They say that a picture is worth a thousand words, so:

As you can see, THE NEW PEAK DETECT CIRCUIT WORKS!  It's always nice to see something work in real life versus simulation.  It's kind of hard to see exactly how close the peak detect output (yellow) matches the EC peak, but according to the automatic scope measurements, it's within 20mv.  Measuring it manually with cursors, it looks closer than that.  I can't measure the levels any closer with the scope because the large DC value exceeds the scope input range at higher vertical resolution.  I'm guessing that measuring it with the averaging effect from the ADC will produce even better results.  The real test will be in measuring actual calibrated solutions.  Right now it's running with the solution represented by a 1K resistor in series with a 10nf capacitor to generate the peaked waveform.  Real EC waveforms will likely be less peaked, which should be even easier for the peak detector to follow.