Computer-controlled titrations: Part 1. Considerations based on systems theory

Automated titrimetric procedures are considered on the basis of systems theory, with emphasis on the dynamic behaviour of the system. In the case of continuous addition of titrant, conditions are derived for the maximum addition speed and a correction procedure is given. Control algorithms for discontinuous addition of titrant are given, including an algorithm for on-line estimation of the dynamic (overall) effects of the titration system; this is useful for determining the waiting time between two successive additions of titrant. Shannon's theorem is utilized in order to decide on the sampling of the titration curve, both for continuous and discontinuous additions of titrant. Finally, confidence intervals for the end-point determination are derived, based on zero crossing statistics, and applied on the second derivative of a sigmoidal titration curve.