USE OF HIGH-PRECISION GAS ISOTOPE RATIO MASS-SPECTROMETRY TO DETERMINE NATURAL-ABUNDANCE C-13 IN LUTEIN ISOLATED FROM C-3 AND C-4 PLANT SOURCES

A method was developed for high-precision stable carbon isotope ratio analysis of lutein isolated from a C-3 (marigold flower) and a C-4 (co rn gluten meal) plant source-using gas chromatography-combustion inter faced isotope ratio mass spectrometry. The natural abundance of C-13 ( expressed as delta(13)C versus the international standard, Pee Dee Bel emnite, in per mil units, denoted parts per thousand) in lutein isolat ed from marigold flower and corn gluten meal was determined to be -29. 90+/-0.20 parts per thousand and -19.77+/-0.27 parts per thousand (mea n+/-S.D.), respectively. The high precision of gas isotope ratio mass spectrometry is potentially applicable to detect differences of isotop ic composition of lutein in the blood, tissues, or excreta of animal m odels or humans that result from differences in the natural abundance of C-13 in C-3 and C-4 plant foods. (C) 1998 Elsevier Science B.V.