Boron analysis in soil extracts and plant tissue by plasma emission spectroscopy

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Abstract
Nine Colorado soils were treated with sodium borate and were subjected to 3 wetting and drying cycles. These soils were extracted with hot water for boron analysis. Plant samples, including NBS standard reference materials (SRM) 1571, 1570, 1573, were dry ashed and wet digested using nitric acid. All soil extracts and plant digests were analyzed for boron using ICP‐AES and colorimetrically using the Azomethine‐H method. A high degree of correlation (r2 = .99) was found between boron determination by ICP and the Azomethine‐H method for soil extracts and plant digests. The Azomethine‐H method gave B values 9% higher than ICP‐AES on the average. Boron levels determined by ICP were similar to NBS boron values for both the dry ashed and wet digested SRM plant samples. Boron levels determined colorimetrically were comparable to the NBS values for dry ashed SRM plant samples. Plant samples digested in nitric acid could not be analyzed for boron by the Azomethine‐H colorimetric method due to interferences resulting from nitrate complexes in the wet digest.