Difficulties with the chloramine-T-Phenol Red method for bromide determination.

The chloramine-T-Phenol Red procedure affords a potentially very sensitive photometric method for the determination of bromide. However, serious problems (poor precision and high reagent blanks) have been encountered in trials which followed exactly the published procedure. The reason for these difficulties was found to be the high ratio of chloramine-T to Phenol Red which was used. In all previously reported applications of this method a ratio in excess of 4 was employed, and these publications also mentioned problems with the reproducibility. In the current work the use of a reagent ratio of 1.5 was found to overcome these difficulties and yield a robust method of excellent precision. At the same time, the previously reported strong interferences by chloride and ammonia were also effectively eliminated.