Rapid measurement of total polyphenol content in tea by kinetic matching approach on microfluidic paper-based analytical devices

In this work, a facile kinetic matching approach for total polyphenol content (TPC) measurement was developed based on the adoption of microfluidic paper-based analytical devices with symmetric channel distribution. A set of Folin-Ciocalteu reactions performed on the same paper chip were activated all at the same time through synchronized filling of sodium carbonate solution among individual channels. Gallic acid was found valid as a standard compound for kinetic matching measurement of tea samples. TPC of tea infusions was successfully measured within ten minutes without any complexed time control procedure needed. Under the optimized conditions, the new developed method showed good linearity in the TPC range of 10-100 mg/L (r > 0.9955) and the inter-chip precision was 5.6% (n = 11). The results measured with the new developed approach were in good agreement with those with the conventional FC assay.