Separation and Detection of Urinary Proteins by Microfluidic Chip Integrated with Contactless Conductivity Detector

On the basis of a self-made analytical microsystem with a microfluidic chip integrated with a contactless conductivity detector, a new method of separating and detecting proteins on microchip integrated with the functions of sample injection, separation and detection is proposed in this paper. Human serum albumin (HSA) and human transferrin (TRF) in urine samples from nephritic syndrome patients were separated on the designed microsystem, and HSA was detected quantitatively. Factors affecting on-chip electrophoresis processes, such as running buffer, separating voltage, injection modes and sampling time, were investigated and optimized. Under the optimized conditions of 10 mM borax buffer (pH 10), 600 V separation voltage, and 300 V/cm electric field strength and 10 s injection time, HAS and TRF were separated in 10 min with a resolution of 2.0. The detection limit of HSA and TRF were 0.4 and 0.8 g L−1 (S/N = 3), respectively. The correlation coefficients of the detection in the linear range of 1–5 g L−1 were 0.9478 and 0.9491, respectively. The recoveries of HSA in the sample of patient urine were in the range 95.4%–104.1%.