Reaction Vessel Volume Research Articles

INFOGEST inter-laboratory recommendations for assaying gastric and pancreatic lipases activities prior to in vitro digestion studies

In vitro digestion studies often use animal digestive enzyme extracts as substitutes of human gastric and pancreatic secretions. Pancreatin from porcine origin is thus commonly used to provide relevant pancreatic enzymes such as proteases, amylase and lipase. Rabbit gastric extracts (RGE) have been recently introduced to provide gastric lipase in addition to pepsin. Before preparing simulated gastric and pancreatic extracts with targeted enzyme activities as described in in vitro digestion protocols, it is important to determine the activities of enzyme preparations using validated methods. The purpose of this inter-laboratory study within the INFOGEST network was to test the repeatability and reproducibility of lipase assays using the pH-stat technique for measuring the activities of gastric and pancreatic lipases from various sources. Twenty-one laboratories having different pH-stat devices received the same protocol with identical batches of RGE and two pancreatin sources. Lipase assays were performed using tributyrin as a substrate and three different amounts (50, 100 and 200 µg) of each enzyme preparation. The repeatability results within individual laboratories were satisfactory with coefficients of variation (CVs) ranging from 4 to 8% regardless of the enzyme amount tested. However, the inter-laboratory variability was high (CV > 15%) compared to existing standards for bioanalytical assays. We identified and weighted the contributions to inter-laboratory variability of several parameters associated with the various pH-stat equipment used in this study (e.g. reaction vessel volume and shape, stirring mode and rate, burette volume for the automated delivery of sodium hydroxide). Based on this, we established recommendations for improving the reproducibility of lipase assays using the pH-stat technique. Defining accurate and complete recommendations on how to correctly quantify activity levels of enzyme preparations is a gateway to promising comparison of in vitro data obtained from different laboratories following the same in vitro digestion protocol.

Oxygen Isotopic Exchange Between CO2 and Phosphoric Acid: Implications for the Measurement of Clumped Isotopes in Carbonates

AbstractExperiments have been conducted in which CO2 gases with varying C and O isotopic compositions and with stochastic and nonstochastic Δ47 values have been allowed to equilibrate with phosphoric acid of two concentrations in reaction vessels of varying dimensions at temperatures of 25 and 90 °C. Rates of 13C18O and 18O exchange between the CO2 and the phosphoric acid varied as a function of the length of exposure, volume of reaction vessel, acid strength, and difference of the initial Δ47 and δ18O values of the CO2 from theoretical equilibrium values. The Δ47 values were also altered by heated stainless steel surfaces such as those found within the Kiel device and other preparation systems. These results have been used to explain variations in the differences in the fractionation between 25 and 90 °C reported for calcite by different workers as well as differences in the slopes between temperature and Δ47 values produced by reacting samples at different temperatures (25 and 90 °C).

Design trade-offs in a column with side-reactor configuration for improving selectivity in multiple reaction systems

The configuration of columns with side-reactors (SRC) can effectively enhance the performance of reaction–separation processes, particularly where the operational limitations of conventional multifunctional reactors, such as reactive distillation systems, negate the overall benefits. Industrial manufacturing processes often use multiple reaction schemes that result in both desired and undesired products. The selectivity and yield of the desired product are usually improved by using large reaction vessels or high recycle flow rates of excess reactant. Therefore, in multiunit chemical processes, the foremost design trade-off is between the reaction vessel volume and the recycle flow rate. In this study, we investigate the competition of these parameters in SRC configurations in achieving specific conversion or yield criteria. Two real chemical processes involving side-reactors of non-reactive distillation columns and recycle streams are considered and their optimal design configurations are detailed. The results affirm the importance of this trade-off and its quantitative analysis to obtain the optimal SRC configuration.

Determining the local origin of hydroxyl radical generation during phacoemulsification

To determine the local origin of hydroxyl radicals during phacoemulsification using an ultrasonic phacoemulsification device that includes longitudinal and torsional modalities. Chemistry and Biochemistry Department, Utah State University, Logan, Utah, USA. Experimental study. Experiments were conducted using the Infiniti Vision System and Ozil handpiece. Hydroxyl radical concentrations during longitudinal and torsional phacoemulsification were quantitated as malondialdehyde (MDA) determined spectrophotometrically using the deoxyribose assay. The difference between the total concentration found in the aspirated solution at steady-state concentrations and the pre-aspirate levels deductively determined the concentration of MDA formed along the interior of the sonicating tip. The time to reach 50% of steady state as a function of reaction vessel volume was determined. The mean maximum for torsional ultrasound at 100% amplitude was 7.70 nM ± 0.38 (SD), 91.1% of which was generated outside the tip. During longitudinal ultrasound at 100% power, MDA concentration in the aspirated solution was 29.5 ± 0.3 nM, 71.6% of which was generated outside the tip. The time (seconds) to reach 50% of maximum for longitudinal ultrasound using 5 mL, 10 mL, and 20 mL reaction vessels was 12.6 ± 1.5, 21.0 ± 1.5, and 25.3 ± 3.4, respectively. Although a significantly greater proportion of the hydroxyl radicals generated during ultrasound modality were formed outside the phaco tip (91.1% torsional; 71.6% longitudinal), torsional ultrasound generated only about one-fourth the amount of MDA as longitudinal ultrasound in total and about one-third that generated outside the tip (7.02 nM versus 21.1 nM). No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

