Development of a preconcentration method for indomethacin in natural waters using dispersive liquid–liquid microextraction based on solidification of floating organic drop technique

A new dispersive liquid–liquid microextraction method based on the solidification of a floating organic drop was developed for the preconcentration of indomethacin in natural waters followed by ultraviolet-visible (UV-Vis) spectrophotometric detection. 1-undecanol and ethanol were used as the extraction solvent and the disperser solvent, respectively. An investigation of the main experimental parameters that may affect the extraction efficiency, such as sample pH, volume of extraction and disperser solvents, sodium chloride concentration and centrifugation time was undertaken. The effect of interfering ions on the recovery of indomethacin was also examined. Under optimal conditions without any preconcentration, the limit of detection was 17.9 μg/L calculated from LOD = 3 Sb/m and was also calculated as 74.9 μg/L from the regression values of the calibration line using 3.19 Se/m. The proposed preconcentration method was successfully applied to determination of indomethacin in spiked tap water and river water samples. The recovery values for spikes added to water samples were between 94.5 and 103.0%.