Use Of Microcalorimetry Research Articles

A review of the use of microcalorimetry to determine the enthalpies of immersion and adsorption on various minerals and their relationship to flotation performance

Microcalorimetry is an important experimental method to quantify the reactions occurring between a solid material and reagents adsorbing at the surface. In the case of flotation which is arguably the most important process used to beneficiate mineral ores the surface reactions occurring between water and reagents such as collectors are measured as the enthalpy of immersion or adsorption respectively using microcalorimetry. There is significant literature on the determination of such values in many solid–liquid systems. However, in the case of flotation, such measurements have mostly been carried out as microcalorimetric studies and no attempts have been made to relate the enthalpies measured to the ultimate flotation performance of the mineral under investigation. This paper reviews the literature in this regard and attempts to show how such measurements may be related to the flotation behaviour of the mineral. Such studies may have significant overall implications for flotation research.

Personalized Treatment Response Assessment for Rare Childhood Tumors Using Microcalorimetry-Exemplified by Use of Carbonic Anhydrase IX and Aquaporin 1 Inhibitors.

We present a novel approach to a personalized therapeutic concept for solid tumors. We illustrate this on a rare childhood tumor for which only a generalized treatment concept exists using carbonic anhydrase IX and aquaporin 1 inhibitors. The use of microcalorimetry as a refined in vitro method for evaluation of drug susceptibility in organotypic slice culture has not previously been established. Rapid microcalorimetric drug response assessment can refine a general treatment concept when it is applied in cases in which tumors do not respond to conventional chemo-radiation treatment. For solid tumors, which do not respond to classical treatment, and especially for rare tumors without an established protocol rapid microcalorimetric drug response testing presents an elegant novel approach to test alternative therapeutic approaches. While improved treatment concepts have led to improved outcome over the past decades, the prognosis of high risk disease is still poor and rethinking of clinical trial design is necessary. A small patient population combined with the necessity to assess experimental therapies for rare solid tumors rather at the time of diagnosis than in relapsed or refractory patients provides great challenges. The possibility to rapidly compare established protocols with innovative therapeutics presents an elegant novel approach to refine and personalize treatment.

Microcalorimetric monitoring of grape withering

This work aimed at monitoring the metabolic activity of grapes during withering by microcalorimetry. Samples of Corvina grapes, a cultivar used in the production of Amarone wine, were dehydrated for about 120 days at an industrial scale plants (fruttaia). Single berries, sampled in the course of the withering process, were closed in ampoules and maintained at constant temperature. As biochemical events (i.e. berry respiration, microbial growth, etc.) are always accompanied by the production of heat (q), the heat-flow (dq/dt) emitted by berries enclosed in the ampoules was used to monitor their metabolic activity during withering, i.e. respiration. For each sampling time, the heat rate production of the berries at 298K was monitored till a steady state signal was achieved (within 60h). Such heat flow value was used as marker during the entire withering process (120 days). Its trend allowed to characterize the changes in the metabolic activity of the grape berries along the withering process. To understand the origin of such changes, the emission of volatile organic compounds (VOCs) were also measured by proton transfer mass spectrometry (PTR-MS). The use of microcalorimetry associated with the analysis of specific VOCs fragments offered a valuable information to describe the withering process.

Comparative Study of Microcalorimetric Behavior of Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae

To analyze the microcalorimetric behaviour of Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae, and to test the prospective use of microcalorimetry in the early diagnosis of infections by enterobacteria. For our experiments we used cultures of E. coli, P. mirabilis and K. pneumoniae. For the experimental setup, we used a Calvet microcalorimeter with the constant temperature of 309 K inside. Using the measured difference of heat power generated by the cells over time, we obtained growth graphs of the three bacterial species grown at different densities. The generated curves have characteristic plot that repeats for each bacterial species at all the concentrations studied. We observed an inversely proportional relationship between inoculum size and the time until signal detection; the smaller inoculum, the longer time for the signal detection. In all conducted experiments, even with low number of bacteria (10 CFU/ml) as inoculum, we could identify bacterial growth in the sample within 8 hours. Microcalorimetry could be an efficient technique used for the early detection and identification of enterobacteria in a culture medium.

