Solid phase microextraction for the determination of chromium in sea-water

Application of solid phase microextraction (SPME) to the extraction of Cr from sea-water after derivatization with the beta-diketonate ligand 1,1,1-trifluoro-2,4-pentadione (trifluoroacetylacetone) is reported. The chelation reaction was conducted in a single (aqueous) phase medium. Both liquid phase and headspace extraction were studied by employing a 100 mum PDMS (polydimethylsiloxane) coated SPME fiber. Capillary gas chromatography (GC) coupled to electron capture detection (ECD), electron impact-mass spectrometry (EI-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) were compared for the quantitation of Cr. Except for the ECD, isotope dilution calibration was applied, using Cr-53 enriched spikes. Detection limits between 0.011-0.015 ng ml(-1) (as Cr) were achieved with all three systems. Accuracy was assessed using CASS-4 Nearshore Seawater Certified Reference Material (CRM) from the National Research Council of Canada (NRCC). The developed method provided accurate results with EI-MS and ICP-MS detection, while significant bias was experienced with the ECD.