USGS Test Method I-2129-85

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Method Name:
Bromide in Water by Colorimetry. Official Name: Bromide, Colorimetric, Fluorescein, Automated-segmented Flow

The sample is buffered to pH5.6 with an acetic acid buffer solution and then reacted with chloramine T to oxidize the bromide to hypobromous acid. The hypobromous acid formed then reacts with fluorescein to form the pink eosin (tetrabromo fluorescein), which is proportional to the bromide concentration.

This method may be used to analyze natural water containing from 0.010 to 0.40 mg/L of bromide. Samples containing greater concentrations need to be diluted.

Methods for the Determination of Inorganic Substances in Water and Fluvial Sediments, Techniques of Water-Resources Investigations of the United States Geological Survey, Book 5, Chapter A1 Edited by Marvin J. Fishman and Linda C. Friedman

Iodide interferes quantitatively, but in most waters the iodide concentration is negligible. It is recommended that a determination for iodide be performed and that the concentration that is found be subtracted from the apparent bromide concentration. Cyanide, as much as 0.50 mg/L, and chloride, as much as 500 mg/L, do not interefere. Thiocyanate interferes linearly, but in most waters its concentration is negligible.

QC Requirements:
Quality-control samples area analyzed at a minimum of one in every ten samples. These QC samples include at least one of each of the following: blanks, quality control samples, third party check solutions, replicates, and spikes. Correlation coefficients for calibration curves must be at least 0.99. QC samples must fall within 1.5 standard deviations of the mean value. If all of the data-acceptance criteria in the SOPs are met, then the analytical data are acceptable.

Maximum Holding Time:
180 days




Single-operator precision for dissolved bromide for six samples, at 10 replicates each, expressed in terms of percent relative standard deviation is as follows: concentration (mg/L), %-RSD; 0.010, 15.0; 0.050, 10.0; 0.100, 5.0; 0.350, 2.0; 0.550, 1.8; 0.860, 2.0.


Revision Number:

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