Flame Photometry Determination of Lithium and Calcium in Novel Hydroxyapatite-Based Materials for Osteoplasty

A technique has been proposed for flame photometry determination of lithium additions and calcium, a major component, in the synthesis of novel hydroxyapatite (HA) based materials in order to find relationships between synthesis conditions, the composition of the material, and its functional properties. Ceramic samples were prepared via coprecipitation with the use of lithium carbonate, followed by calcination at 1300°C. We synthesized materials containing 0.25 to 1 at % lithium. Some of the samples contained 0.25 to 1 at % cerium (Ce(NO₃)₃). Lithium in the HA samples was determined using the standard addition method and appropriate reference solutions. Calcium was determined in separate aliquots after a 50-fold dilution. The results demonstrate that lithium concentrations at a level of 0.1 mg/L in hydroxyapatite solutions can be determined by flame photometry with S_r = 0.1. The material is difficult to dope with lithium via coprecipitation from solution. Moreover, heat treatment in the synthesis process has no effect on its result. We propose codoping of the material with lithium and cerium, which ensures incorporation of at least 0.25 at % Li into the structure of HA. The proposed technique can be employed for lithium and calcium determination with the use of a PFA-378 flame photometer in all steps of synthesis of new HA-based materials.