Estudo da interação do alumínio com o ácido glucônico

Abstract

Parenteral solutions are used for patients with complexes diseases, for pre-term infants and surgical patients. The administration of solutions contaminated by aluminium for a long period of time can lead to severe intoxication, with consequent bone and neurological diseases. Considering that, the FDA (Food and Drug Administration) has been investigating the consume of aluminium through solutions for parenteral nutrition and established a maximum limit of 5 μg Al/kg weight of the patient per day. It has been found elevated aluminium concentration in solutions of phosphates (28 000 μg/L) and calcium gluconate (12 000 μg/L). In this work, the interaction between aluminium and the anion gluconate was evaluated by means of spectrophotometry, ion-exchange experiments and potentiometric titration. By spectrophotometry, the reaction with Morin allowed to calculate the amount of aluminium that reacted with the anion gluconate in solutions of calcium and sodium gluconate and also gluconic acid. Ion-exchange experiments included other ligands with affinity for aluminium and a resin in the Al3+-form. The ability of the ligands citrate, oxalate, EDTA, NTA, and gluconate in the form of gluconic acid, calcium gluconate, and sodium gluconate to withdraw it from the Al3+-form resin was evaluated at different concentrations and periods of time. Aluminium quantification was carried out by atomic absorption spectrometry either by graphite furnace or flame. The results showed that the exchange was bigger in the calcium gluconate solution followed by sodium gluconate and gluconic acid. Comparing with the other complexing agents, gluconic acid showed the lower extraction ability. These results are in agreement with the stability constants found in the literature for the aluminium complexes with these ligands. Potentiometric titration was carried out to evaluate the stability constants of the possible complexes build between aluminium and the ion gluconate in aqueous solution. The results showed that the predominant species in solution have a proportion metalligand 1:1. Stability constants obtained showed a good agreement with the stability constants of the complexes collected from the literature.