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 β-carotene, lutein, zeaxanthin, and β-cryptoxanthin (molecular ion radicals [M]+), canthaxanthin and astaxanthin ([M + Na]+ adducts) and all-trans-retinol ([(M + H)–H2O]+). Using replicate egg samples (n = 5) spiked with β-cryptoxanthin and β-carotene before and after extraction, matrix-sourced ESI(+) enhancement was observed as evidenced by comparable %matrix effect and %process efficiency values for β-cryptoxanthin and β-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 μg/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.