Availability of aluminum from glass and an Al form ion exchanger in the presence of complexing agents and amino acids

Aluminum can exist as contaminant in solutions of amino acids used for parenteral nutrition. It is a problem because these solutions are introduced directly into the circulatory current and aluminum shows toxic effects for some patients, mainly pre-term infants. Amino acids can be responsible for the aluminum contamination of parenteral solutions when they are stored in glass containers. Glass can be a source of aluminum because aluminum is present in its composition to improve chemical resistance. In this work, glass was compared with an available source of aluminum ions, a cation exchanger in Al3+ form. Solutions of amino acids used in parenteral nutrition were placed individually and separately in contact with glass powder and exchanger. The aluminum content of these solutions was measured for up to 60 days after storage. Solutions of species that have strong affinity for aluminum ions, ethylene diaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA) and citrate and oxalate ions were also tested. The measurements were made by atomic absorption spectrometry. The results showed that amino acids with polar lateral chains were able to extract aluminum from both glass and ion-exchange resin and the interaction of the amino acid solutions with the glass surface occurs in the same way as with the exchanger. The sequence ornithine > aspartic acid > lysine > glutamic acid > N-acetyltyrosine congruent to serine congruent to tyrosine congruent to arginine, was found for both glass and exchanger for extraction rates put in decreasing order. The results for complexing agents were also similar for glass and resin, from which it could be concluded that the higher the stability constant of the aluminum complex, the higher the amount of aluminum extracted. The study also showed that some amino acids are able to interact with a glass surface. Interaction of amino acids with an Cu2+ form exchanger confirmed the relation between metal extraction rates and complex stability. The contamination by aluminum of parenteral nutrition solutions stored in glass containers can be attributed to the combination of the ion exchange property of glass and the affinity of some amino acids for this metal ion. (C) 2002 Elsevier Science B.V. All rights reserved.