Colorimetric paper-based device for rapid screening of orlistat in weight loss supplements

The colorimetric paper-based device using lipase inhibition assay was developed for rapid and visual detection of orlistat in weight loss supplements. The paper device with five circular detection zones was simply fabricated from filter paper No 1 using a low-cost paper craft puncher with a design of a flower-like shape. The enzymatic reaction on the detection zone employed a small volume of a substrate, a-naphthyl acetate, a sample, and a lipase enzyme. After incubation, the Fast Blue B solution was used as a chromogenic reagent. The decrease in purple color can be observed by the naked eye, in the presence of orlistat. Under optimized conditions, the paper device showed satisfactory sensitivity and selectivity. The device was applied for rapid screening of orlistat in weight loss supplements and the results agreed with those obtained from TLC analysis.