By April on Wednesday, August 18, 2004 - 09:26 am:

I am a beginner in HPLC.. There are a few terms that I am still unsure even after reading the HPLC glossary.
1) Reversed phase HPLC -Is it if you are using a C18 reversed phase column, then it will called reversed phase HPLC?

2)solvent front (how does it looks like? Anyone has a sample diagram?)
3)negative peak (how does it looks like?)

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By tom jupille on Wednesday, August 18, 2004 - 12:49 pm:

1. Reversed phase. The first chromatography (ca 1903) was done using a column packed with powdered chalk (calcium carbonate, which is very polar) and petroleum ether (very non-polar) as the mobile phase solvent. Some years later, when non-polar column packings were tried with polar solvents, someone noted that the polarity of the two phases had been reversed. Therefore: "reversed phase" refers to separations in which the column packing is non polar and the solvent is polar. "Normal phase", as you might expect, is the original situation with a polar column packing and a non-polar solvent.

2. Solvent front can look like almost anything, depending on what's in the sample and in the mobile phase solvent. Generally, it's the first thing you see on the chromatogram. Here are a couple of examples:

t0.gif

3. A negative peak looks just like a regular peak except that it goes the opposite way (down instead of up).

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By April on Wednesday, August 18, 2004 - 08:33 pm:

Tom Jupille, thanks very much. It's much clearer now. :) lili

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By April on Wednesday, August 18, 2004 - 08:35 pm:

Ooops... it should be :) April

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By Jaime on Thursday, August 19, 2004 - 06:00 am:

Tom Jupille, how were you able to paste that chromatogram? Can any subscriber do that. It makes it easier to describe some problems we might be asking for.

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By tom jupille on Thursday, August 19, 2004 - 10:14 am:

The instructions are in the "Help . . . Formatting . . . Other Formatting" link on the left side of the Forum.

However, we'll be moving to a new platform later this month (I hope).

The new board is at:
http://www.sepsci.com/chromforum/index.php

That platform supports links to images, but not direct insertion.