The Determination of Blood Plasma Carotene in the Bovine using a Photoelectric Colorimeter

Summary 1. A simple phase separation of carotene from bovine plasma has been outlined. 2. When petroleum ether is used as the solvent the boiling point and temperature of extraction are important factors in the amount of carotene extracted. 3. When petroleum ether with a boiling point of 73–76° C. was used and the extraction carried out at 10–12° C. the epiphase gave true carotene values. 4. When the phase separation method is used, the relationship of the amount of carotene in the epiphase to the total amount present in the sample should be established. 5. The temperature at time of pipetting into the absorption cell under ordinary laboratory conditions had no measurable effect on the galvanometer readings. 6. The use of 15 ml. of a 95 per cent ethyl alcohol for precipitation of the proteins from 10 ml. of plasma was found to be advantageous. 7. Shaking the tubes for two to three minute periods gave more consistent results than shaking for one minute. 8. The addition of 0.5 ml. of alcohol to destroy emulsions had no effect on the determination. 9. The method was shown to give consistent results from day to day. 10. Plasma stored at 2.0° C. showed no loss of carotene over a period of three weeks. 11. The use of the phase separation method in conjunction with the photoelectric colorimeter offers a simple and rapid procedure for the determination of carotene in bovine blood plasma.