Department of Chemistry, Universidade Federal de Santa Maria, Santa Maria, Brazil.
JPEN J Parenter Enteral Nutr. 2009 Nov-Dec;33(6):694-701. doi: 10.1177/0148607109333004. Epub 2009 Jul 8.
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.
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.
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.
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.
硅（Si）和铝（Al）可能是肠外营养（PN）溶液中的伴随杂质。硅可以与铝结合形成稳定的羟基铝硅酸盐（HAS），从而降低铝的可用性。通过在玻璃容器中加热含有 PN 成分的溶液来促进 Si 和 Al 的释放，可以研究这种可能性。
通过原子吸收光谱法测量溶液中 Si 和 Al 的总量，并通过与棓酸反应评估与 Si 结合的 Al。
当 Si:Al 摩尔比>5 时，溶液中没有游离 Al。对于比值<5 的情况，发现比值越低，游离 Al 分数越高。然而，在某些氨基酸溶液中，即使 Si:Al 比值较低（<2），游离 Al 的量也低于其他溶液。商业配方中也观察到相同的趋势。尽管在盐溶液中，当 Si 浓度较低时，Al 的游离分数达到近 100%，但在氨基酸配方中，Al 的游离分数不超过 50%。此外，即使 Si:Al 比值>5，氨基酸配方中仍存在游离 Al 的“残余”分数。
PN 溶液中 Al 和 Si 的共存会降低由于 HAS 形成而导致的可用 Al 量。在氨基酸配方中，由于某些氨基酸对 Al 的亲和力，这种影响可能会略有降低。因此，氨基酸的行为可能与硅相似。
