Analysis of tebuthiuron in samples from Cirrus Ag

Tebuthiuron is a thiadiazolyl urea herbicide (Figure 1) primarily used for the control of woody plants. Application is typically via pellet-type products containing tebuthiuron (200-400 mg/g), which may be applied from the ground, or aerially dispersed if a large area is to be treated. As tebuthiuron is highly water-soluble (Bovey et al., 1978), it leaches from the pellets into the soil (Faria et al., 2018), where it is subsequently absorbed by the roots and translocated to the leaf tissue (McNeil et al., 1984). Its mode of action is through inhibition of Photosystem II, thus preventing photosynthesis in the affected plant (Hatzios et al., 1980). The degradation and persistence of tebuthiuron is still an area under investigation, with studies reporting half-lives between 20 days (Cerdeira et al., 2007) and 16-22 days (Qian et al., 2017), to as high as one year (Helling, 2005), 12.9 months (Elanco, 1988), ‘considerably greater’ than 15 months (Chang & Stritzke, 1977) and even 2-7 years (Johnsen Jr. & Morton, 1989). du Toit & Sekwadi (2012) reported that tebuthiuron residue remained active in soil for 8 years after application. The Applied Chemistry research group at CQUniversity were approached by Granular Products in mid-February 2021 with the request of quantifying the active ingredient (tebuthiuron) content in Regain products manufactured by Cirrus Ag, Rockhampton. Between April and August 2021, 25 samples were provided to CQU for method development and quantitative analysis, comprising 5 samples of raw tebuthiuron powder and 20 samples of Regain product. This technical report outlines the method development processes and the results obtained to date by the CQUniversity Applied Chemistry research group.