Question

Measure the number of plates for the electrophoretic peak in Figure 26-20. Use Equation 23-32 for asymmetric peaks to find the number of plates for the chromatographic peak.

Short answer

The number for the electrophoretic peak is$\mathrm{N}=9.2\times {10}^4\mathrm{plates}$

The number for the chromatographic peak is$\mathrm{N}=4.1\times {10}^3\mathrm{plates}$

Step-by-step solution

Step 1:Measure the number for the electrophoretic peak

The number for the electrophoretic peak is calculated as

$$\begin{gathered} \mathrm{N}=\frac{16{\mathrm{t}}_{\mathrm{r}}^2}{{\mathrm{w}}^2} \\ \mathrm{N}=\frac{16\times {\left(6.08\min \right)}^2}{{\left(0.08\min \right)}^2} \\ \mathrm{N}=9.2\times {10}^4\mathrm{plates} \end{gathered}$$

Step 2:Measure the number for the chromatographic peak

The number for the chromatographic peak is calculated as

$$\begin{gathered} \mathrm{N}=\frac{41.7{\left({\mathrm{t}}_{\mathrm{r}}/{\mathrm{w}}_{0.1}\right)}^2}{\mathrm{A}/\mathrm{B}+1.25} \\ \mathrm{N}=\frac{41.7{\left(6.03\min /0.37\min \right)}^2}{1.45\times 1.25} \\ \mathrm{N}=4.1\times {10}^3\mathrm{plates} \end{gathered}$$

Our measurements are 1/3 lower than the values from figure 26-20