Negative Feedback Op-Amp as input to ADC
R44 has nothing to do with anything after your voltage follower (which is the term for the morphology you're using).  R48 does, as does the output impedance of your amplifier.

Whether you have to worry about it or not depends on what your requirements are.  The output impedance of your circuit (which includes R48) forms a voltage divider with the input impedance of your ADC.  The output impedance of the op amp will be very low, so lets not worry about it.  If R48 is 1kOhm and the input impdedance of your ADC is 9kOhm, then you will read 0.9Vout, where Vout is the output voltage of the amplifier.    If R48 is 50 Ohms and the input impdeance remains 9kOhm, you will read 0.994 Vout.  For most purposes, that's "close enough" that you needn't worry about it.