Quotient of two Waves

PUot-Ion Method. Another method, known as the quotient of two waves or pilot-ion method, is less frequently used, but offers some advantages. (This is known more generally as an internal standard method.) A known quantity of a standard pilot substance is added to each investigated solution. This pilot substance must be polarographically active and give a wave or waves in a potential region (preferably at more positive potentials) sufficiently different from that of the compound to be determined. 

The method of quotient of two waves can be applied in cases similar to those in which the simple calibration curve is used. Temperature control is unnecessary, but construction of several calibration curves for different concentrations of the pilot substance is usually necessary. 

The procedure known as quotient of two waves is independent of temperature. In this method a known quantity of a certain polarographically active substance is added to each solution in which another component is to be determined. It is assumed that the ratio of the two waves (for the unknown and for the added standard or pilot) is independent of temperature, viscosity, rate of flow of mercury etc. The calibration curves are constructed by plotting the ratio of the two waves against the concentration of the substance to be determined, keeping the concentration of the pilot constant. These calibration curves are used in the same way as the ordinary curves. 

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See also in sourсe #XX -- [ ]

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