Validação de procedimento analítico empregando SPE e GC-ECD para determinação de pesticidas organoclorados em água e avaliação da permeabilidade destes nos dialisadores utilizados em hemodiálise

Abstract

The dialysis of the blood, within which the most applied modality is the haemodialysis, is a method thoroughly used for the treatment of the renal inadequacy. With this treatment, toxic substances accumulated in the patient´s body that have not been eliminated by the urine, are removed. The process happens as an "artificial kidney (dialyser) that is constituted of that is constituted of a group of fine capillary with semi permeable walls. The blood goes through the inside of these capillary ones and through the outside, in opposite direction, the dialysis solution (a saline solution diluted in water) passes by. The volume of water used in each haemodialysis session is about 120 L per patient. If the water used is not monitored, pollutants can have cumulative effects in the patient, as the organochloride pesticides. With this work, it was developed and validated an analytical procedure for the determination of low concentrations of five organochloride pesticides (α-endosulfan, β-endosulfan, DDE, DDT and endrin) in water, using Solid Phase Extraction for the pre-concentration and Gas Chromatography with Electron Capture Detection for the determination of the pesticides. Tests were accomplished to optimize the pre-concentration method in which cartridges of C18-E having 500 mg of adsorbent material and an eluent mixture of n-hexane:ethyl acetate (7:3, v/v) produced the best results in terms of recovery for the five analyzed pesticides, and the obtained values were between 85.4 and 114.1%, with smaller RSD than 15%. The values of LOQ in the samples were from 14 to 20 ng L-1. After the validation stage, the analysis procedure was applied in simulations of dialysis sessions accomplished in laboratory, to verify whether it happens the passage of the referred pesticides through the membranes used in the process. Dialysers with membranes of cellulose acetate and of polissulfone, which are commercially available, were evaluated. For such, samples of water distilled/deionized, fortified with the five organochloride pesticides were used. It was verified that such membranes are permeable to the referred pesticides. Although the passage of the pesticides through the membranes has happened in low levels (ng L-1), such situation should not be disregarded, since the patients submitted to this kind of treatment are also exposed to great volumes of water in each session, that are frequently repeated for long periods of time. It is also important to highlight that the organochloride pesticides are characterized for presenting cumulative effects.