Vitamin stability in a TPN mixture stored in an EVA plastic bag.

In order to examine the stability of vitamins in a TPN admixture stored in 3-litre plastic (EVA) bags, two different stability studies were performed. In the first experiment the TPN admixture was stored in darkness at 2-8 degrees C for 96 h and the stability of vitamins determined. The vitamins examined were retinyl palmitate, alpha-tocopherol, thiamine mononitrate, sodium ascorbate (analysed as reduced ascorbic acid and dehydroascorbic acid), sodium riboflavin-5'-phosphate, pyridoxine hydrochloride, nicotinamide, folic acid, biotin, sodium pantothenate and cyanocobalamin. In the second test the stability of vitamins was determined during simulated infusion from the bag containing the admixture. The vitamins examined were retinyl palmitate, alpha-tocopherol, sodium riboflavin-5'-phosphate and sodium ascorbate (analysed as reduced ascorbic acid and dehydroascorbic acid). The vitamin stability was found to be acceptable for all vitamins except ascorbic acid and folic acid. Total ascorbic acid is the sum of reduced ascorbic acid and dehydroascorbic acid (DHA). It is important to estimate the total ascorbic acid concentration because DHA is also biological active. About 50% of the nominal total ascorbic acid remained after 96 h of storage at 2-8 degrees C in darkness, or after 24 h of simulated infusion initiated immediately after mixing. With folic acid there appears to be assay interference which requires further investigation.