Method for rapid screening of pesticide mineralization in soil

A method has been developed for the analysis of ¹⁴CO ₂ evolution from the mineralization of ¹⁴C-labelled organic compounds in soil samples. The new method is less space demanding and substantially cuts down laborious manual work compared to the traditional incubation bottle method used. Furthermore, the use of scintillation cocktail is largely reduced with the new method. In the new method, ¹⁴CO ₂ is trapped in filter paper held in the lid of a 20 ml glass vial by surface tension. The trapping solution used is Ca(OH) ₂, which fixates CO ₂ in the filter paper and the analysis of trapped ¹⁴CO ₂ is done using the Cyclone™ Storage Phosphor system. The lids are placed in a 32 well holder and exposed to a phosphor screen prior to scanning in a Cyclone™ scanner. The new filter method has been tested and compared to results obtained using the traditional method. The results show good agreement but due to a smaller capacity for CO ₂ with the filter method compared to the traditional method, the interval between sampling has to be shorter using the filter method when the CO ₂ development is high. The detection limits for the filter method is higher compared to the traditional method. With the filter method, the level of radioactivity has to exceed 300 dpm before detection is possible, while the same limit for the traditional method is around 30 dpm. On the other hand, the gas trapping faster and the efficiency is higher with the filter method.