The following table shows a list of common buffers and their working buffer ranges:
|trifluoroacetic acid (TFA)||1.5-2.5|
|phosphoric acid/monobasic phosphate (pKa 1)||1.1-3.1|
|mono/dibasic phosphate (pKa 2)||6.2-8.2|
As for concentration, about 5mM is suitable for Cogent TYPE-C Silica™ columns while 25mM can be used with columns based on type B silica.