title: Low availability of aluminum in formulations for parenteral nutrition containing silicate.
abstract: BACKGROUND
  Silicate (Si) and aluminum (Al) may be concomitant impurities in solutions for parenteral nutrition (PN). Silicate can bind to Al to form stable hydroxyaluminosilicates (HAS), thus reducing Al availability. This possibility is investigated by heating solutions containing constituents of PN in glass containers to promote the release of Si and Al.
  
  
  METHODS
  The total amount of Si and Al in solution is measured by atomic absorption spectrometry, and the Al not bound to Si is evaluated by reaction with morin.
  
  
  RESULTS
  When the Si:Al molar ratio is >5, no free Al is found in solution. For ratios <5, it is found that the lower the ratio, the higher the free Al fraction. However, in solutions of some amino acids, even with a low Si:Al ratio (<2), the amount of free Al is lower than that found in other solutions. The same tendency is observed among commercial formulations. Although in salt solutions the free fraction of Al reaches almost 100% when the Si concentration is low, in amino acid formulations the free fraction of Al does not surpass 50%. Moreover, even for Si:Al ratios >5, there is a "residual" fraction of free Al in amino acid formulations.
  
  
  CONCLUSIONS
  The concomitant presence of Al and Si in solutions for PN reduces the amount of Al available attributable to the formation of HAS. In amino acid formulations this effect may be slightly reduced given the affinity of certain amino acids for Al. Therefore, amino acids may behave in the same fashion as silicate.
authors: Department of Chemistry, Universidade Federal de Santa Maria, Santa Maria, Brazil. ndenise@quimica.ufsm.br
authors: Denise
authors: D
authors: Bohrer
authors: Fabiana
authors: F
authors: Bortoluzzi
authors: Paulo Cícero
authors: PC
authors: do Nascimento
authors: Leandro Machado
authors: LM
authors: de Carvalho
authors: Sandra Ribeiro
authors: SR
authors: de Oliveira
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D000596:Amino Acids / Q000737:chemistry; D005419:Flavonoids / Q000737:chemistry; D005506:Food Contamination; D005526:Food, Formulated; D006358:Hot Temperature; D007202:Indicators and Reagents; D010288:Parenteral Nutrition; D017640:Silicates / Q000737:chemistry*; D013054:Spectrophotometry, Atomic / Q000379:methods; D047309:Flavones
chemical_list: D000535:Aluminum; D000596:Amino Acids; D005419:Flavonoids; D007202:Indicators and Reagents; D017640:Silicates; C008548:morin; D047309:Flavones