Solid-phase extraction of mono- and di-substituted organotin compounds in seawater

The solid-phase extraction (SPE) of organotin compounds, such as monobutyltin (MBT), monophenyltin (MPT), dibutyltin (DBT) and diphenyltin (DPT) in seawater has been developed. An ion exchange-type solid-phase sorbent (Excelpak SPE-ION/C224, Yokogawa Analytical Systems Inc., Japan) having a hydrophillic and strong acidic sulfopropyl group and a cation-exchange resin (CK08P, Mitsubishi Chemicals,Japan) were comparatively investigated. The recovery of organotin compounds was measured by atomic-absorption spectrometry, and hydride purge & trap/ICP-MS in the case of ultratrace organotin compounds. The variables affecting SPE were investigated by using a 2.5% sodium chloride solution instead of seawater, such as the amounts of sorbent, the conditioning of cation exchange resins, the flow rate and pH of sample solutions, the effect of the amounts of sodium ion, removing of adsorbed sodium, and an eluting agent. After all, thr cation exchange resin was chosen to be a SPE sorbent, because it has a higher ion-exchange capacity and exhibits better recoveries of organotin compounds. Ten to twelve mi of a strong acidic cation exchange resin (pH 1.0) of sample solutions and a flow rate of 5 similar to 6 mi min(-1) gave good results. For removing adsorbed sodium ions from the resins, 100 mi of 0.5 M hydrochloric acid was rinsed after injecting every 125 mi of a sample solution of 2.5% sodium chloride solution containing organotin compounds. The eluent was 14 mi of 0.5 M hydrochloric acid-methanol solution. DBT and DPT were completely recovered from the solution up to 500 mi of artificial seawater, also MBT and MPT were also recovered up to 250 mi. Ultra traces of MET, MPT, DBT and DPT were determined perfectly by using die present SPE system followed by the hydride purge & trap/ICP-MS.