Thermolysis of 1-R1,R2-nitromethyl-3-R-1,2,4-triazoles

In this work thermolysis kinetics of compounds I– V was studied aiming to elucidate influence of additive substituents R1 and R2 on the rate and mechanism of decomposition reaction. maximal and initial rate is 2.0). Ratios between substance mass and reaction vessel volume (m/V = 2– 24×10 g cm) and between the vessel surface and its volume (S/V = 3.2–4.6 cm) do not affect the reaction rate constant suggesting that this reaction is homogeneous. Additives to starting material of gaseous reaction products (P0 = 106–172 mm Hg), forming during the reaction progress at 8–10% conversion, do not affect the reaction rate constant. This indicates that autocatalysis is absent in the thermolysis of compounds II–IV in the melt. The decomposition of compounds I–IV in solution and compound V in the gas phase to 45–50% conversion is described by equation of the first order reaction. The substance concentration in solution (1–5 wt %) and the dielectric constant of the solvent (6.4–20.6) have no effect on the rate constant. In the gas phase the ratio S/V was no more than 0.55 cm. The kinetic parameters of thermolysis are presented in the table. The solution concentration was 2 wt %. The measurements were performed for solutions in DOI: 10.1134/S1070363210060265

From Biochemistry to Physiology: The Calorimetry Connection

This article provides guidelines for selecting optimal calorimetric instrumentation for applications in biochemistry and biophysics. Applications include determining thermodynamics of interactions in non-covalently bonded structures, and determining function through measurements of enzyme kinetics and metabolic rates. Specific examples illustrating current capabilities and methods in biological calorimetry are provided. Commercially available calorimeters are categorized by application and by instrument characteristics (isothermal or temperature-scanning, reaction vessel volume, heat rate detection limit, fixed or removable reaction vessels, etc.). Advantages and limitations of commercially available calorimeters are listed for each application in biochemistry, biophysics, and physiology.

Description of a new Gill titration calorimeter for the study of biochemical reactions. I: assembly and basic response of the instrument

A detailed account of the assembly of a thermopile heat-conduction isothermal titration calorimeter to be used in the study of biomolecular interactions is given. The instrument is built according to the twin-cell principle with a sensitivity of 5 mu J. Its reaction vessel volume is only 200 mu l. Stirring heats of the reaction vessel are below 5 mu J.

The synthesis of substances under high static pressures

Phase transitions of many substances occur under extremely high pressures and temperatures. The development of such conditions is possible within a limited reaction vessel volume of a special high pressure apparatus. In order to obtain pressures of 5 to 8 GPa in a reaction volume a high-pressure apparatus is loaded by anvils of hydraulic presses whose working force is 1 to 10 MN. The heating of substances up to 1500–2000 K is carried out by direct current transmission or a reaction vessel is provided with special resistors. The high pressure apparatus (HPA) consists of a number of elements whose yield and heat conductivities differ. This defines the pressure and temperature gradients within the reaction vessel volume and throughout the HPA as a whole. The dimensions and the design pecularities of HPA substantially affect its temperature and pressure fields. The basic principles of the theory of large plastic deformations and those of the mechanics of deformation in solids are considered. The temperature and pressure fields in the HPA reaction volume of model shape and dimensions are defined as a result of solving associated non-linear non-stationary problems of electro- and heat-conductivity in HPA and those of thermal plasticity by the method of finite elements. The probable arrangement and volume of various phases (initial low pressure phase, synthesized high pressure phase and those of the solid and melted metal solvent) were investigated. The characteristics allowing the quantitative evaluation of the efficiency of the selected pressure level within the reaction vessel prior to the heating cycle were proved to be valid.

Minimum self-ignition temperature of petroleum products

1. The self-ignition temperature of petroleum products depends considerably on the reaction vessel volume. 2. The basic thermophysical conditions which are characteristic of large-volume vessels have been stimulated in the laboratory setup which is described. 3. The results obtained by the method described make it possible to determine the minimum self-ignition temperature values and can serve as a reliable criterion of the explosion hazard of petroleum products.

STUDIES ON THE EXPLOSION OF GASES THROUGH THE GAS PHASE ACETYLATION OF CELLULOSE FIBER AND IT'S PRACTICAL HANDLING METHOD IN FACTORIES

The explosion of gases through the gas phase acetylation of cellulose fiber was one of difficult points to industrialize.1. The explosion range of three components gases, oxygen, nitrogen and acetic-acid acetic-anhydride mixture is shown in Fig. 3, Fig. 4 and Fig. 5.2. In Fig. 7, it is evident that the explosion through the gas phase acetylation of cellulose fiber can be avoided, if operated along the line A-B-C-D-E-A. At the start of running 1.5 times of nytrogen as much as volume of reaction vessel, and at the stop of running 2.2 times of it was used respectively, therefore if the held up gas in the reaction vessel were replaced, the possibility of explosion may be prevented.