We report on a new solid phase for microextraction (SPME) of Methylene Blue (MB). It was obtained by immobilizing carboxy graphene (G-COOH) on a stainless steel wire. Scanning electron micrography showed the surface to be homogeneous, porous and wrinkled. The effects of sample solution pH, extraction time, stirring rate, desorption time and of desorption solvent on the efficiency of extraction of MB were optimized. The new SPME was coupled to electrochemiluminescence detection of MB and gave a linear analytical range from 2.7 nM to 1.3 μM, and the detection limit is 0.89 nM which is better than other methods. When considering the enrichment factor of ~20, the resulting detection limit is estimated to be 45 pM. The new SPME fiber was successfully applied to the analysis of MB in spiked real water samples. Recoveries range from 95.7 % to 113.0 %, and relative standard deviations are <5.0 %, which showed the good reproducibility of the method.

Gentian violet (GV) was found to quench the electrochemiluminescence (ECL) of the tris(2,2′-bipyridyl)ruthenium(II)/tris-n-propylamine (Ru(bpy)32+-TPA) system at a glass carbon electrode (GCE). Based on the ECL signal changes, a simple and ultrasensitive detection method for GV in aquatic water was established. Under the optimized conditions, the quenched ECL intensity versus the logarithm of the concentration of GV was linear over a concentration range from 1.0 × 10−10 to 5.0 × 10−7 mol L−1, and the limit of detection (LOD) was found to be 4.5 × 10−12 mol L−1 (S/N = 3). The results obtained by the ECL system were better than other reported methods in literatures in terms of sensitivity or linear response range. The method was successfully applied to determine GV in aquatic water, and the relative standard deviations (RSDs) were found less than 6.3%, and the recoveries were obtained from 98.7 to 111.0%. Moreover, a possible mechanism of the quenching effect was primarily discussed based on UV–visible absorption spectra, cyclic voltammograms and IECL–E curves.

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 ([C8mim][PF6]), 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 [C8mim][PF6], 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.