Anhydroretinylic cation is a product of the reaction between Vitamin A and a chromogenic reagent. The reaction is referred as the Carr-Price reaction. Anhydroretinylic cation is also referred to as the Carr-Price product or the blue colour product because its formation is remarked by the blue colour. The colour is the basic fundamental in vitamin A assaying in various food carriers. Studies have shown that the blue colour fades so rapidly within 5 seconds upon formation due to instability of the cation. The instability is caused by different factors. The colour’s rapid fading makes assaying of vitamin A to be more challenging and affects the precision and accuracy of the results. Therefore, this study investigated the effects of different factors such as mass of oil sample, temperature, light brightness, kind of solvent, reacting volume ratio of sample aliquot to chromogenic reagent, type and concentration of chromogenic reagent on the stability of the blue colour product. In order to achieve the objective, the study used observation to qualitatively record colour fading time and spectrophotometric method was used to monitor changes in the concentration of the blue colour product with reference to time taken for the concentration to drop. The study found that the Carr-Price reaction done outside the spectrophotometer in a 25 oC water bath with 5.00 g oil sample and a 20 % TCA dissolved in DCM under darkness stabilized the blue colour for 160±10 seconds. Statistical regression indicated that the concentration of the blue colour product (p value = 0.917) was the same within the said period. The optimum conditions attained in the study showed that 160 seconds stable cation had a recovery of 98.36 %. The percentage recovery is within recommended standard range of between 80 and 110. Spectrophotometric procedure for vitamin A assaying that includes 25 oC water bath has potential to achieve stability of the blue colour product and be able to help analyst to obtain accurate and precise results with minimal human error as 160 seconds is long enough to do the measurements.

Vitamin A

Carr-Price product

spectrophotometric procedure

anhydroretinylic cation