page_title: Isothermal microcalorimetry
section_title: Data obtained
hierarchical_section_title: Isothermal microcalorimetry / Overview / Data obtained
caption_attribution_description: English: A plot of IMC data for a generic exothermic rate process in a sealed ampoule in which the process (and thus the heat flow) begins, accelerates, reaches a peak and then subsides. Below the heat flow plot is a plot showing integration of the heat flow data to give accumulated heat vs. time. As illustrated graphically, the lag phase duration and maximum heat generation rate (growth rate) can be calculated from the integrated data (after Howell, et al 2011. Used with publisher permission).
context_page_description: Isothermal microcalorimetry 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 at a constant set temperature.
  IMC accomplishes this dynamic analysis by measuring and recording vs. elapsed time the net rate of heat flow to or from the specimen ampoule, and the cumulative amount of heat consumed or produced.
  IMC is a powerful and versatile analytical tool for four closely related reasons:
  All chemical and physical processes are either exothermic or endothermic—produce or consume heat.
  The rate of heat flow is proportional to the rate of the process taking place.
  IMC is sensitive enough to detect and follow either slow processes in a few grams of material, or processes which generate minuscule amounts of heat.
  IMC instruments generally have a huge dynamic range—heat flows as low as ca. 1 μW and as high as ca. 50,000 μW can be measured by the same instrument.
  The IMC method of studying rates of processes is thus broadly applicable, provides real-time continuous data, and is sensitive.
context_section_description: A graphic display of a common type of IMC data is shown in Fig. 2. At the top is a plot of recorded heat flow (μ W=μ J/s) vs. time from a specimen in a sealed ampoule, due to an exothermic rate process which begins, accelerates, reaches a peak heat flow and then subsides. Such data are directly useful (e.g. detection of a process and its duration under fixed conditions) but the data are also easily assessed mathematically to determine process parameters. For example, Fig. 2 also shows an integration of the heat flow data, giving accumulated heat (J) vs. time. As shown, parameters such as the maximum growth (heat generation) rate of the process, and the duration time of the lag phase before the process reaches maximum heat can be calculated from the integrated data. Calculations using heat flow rate data stored as computer files are easily automated. Analyzing IMC data in this manner to determine growth parameters has important applications the life sciences (Applications: Biology and medicine). Also, heat flow rates obtained at a series of temperatures can be used to obtain the activation energy of the process being evaluated (Hardison et al. 2003).
caption: A plot of IMC data for a generic exothermic rate process in a sealed ampoule in which the process (and thus the heat flow) begins, accelerates, reaches a peak and then subsides. Below the heat flow plot is a plot showing integration of the heat flow data to give accumulated heat vs. time. As illustrated graphically, the lag phase duration and maximum heat generation rate (growth rate) can be calculated from the integrated data (after Howell, et al. 2011. Used with publisher permission).
  Fig. 2
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