By Anonymous on Friday, July 12, 2002 - 05:38 am:
HELLO!
IīM LOOKING FOR SOME BUFFERS OF PH 3, 4, 5 .i NEED THEM NOT TO ABSORB TOO MUCH IN 215nm.
I CANīT FIND ANY..
THANKS
By Jean-Philippe Lambert on Friday, July 12, 2002 - 06:36 am:
Hi,
for pH 3 I don't have any suggestion but for pH 4 and 5 a buffer made of acetic acid and ammonium acetate should do just fine.
You might wanna try citrate buffer at pH 3 but it does absorbs at 215nm.
Good Luck
By Anonymous on Friday, July 12, 2002 - 03:36 pm:
For pH = 3 you can use sodium (potassium or ammonium too) phosphate can do it well
Na or Ammonium Acetate for pH=4 or 5 is suitable but 10 - 40 mM carboxilic acid solutions absorb at 215 nm
Regards
By Anonymous on Saturday, July 13, 2002 - 03:02 am:
Formic acid with amonium and adjust to pH 3.0 would be another good option
By colin.crowley on Monday, July 15, 2002 - 03:06 am:
Formic acid and TFA have a UV cut off of 210 nm, but will probably have an absorbance at 215 nm. Phosphoric acid cuts off at less than 200nm. all 3 are Ok at Ph3, but formic acid just squeezes in (pKa +/- 1) as its pKa is 3.8.
By Anonymous on Monday, July 15, 2002 - 06:02 am:
Im not sure what solvents you're going to be using but i've found that methylphosphonic acid works well in ACN/MeOH. you can easily get down to pH 3
By Andreas Neumaier on Thursday, July 18, 2002 - 03:22 am:
If you're using acetic acid, TFA or some other organic acids in a concentration of 0.2% or higher, you'll get a real high absorbance at 215 nm. It depends on your detector, if it's too high. Phosphoric acid buffers are only for use < pH 3.3
Maybe you should give ammonniumsulfat-buffer (NH4)2SO4 a try...