Quantification of Phthalates in Citrus Oils by Stable Isotope Dilution Assay Using GC-MS with Selective Ion Monitoring.

Abstract

The goal of this work was to develop a method to determine bis-(2-ethylhexyl) phthalate in citrus oils based on the existing AR (Agricultural Residue) method. The feasibility of using one stable isotopic labeled phthalate to quantify a series of other phthalates was explored at the same time. Three other phthalates were chosen for this purpose. Commercially available deuterated phthalate, 3,4,5,6-d4-bis-(2-ethylhexyl) phthalate, was found to be a good internal standard in terms of its labeling positions and EI spectrum. The chromatographic behavior of the four phthalates allowed them to be analyzed simultaneously with the ARs using the AR method. The sensitivity of the method is more than sufficient for real applications. The linearities of the calibration curves for the four phthalates were very good (R2 > 0.999). The recoveries of the phthalates were generally good (90 - 120 %) and the reproducibility of the method was perfect.