A quantum leap in sensitivity was the step from the 16 bit ADS1115 to the 32 bit ADS1262, which increased the sensitivity by a factor of more than 10,000 for my Raspberry Pi seismometer project:
http://www.seismometer.info.
The source code for programming the 32 bit analog-to-digital converter ADS1262 from Texas Instruments on the Raspberry Pi is again open source and can be found here:
https://github.com/ATILIUS-REGULUS/ads1262_pascal_library.