A comparison of the performance of calorimeters

Isothermal calorimetry is finding extensive application in a number of research areas. This popularity is reflected in the number of commercially available instruments which are capable of yielding a variety of thermodynamic and kinetic parameters. Whilst there has been much discussion of ways in which to validate any values returned from these instruments very little has been done quantitatively to compare the relative performances of different instruments. This paper highlights the use of a test and reference reaction quantitatively to compare the performance of three instruments (Thermometric TAM, THT μRC and a Setaram HSDSC III); the specifications of these instruments provide a range from high-sensitivity, long equilibration time to lower-sensitivity, short equilibration time. The comparison is made through a statistical analysis of values returned for the rate constant, enthalpy of reaction and activation energy for the base catalysed hydrolysis of methyl paraben. The statistical analysis from the data set discussed here indicates that there is no significant difference between the returned thermodynamic and kinetic parameters from the TAM and μRC. The analysis revealed however that the HSDSC returns values for the rate constant which are significantly different from both the TAM and μRC, although it is noted that this instrument was not specifically designed to operate in a step-isothermal mode and that it was possible to apply a correction to the data. In all cases the enthalpy data returned from all instruments were statistically similar although the μRC and HSDSC returned values which were, for the rate constant and activation energy, less precise than those obtained from the TAM. As well as highlighting the importance of using test and reference reactions, this study also shows that proper instrument selection is an important factor when designing a calorimetric experimental series.     

Gas-phase optrode measurements of oxygen in calorimetric vessels

Simultaneous measurements of oxygen and heat rates are useful for the determination of thermodynamics and kinetics of metabolic and chemical reactions involving oxygen. Optrodes have not previously been used to measure oxygen inside calorimetric vessels. The optrode used in this study produces <2 μW and can be used to make measurements in both gaseous and aqueous systems. An external syringe injection of air was used to calibrate the optrode, and zinc–air batteries were used to evaluate the system. Data on maple leaf buds were collected to demonstrate application to respiration measurements.     

Comparison of thermokinetic data obtained by isothermal, isoperibolic, adiabatic and temperature programmed measurements

In this paper isothermal, isoperibolic and adiabatic calorimeters and a Power-Compensating DSC are compared by determining kinetic data of a simple test reaction. First, the kinetic parameters were analyzed using a conventional isothermal method, based on the analytic determination of the course of reaction. Subsequently, the kinetic data of the performed reaction were determined for the different types of calorimeters by simultaneously evaluating several measurements with identical initial conditions but different temperature courses. The kinetic parameters obtained by the different calorimeters agree reasonable well, indicating the reliability of kinetic data derived from thermokinetic methods.The authors are thankful for the financial support by the Department of Education and Research of the Federal Republic of Germany (BMBF).     

Electrical calibration and testing of calorimeters with simulated, time-variable reaction power

For calorimetric investigations where the reconstruction of the real heat-flow rate during the experiment is required, the usual electrical calibration with constant power is often not sufficient. However, the use of a chemical calibration is limited by the number of suitable and certified reactions showing a known dynamics of the heat-flow rate. Therefore, a computer controlled electrical calibration unit was developed capable of duplicating any simulated reaction power-time curve in the calorimetric cell. The calibration unit consists of a universal simulation software with an interface to a programmable precision current supply connected to the calibration heater inside the calorimetric vessel. The reliability of the electrical calibration was proved with a continuous titration calorimeter using different recommended test reactions (TRIS+HCl, dilution of aqueous KCl, NaCl and urea solutions).

In order to test the electrical calibration procedure in the dynamic mode the heat-flow rate of a first-order equilibrium reaction during a continuous titration experiment was simulated. It is demonstrated that the combination of simulation software and electrical calibration hardware provides a very close adaptation of calibration and experiment, allows a more reliable estimation of experimental uncertainties, simplifies the verification of complex data analysis procedures and opens up new possibilities for the optimization of experimental parameters.     

Nitrosation reaction using isothermal power compensation calorimetry

Initial plant scale trials of the nitrosation of an amino acid revealed a number of issues: _ Much lower yield compared to laboratory scale _ Considerable loss of mass balance _ Large excess of nitrosating agent required for complete reaction _ Highly reactive off-gases produced causing fires in the carbon absorber _ Reaction sensitive to agitation speed _ The by-product produces an impurity in the next process stage which has high human toxicity A kinetic and mechanistic study of the nitrosation reaction, using isothermal power compensation calorimetry and GC/mass spectrometry, has been undertaken in order to understand the above observations and to produce an improved manufacturing process - more robust, higher yielding, reduced effluent volumes and toxicity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Introduction of a calibration-free reaction calorimeter that combines the benefits of DSCS and reaction calorimeters

The reaction calorimeter CAP202 (chemical process analyzer) determines thermal effects by measuring the true heat flow (THF) based on unique design principles. In particular, measurements can be performed without requiring any calibration procedures and the obtained results are most reliable and exhibit extremely stable baselines. The benefits in respect of experimental speed, data quality and long term performance are obvious. Due its broad dynamic range the instrument can be employed for measurements ranging from small physical heat to energetic chemical reactions. The CPA allows running experiments seamlessly with reaction volumes between 10 and 180 mL. This volume flexibility simplifies the investigation of multi-step operations and is the basis for various applications employing precious or highly energetic compounds. Due to the fact that calibrations are not required, altering conditions during a single experiment like changes in viscosities, liquid levels or stirring speeds do not affect the results of the measurements.     

