Question

Which is(are) INCORRECT about the general elution problem?

I           It states that one set of conditions is not suitable to separate a complex mixture of analytes in a reasonable amount of time.

II         It is overcome in GC using an isothermal separation

III        It is overcome in LC using gradient elution

IV        It is overcome in GC using a temperature program

	A.	I and II
	B.	II
	C.	I, II, and IV
	D.	III, and IV
	E.	IV

Answer 1

General elution problem refers to the problem of finding a single set of conditions which can be used to separate the anaylates with varying distribution constant. Thus I is correct.

It can be overcome by making gradual adjustments over time.

It is overcome in gas chromatography using temperature programming in which the temperature is gradually raised. So, IV is also correct.

In liquid chromatography, it is overcome using steadily changing the mobile phase composition i.e. gradient elution. Thus, III is also correct.

However, in isothermal elution, temperature is constant which doesn't tackle the problem. Thus, II is false.

So the answer will be B. II