Rapid simultaneous determination of four indole compounds in dietary supplements by micellar electrokinetic chromatography with a dilute and shoot step

Abstract

A simple micellar electrokinetic chromatography (MEKC) method with UV detection was developed for the simultaneous determination of indole-3-carbinol, indole-3-acetonitrile, indole-3-acetic acid and 3,3′-diindolylmethane. These compounds are potentially used in cancer prevention. Investigation of solvent effects (methanol and dimethylformamide) on MEKC analysis was carried out. A dilute and shoot strategy was used for sample preparation to reduce the time required for multiple steps such as solvent evaporation. The final conditions were electrokinetic injection for 3.0 s at 423 V cm⁻¹ and 20.0 mM borate buffer (pH 9.00) containing 20.0 mM SDS. Analysis was rapid, achieved in less than 4.5 min. Linear calibration curves for the indole compounds in the range 5–200 μg mL⁻¹ (r² > 0.999) were obtained. Intra- and inter-day precisions were 2.0–7.9% RSD, with LOQs in the range of 1.5–4.0 μg mL⁻¹ and recoveries in the range of 90–110% (n = 5).