Planimeter, polar

Two methods used to find the area under the photometer trace are peak-height-times-half-width approximations and actual measurements with a polar planimeter. Both methods are time consuming and offer little increase in total accuracy over the peak center method. Another method involves computer fitting an assumed scattering function, usually a Gaussian or Lorentzian (though more exotic functions have also been used) to the scan data. The integrated area under the mathematical curve is then calculated. 

Integrator—Means must be provided for determining the accumulated area under the chromatogram. This can be done manually by means of a polar planimeter. Mechanical means, such as the disc integrator, may be used also. However, best precision and automatic operation can be achieved with electronic int ration. 

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