Losses evaluation in converters using the calorimetric technique

In this paper, a measurement technique of losses in the switching cell, based on calorimetric technique is presented. A special calorimeter was designed to be able to access the heat generated by an operating converter. Power component losses are studied according to the cyclic ratio and to operating frequency and an extraction method of the different terms of these losses, using calorimetric measurements, is presented. An accurate expression of the switching losses in the power semiconductors devices is proposed.     

Performance validation of step-isothermal calorimeters

Isothermal calorimetry is becoming indispensable as a tool for the study of a wide variety of systems. As with all scientific instruments it is essential that robust calibration routines be developed in order to validate the data obtained. Chemical test reactions offer many advantages over (the traditionally used) joule effect heating methods, not least because they have the potential to validate instrument performance (i.e. they can be used to assess all aspects of calorimeter operation). In this work the results of a validation exercise, conducted by Thermal Hazard Technology as part of an installation routine, using the base catalysed hydrolysis of methyl paraben are discussed. In the case described, a systematic misreporting of the reported temperature of a calorimeter was identified, caused by an upgrade to the calorimeter's firmware, a discrepancy which may not have been noted using traditional electrical calibration methods and one which highlights the importance of both manufacturers and end-users adopting chemical test reactions into their test and validation routines.     

N-溴代丁二酰亚胺氧化异丙醇反应的热动力学研究

利用Batch型热导式热量计测定了N-溴代丁二酰亚胺(NBS)氧化异丙醇反应的热谱曲线,并分别利用简单级数反应和连续一级反应热动力学特征对比参量法的数学模型计算了反应的动力学参数,计算结果表明:利用连续一级反应热动力学研究法处理得到的动力学参数与文献通过碘量法的测定值是吻合的,因此,在质子性溶剂中的NBS氧化异丙醇反应遵从连续一级反应的动力学规律。     

Model of a calorimetric sensor for medical application

A calorimetric sensor has been developed to measure surface heat dissipations in the human body. An experimental prototype has been built in order to study its performance and a simple model that represents acceptably the experimental system has been proposed.     

Enthalpy of vaporization measurements by calorimetric techniques

Journal of Thermal Analysis and Calorimetry - Enthalpies of vaporization, $$ \Delta _{\text{vap}} H^{\circ }_{298} $$ , were determined for perfluorooctyl-1-bromide (PFOB) at the temperature...     

The integration of an ultraviolet-visible spectrometer and a reaction calorimeter

A small ultraviolet-visible absorption spectrometer which uses fibre optic coupled immersion probes has been incorporated into a laboratory scale reaction calorimeter. The combined instrument has been tried out using the hydrolysis of acetic anhydride as a test reaction. With the calorimeter operating in the isoperibolic mode good agreement is found for the pseudo-first order reaction rate constant as determined from spectroscopic and calorimetric measurements. Experiments have been made in order to follow the reaction indirectly using optical pH measurements with acid-base indicators. The possibility of determining the temperature dependence of the rate constant in a single experiment has also been investigated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development of an efficient and safe process for a grignard reaction via reaction caloremetry

A Grignard reaction of reactantA and phenyl magnesium chloride is used to make a pharmaceutical intermediate at the production scale. The elimination of protecting groups onA was proposed as a means to reduce synthesis costs. This new synthesis route, however, had process efficiency and safety issues associated with it: (1) build-up of unreactedA in the reactor, (2) influence ofA's particle size on the reaction rate, (3) the sensitivity of the reaction rate to the reaction temperature and to the (changing) solvent composition, and (4) the highly exothermic nature of the reaction.The Mettler RC1 Reaction Calorimeter was used to quantify the influence of solvent composition, temperature, and particle size on the reaction rate. Results indicated a dramatic effect of solvent composition and reaction temperature on the reaction rate; for example, over a temperature range of just 30°C, the reaction time decreased from more than a day to just a few minutes. At such high reaction rates, the vessel jacket could not remove the reaction heat sufficiently and the internal temperature rose adiabatically.These results were used to make process design and operation recommendations for safe and efficient plant operation with this modified Grignard reaction system.The authors would like to thank the following for their assistance in this work: E. Daugs for preparing the Grignard reagents, K.L. Gonzales for her help in running the experiments and in the subsequent data work-up; P.M. Russell for his assistance in the design of the slurry addition assembly, and K. Chritz and J. Engel for performing the HPLC analyses of the samples.     

