AbstractAn improved synthetic route to [210Pb]‐(CH3)3PbCl is described in which chelated210Pb2+is methylated to [210Pb]‐(CH3)4Pb with methylmagnesium bromide (CH3MgBr) in the presence of methyl iodide. Controlled oxidation of the product with anhydrous hydrochloric acid and purification of the crude product by reversed‐phase high‐pressure liquid chromotography (HPLC) resulted in [210Pb]‐(CH3)3PbCl in 71% radiochemical yield. Whereas storage of the purified product at −10 °C resulted in complete conversion to Pb2+during one year, storage in 20% acetic acid at 4 °C resulted in less than 15% decomposition during six months. Periodic complexometric extractions to remove210Pb radioactive daughters (210Bi, 100% β,Emax= 1.16 MeV;210Po, 100% α,E= 5.305 MeV) from the storage solution did not alter the rate of decomposition. The rate of translocation of [210Pb]‐(CH3)3Pb+across an isolated tomato cuticle was approximately twice the rate of transfer of inorganic lead(II) and was not influenced by the presence of increasing amounts of disodium ethylenediam