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Caffeine without buffered MP

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

7 posts Page 1 of 1
Dear All,
I am trying separate Caffeine with HPLC using a C18 column. I would like to avoid using buffers if possible but I am getting distorted peaks and even split peaks in some chromatographic conditions. I found it difficult to get good retention with good peak shape using Methanol and Water only as the mobile phase. I have an access to a C8 columns if it may help.

I appreciate your suggestions.

Many thanks in advance.
What is your sample dissolved in? Using your mobile phase as the diluent can minimize peak shape problems.
-- Tom Jupille
LC Resources / Separation Science Associates
tjupille@lcresources.com
+ 1 (925) 297-5374
Thanks Tom.
I tried the MP and Water but I found no clear difference.
try 70:30 MeOH:H2O as both diluent and mobile phase. on a C18, 4.6x75mm column with 10ul injection, you get a nice clean peak, in under 3 minutes; using a 1ml/min flow rate. Waters uses this method for some of their instrument qualification analysis.
I use a mobile phase of methanol/water 70:30 with 1% acetic acid to analyze caffeine and benzoic acid from direct injections of soda pop. This makes a great demonstration for school classrooms.
Methanol: Water 70:30 and a Standard C18 column, directly from a coffee mug, inject and you should get a nice Peak. Or you take a sample from Coca Cola, ultrasonic a Little bit and inject. Also a nice Peak.
Gerhard Kratz, Kratz_Gerhard@web.de
Many thanks for all of you!

The job seems to be easier than what I thought!
I tried a new C18 column after reading your suggestions and every thing went well! :D
I think the OLD column is reaching its lifetime end!

Thanks again.
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