A field deployable chemical reaction for colourimetric and fluorescence detection of atrazine in soil

Abstract Pesticides are widely used in agriculture to increase crop yields, but they also pose a risk to human health. As a result, there are guidelines to monitor their use in most countries. Atrazine is one of the most popular herbicides. It is also one of the most controversial with its use banned in Europe and its use recently reaffirmed in the United States. Methods to detect it have traditionally relied on laboratory-based chromatographic methods after purification and/or pre-concentration of the sample. Herein, we optimize the König chemical reaction to detect atrazine without pre-concentration or purification. The assay incorporates extraction of atrazine from soil, is made simpler to enable field use and gives an easy visualization to interpret colourless to purple colour change or pink fluorescence under an LED torch. The assay can be used with spectrophotometers or with a paper-based visual detection for humans. Moreover, we demonstrate atrazine that has been applied to soil can be detected at meaningfully relevant concentrations (approx. 1 µg ml−1) and that lower concentrations are detectable (up to approx. 0.05 µg ml−1 using a fluorescence spectrophotometer) potentially extending the use of the assay to other sample matrices such as food.