Real-Time pH Monitoring of Ultra-Diluted Chemistry with a Micro-Sampling pH Monitor

Abstract

Real-time monitoring of pH and concentration estimation from pH data were studied using a newly developed micro-sampling pH monitor. Continuous monitoring of diluted ammonia solution with air and N2 bubbling clearly detected the real-time pH response to CO2 dissolution. With this new monitor, pH of low concentration ammonia, HF and BHF (HF and NH4F mixture) was measured and correlation to their respective concentrations was investigated. At <10 ppm, ammonia resolution was +/- 3 ppm and HF resolution was +/- 2 ppm. For BHF, when the NH4F concentration is provided by NIR concentration monitor, HF concentration resolution based on pH measurement was +/- 2 ppm. By utilizing this real-time pH monitoring technology, precise wet process control of diluted chemistry can be achieved.