Off-line solid-phase extraction procedure for the determination of phenyl and butyltin compounds from aqueous matrices followed by GC-FPD determination

An analytical methodlogy for the determination of organotin compounds (OTs) in aqueous matrices based on solid-phase extraction (SPE) followed by Grignard pentylation and gas chromatography-flame photometric detector (GC-FPD) determination was developed. Spiked OTs, mono-, di- and tributyltin (MBT, DBT and TBT); and mono-, di- and triphenyltin (MPhT, DPhT and TPhT) were pre-concentrated from aqueous samples as OT chlorides in two different sorbents. A macroporous copolymer containing either lipophilic divinylbenzene, hydrophilicN-vinylpyrrolidone or conventional hydrophobic octadecyl (C18) bonded silica were evaluated by using an automated off-line SPE system. Optimization of the SPE preconcentration included the presence of a complexing agent, sample pH, loading the sorbent with a complexing agent (tropolone), eluent type and volume, breakthrough volume and the sorbent mass. Recoveries of OTs in spiked water samples at 100 ng L−1 ranged from 70 to 90%. Detection limits for butyltin and phenyltin compounds ranged from 10 ng L−1 to 20 ng L−1. Automation of the SPE procedure provides a higher sample throughput in comparison with the use of conventional C18 disks. A new polymeric SPE sorbent evaluated provides higher recoveries, better sample capacities and higher reproducibility in comparison with conventional hydrophobic C18 silica cartridges, and also uses lower sorbent mass.