Metabolic evaluation of cooled equine spermatozoa

Microscopy has been used in the routine evaluation of sperm metabolism. Nevertheless, it has limited capacity to preview male fertility. As calorimetry may be used to evaluate directly the metabolic activity of a biological system, the aim of this study was to use microcalorimetry as an additive method for sperm metabolism evaluation of cooled equine semen. Two ejaculates of four stallions were collected and motility, viability (eosin 3%) and membrane functional integrity (hyposmotic swelling test) of spermatozoa were evaluated. Sperm samples were processed following different protocols and the metabolism of these samples was accessed by calorimetry. Centrifugation is part of some of these processing protocols and although this procedure has been deleterious for sperm viability and plasma membrane integrity, no decrease in sperm motility was observed. Microcalorimetry was capable of detecting the positive effect of re-suspending the sperm pellet with Kenney extender. Thus, the use of microcalorimetry offered additional information for equine sperm metabolism evaluation and was efficient in detecting important information from sperm cell metabolism.

Methodological aspects of microcalorimetry used to assess the dynamics of microbial activity during composting

Isothermal microcalorimetry is a sensitive non-invasive analytical tool that can become useful in research on compost and other biosolids. The aim of the present study was to address several methodological aspects that are critical to the use of microcalorimetry to assess the dynamics of microbial activity in such systems. The results show that: (1) The calorimetric baseline is strongly influenced by the run temperature in the range relevant to composting systems (20–60 °C), and is also affected by addition of the water that is required to maintain or optimize microbial activity, presumably because some water evaporates through ampoule gaskets. (2) Amending mature compost with readily available substrates requires additional careful baseline treatment. (3) Sample heterogeneity can be successfully minimized by passing through a 2-mm sieve. Additional size separation can be useful to enable focusing on the more active fractions. (4) Oxygen depletion is a key feature in batch calorimetric analysis; for samples of highly active composts or manure, the total amount of heat released relative to the oxygen available in the ampoule may indicate the co-existence of anaerobic and aerobic metabolic pathways. Finally, practical recommendations for microcalorimetry analyses of pre-mature and mature composts are outlined.

The use of microcalorimetry to compare the biological activity of a CAS and a MBR sludge—application to pharmaceutical active compounds

Micropollutants removal, such as pharmaceutical substances, during wastewater treatment processes is becoming a greater issue everyday. In order to optimize it, their biodegradation processes have to be better understood. So far, microcalorimetry has been used worldwide to investigate chemical reactions. For few years now it has also been developed to model and control biological processes. In the case of micropollutants, respirometry is, most of the time, not precise enough to determine biodegradation. That is why, microcalorimetric experiments have been set up. For this purpose, a 2 L Bio-RC1 (Mettler-Toledo) has been modified to reach a resolution of 5-10 mW.L(-1).In this study, the biodegradation rate of standard substrates (Ethanol and Ammonia) by an activated sludge from a full-scale CAS and one from a MBR pilot plant operating in parallel have been compared by means of microcalorimetry. Then few trials to determine the biodegradation of selected pharmaceutical substances, as well as the eventual inhibition induced by them have been made. The first results did not exhibit any biological activity. However, they have displayed inhibition for both studied substances.

Isothermal Microcalorimetry: A Review of Applications in Soil and Environmental Sciences

Isothermal microcalorimetry provides thermodynamic and kinetic information on various reactions and processes and is thereby a powerful tool to elucidate their mechanisms. Certain improvement in isotherma! microcalorimetry with regard to the studies on soil and environmental sciences is briefly described. This review mainly focuses on the use of microcalorimetry in the determination of soil microbial activity, monitoring the toxicity and biodegradation of soil organic pollutants, the risk evaluation of metals and metalloids, the heat effect of ion exchange and adsorption in soil, and environmental researches. Promising prospects for the applications of the technique in the field are also discussed.

Use of Microcalorimetry and Its Correlation with Size Exclusion Chromatography for Rapid Screening of the Physical Stability of Large Pharmaceutical Proteins in Solution

The utility of microcalorimetry as a rapid screening tool for assessing the solution stability of high molecular weight pharmaceutical proteins was evaluated by using model recombinant antibodies, Protein I and Protein II. Changes in the transition midpoint, Tm, were monitored as a function of pH and/or in the presence of excipients, and results were compared with traditional accelerated stability data from samples that were analyzed by size exclusion chromatography (SEC). The data from microcalorimetry were well correlated with those from SEC for predicting both optimal solution pH as well as excipient effects on solution stability. These results indicate that microcalorimetry can be an efficient screening tool useful in identifying optimal pH conditions and excipients to stabilize pharmaceutical proteins in solution formulations.