A calorimetric study of egg white proteins

Egg white is of great interest for many culinary and industrial applications. Egg white is used for coating, gluing, thickening and so on in pasta, desserts, etc. There is thus a great interest from the industrial point of view to better know this raw material, used in very large amounts in the dessert production for example, and to obtain egg white fractions with different functional properties.Various egg white fractions prepared by selected procedures were analyzed by differential scanning calorimetry (DSC). The products resulting from a given fractionation procedure can thus be described by the thermal denaturation parameters (temperatures and enthalpies) of the egg white proteins.This work demonstrates the interest of the DSC technique and proves that the fractionation procedures selected here give the expected protein fractions.     

A new reaction calorimeter and calorimetric tools for safety testing at laboratory scale

Calorimetry combined with thermal analysis is an essential tool for the evaluation of thermal risks linked with chemical reactions at industrial scale. The energies of synthesis reactions or decomposition reactions as well as the heat capacities of reaction masses can be measured using such techniques. The capacity of the SETARAM differential reaction calorimeter (DRC) to determine essential safety data has been demonstrated with the measurement of heat capacities of cyclohexane and propanoic acid. Results of an industrial reaction are also presented.     

The application of the reaction calorimetry to investigate reactions involving unstable compounds

The RC1 calorimeter revealed itself a suitable instrument to obtain information about safety and mechanisms involved in the reaction between cyclohexanecarboxylic acid (AEB) and oleum. A previous hypothesis about the existence of an unstable intermediate was confirmed and its heat of formation was calculated. The heat of sulphonation related to undesirable by-products production and the heat of protonation of AEB with H₂SO₄ were also evaluated. Therefore, it was possible to distinguish the reactions involved in the process and, through their thermal behaviour, to determine the limit conditions to avoid the by-products formation.

---

Zusammenfassung Das RC1 Kalorimeter erwies sich als ein geeignetes Instrument, um Informationen über Sicherheit und Mechanismen bei der Reaktion von Cyclohexancarbonsäure (AEB) und Oleum zu gewinnen. Eine bereits bestehende Hypothese über die Existenz eines instabilen Zwischenproduktes konnte bestätigt und dessen Bildungswärme berechnet werden. Weiterhin wurde auch die Sulphonierungswärme bezogen auf die Entstehung von unerwünschten Nebenprodukten und die Protonierungswärme von AEB durch H₂SO₄ ermittelt. Es ist deshalb möglich, die einzelnen Reaktionen innerhalb dieses Prozesses über ihr thermisches Verhalten voneinander zu unterscheiden, um die Grenzbedingungen zur Vermei-dung der Bildung von Nebenprodukten zu ermitteln.

     

Concentration dependencies of NaCl salting of lysozyme by calorimetric methods

Concentration dependence of NaCl salting of lysozyme was investigated in the range of 0.5-9 mM lysozyme concentration in 0.1 M sodium acetate buffer, pH=4.25and the concentration of NaCl up to 0.1 M. Calorimetric experiments were performed with the use of a titration ITC Omega MicroCal calorimeter. It was found that the estimated number of bonding sites depended on the lysozyme concentration. For infinitely diluted lysozyme solution, the number of binding sites could be roughly estimated to ∼50. In the range of 2-9 mM protein concentration, the number of weakly binding (K=2.7±0.8 M⁻¹) sites on the protein surface was estimated to 35±7. McMillan and Mayer’s approach reduced to the third order virial coefficients demonstrates that besides the dominating effect of the protein—salt interaction (a₁₁) the coefficient describing the lysozyme aggregation upon salt addition (a₁₂) is statistically significant.     

Hierarchical structure in polymer‐based drug delivery systems as probed by calorimetric measurements

Thermoporosimetry (TPM), a differential scanning calorimetry technique that relies on the shift of transition temperatures caused by the confinement of liquids, was applied to elucidate the complex morphology of drug‐loaded polymeric microcapsules prepared by the emulsion solvent evaporation method. For the very first time, TPM has been applied simultaneously with two liquids as structural probes. It was found that Miglyol, which dissolves the selected drug (Ibuprofen), is confined inside vesicles having a mean radius of 26.3 nm, whereas water, which is the continuous phase, is trapped inside a swollen polymeric network of Eudragit with an average mesh radius of 1.7 nm. A proposed hierarchical structure is given, which predicts that Eudragit microcapsules are formed from a collection of inert oil vesicles partitioned by polymeric Eudragit membranes swollen by water. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1939–1945, 2010     

Kinetic method by using calorimetry to mechanism of epoxy-amine cure reaction

In this paper, it is clearly demonstrated that the dependence of the rate of evolving heat on time is completely described by using Mangelsdorf's method in terms of three processes with excellent precision. The first two exothermic processes take into account the fact, that the reaction occurs by two competitive mechanisms: one is a non-catalytic mechanism and the other is catalyzed by OH-groups formed during the reaction. The third one refers to the endothermic process where the reaction is accompanied by diffusion of the reaction products. The distinctive feature of this diffusion process is that it is the coupling of the reaction kinetics and rearrangement of the chains built to the rigid supramolecular structure. This simple model allows accurate simulation of kinetic behaviour. This revised version was published online in July 2006 with corrections to the Cover Date.