A chemical amplification method for the sequential estimation of phosphorus, arsenic and silicon at ng/ml levels by d.c. polarography

A method is described for the sequential determination of phosphorus, arsenic and silicon at ng/ml levels by d.c. polarography. These elements are converted into their heteropolymolybdates and separated by selective solvent extraction. Determination of the molybdenum in the extract gives an enhancement factor of 12 for determination of the hetero-atom. A further enhancement by a factor of 40 is achieved by determining the molybdenum by catalytic polarography in nitrate medium. Charging-current compensation is employed to improve precision and the detection limit. The detection limits for phosphorus, arsenic and silicon are 0.5, 4.7 and 3.1 μ/gl., respectively and the relative standard deviation is 2–2.5%.