Analysis of feed blends containing microencapsulated 2-ethyl-1-hexanol: verification of homogeneity and stability

2-Ethyl-1-hexanol (2-EH) was nominated for carcinogenicity testing by the National Toxicology Program because it is a high-volume chemical and a major metabolite of di(2-ethylhexyl)phthalate, a known hepatocarcinogen and a known contaminant in blood storage bags. In addition to uses as an intermediate in the manufacture of plasticizers. 2-EH is also used as a solvent, a lubricant and as a finishing compound for paper and textiles. The preferred route of administration for the carcinogenicity studies was oral via the diet. However, feed blends containing neat 2-EH were not sufficiently stable for feed studies. Dosed feed blends prepared with neat 2-EH retained only 86% of the theoretical concentration after blending, and 46% of theoretical after storage for 2 days in a rat cage environment. Feed blends containing microencapsulated 2-EH were sufficiently stable for toxicity studies: no losses of 2-EH were observed after blending, feed blends stored for 7 days in a rat cage retained 99% of the theoretical concentration and blends stored in sealed containers at room temperature for 21 days retained 97% of the theoretical concentration. These studies demonstrate the potential for microencapsulation technology to eliminate dose formulation problems associated with volatile chemicals.