Determination of nitrophenols in water using dynamic liquid-liquid-liquid microextraction under non-equilibrium consideration

To pursue optimum condition in liquid-liquid-liquid microextraction (LLLME), extraction parameters dominating extraction efficiency were investigated by theoretical considerations. The theoretical considerations discussed equilibrium model for equilibrium LLLME and non-equilibrium model for dynamic LLLME. A method described here is a dynamic LLLME technique combined with high-performance liquid-chromatography ultraviolet absorbance detection (HPLC/UV) to determine traces of nitrophenols in water. Analytical parameters such as organic phase, acceptor phase volume, sample agitation, extraction time, acceptor phase NaOH concentration, donor phase HCl concentration, salt addition, and absorption wavelength were identified as variable settings. Relative standard deviation (RSD, 1.8-4.4%), coefficient of estimation (R(2), 0.9994-0.9999), and detection limit (0.032-0.065 ng mL(-1)) were achieved under the variable settings. The proposed method was successfully applied to the analysis of a lake water sample, and the relative recoveries of nitrophenols from spiked water sample were up to 92.5%. The variable settings of LLLME close to optimization was responsible for an acceptable extraction efficiency.