I think the +/-1uA is probably pushing it. I think you would probably want something more like a +/-50 or 100nA range. It is possible to modify the Rodeostat to reduce the current range. We have made modified versions with +/-60nA and +/-100nA ragnes. There are some notes on how to do this in the "hardware/pcbs/teensy_shield/notes" sub-directory of the project repository https://bitbucket.org/iorodeo/potentiostat See the file named "nano_amp_mods.txt". We made two versions the 2nd worked best. The changes were as follows:
R5 = 6.04 MOhm, C19 = 10nF capacitor (100nF range)
Digikey PN: 541-6.04MCCT-ND, and 311-1136-1-ND
R6 = 10 MOhm, C20 = 100nF (60nF range)
Digikey PN: 541-10MAZCT-ND and Digikey 311-1361-1-ND
There is modified firmware available for these ranges you just need to enable the CURRENT_VARIANT_NANO_AMP #define in the in ps_hardware_variant_defs.h and comment out the CURRENT_VARIANT_MICRO_AMP #define. The ps_hardware_variant_defs.h is found in the firmware/libraries/potentiostat/ sub-directory.