Assessing the Accuracy of Nitrate Concentration Data for Water Quality Monitoring Using Visual and Cell Phone Quantification Methods

In this methodological project we tested the accuracy of two systems used to quantify results obtained using the Hach© nitrate strip for water quality volunteer monitoring programs. The test strip determines nitrate concentration in accordance with the Lambert-Beer law as increased nitrate concentrations result in greater color intensity on the strip’s sampling pad. In this study, first-time volunteers estimated nitrate concentrations with the test strip, either visually or using the Deltares Nitrate App, a smartphone application that uses the phone’s camera as a spectrometer. Results from two different series of tests indicate that volunteers using visual methods produce the more accurate results. Although cell phone apps might have the potential to increase data quality for colorimetric assays such as the one employed by the Hach© nitrate test strip, the current technology was not an improvement relative to visual interpolation.