Apparent increase of insulin peak area in HPLC analysis of a preparation consisting of a mixture of insulin and total parenteral nutrition

The peak area of insulin in a mixture of K.C.L. injection and hyperalimentation fluid was found to increase in a time dependent manner up to 24 h in measurement by a high-performance liquid chromatograph. The increase of peak area corresponding to the insulin was detected at wavelengths of both 210 and 280 nm. This increase was only observed in the presence of the sugars, tryptophan, riboflavin, and insulin, and ascorbate was shown to counteract the increase. These results suggest the possibility that insulin forms a mixture caused by the oxidation reaction in a hyperalimentation fluid.