Dispersive liquid-liquid microextraction based on liquid anion exchanger for the direct extraction of inorganic anions.

For the first time, the possibility of the use of liquid anion exchangers in dispersive liquid-liquid microextraction for the direct extraction of some inorganic anions (nitrite, nitrate, and iodide) was evaluated. In this technique, chloroform containing a liquid anion exchanger (trioctylamine) was used as extractant. The mixture of the extractant and disperser solvent (acetonitrile) was injected into the acidic sample solution. The protonated trioctylamine formed a water-insoluble salt with the inorganic anions (analytes). After the phase separation and stripping of the analytes from the extractant, the analytes were determined by liquid chromatography with UV detection. Various parameters affecting the extraction efficiency were investigated. Under the optimum conditions, broad linear dynamic ranges, with determination coefficients (r) higher than 0.998, and enrichment factors between 94 and 244 were obtained. The limits of detection and quantification were in the range of 0.1-0.5 and 0.4-1.7 μg L, respectively. Also, the values of intra- and inter-day relative standard deviations were 3.5-5.8% and 5.5-7.8%, respectively. Various real water samples including sea, tap, river, spring and mineral water were analyzed by the method. The method was sensitive, simple, inexpensive and capable of the simultaneous extraction and determination of the selected inorganic anions.