Determination of bromide in fumigated and natural samples by conversion into bromophenols followed by gas chromatography-mass spectrometry

Interference by large chloride matrix and high acidity in the sample, which makes chromatographic determination of low (µgl-1) level of bromide difficult, can be avoided by pre-column reaction of bromide with 2-iodosobenzoic acid and 2,6-dimethylphenol or 2-tertbutyl-4-methylphenol to form within 1min 4-bromo-2,6-dimethylphenol and 6-bromo-2-tertbutyl-4-methylphenol, respectively. The derivative was extracted into cyclohexane and injected into the GC. The aqueous sample could be subjected to clean-up using LiChrolut EN sorbent to remove organic matter before derivatization. The bromo derivative could be extracted from up to 250ml of sample without any breakthrough. A rectilinear calibration graph was obtained for 0.02-100µgl-1 bromide with a correlation coefficient of 0.9993 (10 calibration points) using 2-tert-butyl-4-methylphenol as reagent and the method has a limit of detection of 5ngl-1 bromide. This method has also been applied to determine bromide in table salt and concentrated hydrochloric acid and to the spiked samples when the recovery was in the range 98-104% (R.S.D. 0.8-2.2%). The proposed method is simple and precise and high concentrations of ionic impurities including chloride, as found in sea water and table salt and acidity, as in concentrated hydrochloric acid, can be tolerated.