Stability of arsenic during soil treatment and storage

There are many studies in the area of identifying and measuring arsenic (As) and its species in soil samples. However, stability of total As, As(V) and As(III) during sample drying and storage has received little attention. The present study evaluates the stability of total As, As(V) and As(III) in four soils with differing agricultural uses and physicochemical properties. Moisture elimination conditions were evaluated, i.e. lyophilization for 1 day vs. drying at 50°C for 3 days, along with different storage conditions, i.e. room temperature for 2 days vs. -20°C for 2 days. The results show that the recovered levels of native As(V) and As(III) are highest using lyophilization and storage at -20°C. Under these optimal conditions, total As content and the levels of As(V) and As(III) remain stable up to 10 days of storage with an error of ±20%.