Electrokinetic supercharging preconcentration and microchip gel electrophoretic separation of sodium dodecyl sulfate-protein complexes

A microchip gel electrophoresis (MCGE) method with electrokinetic supercharging (EKS, electrokinetic injection with transient isotachophoresis) on a single channel chip was developed for high-sensitive detection of a standard mixture of six proteins (phosphorylase b, albumin, ovalbumin, carbonic anhydrase, trypsin inhibitor, and alpha-lactalbumin) in the form of sodium dodecyl sulfate (SDS) complexes. An average lower limit of detectable concentration (LLDC) achieved using UV detection at 214 nm was 0.27 microg/mL that is 30 times lower than that of conventional MCGE on a cross geometry chip. The calibration curves for molecular weight and concentration of SDS-protein complexes suggested that the present EKS-MCGE method had a better linear dynamic range and benefited future applications for qualitative and quantitative analysis of unknown protein samples. It was found that an excessive amount of unbound SDS in the sample deteriorated the preconcentration effect and resolution. The developed method appears greatly promising for high-speed and high sensitive analysis of SDS-proteins by MCGE.