Evaluation of nitrate analysis using test strips: Comparison with two analytical laboratory methods

Abstract

Nitrate remains a contaminant of concern for users of well water. Well‐water evaluation, either to assess nitrate contamination or to evaluate sites prior to including them in a larger water quality study, often involves costly laboratory analysis. A cost effective alternative to laboratory analysis are dip‐style test strips. However, the accuracy of these types of products must be reliable, as failure to identify the contaminant may, for example, persuade a homeowner to neglect to have a potential problem further investigated. The testing of nitrate using such strips typically involves dipping the strip into the water sample and reading the color development after a specific period of time. The color development is then compared to a color scale which corresponds to concentration provided with the test. The results of these types of analysis are especially open to interpretation by the evaluator of the results. An experiment was conducted to evaluate test strips in which individuals or “readers” tested water samples collected in the field and nitrate standards prepared in the laboratory with nitrate test strips. The results obtained by the “readers” were compared to analysis of nitrate by high performance liquid chromatography and colorimetric analysis using a colorimetric ion analyzer. There was a good agreement between the “readers” results and the analytical methodologies used. Use of the test strips by non‐technical persons, such as homeowners, could provide an accurate determination of nitrate in well water without the expense involved in a detailed laboratory analysis. The test strips can also be relied upon to accurately determine nitrate concentration when screening wells prior to designing field experiments.