Reagent	Final concentration	Amount (20 mL)
MeCN	10% (v/v)	2 mL
TFA	0.2% (v/v) aqueous solution	40 μL
MilliQ water		17.96 mL
Prepare freshly before each use. ∼0.5 mL of Phosphopeptide Wash buffer 2 is needed for each sample