Separation and determination of astaxanthin from microalgal and yeast samples by molecularly imprinted microspheres

In this work, molecularly imprinted microspheres (MIMs) were synthesized by aqueous microsuspension polymerization using astaxanthin (3,3'-dihydroxy-beta,beta'-carotene-4,4'-dione) as imprinting molecule. The MIMs obtained were subsequently packed into the stainless steel column and the chromatographic characterization of the column was investigated. The effects of pH and composition of the mobile phase on the retention factor (k') were investigated in detail. The mixture of methanol and dichloromethane (DCM) (8:2, v/v) was used as mobile phase A while the mixture of methanol and water (5:5, v/v) as mobile phase B. The separation of astaxanthin and zeaxanthin (3,3'-dihydroxyl-beta-carotene) was obtained when the concentration of mobile phase B was higher than 30% (v/v) due to their strong lipophilicity. The method developed was successfully applied to separate astaxanthin in the saponified samples of the microalga Haematococcus pluvialis and the yeast Phaffia rhodozyma. The recovery of adding 40 mg astaxanthin to 1.0 g microalgal sample was 95.5% with an R.S.D. (n =5) of 5.3%. The results of determination of astaxanthin in the microalga and the yeast were 3.7% (R.S.D (n = 1.5%, n = 9) and 0.041% (R.S.D n= 7.3%, n = 9), respectively.