You can find good schematics in older databooks from Harris
Semiconductor, Intersil (back when the two were distinct),
Data General, even RCA CD4000 logic. You need a demux
and a rack of switches. But then come the niceties like
break-before-make (so as not to cross-contaminate sample
voltages), charge injection (ditto), tradeoffs in on resistance
vs capacitance, vs leakage, vs settling time and so on.
A very fast ADC with surplus headroom may get by with a
simpler mux than a general purpose piece-part that has
to have good on-resistance linearity across the common
mode range (like, NMOS-only switches with maybe a
charge injection compensation).