May 9, 2022 · 10 to 100 mmol/L perchloric acid aqueous solution or mixtures of such with an organic solvent. (For the organic solvent, use acetonitrile, methanol, or ethanol.) 10 mmol/L trifluoroacetic acid (TFA) organic solvent. (For the organic solvent, use acetonitrile, methanol, or ethanol. Note that trifluoroacetic acid will be detected when n