Systematic errors in isothermal titration calorimetry: concentrations and baselines.

In the study of 1:1 binding by isothermal titration calorimetry, reagent concentration errors are fully absorbed in the data analysis, giving incorrect values for the key parameters--K, ΔH, and n--with no effect on the least-squares statistics. Reanalysis of results from an interlaboratory study of a selected biochemical process demonstrates that concentration errors are likely responsible for most of the overall statistical error in these parameters. The concentration errors are approximately 10%, greatly exceeding expected levels. Furthermore, examination of selected data sets reveals a surprising sensitivity to the baseline, suggesting a need for great care in treating dilution heats.