• VNIIM Calorimetry Laboratory has developed a new reference titration microcalorimeter MKT for measuring small heat effects of dissolution and chemical reactions in the range from 100 to 5000 μJ with an expanded uncertainty of 1.2 % to 8.6 %.

• Isothermal titration calorimetry (ITC) has been widely used as a method for determining heat of reactions in chemical and biological research. Many publications include experimental data obtained using ITC, so its accuracy and reliability as well as methods and means for ensuring them are attracting increasing attention. Until now, such methods and means have included only electrical calibration of calorimeters using a built-in heater and conducting chemical reactions with heats known from literature data. Since procedures and materials used for calibration are not standardized, this leads to inconsistency in the results obtained on different models of titration microcalorimeters.

• VNIIM Calorimetry laboratory proposed a new approach to ensuring traceability and uniformity of measurements in ITC, which involved the development of the reference titration microcalorimeter (MKT) and certified reference materials (CRMs) intended for calibration of measuring instruments.

• To implement this approach, MKT – a differential titration heat flow microcalorimeter – was developed and manufactured. Unlike commercial titration microcalorimeters, for which duration of an experiment and the amount of the substance used are considered as important characteristics, all design solutions (cell volume, heat sensor materials and control system) implemented in the MKT microcalorimeter were aimed at increasing the accuracy of measurements.

MKT (left) and its 3D-model (right):

1 – calorimetric block; 2 – sample cell; 3 – reference cell; 4 – dosing system; 5 – control system.

  Objectives of the current research are development of the standardized calibration procedure and CRMs of heats of dissolution and chemical reactions for realization of this procedure.

Contributor: E.N. Korchagina, VNIIM, Russia