I wouldn't use a "for" loop (as you have done) to separate the two actions of sending volts and sending temperature.
I would have a short function that sends the volts and another that sends the temperature.
In my "loop()" I would call each of those functions in turn.
If I needed a time space between the two functions I would create variables (in setup()) to record the interval between the sends, the time of the last send and a record of which thing was sent the last time. Then the code in my loop would check if the interval had elapsed, would then check which thing had been sent the last time and send the other thing.
I find it very useful if I have a difficult piece of logic to write it as a series of steps in a column down the left-hand edge of a page and then fill in successive columns on the page with the subsequent runs of the loop.