Desenvolvimento de procedimento DPX para determinação sensível de Cu(II) em água para hemodiálise por F AAS utilizando sementes de Moringa oleifera como fase sólida

Abstract

Copper is an essential micronutrient for maintaining the biological functions of many living organisms, so low concentrations of this element can be harmful in some environments. In water for hemodialysis, concentrations above 100 μg L-1 of copper can compromise the health of patients undergoing dialysis treatment. Different copper preconcentration techniques have been extensively investigated in the sample preparation stage and detection by AAS, UV-Vis and electroanalytical techniques, in different matrices. Disposable Pipette Extraction (DPX) is a solid phase extraction technique on disposable tips with rapid extraction of analytes, reduced amounts of adsorbent and low volumes of solvents and samples. Another advantage of this technique is the possibility of using varied solid phases stored inside the tip. Thus, the use of DPX with the use of Moringa oleifera seeds pulp presents a viable and low cost alternative. A review of the literature shows that the use of DPX in the determination of metals has been little explored, and most of the work involves DPX in the determination of organic compounds in several matrices. The DPX device is a commercial patent, however, adaptations with micropipette tips allow the use of the technique with the use of accessible and low cost devices. Moringa oleifera Lam. seeds are natural, low cost and with a high adsorptive potential, widely used in extraction and preconcentration procedures for various metals. This work developed an extraction and preconcentration procedure using the DPX with the adapted device and Moringa oleifera Lamarck seeds pulp as a solid phase in the determination of Cu(II) ions in hemodialysis water at μg L-1 levels, by F AAS. The proposed DPX device allows the use of 5 mL micropipette tips, 20 mL syringe, cylindrical polyethylene adapter, glass wool, being easy to operate, simple and low cost. Characterization tests show that Moringa seeds have functional groups characteristic of protein content (FT-IR), an irregular and rough surface, allowing unfilled spaces, characteristic of a relatively porous heterogeneous matrix (SEM) and negative surface above pH 4.2 favorable to interaction with cationic species (pHPCZ = 4.2). The optimized extraction and preconcentration variables allowed the use of 10 mg of the solid phase at 250 μm, 6 extraction cycles with new sample portions at pH 6 and elution with 0.5 mol L-1 hydrochloric acid solution (250 μL). The preconcentration curve showed satisfactory linearity according to the parameters evaluated (r = 0.9991, random distribution of residues and Mandel test (9.14 < F = 10.01). Preconcentration factor, detection limit and recovery of 50, 0.64 μg L-1 and 92.9-100.5%, respectively, were obtained. The accuracy was 6.2% (n = 9). The performance results of the extraction and preconcentration procedure with the adapted DPX device are promising for determinations of Cu(II) ions in hemodialysis water.