Analysis of alkyl gallates and nordihydroguaiaretic acid using plastic capillary electrophoresis - microchips

A simple and fast method for the simultaneous determination of the antioxidants propyl gallate (PG), octyl gallate (OG), lauryl gallate (LG), and nordihydroguaiaretic acid (NDGA) has been established by using microchip micellar electrokinetic chromatography with pulsed amperometric detection. Under the optimum conditions (30 mM borate buffer, pH 9.7, 30 mM sodium dodecyl sulfate, separation voltage of 1200 V and 5 s injection time) the analytes were baseline separated. Linear relationships were found between the concentration and peak current for all the selected antioxidants. The measured detection limits (S/N ≥ 3) of PG, OG, LG, and NDGA were 2.2, 1.4, 2.3, and 4.6 μM, respectively, which corresponds to 2-6 fmol of analyte. This approach has remarkable advantages with respect to other methodologies involving separations and electrochemical detection including minimal sample consumption, higher analysis speed, lower cost, and portability. Additionally, a highly reproducible signal (migration time and peak current) was obtained for a series of injections (n = 30). In order to demonstrate the capabilities of the method, the determination of antioxidants in a commercial food sample is also presented.