Application of solidification of floating organic drop microextraction for inorganic anions: Determination of phosphate in water samples

Abstract

A novel dispersive liquid–liquid microextraction based on solidification of a floating organic drop (DLLME-SFO) for determination of orthophosphate was developed. The method includes the formation of molybdoantimonatophosphoric heteropoly blue (HPB) followed by a DLLME-SFO procedure and subsequent absorbance measurement using a micro volume cell (5μL) with 10mm path length. The final experimental conditions for HPB extraction were found to be: 0.6mL of ethanol as dispersive solvent containing 55μL of 1-undecanol as extraction solvent, magnetic stirring at 500rpm, 10min extraction time, decreasing the stirring rate to 150rpm in order to group all the droplets and then solidification of the organic droplet in an ice bath for 5min under continuous magnetic stirring. It should be pointed out that no centrifugation step is required. The calibration plot was linear in the range 4.0–60×10−8molL−1 of phosphate, with a correlation coefficient of 0.9982. The limit of detection (LOD), calculated as three times the standard deviation of the blank test (n=10), was 7.4×10−9molL−1 of phosphate. The reported procedure was applied for determination of phosphate in real water samples.