Analysis of Fluoride in Water

A rapid and simple method for the measurement of fluoride concentration in water in the range of 0.1- 100 ppm.

Equipment Required

1. Ion analyzer or pH meter with millivolt scale
2. 3221 detectIONTM Fluoride Combination Ion selective electrode

 Reagents

1. 100 ppm fluoride standard
2. Total ionic strength adjustment buffer (TISAB)

Sample Preparation

To a volume of sample add an equal volume of TISAB.

Standard Preparation

Make up standards of 0.1, 1, 10, and 100 ppm by serial dilution of the 100 ppm standard.

Dilute each standard with an equal volume of TISAB.

Method

Immerse the electrodes in each of the standards, least concentrated first and most concentrated last, rinsing the electrodes between standards.

Plot a graph on semi-log paper of mV response against standard concentration.

Immerse the electrodes in the sample and plot sample concentration from the graph.

This determination may be carried out directly in concentration units by use of the “activity” (or “ISE”) modes on pH/ION analyzers.

Calculations 

As both standards and samples have been diluted by the same amount, the result obtained from the graph is the concentration of the original sample.