Titrimetric determination of phosphates and monofluorophosphates in tooth pastes

Summary Titrimetric methods for a fast determination of phosphates and monofluorophosphates in tooth pastes are described. They are based on the precipitation of PO₄^3–-ions (directly or after the hydrolysis of PO₃F^2–-ions) as BiPO₄ in nitric acid (pH 0.1–0.5). The end-points are detected visually (back EDTA-titration of the non-bonded Bi³⁺-ions), or potentiometrically (direct titration of phosphates with bismuth by a specially prepared Bi/Bi₂O₃-electrode). The titrations are performed without separating the precipitate. An ultrasonic field is applied to accelerate the destruction of the dentifrices.