A Method for Speciation Analysis of Bromine in Cherries and Its Application for Traceability Analysis of Methyl Bromide Fumigation

An analytical method for the speciation of bromine in cherries fumigated with methyl bromide was established and applied to compare the contents of methyl bromide and inorganic bromine in un-fumigated and fumigated cherries in order to explore the relationship between methyl bromide fumigation and bromine residue. The samples were ultrasonically extracted with water and the extract was separated on an anion exchange column using a mobile phase composed of 36 mmol/L nitric acid and 67 mmol/L aqueous ammonia before being analyzed by high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Total bromine was determined by ICP-MS and methyl bromide by headspace sampling-gas chromatography with an electron capture detector (HS-GC-ECD). The results showed that recovery of the spiked bromate ranged from 89.7% to 101.4% with relative standard deviations (RSDs) of 2.1%‒3.5%. The recoveries of the spiked bromide ion were 85.5%‒107.3% with RSDs of 4.4%‒7.0%. The limit of quantification of the developed method was 0.10 mg/kg. Only bromide ions were found to exist in cherries fumigated with methyl bromide and the content of bromide ions was consistent with the content of total bromine. Methyl bromide residues in fumigated cherries decreased over time. The content of total bromine in fumigated cherries was significantly higher than that in un-fumigated cherries, and did not significantly change with storage time or conditions. Therefore, this method, which is useful to trace methyl bromide fumigation of cherries, provides a basis for risk monitoring and quality control of fruit import and export.