Complete isotherms (Adsorption - desorption) of N2 was done using QuantaChrome iQC 6.... some of the data results are said to be non-monotonic pressure, what is the meaning of this message and what is the cause?? how we ca avoid this issue for next analysis ??
In the context of a gas adsorption isotherm measurement, non-monotonic points detected means that you have measured points which do not follow the real and expected trend of increasing adsorbed amount with increasing pressure (adsorption branch) or decreasing adsorbed amount with decreasing pressure (desorption branch). In other words, somewhere in your isotherm you have a non-real “kink“ where a measured point is either lower than the previous point on the adsorption branch, or higher than the previous point on the desorption branch.
This behavior is unreal and is an indication of an experimental error. Could be an indication of an instrument problem, improper sample preparation, or incorrect analysis parameters.
You can email quantachrome and their applications or service teams can help you troubleshoot such errors.
Valuable answer Francisco Sotomayor
I have repeated the analysis once again but this time the outgas time was overnight , and the result was perfect. I have also changed the Equ. and Tol.
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