Quantitative drinking water arsenic concentrations in field environments using mobile phone photometry of field kits

Abstract

Arsenic (As) groundwater contamination is common yet spatially heterogeneous within most environments. It is therefore necessary to measure As concentrations to determine whether a water source is safe to drink. Measurement of As in the field involves using a test strip that changes color in the presence of As. These tests are relatively inexpensive, but results are subjective and provide binned categorical data rather than exact determinations of As concentration. The goal of this work was to determine if photos of field kit test strips taken on mobile phone cameras could be used to extract more precise, continuous As concentrations. As concentrations for 376 wells sampled from Araihazar, Bangladesh were analyzed using ICP-MS, field kit and the new mobile phone photo method. Results from the field and lab indicate that normalized RGB color data extracted from images were able to accurately predict As concentrations as measured by ICP-MS, achieving detection limits of 9.2μg/L, and 21.9μg/L for the lab and field respectively. Data analysis is most consistent in the laboratory, but can successfully be carried out offline following image analysis, or on the mobile phone using basic image analysis software. The accuracy of the field method was limited by variability in image saturation, and variation in the illumination spectrum (lighting) and camera response. This work indicates that mobile phone cameras can be used as an analytical tool for quantitative measures of As and could change how water samples are analyzed in the field more widely, and that modest improvements in the consistency of photographic image collection and processing could yield measurements that are both accurate and precise.

Field-Tests versus Laboratory Methods for Determining Metal Pollutants in Soil Extracts

“…This leads to a fast semi-quantitative result. Individual differences in color recognition can be avoided using smartphone apps measuring the R, G and B value of the colored test solutions (Peng et al 2019) or of commercially available field test kits for selected soil contaminants like As (Haque et al 2016). Furthermore, there is no problem with the disposal of the chemicals, since everything is kept in the closed tubes.…”

Highly sensitive determination of arsenic in water samples by hydrogen-doped solution anode glow discharge-optical emission spectrometry

“…10–14 However, commercially available colorimetric field kits with poor sensitivity struggle to meet the drinking water standard limits (10 μg L −1 ) and are also proven not completely reliable for As measurements. 15,16 Electrochemical methods offer the advantage of having good sensitivity and small-size but they are susceptible to matrix interference and field analysis with electrochemical analyzers is rarely robust for real samples. 11 Atomic spectrometry techniques ( e.g.…”

“…[10][11][12][13][14] However, commercially available colorimetric eld kits with poor sensitivity struggle to meet the drinking water standard limits (10 mg L −1 ) and are also proven not completely reliable for As measurements. 15,16 Electrochemical methods offer the advantage of having good sensitivity and small-size but they are susceptible to matrix interference and eld analysis with electrochemical analyzers is rarely robust for real samples. 11 Atomic spectrometry techniques (e.g., atomic absorption spectrometry (AAS), atomic uorescence spectrometry (AFS), inductively coupled plasma optical emission spectrometry/mass spectrometry (ICP-OES/ MS)) are commonly used for the determination of elements (including As) with high sensitivity and accuracy.…”

Hue‐shifting for accurate and precise quantification of biochemical substances using diagnostic test strips

“…Test strips have been examined for the quantification of chemical substances in various samples. The precise quantitative use of test strips has been demonstrated 9 . Improving their accuracy should further broaden the quantitative application of test strips 10 …”