Smartphone Self-Contained NIR Colorimeter

A self-contained smartphone-based near infrared (NIR) colorimeter is reported for the first time by utilizing the inbuilt NIR emitter Delta lambda approximate to 770-1000 nm) and macrolens complementary metal-oxide semiconductor (CMOS) camera of the phone. The emitted NIR light is guided through a low-cost multimode plastic fiber to illuminate the test sample, and the phone's CMOS camera is utilized to collect and digitize the transmitted light through the sample. An easy-to-use customized Android app has been developed to operate this ultra-low-cost (<$2) and field-portable (similar to 174 g) smartphone-based NIR colorimeter fabricated by polyvinyl chloride material. The performance of the instrument is evaluated by measuring the free fatty acid (FFA) percentage in the recycled palm oil samples with a 0.21% average error of detection compared to the standard titration-based assessment. FFA is a significant quality indicator of vegetable oil, generally quantified in terms of oleic acid having an absorption peak at lambda(P) approximate to 930 nm, which complies with the operating wavelength band Delta lambda approximate to 910-980 nm) of this instrument.