Isothermal microcalorimetry
_instrument_and_one_of_its_measurement_units.jpg) |
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| Acronym | IMC |
|---|---|
| Classification | Thermal analysis |
| Other techniques | |
| Related |
Isothermal titration calorimetry Differential scanning calorimetry |
Isothermal microcalorimetry (IMC) is a laboratory method for real-time monitoring and dynamic analysis of chemical, physical and biological processes. Over a period of hours or days, IMC determines the onset, rate, extent and energetics of such processes for specimens in small ampoules (e.g. 3–20 ml) at a constant set temperature (c. 15 °C–150 °C).
IMC accomplishes this dynamic analysis by measuring and recording vs. elapsed time the net rate of heat flow (μJ/sec = μW) to or from the specimen ampoule, and the cumulative amount of heat (J) consumed or produced.
IMC is a powerful and versatile analytical tool for four closely related reasons:
The IMC method of studying rates of processes is thus broadly applicable, provides real-time continuous data, and is sensitive. The measurement is simple to make, takes place unattended and is non-interfering (e.g. no fluorescent or radioactive markers are needed).
However, there are two main caveats that must be heeded in use of IMC:
In general, possible applications of IMC are only limited by the imagination of the person who chooses to employ it as an analytical tool and the physical constraints of the method. Besides the two general limitations (main caveats) described above, these constraints include specimen and ampoule size, and the temperatures at which measurements can be made. IMC is generally best suited to evaluating processes which take place over hours or days. IMC has been used in an extremely wide range of applications, and many examples are discussed in this article, supported by references to published literature. Applications discussed range from measurement of slow oxidative degradation of polymers and instability of hazardous industrial chemicals to detection of bacteria in urine and evaluation of the effects of drugs on parasitic worms. The present emphasis in this article is applications of the latter type—biology and medicine.
Calorimetry is the science of measuring the heat of chemical reactions or physical changes. Calorimetry is performed with a calorimeter.
Isothermal microcalorimetry (IMC) is a laboratory method for real-time, continuous measurement of the heat flow rate (μJ/sec = μW) and cumulative amount of heat (J) consumed or produced at essentially constant temperature by a specimen placed in an IMC instrument. Such heat is due to chemical or physical changes taking place in the specimen. The heat flow is proportional to the aggregate rate of changes taking place at a given time. The aggregate heat produced during a given time interval is proportional to the cumulative amount of aggregate changes which have taken place.
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