Here are some pictures of the software for an early (circa 1995) pKa assay which was developed in the Physical Measurements Laboratory at Pfizer. The software written in Origin was utilized to perform automated curve fitting of absorbance vs. pH data captured on a platereader spectrophotometer. It was capable of running 12 samples at time.

The figure above shows the software interface designed in Origin for analyzing the pKa data. Pressing the “DoMe” button in the upper left corner caused the software to automatically fit the data for all samples using a rules based system. It was also possible for the operator to hand fit the data to any wavelength and either the bis or mono pKa equation by using the “manfit” GUI located on the bottom left portion of the screen. The fitted pKa’s are shown as well as the r^2 (or cod) value (which represents the “goodness” of the fit.) The plot shows the raw datapoints in black with the fitted curve in red. Below is the identical screen but with a bis pKa example.