Determination of carotenoids and all-trans-retinol in fish eggs by liquid chromatography-electrospray ionization-tandem mass spectrometry

A novel method was developed for the combined determination of carotenoids and retinoids in fish eggs, which incorporates prior analyte isolation using liquid-liquid partitioning to minimize analyte degradation, and fraction analysis using high-performance liquid chromatography-electrospray (positive)-quadrupole mass spectrometry (LC-ESI(+)-MS; SIM or MRM modes). Eggs from Chinook salmon (Oncorhynchus tshawytscha) were used as the model fish egg matrix. The methodology was assessed and validated for beta-carotene, lutein, zeaxanthin, and beta-cryptoxanthin (molecular ion radicals [M](+)), canthaxanthin and astaxanthin ([M+Na](+) adducts) and all-trans-retinol ([(M+H)-H(2)O](+)). Using replicate egg samples (n=5) spiked with beta-cryptoxanthin and beta-carotene before and after extraction, matrix-sourced ESI(+) enhancement was observed as evidenced by comparable %matrix effect and %process efficiency values for beta-cryptoxanthin and beta-carotene of 114-119%. In aquaculture-raised eggs from adult Chinook salmon astaxanthin, all-trans-retinol, lutein and canthaxanthin were identified and determined at concentrations of 4.12, 1.06, 0.12 and 0.45 microg/g (egg wet weight), respectively. To our knowledge, this is the first report on a method for LC-MS determination of carotenoids and retinoids in a fish egg matrix, and the first carotenoid-specific determination in any fish egg sample.