Quantitative determination of the stabilizers octanoic acid and N-acetyl-DL-tryptophan in human albumin products.

Methods were developed for the determination of octanoic acid and N-acetyl-DL-tryptophan, which are used as stabilizers in the human blood-derived therapeutic products normal serum albumin and plasma protein fraction. The method for octanoic acid uses GC; quantitation is achieved using heptanoic acid as the internal standard. The method for N-acetyl-DL-tryptophan is based on UV spectrophotometry of the acid-soluble fraction remaining after precipitation of the protein (epsilon 280 for N-acetyl-DL-tryptophan, 5250). The coefficient of variation for replicate determinations of octanoic acid averaged 3.9% (range 2.1-5.5%); that of N-acetyl-DL-tryptophan averaged 1.9% (range 0.5-4.0%). Use of these methods for the analysis of 138 lots of commercial products for octanoic acid and 159 lots for N-acetyl-DL-tryptophan showed that the stabilizer contents of 132 and 158 of these lots, respectively, were within 20% of the value indicated on the product label.