Titratable acidities of crystalline amino acid admixtures

Titration curves for total parenteral nutrient (TPN) products were developed and used to determine the amount of alkali needed to make various pH changes. Equations and graphs for determining the titratable acidities of TPN solutions are presented. Samples of five crystalline amino acid products and of 1:1 mixtures of the products with 50% dextrose solutions were titrated to pH 7.4 (with a standard sodium bicarbonate solution) or 8.0 (with a standard sodium hydroxide solution). The samples titrated with sodium hydroxide were first adjusted to pH 5.0 with hydrochloric acid. The pH of the sample was measured after each 0.1-ml addition of hydroxide or bicarbonate to develop a titration curve. Titratable acidities for the five crystalline amino acid products varied widely, ranging from 13.4--45.2 meq of hydroxide/liter and from 135--420 meq of bicarbonate/liter. The amino acid/dextrose mixtures had titratable acidities ranging from 7.8--24.8 meq of hydroxide/liter and from 87--226 meq of bicarbonate/liter. The pH titration data can be used as a guide for determining the amount of base to add to TPN solutions to obtain the desired pH.