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

A preliminary investigation of the behaviour of the electronic absorpt ion spectra of selected carotenoids in supercritical fluid chromatogra phy (SFC) with CO2 on a C18 column has been undertaken. A significant hypsochromic shift in the visible ((1)Bu(+)) lambda(max) of beta-carot ene (beta,beta-carotene), lycopene (psi,psi-carotene), zeaxanthin (bet a,beta-carotene-3,3'-diol), canthaxanthin (beta,beta-carotene-4,4'-dio ne) and astaxanthin (3,3'-dihydroxy-beta,beta-carotene-4,4'-dione) in supercritical CO2 was observed in comparison to that in hexane. In add ition, the effects of variations in pressure (1500-6000 psi) and tempe rature (35-50 degrees C) on the wavelength shift of all-trans-beta-car otene have been assessed. Parallel studies were also performed on 15-c is-beta-carotene, and a similar hypsochromic shift in the main, visibl e, lambda(max) was observed. The cis-peak (Ag-1(+)) of this carotenoid also exhibited a significant, but smaller, hypsochromic shift in comp arison to that measured in hexane. However, in contrast to the behavio ur 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,