Figure 5.

(A) Stability test of PRA. At specific time intervals, changes in the absorbance were determined through UV absorbance spectroscopy at 350 nm. The concentration of intact RA in the methanol solution rapidly decreased as compared to that of PRA during incubation at room temperature under light exposure. Each experiment was performed in triplicate. Values are means ± SD (J Nutr Biochem 2007, 18:322–331). (B) Headspace-oxygen depletion by CLA and PCLA. Headspace oxygen in the sample bottles was analyzed by injecting a 100 μL headspace air sample into a HP 5890 GC (Avondale, PA), equipped with a stainless steel molecular sieve column (13×, 80:100; Alltech, Deerfield, IL) and a thermal conductivity detector. High purity helium (99.99%) was used as the carrier gas. The flow rate was 40 mL/min. The GC oven temperature was maintained at 40°C. The injector port and detector temperatures were maintained at 120 and 150°C, respectively. Each sample was analyzed in triplicate. Oxygen contents were quantified by an HP 3396A integrator (unpublished data).