A pH 3.0 ammonium formate buffer was prepared by mixing 1 mL of
ammonium formate 1 M (dissolving ammonium formate 3153 g in 50 mL of
water) and 0.5 mL of formic acid, and adding water until 500 mL. Drug-free
urine was obtained from healthy volunteers.
A mixture methanol:hydrochloric acid (MeOH:HCl, 99:1 v/v), was prepared
by mixing 9.9 mL of methanol and 0.1 mL of hydrochloric acid 25%.