Chromatography Forum

We had a question set for further reading but i can't find the answer anywhere, not in any of the set texts or from searching online.

The question is "what is the special valve found only in an HPLC machine and how does this negate the need for an internal standard?"

Some of the literature i've read actually calls for an internal standard in an HPLC so i've no idea how to approach this question.

Since it's Hallowe'en and not April Fools day I have to assume that this is a real question. I suspect that the answer that is required is " the 6-port injector valve" and that the fixed loop ensures a constant injection volume (as oppposed to say a vaporizing inlet in GC where what gets into the column can be highely variable) so there is no need for an internal standard to correct for injection volume. The trouble with this is that there are plenty of ways that a 6-port valve can give erratic injections (most of them operator related) and that an internal standard, properly applied, corrects for a host of sample prep variation besides injection volume.

First rule of tests and exams - give the examiners what they are looking for.

thank you Peter Apps. Yes it was a real question, i think i was reading too much into the question.