By Uwe Neue on Wednesday, October 15, 2003 - 12:24 pm:
Dear colleagues!
I tried to find solubility data of common HPLC buffers in common HPLC mobile phases, such as water-acetonitrile and water-methanol mixtures. To my amazement, I can't find anything. I know that this is a complex subject. Potassium phosphate is different from sodium phosphate, and sodium acetate at pH 5.25 has a different solubility than sodium acetate at pH 4.75... But this is an everyday problem of every chromatographer, so I would expect that tables exist somewhere.
Can anybody help?
By R.C. on Thursday, October 16, 2003 - 10:39 am:
I've never found comprehensive tables either. The only thing I have is this link: http://www.chromatography.co.uk/TECHNIQS/hplc/valves.htm
It lists some ('bout 5 actually) common buffer problems.
By R.C. on Thursday, October 16, 2003 - 10:41 am:
Oops, only 3. Sodium Phasphate and acetonitrile, potassium salts and SDS, and silic acid.
By Uwe Neue on Thursday, October 16, 2003 - 03:08 pm:
Thanks, R.C., but the information is too vague to be of use. In addition, I have some doubts about the quality of the information stated there... They are talking about volatile silicic acid...
By HW Mueller on Friday, October 17, 2003 - 12:11 am:
Someone recently pointed out that its more simple to test than bother with a table. Just add organic slowly, with a pipet, to your buffer and observe the interface (dissolution or precipitation) in a test tube. The only problem can be supersaturation, but this can be counteracted by adding more organic than wanted. If you get a precipitate soon after the wanted %, forget it. Also, the swirling interface during addition, having local high concentrations, may give you an indication of possible trouble.....
If more organic than buffer is used you may want to reverse the addition (add buffer to organic).