CuSO4 in SO2/SO3 gas sampling in Sulphuric Acid Production What role does $\ce{CuSO4}$ has in the gas sampling of an $\ce{SO2/SO3}$ gas mix in a catalytic converter for sulphuric acid production?


To give you a little context: We take gas samples from the beds of the catalytic converter to determine the efficiency of the catalyst. We use "cartridges" that we make with glass tubes filled with $\ce{CuSO4}$. The $\ce{CuSO4}$ (lab grade) comes in crystal version as a pentahydrate. We heat it for around $\pu{30 minutes}$ at $\pu{105 ^\circ C}$ and then we use it to make the cartridges. The cartridges are placed between the sampling point and the sampling bag (made of Teflon). This is a process that has been made since many  years but nobody here is able to tell me why. The answer they give me is that the cartridges are used to "remove" the $\ce{SO3}$ from the sample but I can't see how that could happen. My theory is that because anhydrous $\ce{CuSO4}$ is hygroscopic (I've read it's been used as a desiccant) it may be used to avoid the formation of $\ce{H2SO4}$ that could damage the gas analyzer (a SICK S700). I've really googled it but can´t find the answer. Hope someone could enlighten me in the subject.
Heating hydrate copper sulfate at 105 degrees does nothing. The chemically bound water takes a higher temperature to remove all water molecules (water is lost in steps as a function of temperature). This low temperature removes only two water molecules out of five. I think the major role of copper sulfate, besides being a gentle dessicant, is to oxidize sulfur dioxide to trioxide. Cu(II) ion is a mild oxidizing agent, and mild enough that it can oxidize sulfur dioxide to the trioxide.