in tap water samples in San Luis, Argentina.

Abstract: A cloud point pre-concentration and flow injection (FI) analysis methodology for aluminum(iii) determination has been developed. The analyte in the initial aqueous solution was complexed with Chrome Azurol S (CAS) in the presence of the cationic surfactant benzyldimethyltetradecylammonium chloride (BDTAC). The absorption spectroscopic characteristics of the ternary complex [Al(iii)-CAS-BDTAC] were examined in detail. The pre-concentration step was carried out by means of the non-ionic surfactant polyethylene glycol p-nonylphenyl ether (PONPE 7.5). The enriched analyte solution was injected into an FI system using an HPLC pump. The chemical variables affecting the analytical performance of the combined methodology were studied and optimized. The developed approach was successfully applied to the determination of trace amounts of aluminum in parenteral solutions without previous treatment. Under the optimum experimental conditions, 99.9% extraction was achieved for a pre-concentration factor of 50. The limit of detection was 1.12 x 10^-7 mol L-1. The calibration plot was linear over at least two orders of magnitude of aluminum concentration. The developed coupled methodology, which thoroughly satisfies the typical requirements for pharmaceutical control processes, is appropriate for monitoring the aluminum concentration in parenteral nutrition.