Abstract
Gravimetric single standard addition and double standard addition ion-selective electrode measurements are described and used for the determination of fluoride in dilute sodium hydroxide solutions. Fluoride concentrations below 5 μg g −1 were determined accurately when the electrode was regularly conditioned with 0.06 M lanthanum nitrate solution at pH 2.0–2.3. The only significant errors in the technique described arise from the millivolt and response slope measurements; the latter require careful measurement of blanks. It is shown that the relative error in concentration measurement by single standard addition will not exceed ± 0.8% if the error in the response slope of the electrode does not exceed ± 0.1 mV/decade, and if the potential difference after standard addition is at least 20 mV with an error not exceeding ± 0.1 mV. Single standard addition is as satisfactory as double standard addition for accurate measurements of fluoride in simple solutions.
Published Version
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