Systematic errors in isothermal titration calorimetry : the role of feedback power and effects of mixing and diffusion on concentrations

Medoš, Žiga (author), Bešter-Rogač, Marija (author), Leontidis, Epameinondas (author), Tellinghuisen, Joel (author)

Using experiments based on the NaCl dilution calibration method, we examine several previously unstudied instrumental effects that can lead to systematic errors in isothermal titration calorimetry (ITC). We confirm earlier results that power feedback can affect estimated heats and find further that it can also affect cell temperature and introduce temperature “noise.” To estimate effects from loss of titrant from the syringe through diffusion, and concentration changes in the cell from mixing with the overflow volume, we conduct experiments with injections separated by time intervals Δt from 8 to 60 min, giving run durations from 6 h to over 2 days. Because the effects are small, we have developed a global least-squares fitting algorithm to analyze 20 datasets simultaneously, from which three parameters governing diffusion and mixing (“leakage”) are estimated, along with calibration parameters for heat and cell volume. Expressed as an effective volume loss from the syringe, Δv$_{dif}$ is found to be of order ∼0.03 μL per injection for NaCl into water. Its effect is predicted to be negligible in many ITC applications. The effects from leakage are more significant but their neglect is still predicted to affect both NaCl calibration and 1:1 binding results by ∼1 %, which is marginally significant for calibration but seldom so for 1:1 binding. The calibration results for the cell volume V$_0$ are particularly sensitive to temperature and to the literature source for the relative molar enthalpy function for NaCl(aq).

• Language: English
• Keywords: isothermal titration calorimetry, calibration, diffusion and mixing, NaCl dilution, feedback power control, global least-squares analysis
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 7 str.
• Numbering: Vol. 709, art. 116010
• PID: 20.500.12556/RUL-179688
• UDC: 536.6
• ISSN on article: 0003-2697
• DOI: 10.1016/j.ab.2025.116010
• COBISS.SI-ID: 263754243
• Publication date in RUL: 20.02.2026

Record is a part of a journal

• Title: Analytical biochemistry
• Shortened title: Anal. biochem.
• Publisher: Academic Press.
• ISSN: 0003-2697
• COBISS.SI-ID: 6506759

Licences

• License: CC BY-NC 4.0, Creative Commons Attribution-NonCommercial 4.0 International
• Link: http://creativecommons.org/licenses/by-nc/4.0/
• Description: A creative commons license that bans commercial use, but the users don’t have to license their derivative works on the same terms.

Secondary language

• Language: Slovenian
• Keywords: izotermna titracijska kalorimetrija, kalibracija, difuzija in mešanje, redčenje NaCl, kontrola povratne moči, globalna analiza z metodo najmanjših kvadratov

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P1-0201-2022
• Name: Fizikalna kemija

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: N1-0186-2021
• Name: Metalcarborani kot edinstveno izhodišče za pripravo funkcionalnih nanostrukturiranih in polimernih materialov