Controlling the nucleation processes of a material can improve the quality of the final product and size distribution of its particles. As material properties can vary depending on the particle sizes (cf. quantum confinement), understanding and monitoring the formation process is beneficial for manufacturers. Using an automated titrator allows deeper insight into some of these events, helping to gain more control over a complex process which affects the properties of the finished material.

The monitored graph is related to the LaMer model, a kinetically controlled formation from a supersaturated precursor solution which undergoes nuclei formation. It is possible to monitor the solubility product, nucleation events, and crystal growth. Metrohm provides the required sensors and dosing components to investigate the ideal conditions for investigation, synthesis, and process control purposes. This Application Note covers the formation of calcium carbonate from solution.

Sensors and titrant solutions are used accordingly depending on the material and conditions to be investigated. As an example, the formation of calcium carbonate was examined. An OMNIS titrator was used in combination with OMNIS dosing modules (Figure 1) and a 902 Titrando. A carbonate solution was placed in a titration beaker and the pH was adjusted to 11 with a SET pH titration. After pH 11 was reached, a calcium chloride solution was added while the free Ca²⁺ concentration was measured in a MET U titration. Concurrently, a MEAS U with the Optrode was executed to monitor the qualitative transmittance of the solution. The pH of the solution was held at a static level with the STAT pH command executed via the 902 Titrando. For screening and optimizing parameters, a sample robot can be applied to increase sample throughput.