Energetic Cost of Subacute Chlorpyrifos Intoxication in the German Cockroach (Dictyoptera: Blattellidae)

The energetic cost of a sublethal treatment with chlorpyrifos was estimated by use of direct microcalorimetry to measure metabolic heat in susceptible and resistant strains of the German cockroach Blattella germanica L. Moreover, one of the detoxification enzyme systems known to be involved in detoxification of chlorpyrifos, glutathione-S-transferase, was measured. Individual cockroaches were exposed for 20 min on a glass-surfaces treated with 1.14 μg/cm2 of chlorpyrifos. There was no difference in glutathione-S-transferase activity of susceptible or resistant strains after the treatment. The heat production increased in the susceptible strain ≈30 min after exposure and declined again after ≈120 min to the basal level. The energetic cost of the exposure to the insecticide corresponds ≈5 h of normal metabolism. There were no significant differences in heat production after toxic treatment in any of the resistant strains. It was shown that measurement of heat production is a sensitive method to prove toxic reactions after exposure to a low dose of insecticide. The use of microcalorimetry as a promising biomarker technology was shown.

Comments on the paper titled "Use of microcalorimetry to study microbial activity during the transition from oxic to anoxic conditions"

Comments on the paper titled "Use of microcalorimetry to study microbial activity during the transition from oxic to anoxic conditions"

Use of microcalorimetry to study microbial activity during the transition from oxic to anoxic conditions

Microbial heat production is a nonspecific measure for microbial activity irrespective of O2 availability in soils. In a series of long-term batch microcalorimeter experiments with closed ampoules, we examined the microbial activity in glucose-amended soil aggregates from different soil depths of a clay forest soil during the transition from aerobic to anaerobic conditions. Furthermore, the influence of the soil aggregate size on the long-term metabolic heat production was examined. Heat output curves showed a distinct pattern for soil samples from different soil depths and aggregate sizes and led to the following conclusions: 1. Microbial biomass and microbial activity strongly decreased with increasing soil depth as well as increasing soil aggregate size despite relatively constant organic C concentrations. 2. The transition from aerobic to anaerobic conditions led to a considerable drop in microbial activity. However, based on the energy balance, 10–26% of the heat production during the aerobic phase is attributable to anoxic or partly anoxic metabolism. 3. After O2 exhaustion, a lag phase of low but constant heat output was observed, followed by a peak of anaerobic metabolic activity. Heat production during the lag phase was hypothesised to be an indicator for the biomass of facultatively anaerobic microorganisms in the soil.

Calorimetric and IR spectroscopic study of the interaction of NH3 with variously prepared defective silicalites

Abstract Nature, population and acidic properties of the hydroxylated species (hydroxyl nests) present in the nanocavities of variously prepared defective silicalites have been characterised by the adsorption of NH 3 , monitored through the combined use of microcalorimetry and IR spectroscopy. The experimental data (enthalpy of adsorption, stretching frequency of the O–H bonds perturbed by the interaction with NH 3 ) have been compared with ab initio computational results (binding energy, red shift of the stretching frequency) and were found to be in good agreement. The presence of rings of mutually interacting silanols has been postulated (on the basis of both experimental and computational results) in the case of chemically very pure, defective silicalites. The dimension of the rings depends on the preparation conditions. A perfect silicalite sample, taken as hydrophobic reference material, was found to be virtually unreactive towards NH 3 , in that it interacts very scarcely with ammonia, showing a heat of adsorption much lower than the heat of liquefaction of NH 3 itself.

Compatibility Testing of Energetic Materials, Which Technique?

Compatibility is an important safety aspect related to the production and storage of energetic materials. To test different combinations of materials a simple test method with clear criteria is advisable. At the last ESTAC the use of microcalorimetry and the vacuum stability test for the compatibility testing of propellants were presented. This paper presents DSC, DTA/TG and (pressure) vacuum stability test results for the same combination. For three polymers (PMMA, PVC and CA) the results for all tests are the same. Only Nylon-6/6 gives a variable result for the different test methods.

