Ratiometric detection of total bromine in E-waste polymers by colloidal gold-based headspace single-drop microextraction and microvolume spectrophotometry

A ratiometric analysis method for total bromine determination in E-waste polymers based on the significant effect of molecular bromine in the UV–vis spectra of gold nanoparticles (AuNPs) is presented herein. The proposed method involves alkaline fusion of polymeric samples, in situ conversion of resulting bromide ions into molecular bromine and exposure of a microdrop of AuNPs to the evolved volatile prior to microvolume UV–vis spectrophotometric analysis. Experimental parameters affecting the trapping/sensing of molecular bromine by the colloidal solution were optimized by a two-stage multivariate optimization approach involving Placket-Burman and central composite designs for screening and optimization, respectively. Under optimal conditions, the method yielded limits of detection (LOD) and quantification (LOQ) of 8.8 and 29.4 ng/mL Br, respectively, corresponding to 17.0 and 56.7 μg/g Br, respectively. The repeatability, expressed as relative standard deviation (RSD), was found to be 4.8% (n = 10). The proposed method was validated against two certified reference materials (BCR-681 Trace elements in polyethylene (low level) and ERM®-EC680 m low-density polyethylene), and applied to the determination of total bromine in plastics from E-wastes. The results obtained with the proposed method were in good agreement with those obtained by ion chromatography (paired t-test, α 0.05, 2 tails).