Question

Electrophoretic mobility of the anionic form A2 of the weak acid phenol $(\mathrm{HA}=C_6{H}_5\mathrm{OH})$and its derivatives are:

(a) Explain the trend in electrophoretic mobility from phenol to 4-methylphenol to 4-ethylphenol.

(b) Predict the electrophoretic mobility of the analytes at pH 10.0. Explain why the predicted mobility differs from mA2. (c) The electroosmotic mobility is toward the cathode and greater in magnitude than the analyte electrophoretic mobilities. In what order will the peaks appear in the electropherogram at pH 10.0?

Short answer

(a)$\mathrm{\mu }$ depends on the analyte size, the bigger the molecules the lower is electrophoretic mobility.

(b) The electrophoretic mobility would be a fraction of$\mathrm{\mu }\left(\mathrm{A}\right)$

(c)role="math" localid="1663687398456" $4-\mathrm{ethylphenol}=4-\mathrm{methylphenol}<\mathrm{phenol}<\mathrm{trichlorophenol}$

Step-by-step solution

Define electrophoretic mobility:

The electrophoretic flow of the compound depends on its charge and in contrast to its magnitude and viscosity of the medium.

Explaining the response of electrophoretic mobility:

Electrophoretic mobility is the response of the solute to the applied electrical field.

 Step 3: The factors:

There are two factors that affect electrophoretic mobility:

(1) Charge - higher charge = higher electrophoretic mobility.

(2) Size - bigger molecules = lower electrophoretic mobility.

Analyte the size of electrophoretic mobility:

(a)

$\mu$depends on the analyte size, the bigger the molecules the lower is electrophoretic mobility.

Predict the electrophoretic mobility of the analytes at pH 10.0:

(b)

Atthe electrophoretic mobilities would be$\mathrm{\mu }\left(\mathrm{phenol}\right)=-1.53\times {10}^8$

$\mathrm{\mu }\left(\mathrm{trichlorophenol}\right)=-2.85\times {10}^8$

Where only a fraction of HA would be ionized - therefore the electrophoretic mobility would be a fraction of$\mathrm{\mu }\left(\mathrm{A}\right)$

State in what order will the peaks appear in the electropherogram at pH 10.0:

(C)

This is the order the peaks appear in the electropherogram at

$4-\mathrm{ethylphenol}=4-\mathrm{methylphenol}<\mathrm{phenol}<\mathrm{trichlorophenol}$