The membraneless-gas separation microfluidic paper-based analytical device (ML-GS μPAD), consisting of donor, spacer, and acceptor layers, was developed to monitor total ammonia in fish pond water. The principle of the analysis involved the addition of sodium hydroxide solution to the sample zone in the donor layer containing ammonia/ammonium, and the produced ammonia gas diffuses through the spacer to the detection zone in the acceptor layer containing red rose extract to produce a color change from pink to blue corresponding to the ammonia/ammonium concentration. Under optimum conditions, the proposed method provided good linearity of ammonia in the range concentration of 0–100 mg L−1 (R2 = 0.9993) with LOD and LOQ of 2.25 and 7.51 mg L−1, respectively. This method was successfully applied to fish pond water samples without significant influence of interfering compounds with recoveries in the range of 103–110%, indicating good selectivity and accuracy of the proposed method.
Reference: Mufidah Sari, P.; Daud, A.; Sulistyarti, H.; Sabarudin, A.; Nacapricha, D., An application study of membraneless-gas separation microfluidic paper-based analytical device for monitoring total ammonia in fish pond water using natural reagent. Analytical Sciences 2022, 38 (5), 759-767.