Use of high-precision gas isotope ratio mass spectrometry to determine natural abundance 13C in lutein isolated from C3 and C4 plant sources.

A method was developed for high-precision stable carbon isotope ratio analysis of lutein isolated from a C3 (marigold flower) and a C4 (corn gluten meal) plant source using gas chromatography-combustion interfaced isotope ratio mass spectrometry. The natural abundance of 13C (expressed as delta 13C versus the international standard, Pee Dee Belemnite, in per mil units, denoted /1000) in lutein isolated from marigold flower and corn gluten meal was determined to be -29.90 +/- 0.20/1000 and -19.77 +/- 0.27/1000 (mean +/- S.D.), respectively. The high precision of gas isotope ratio mass spectrometry is potentially applicable to detect differences of isotopic composition of lutein in the blood, tissues, or excreta of animal models or humans that result from differences in the natural abundance of 13C in C3 and C4 plant foods.