Optimum points for the measurement of the number of theoretical plates and peak areas in g. c.

In calculating the peak area A or number of theoretical plates N from peak shapes, the width of the peak at a certain height is measured and then substituted in the formula for A or N. In this paper, it is shown that the width may be measured at any fractional height so long as the proper constant is substituted in the equation. It is shown, however, that the uncertainty in the computed values due to an uncertainty in the height is different at different fractional heights and is a minimum at a fractional height equal to 1/e, which is the optimum height for the measurement of the peak width. The formulas for evaluating the constants at different fractional heights are derived and plotted, and a method for the accurate and convenient determination of A and N is outlined. The treatment is rigorous only for Gaussian peaks but it is shown that the derived formulas are sufficiently accurate for peaks of moderate asymmetry.