DETECTION OF CAROTENOIDS ON SUPERCRITICAL-FLUID CHROMATOGRAPHY (SFC) - A PRELIMINARY INVESTIGATION ON THE SPECTRAL SHIFTS OF CAROTENOIDS IN SUPERCRITICAL CARBON-DIOXIDE

A preliminary investigation of the behaviour of the electronic absorption spectra of selected carotenoids in supercritical fluid chromatography (SFC) with CO2 on a C18 column has been undertaken. A significant hypsochromic shift in the visible ((1)Bu(+)) lambda(max) of beta-carotene (beta,beta-carotene), lycopene (psi,psi-carotene), zeaxanthin (beta,beta-carotene-3,3'-diol), canthaxanthin (beta,beta-carotene-4,4'-dione) and astaxanthin (3,3'-dihydroxy-beta,beta-carotene-4,4'-dione) in supercritical CO2 was observed in comparison to that in hexane. In addition, the effects of variations in pressure (1500-6000 psi) and temperature (35-50 degrees C) on the wavelength shift of all-trans-beta-carotene have been assessed. Parallel studies were also performed on 15-cis-beta-carotene, and a similar hypsochromic shift in the main, visible, lambda(max) was observed. The cis-peak (Ag-1(+)) of this carotenoid also exhibited a significant, but smaller, hypsochromic shift in comparison to that measured in hexane. However, in contrast to the behaviour of the visible maxima, subsequent alterations to both the pressure and temperature of supercritical CO2 did not further alter the lambda(max) of the cis-peak of 15-cis-beta-carotene,