Anionic surfactant coacervation extraction-magnetic solid phase microextraction for determination of malachite green

A novel, fast, and efficient two-step microextraction technique for preconcentration and extraction of trace amounts of malachite green in fishpond water, river water and flesh of fish was developed using spectrophotometry. MG with a pH of 6.5 was extracted and mediated by the coacervation phase of the anionic surfactant sodium dodecyl benzene sulfonate. The coacervation phase was then trapped by diatomite bonded Fe3O4 magnetic nanoparticles (DBMNPs) that can rapidly achieve two-phase separation in a magnetic field. The extracted surfactant-rich phase was diluted with ethanol and its absorbance was measured at 624 nm. A number of important parameters affecting extraction efficiency, such as the volume of extraction solvent, amount of salt, pH, amount of DBMNPs, equilibration temperature and time, were investigated. The calibration graph was linear for MG ranging from 2 ng mL(-1) to 180 ng mL(-1) in the initial solution, with r(2) = 0.9994 (n = 10). The detection limit based on three times the standard deviation of the blank (3S(b)) was 0.67 ng mL(-1) and the relative standard deviation for 20 ng mL(-1) of MG was 1.12% (n = 5). The method was applied to determine the trace amounts of MG from fishpond water, river water and flesh of fish.