Determination of Citric Acid in Urine by Enzymatic Flow Injection System Based on a Novel Microfluidic Chip

A flow injection analysis (FIA) system with enzymatic detection has been proposed for determination of citric acid in urine using a novel microfluidic chip. A microfluidic device based on PDMS channels is designed and fabricated. To determinate the citric acid concentration in real samples and explore interference factors, three models are established based on different standard solutions of citrate, which are prepared with deionized water, artificial urine and real sample without citrate, respectively. The correlation coefficients of these models are 0.9989, 0.9955 and 0.9976 within the range from 0.1mM to 6mM. Meanwhile, a strong correlation is obtained between the three models (Each R2>0.986) with regression analysis. At last, 20 urine samples are tested and an analysis of the correlation between the results measured by the proposed method and by the capillary electrophoresis method is made. Results indicate that this method looks promising in urine citrate analysis because of its high sensitivity, high selectivity and low consumption of solvent.