Study of aldehyde oxidase by micellar electrokinetic chromatography separation of O

A separation method for O6 -benzylguanine (O6 -BG) and 8-oxo-O6 -benzylguanine (8-oxo-O6 -BG) is developed by using MEKC. This study includes the optimization of separation and incubation parameters for both off-line and on-line procedures. The BGE consisted of 25 mM sodium phosphate buffer-methanol (70:30, v/v), apparent pH 7.4, in which SDS and methyl-β-cyclodextrin were dissolved yielding final concentrations of 50 and 15 mM, respectively. Separations were performed at 15 kV using an untreated fused-silica capillary (40 cm length, effective length is 30 cm) with the detection wavelength at 195 nm. The capillary was kept at 15°C. Good performances were demonstrated for the repeatability and linearity. The LOQ was determined to be 14 μM for 8-oxo-O6 -BG (S/N = 10). The accuracy values showed a bias of +7.9% for 50 μM and -7.0% for 100 μM. Premix and transverse diffusion of laminar flow profiles (TDLFP) methods were used for on-line mixing and reaction of the substrate O6 -BG with aldehyde oxidase. Both procedures were successful in mixing as well as subsequent separation of the substrate and the metabolite, while the repeatability of TDLFP (14.7% (n = 3)) was much better than the premix technique.