# How to quantify the adsorption affinity of gases?

Is there a term/quantity which shows how 'sticky/adsorptive' a molecule is? I am interested in gas adsorption on steel surfaces in our mass spectrometer and would like to estimate which gases have a higher propensity to adsorb.

The term you are looking for is "adsorption enthalpy". However calculating that value will depend on a variety of factors mainly the absorbate and substrate, but it is not that simple. The surface structure of substrates matters and a $$[111]$$ oriented crystallographic face will have a different adsorption enthalpy with a given absorbate that say a $$[001]$$ crystallographic face.

I suggest you study this more, namely the Langmuir adsorption model and Brunauer–Emmett–Teller Theory (BET). Especially since BET is a popular technique to measure adsorption.

• Okay, so there is no simple way of estimating this gas is stickier than that gas provided we talk about the same absorbent,or? – Zorg Oct 14 '18 at 16:14
• @Zorg Critical point is quite useful in that sense. A least you can have some idea form the boiling point of the molecule. – Nando Oct 18 '18 at 14:38