The following formulations were tested to determine the substantivity of cetylpyridinium chloride to HAP that had been treated with the test compounds in a separate step, prior to exposing the HAP to the cetylpyridinium chloride; water (control); phytic acid; sodium phosphate (NaH2PO4); and tin/phytic acid/phosphate (Sn-PaP). The phytic acid was used at 0.0015M and prepared from a 0.045M stock solution by removing a 5 mL aliquot to a vial and diluting with 10 mL of water. The pH of this solution was 2.5. The tin/phytic acid solution in 0.5M phosphate buffer was prepared by weighing 0.0051±0.0001 g SnCl2 into a vial and brought into solution by the addition of 5 mL of water. A 5 mL aliquot of 0.0045M phytic acid and a 5 mL aliquot of 1.5M phosphate buffer were added to the tin solution to produce a formulation with 0.0015M Sn; 0.0015M phytic acid; and 0.5M phosphate.
