EXTRACTION OF BORON FROM SOIL BY MICROWAVE-HEATING FOR ICP-AES DETERMINATION

Extraction with hot water is the most widely used procedure to determine boron (B) in soils for the diagnosis of the nutrient availability for plants. However, this procedure is tedious for routine conditions and requires some special precautions. An alternative extraction procedure was developed, consisting in the extraction of B with a 1.25 g/L solution of barium chloride (BaCl2) or with water heated in a domestic microwave oven. Boron was determined either by inductively coupled argon plasma emission spectrometry (ICP-AES) and by spectrophotometry with azomethine-H. Good correlations were found between the extraction by boiling water under reflux and the extraction by the microwave heating for 13 Brazilian soils, and the contents of B obtained by spectrophotometry did not differ significantly from those obtained by ICP-AES. Considering the calculated standard deviations, it can be concluded that microwave heating followed by ICP-AES determination is an adequate procedure for the determination of hot water extractable B in soils.2519-203321333