A method of ionic liquid-based hollow fiber liquid-phase microextraction enhanced electrically was successfully developed and applied to the extraction and determination of neutral red (NR) dye, which was selected as the model analyte. A room temperature ionic liquid, 1-octyl-3-methylimidazolium hexafluorophosphate ([Cmim][PF]), was placed in the pores of a polytetrafluoethylene hollow fiber, which acts as a liquid membrane and the acceptor solution. The extraction parameters affecting the enrichment factor of NR, such as pH, extraction time, elution time, stirring rate, and the voltage were optimized. In addition, UV-Visible (UV-Vis) or electrochemiluminescence spectra were also determined. The extraction rate and capacity of NR could be improved significantly by cathodic polarization. Under the optimized extraction conditions (organic liquid microextraction phase [Cmim][PF], pH 7, stirring rate 300 rpm, extraction time 20 minutes, ultrasonic-assisted elution time 3 minutes, voltage -70 V), the detection limit of 0.38 μg/L and linear correlation coefficient of r > 0.99 were obtained. The established method was successfully applied to the analysis of three soft drink samples, which were spiked with NR standards at the concentrations of 0.1, 1.0, and 5.0 mg/L, and satisfactory results were obtained.
A novel electrochemiluminescence (ECL) sensor for napropamide determination was prepared using the water‐soluble sulfonated graphene (sulfonated‐G) as solid‐phase microextraction (SPME) material, based on selective preconcentration of target onto an electrode and followed by luminol ECL detection. The effects of pH, adsorption time, buffer solution and the luminescence agent on ECL intensity were optimized. Under the optimized conditions (pH 6; adsorption time 5 min; buffer solution pH 11.0 Na2CO3aHCO3; luminescence agent luminol; stirring speed 400 rpm), the lowest detection limits (1.0 µg L−1) and good linear range (r2≥0.99) were obtained for the analyte, indicating the superior performance of Nafion/sulfonated‐G/GCE for detecting napropamide.
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