91Ó°ÊÓ

(a) A long thin molecule has a greater friction coefficient than a short fat molecule. Predict whether fumarate or maleate will have greater electrophoretic mobility.

(b) Electrophoresis is run with the injection end positive and the detection end negative. At pH 8.5, both anions have a charge of 22.The electroosmotic fl ow from the positive terminal to the negative terminal is greater than the electrophoretic flow, so these two anions have a net migration from the positive to the negative end of the capillary in electrophoresis. From your answer to part (a), predict the order of elution of these two species. (c)At pH 4.0, both anions have a charge close to 21, and the electroosmotic fl ow is weak. Therefore electrophoresis is run with the injection end negative and the detection end positive. The anions migrate from the negative end of the capillary to the positive end.Predict the order of elution.

Step by step solution

01

Step 1:Predict whether fumarate or maleate will have greater electrophoretic mobility

a)From picture in the task we can see that fumerate has a longer chain than maleate,so that fumerate has a greater frictional coefficient

Considering that both molecules have the same charge,we can say that maleate will have a greater electrophoretic mobility than fumarate.

02

Step 2:Predict the order of elution of these two species

In this case maleate would move faster upstream than fumarate,so fumarate would be eluted first.

03

Step 3:At pH=4.0 we will predict the order of elution

At pH=4.0 the maleate is the faster molecule and would be eluted first considering that anions move faster than the endosmotic flow.

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