The present invention discloses the reactivity of ponytail ("PT") sulfonates as leaving groups in nucleophilic fluorination reactions. The results showed that using a pentafluorobenzenesulfonate precursor is a suitable leaving group for n. c. a. nucleophilic .sup.18F-fluorination in synthesis of [.sup.18F]fluoromethyl benzene, wherein this is a suitable leaving group for 18F-labeling with moderate reactivity. The PT-precursor seems to be quite stable. In an attempt to purify the crude 18F-labeled product using fluorous solid phase extraction (F-SPE), the radio labeled impurities decreased significantly. This provides an opportunity for utilizing PT methodology in both simple and fast purification methods.