Cold production is a need of development in many fields; it represents an energy cost equivalent to 15% of the electricity consumed in industrialized countries. Including the direct impact of current hydrofluorocarbon refrigerants, with a high global warming potential, the refrigeration industry accounts for 8% of greenhouse gas emissions. Moreover, new European regulation and constraints on refrigerants (F-gas, 2015) imposes technological adaptation oriented towards the implementation of alternative refrigerants or processes limiting refrigerant amount, such as secondary refrigeration. Known for their cold storage capacities, as well as, their high melting latent heat, CO2 hydrates are particularly interesting for offering promising solutions to many industrial problems. Nonetheless, these PCMs are capable of carrying cold in secondary loops which reduces the environmental impact of refrigeration systems. The crystallization kinetics of these PCMs is not fully understood. In particular, the quantification of dissolved CO2 during the process of hydrates formation is mandatory, since it is related to CO2 hydrate fraction. The aim of this work is to continuously and in situ quantify molecular CO2 in liquid phase during the solubilization, supersaturation and formation of hydrates, with and without additives. Then, CO2 hydrates were formed inside a reactor equipped with an Attenuated Total Reflection (ATR) probe coupled with a Fourier Transform Infrared (FTIR) analyzer. The concentration of molecular CO2 is estimated by measuring the heights of the (C=O) bond peaks vibrating at an IR wave number of 2340 cm-1. Hence, a protocol was developed and validated to quantify CO2 in the liquid phase at different CO2 pressures going from 5 to 25 bars in a temperature range of -2 to 19°C. Finally, the calibration and hydrate formation kinetic curves, at different additive concentrations, were presented and compared.