An Automated Computer-Vision "Bubble-Counting" Technique to Characterise CO 2 Dissolution into an Acetonitrile Flow Stream in a Teflon AF-2400 Tube-in-Tube Flow Device.

A Teflon AF-2400 based tube-in-tube device was used to generate flow streams of CO ₂ in acetonitrile and a computer-vision based 'bubble counting' technique was used to estimate the amount of CO ₂ that had passed into solution whilst in the tube-in-tube device by quantifying the amount of CO ₂ that left solution (forming separate gas-phase segments) downstream of the back-pressure regulator. For both CO ₂ pressures used, there appeared to be a minimum residence time below which no CO ₂ was observed to leave solution. This was assumed to be due to residual CO ₂ below (or close to) the saturation concentration at atmospheric pressure and, by taking this into account, we were able to fit curves corresponding to simple gradient-driven diffusion and which closely matched previously obtained colorimetric titration data for the same system. The estimated value for the residual concentration of CO ₂ (0.37 M) is higher than, but in reasonable general correspondence with, saturation concentrations previously reported for CO ₂ in acetonitrile (0.27 M).
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