I am following usp method, at the development section was okay, and the system suitability was okay. But when it went for verification, the tailing did not meet specification (NMT 1.3). I already washed the column using TEA 0.1% combined with the washing method, but the tailing did not improve. I am reading the question section from other people and the answer mostly added TFA 0.1%. Is it okay? my mobile phase contains Methanol : Glacial acetic acid : Water (28:3:69,v/v/v). Thank you.