Any better lower noise than ADC AD7982?

In our application, we need to measure 10uV signal through ADC AD7982. But we found in this low signal area, measurement error is more than or near 10uV.  We check AD7982 Datasheet and see its typical noise is 40uV RMS. Too high for our application.

My question is: is there any way to decrease that noise level? Or do you have any better low noise ADC which have similar pin definition and package to AD7982. It should have equal or more than 18bit. Looking forward to your reply soon. Thanks.