A comparison has been made between the picrate and the inductively coupled plasma-atomic emission spectroscopy methods for detection of the metals UO22+ Cu2+, Eu3+, Cd2+, Cr3+, and Pb2+ after extraction from aqueous solution into chloroform with a series of calix[4]arene amide and amines. These data reveal that the picrate method gives consistently higher analytical results because of salt formation between the picrate anion and the protonated amide or amine cation. By comparison, a calix[4]arene ester that has no centers that can be protonated by picric acid shows no difference between the two methods.