Headspace single-drop microextraction coupled with microvolume fluorospectrometry for highly sensitive determination of bromide.

This work reports on the development of a novel methodology for bromide determination by combining headspace single-drop microextraction with microvolume fluorospectrometry. The method lies in the in situ generation of bromine, transfer of the volatile to the headspace and trapping/reaction onto a fluorescein-containing aqueous drop exposed to the gas phase. The decrease in the fluorescence intensity enabled the determination of bromide without dilution of the enriched microdrop. Experimental parameters influencing the performance of the method, namely, fluorescence parameters, extractant phase composition, bromine generation conditions and microextraction time, were evaluated and controlled. Under optimal conditions, an enrichment factor of 243 was attained. The limits of detection and quantification achieved under optimal conditions for bromide were found to be 1.4 and 4.4µgL, respectively. The intra-day repeatability, expressed as relative standard deviation, was 4.4% (n=6). Besides, the inter-day reproducibility, performed at four different days, was 7.1%. Finally, the developed method was successfully applied to the determination of bromide in different water samples, showing recovery values in the range of 95-110%, and validated against certified reference material BCR-611 (ground water, Br low level). The proposed method represents a highly convenient approach for monitoring of bromide at very low concentrations.