Quantitative pH Determination Based on the Dominant Wavelength Analysis of Commercial Test Strips

Abstract

The determination of pH values is essential in many chemical, medical, and environmental monitoring processes, which has been relying on conventional pH meters (glass electrodes) for quantitation and pH test strips for qualitative (or semiquantitative) assessment. In this work, we demonstrate a smartphone-based pH determination technique, which performs digital image analysis of commercial test strips, particularly the determination of either the dominant wavelength (λ d ) or complementary wavelength (λ c ) of the color image. In conjunction with a 3D-printed optical accessory (with a surface light source and a macro lens), the quality of captured images have been warranted, and the quantitation accuracy of 0.05 pH units has been achieved. More importantly, the performance of this smartphone-based pH reading system (namely "Smart-pH-Reader") was validated using multiple real-world samples, as the results are consistent with those determined with a standard pH meter. The Smart-pH-Reader is envisioned to be a simple, portable, and accurate tool for pH determination in the fields of environmental monitoring, medical diagnosis, and beyond.

Classification of ballpoint pen inks based on selective extraction and subsequent digital color and cluster analyses

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“…23 The cost-efficiency of both the equipment needed to perform the analysis and the analysis itself can nowadays be achieved through the use of inexpensive reading devices: scanners, 24 digital cameras 25 and even smartphones. 26–29…”

Automatic Measurement System for Nitrite and Nitrate in Water Bodies

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A smartphone-based device for simultaneous measurement of ratiometric fluorescence and absorbance demonstrated by the determination of hypochlorous acid

“…[12][13][14][15] A smartphone-based analytical device provides remarkable advantages in portability, low power consumption, inexpensiveness, and convenience in position location and data exchange for field analysis. 16,17 Typical examples include the visual colorimetric [18][19][20][21][22] and fluorometric determinations, [23][24][25][26] chemical education, 27,28 as well as data analysis and control interfaces. 29,30 Usually, the fluorometric and colorimetric determination is performed independently using different smartphone-based portable devices.…”