Stability of ascorbic acid, carotenoids, retinol, and tocopherols in plasma stored at -70 degrees C for 4 years

Aliquots from 40 plasma pools preserved with metaphosphoric acid were assayed for their ascorbic acid values after 12, 24, and 42 months of storage at -70 degrees C. Similarly, aliquots from 16 plasma pools were assayed for values of retinol, several carotenoids, and two tocopherols at 15.5, 27.5, and 51.5 months of storage at -70 degrees C. There were no indications of important losses of these antioxidant micronutrients during storage from the first to the last assay.