Limitations to Bromide Determinations in Alfalfa Using the Bromide-Selective Electrode
- L. L. Meyers and
- M. P. Russelle
Bromide is a potential tracer of nutrient uptake by plant roots in soil-plant systems, yet traditional methods of Br analysis have been time consuming, expensive, or difficult to complete. The bromide-selective electrode (BrSE) has been used with some success as a simple means to accurately determine Br in soils and plant materials. We tested 0.1 M NaNO3 and 0.025 M Al2(SO4)3 as extractants of Br in alfalfa (Medicago sativa L.) for determination with a BrSE and investigated BrSE interferences from Cl and soluble proteins. Sodium nitrate was eliminated as an extractant due to unstable potentials and gross overestimation of added Br. Extraction with Al2(SO4)3 resulted in stable potentials and accurate recovery of added Br, but x-ray fluorescence analysis showed that the BrSE overestimated tissue Br by 1.3 to 14 times. Overestimation of Br was strongly correlated with the ratio of Cl:Br in the extracts and the BrSE was affected by relatively low [Cl] at [Br] lower than 4 mg L−1. The BrSE is neither an accurate nor a simple means of Br analysis in alfalfa.
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