Calorimetric sensitivity

The calorimetric sensitivity is found from the calibration with indium ... 

The calorimetric sensitivity E[n is then used for calculating an unknown AH of an investigated substance ... 

A high calorimetric sensitivity, since the energies of displacement to be measured are usually very small. 

Figure 22.5 An example of reactions involved in an enzyme-catalyzed recycling processes for amplification of the sensitivity. In the left part (A) of the figure the enzyme-pair hexokinase and pyruvate kinase is used for recycling of the coenzyme ATP/ADP. In the right part (B), substrate recycling of pymvate or lactate is accomplished using the enzyme-pair lactate oxidase/lactate dehydrogenase. A multiplication effect is obtained by combination of A and B resulting in a very high sensitivity [27], The calorimetric sensitivity is further inreased by including catalase (cat).

One unique feature of the balance is the ability to use samples up to 6 g however, the electrical weighing range is only —2--i-2g. Reproducibility of the mass-measuring system is 10 with a linearity of 10 "4. Alumina cups, of 50 pL capacity, are used to contain the sample and reference materials. Calorimetric sensitivity of the DSC measurements is 2.5 pV/mW, with an accuracy of + 5% and a reproducibility of 2%. 

The temperature dependence of K for the DuPont DTA sample holder is illustrated in Figure 5.39 (106). As can be seen, the calorimetric sensitivity of the apparatus decreases with temperature that is, more heat is required per unit area. In differential scanning calorimetry, such as with the Perkin-Elmer instrument, K is independent of temperature hence, only a one-temperature calibration is required. The problem of multitemperature calibration in DTA is also eliminated in the technique of constant-sensitivity DTA proposed by Wendlandt and Williams (107). 

The DSC-2 features a temperature readout accuracy of l.OcC with a precision of 0.1 C. Calorimetric sensitivity ranges from 0.1 to 20.0 meal sec"1 full-scale deflection using a 10-mV recorder. The furnace atmosphere may be N2 or Ar. static or dynamic, at a pressure of 0.5 to 3 atm. Helium gas is required for low-temperature operation. 

In Eq. (21), RC is the already defined tau signal (Xs) its value, given in the instrument handbook, can be inserted in the configuration list. The tau signal accounts for the type of crucible used (whether aluminum, gold, or glass). The product RS is called the calorimetric sensitivity and is replaced with E. Both R and S depend on temperature. The calorimetric sensitivity E can be divided into two terms, one of which, Ein, does not depend on temperature, while the other, rel, does depend on temperature, and its temperature dependence is contained in the TA processor as a polynomial,... 

Therefore the T dependence of the relative calorimetric sensitivity is directly governed by the instrument s software. The heat flow to the sample (dHIdt) is given by... 

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