The efficiency of dual-layer solid-phase extraction(graphitized carbon/NH2 SPE), sorbents characterized by different mechanisms of sorption, was evaluated in view of sample clean-up procedure of multiresidue method(MRM).
Individually graphitized car...
The efficiency of dual-layer solid-phase extraction(graphitized carbon/NH2 SPE), sorbents characterized by different mechanisms of sorption, was evaluated in view of sample clean-up procedure of multiresidue method(MRM).
Individually graphitized carbon block(GCB) and aminopropyl(NH2) SPE were evaluated with several clean-up solvent systems. Suitable elution solvents were selected toluene for GCB SPE and acetone, ethylacetate for NH2 SPE. Then selected solvents were mixed to various ratio and tested as a GCB/NH2 dual-layer SPE eluent.
Suitable elution solvents for 40 pesticides with a wide range of polarity were studied 65% ethyl acetate/toluene, 70% acetone/toluene. Two solvents were compared in clean-up for lettuce. As a result, 65% ethyl acetate/toluene was showed more efficiency to remove sample matrix and selected most appropriate elution solvent for clean-up of GCB/NH2 dual-layer SPE.
The solvent of 65% ethyl acetate/toluene was showed over 90% of recovery in almost pesticides, but some polar pesticides such as clothianidin, thiamethoxam, and carbendazim were eluted insufficiently.
And cymoxanil, pyroquilon, thiacloprid and boscalid were affected by matrix co-extractives in low level test. Nevertheless, these pesticides also showed 90~110% recovery reducing the affection of co-extractives of sample matrix by HPLC/MS analysis.