Speciation of Organotin Compounds in Seawater by Headspace Solid Phase Microextraction and Gas Chromatography-Tandem Mass After Ethylation

Abstract

A method for the determination of five organotin compounds( OTs),monobutyltin( MBT),dibutyltin( DBT),tributyltin( TBT),monophenyltin( MPhT) and diphenyltin( DPhT),in seawater was developed using solid phase microextraction( SPME) coupled with gas chromatography and triple quadrupole tandem mass spectrometer( GC-MS/MS) after ethylation with sodium tetraethylbroate( NaBEt4).After the internal standard( Tripropyltin,TPrT) was added,the pH was adjusted to 5.0 by HAc-NaAc buffer,and NaBEt4 was added,the seawater sample was stirred with a magnetic agitator and the headspace solid phase microextraction was performed with a 75 μm polydimethylsiloxane/carboxen( PDMS/CAR) fiber for 20 min.After extraction,the SPME fiber was directly injected into the GC inlet for GC-MS/MS analysis.The method has very low detection limits for the five organotin compounds in the range of 0.10-0.20 ng/L( Sn).The recoveries are in the range of 80.2%-93.6%,and the relative standard deviations are all below 13% for the five organotin compounds at the spike level of 20 ng/L( Sn).The method is simple,fast,sensitive and solventless.No more than 25 minutes were needed for each sample in routine analysis.The proposed method was applied to96 seawater samples collected from mariculture areas along the Bohai Bay and the detection rate was 42.7%.