It is shown that boron can be estimated by dc polarography at mu g/ ml level by using two chemical amplification reactions in sequence. In this method, boron is converted into molybdotungstoboric acid by its reaction with ammonium molybdate and sodium tungstate under suitable conditions and is separated by solvent extraction. Determination of molybdenum in the organic extract gives an indirect estimation of boron with an enhancement factor of 6. A further enhancement by a factor of 40 is achieved by determining molybdenum through catalytic dc polarography in nitrate medium. With the overall enhancement factor of 240 and with the use of charging current compensation to minimize the background, the detection limit for boron is 0. 25 mu g/ml and the relative standard deviation is 5% (at 20 mu g level).
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