Optimisation of a Microwave Assisted Solvent Extraction Method for the Determination of 4-Nonylphenol and 4-Nonylphenol Ethoxylates in River Sediments

The efficiency of microwave assisted solvent extraction (MASE) for the simultaneous determination of nonylphenol and nonylphenol ethoxylates in river sediments has been evaluated. An optimisation study was carried out in order to identify the variables having the greatest influence on the extraction efficiency. The comparison between the solvents (methanol and acetone-hexane 1:1) showed clearly that the more polar solvent (i.e. methanol) allowed a more effective extraction of NP and NPE from sediments. Analytical results show that there is not a considerable improvement by doubling extraction time, while it is significant the increase of solvent volume from 30 to 40 ml, which is the maximum allowable volume for vessels used for these experiments. The comparative study with Soxhlet and pressurised liquid extraction (PLE) methods demonstrated that Microwave Assisted Solvent Extraction is an alternative suitable extraction method for the 4- NP and 4-NPEO determination in river sediments, showing an accuracy and precision comparable to that obtained with PLE and better than those obtained with Soxhlet.