Calorimetric studies of special cements

The kinetics and even the mechanism of cement reaction with water can be successfully investigated by use of microcalorimetry. In this study this method was applied to follow the hydration of the new family of portland cements containing C12A7 * and C11A7·CaF2 addition as well as special cement with C3A replacement by calcium sulphoaluminate. It has been found that C11A7·CaF2 acted as hydration retarder. The heat evolution curves for C12A7 containing samples without CaF2 are very similar to those for the reference portland cement samples. XRD and SEM studies confirm the results described above, relating to the retardation of alite hydration. The process is positively modified by the addition of anhydrite. In the presence of calcium sulphoaluminate (4CaO·3Al2O3·SO3) the hydration at early stage occurs with the rapid formation of large amount of the ettringite phase. The calcium fluoride acts as a set retarder. The full compatibility of calorimetry with SEM and XRD results should be underlined.

Use of Microcalorimetry in the Field of Pharmaceutical Sciences. I. Measurement of Drug Dissolution from Solid Dosage Forms.

A microcalorimetric method for measurement of the dissolution rate of sodium chloride was presented. The method applied the deconvolution theory to heat conduction microcalorimetry. When a calorimetric curve for the heat of dilution was regarded as the response for a unit impulse input (heat conduction profile), a calorimetric curve for the heat of solution was considered to be the convolution of dissolution profile and heat conduction profile. Thus, the dissolution profile was calculated from the calorimetric curves for the heat of dilution and for the heat of solution by a numerical deconvolution. Dissolution rate determined by the calorimetric method coincided well with that obtained by a titration method.

Microcalorimetric study of the acidity and basicity of metal oxide surfaces

The adsorption of probe molecules such as NH{sub 3} and CO{sub 2} was studied on about 20 simple metallic oxides by use of microcalorimetry in order to determine the number and character of basic and acidic surface sites. Microcalorimetry allowed a simultaneous determination of the strength and energy distribution of the adsorption sites. The adsorption isotherms, the differential heats, the integral heats, and the energetic histograms are given for NH{sub 3} and CO{sub 2} adsorptions. Relationships between the average adsorption heats of NH{sub 3} and CO{sub 2} have been found as a function of the ionic character percentage and of the charge/radius ratio.

The use of microcalorimetry to measure thermodynamic parameters of the binding of ligands to insulin.

Flow microcalorimetry was used to measure the free energies, enthalpies, and entropies of interactions between the hormone insulin and small ligand molecules or ions. Measurable amounts of heat were obtained for binding of four phenolic preservative molecules--phenol, meta-cresol, resorcinol, and methylparaben--to both two-zinc and zinc-free insulin and for binding of zinc ions to zinc-free insulin. All of the reactions were spontaneous, but the phenolic binding was driven by enthalpy, while that of zinc was entropy-driven. A combination of van der Waals interactions, hydrophobic effects, and protein conformational changes appeared to be involved in binding of the phenolic ligands. Zinc ions displayed two types of binding to insulin, both involving ion-dipole interactions.

Adsorption calorimetry in surface chemistry

The measurement of the energy of interaction of a molecule with a surface as a function of coverage provides information on the state of the surface and on the thermodynamic characteristics of the adsorption process. Access to Δ ads H is usually obtained on polycrystalline materials by means of a microcalorimeter connected to a dosing device which enables the simultaneous measurement of small uptakes and related heats. Small increments in the adsorba te from the lowest coverage to saturation can thus be evaluated. Successive adsorption-desorption cycles allow the separation of effects due to reversible and irreversible phenomena. The adsorption of the same adsorptive onto variously pretreated solids or on materials of different origin yield evidence of differences in the state of the surface. The application of this technique in various fields of surface science will be reported and the usefulness of joint use of microcalorimetry with other techniques will be stressed.

The use of microcalorimetry in studies of mammalian cells

Recent developments in instrumentation and working procedure in microcalorimetry have led to an increased interest in the direct measurements of heat production rates of living cells. Specific problems connected in particular with work on mammalian cells are briefly discussed and a system of microcalorimeters suitable for work on such cells is described. A few examples of its use in studies ofT-lymphoma cells are briefly discussed.