A dispersive liquid-liquid microextraction based on solidification of floating organic drop and spectrophotometric determination of uranium in breast milk after optimization using Box-Behnken design

A new procedure developed based on a preconcentration system using a dispersive liquid-liquid microextraction technique based on solidification of floating organic drop (DLLME-SFO) was combined with the molecular absorption spectrometry to determine uranium using 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (BrPADAP) as the complexing reagent. The optimization step was performed using two-level factorial design and the Box-Behnken design. The parameters analyzed were pH, Br-PADAP volume, extractant solvent volume and disperser solvent volume. The method allowed determining uranium with a limit of detection of 0.46 mu g L-1, limit of quantification 1.53 mu g L-1. The enrichment factor was estimated to be 76 -fold. The precision expressed as relative standard deviation (RSD) for uranium concentrations of 2 and 10 mu g L-1 was 4.91% and 1.85% (n = 15), respectively. Accuracy was assessed using recovery values ranging from 95.28% to 103.86%, which proves that this method does not suffer from a matrix effect and can be satisfactorily applied. The proposed method was applied to determine uranium in human milk samples. Fifteen samples were analyzed, and the uranium concentration ranged from 45.87 +/- 3.62 mu g L-1 to 160.97 +/- 7.00 mu g L-1. (C) 2017 Published by Elsevier B.V.