Adding an analog switch at CE0 for impedance and electrochemical measurement with the AD5940 or ADuCM355

Greetings,

I am designing a portable potentiostat device to perform both electrochemical (gas) and tissue/body impedance measurements. I have selected either the AD5940/1 or the ADuCM355 as ideal candidates to design around. I have a couple of clarification questions so that I can utilize the ICs appropriately. 

1) I noticed for the AD5940/1 that the CE0 pin is used for excitation of electrochemical measurements as well as for body impedance measurements. If I wanted to perform these measurements with the same device would an analog switch at CE0 be necessary? Or is it recommended that separate front-ends be used for electrochemical or impedance measurements, respectively?

2) Also, I am hoping to understand the limitations for the number of gas cells or 3-electrode electrochemical sensors that can be connected to either the AD5940/1 or ADuCM355 (operating at different times). Connecting 2 sensors with the ADuCM355 seems straightforward, but would it be possible to use an analog switch to connect additional sensors (particularly along SE0, RE0, CE0, and DE0)? If so are there any analog switches that can be recommended for this application? For example if I had 4 gas sensors would it be reasonable to incorporate the analog switch with  a single AD5940 front-end or is it preferred to use multiple front-ends.

These limitations were a bit unclear after looking through the documentation. Any insight related to multiplexing gas sensors + impedance measurements to the inputs/outputs of these front-ends, and any recommendations about which option would be most appropriate for integrating 2-4 electrochemical sensors and 1 body impedance sensor with a single front end would be appreciated. Thanks!

Best,

Justin