Graphene reinforced multiple monolithic fiber solid-phase microextraction of phenoxyacetic acid herbicides in complex samples

To increase the specific surface area (SSA) of monolith-based adsorbent for the extraction of phenoxyacetic acid herbicides (PAAs) in complex samples, graphene was embedded in an adsorbent based on poly (4-vinylpyridine-co-ethylene glycol dimethacrylate) monolith (GEM). The new adsorbent was employed as extraction phase of multiple monolithic fiber solid-phase microextraction (MMF-SPME). The influences of preparation conditions and extraction parameters on the enrichment performance of GEM/MMF-SPME for PAAs were investigated in detail. Results well indicated that the embedded graphene could obviously enhance the SSA of the adsorbent and introduce pi-pi electrostatic stacking groups. The prepared GEM/MMF-SPME could extract PAAs effectively by means of pi-pi electrostatic stacking, hydrophobic, ion-exchange and hydrogen bonding interactions. Under the most favorable conditions, a convenient, sensitive, cost-effective and environmentally friendly method for the determination of trace PAAs in water and rice samples was developed by the combination of GEM/MMF-SPME and high performance liquid chromatography-diode array detection (HPLC-DAD). Results showed that for water sample, the limits of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) values were in the range of 0.093-0.12 mu g/L and 0.31-0.41 mu g/L, respectively. The corresponding values in rice sample were 0.36-0.66 mu g/kg and 1.18-2.27 mu g/kg, respectively. The proposed method was successfully applied to quantify trace PAAs in water and rice samples. Recoveries achieved for water and rice samples at different spiked concentrations were in the ranges of 70.0-118% and 70.0-117%, respectively. The RSDs varied from 0.3% to 10% for all analytes. The results well revealed the potential application of GEM/MMF-SPME as an effective sample preparation processes for the monitoring of PAAs in water, rice and other complex samples.