Measurement ( IF 3.364 ) Pub Date : 2020-10-16 , DOI: 10.1016/j.measurement.2020.108607 Hojat Heidari-Bafroui; Brenno Ribeiro; Amer Charbaji; Constantine Anagnostopoulos; Mohammad Faghri
Herein, we report the development of a portable, iPhone controlled, and inexpensive infrared lightbox for improving the detection limits of paper-based phosphate devices. Commercial devices utilize the molybdenum blue protocol for phosphate detection. Although these devices are user-friendly and have a long shelf life, their standard mode of operation suffers from low sensitivity since it gives semi-quantitative results by comparing to a color chart. To improve the results, we constructed a compact infrared lightbox that communicates wirelessly with a smartphone equipped with a developed colorimetric analyzer. This system measures the absorbance of radiation for the molybdenum blue reaction in the infrared region of the spectrum. By using the infrared lightbox, the detection limits for two popular paper-based commercial devices were improved by a factor of 4 for the Quantofix devices and a factor of 6 for the Indigo units with repeatability of less than or equal to 1.2% RSD.