Development and Evaluation of a 66-Well Plate Using a Porous Sorbent in a Four-Phase Extraction Assisted by Electric Field Approach.

In this work, cellulose cone tips were used as a hydrophilic sorbent supporting an aqueous electrolyte solution in a four-phase electric-field-assisted extraction. The wetted tips were immersed in an immiscible organic phase, acting as a filter to extract analytes present in an aqueous sample. Simultaneous four-phase extractions were carried out under the influence of an electric field using a 66-well plate constructed with inexpensive and readily available laboratory materials. Several parameters that control the electric resistivity of the system were evaluated, and the cone tips provided reproducible and stable electric current during application of electric potential difference. In a final application, a cationic dye and its metabolite, crystal and leuco crystal violet, were extracted from spiked fish extracts and quantified by a digital image analysis method. The method presented a linear range of 2-100 ng mL-1 ( r > 0.999), limit of detection of 1.37 ng mL-1, inter- (3 consecutive days) and intraday precision determined for 4 concentration levels ( n = 6, each) were lower than 29% and mean recoveries for these concentrations ranging from 95% to 115%. The results demonstrated that the 66-well plate provides a stable, reproducible, and simple way to conduct extractions of ionic compounds from complex aqueous matrixes. The effectiveness of the low-cost cellulose cone tips used as a solid fourth phase also confirmed that it can easily overcome many drawbacks of similar liquid-liquid-liquid approaches.