Grumpy_Mike:
I guess my question is, would there be any reason that the arduino's analog input load as adding noise to the signal as it passes into the arduino
I doubt it.
What exactly is the scope connected to?
At a guess I would say that this signal was being generated by your op amp and being filtered out later.
However at 1MHz that can't be a signal through the A/D because you can't sample that fast.
it's 318 kHz not 1MHz, the blue signal isn't being read from the oscilloscope, you can ignore that.
the oscilloscope is connected to the output of the buffer going to the Analog Input of the arduino. I can post a measurement of the signal coming from the 2nd buffer then then goes on to additional filtering, but basically it's a "flat" line at 0.2v (what seems to be the center of the noisy signal from the buffer going to the analog input) without this consistent noise