End Point Of Reaction Research Articles

Process control of rice protein enzymolysis by field monitoring

By devising a novel near-infrared (NIR) in-situ online monitoring system, this study proposed a new process control method for rice protein (RP) enzymatic hydrolysis in order to address the challenge of monitoring certain chemical indices in real-time. The endpoint of the enzymatic hydrolysis reaction and the flexible switching point of dual-enzyme hydrolysis were determined through real-time spectrum collection. Correction and prediction models were constructed to predict the angiotensin I-converting enzyme (ACE) inhibitory activity of RP hydrolysis as well as the endpoint and the dual-enzyme flexible switching point at different substrate concentrations in an attempt to establish the new control system. At the RP substrate concentrations of 35, 40, and 45 g/L, the R2 of predicted and measured ACE inhibitory activity values under hydrolysis with a single alcalase were 0.8852, 0.8360, and 0.8613, respectively. In addition, the ACE inhibitory activity of dual-enzyme hydrolysis showed a high growth trend before and after the flexible switching point, and the hydrolysis time was significantly shortened at the same endpoint threshold as that of single alcalase hydrolysis. The results indicated that this method is capable of accurately determining and regulating the endpoint and adaptable transition point of RP hydrolysis. Consequently, this approach holds promise for the regulation of food basic materials during large-scale processing operations.

Detection of iodine in aqueous extract of plants through modified Mohr’s method

Abstract This article explores the extraction of iodine contents in Ipomoea pes-caprae plants using the modified Mohr’s method applied to a biological extract prepared in an aqueous solution. The plants were collected from three coastal regions of the Arabian Sea at Karachi coast, privileged as iodine resource areas. The size of the stem, leaves, and flowers of collected plants was measured after transportation into the laboratory before preparation of aqueous extract. It was found to be significantly different in size from each other. The electrical conductivity of the biological extract was recorded through a conductometer. For this purpose, the extract of different parts of the I. pes-caprae plants was prepared, followed by heating and filtration, while silver nitrate (AgNO3) was used as a precipitating agent. It was interesting to note that when filtrate was titrated with AgNO3, the precipitate started to settle down. Results showed the lowest iodine concentration in the flowers of all tested plants, followed by the highest in the leaves. Conductometric precipitation reaction was influential in determining iodine in herbal medicinal plants. It was observed that the size of the plants and collection sites impacted the iodine concentration. It was lowest in I. pes-caprae, collected from sea view Karachi, while highest in plants of Hawksbay. The endpoint of this biochemical reaction was taken when conductivity started rising. The standard curve of KI was prepared to determine the concentration of iodine in plant samples through conductometric titration. Moreover, the presence of Iodine was confirmed through a chemical testing method using HNO3, NH4OH, and H2SO4, after a complete precipitation reaction. The iodine quantification was done using a spectrophotometer through hexane solvent after being treated with H2SO4.

In-line monitoring of magnetic nanoparticles synthesis using reactor integrated on-chip magnetometer

The excellent multifunctional properties of magnetic nanoparticles (MNPs) allow them to be used in a wide range of applications. However, the required processes for the MNPs synthesis and characterization are still time-consuming and laborious, which further delays the research and development of the synthesis of MNPs. To overcome these difficulties, an on-chip magnetometer consisting of a planar Hall magnetoresistive (PHMR) sensor with a reactor was developed to optimize synthesis conditions for MNPs effectively. The microreactor was fabricated on the PHMR sensor, and the induced field from the synthesized magnetic particles was directly detected in the form of an output signal. Since the on-chip magnetometer enables simultaneous synthesis and measurement, it successfully monitored from the start point to the endpoint of the MNPs synthesis reaction. We studied the effect of the reagent ratio on the particle with iron chloride and aqueous ammonia solution, and we found the most suitable combination using a multi-array on-chip magnetometer. Experiments under various conditions were conducted simultaneously, and the experimental conditions were optimized in a short duration of time. Even though the synthesis reaction took place in a short time, the sensor's fast measurement rate and sensitivity allowed in-line measurement of the particle formation process. In addition, the developed on-chip magnetometer can be flexibly combined according to the desired configuration. Therefore, it is expected to be widely used as a new device for the simultaneous synthesis and analysis of MNPs.

Real-time monitoring control of sequencing batch anammox process.

Rapid recognition and timely management of the emergent situation in wastewater treatment are crucial to maintaining the stable operation of anammox process. In this study, the feasibility of pH, conductivity(Cond) and oxidation reduction potential (ORP) profiles for monitoring and controlling anammox process for synthetic wastewater treatment was evaluated, and the practicability of the method was further verified by using real wastewater. The results showed that the characteristic values of these parameter profiles exhibited high accuracy and reproducibility in indicating the endpoint of the anammox reaction. Moreover, the positive correlations between TN removal and ΔpH, ΔCond and ΔORP were found. Nevertheless, only the slope of the Cond curve was found to be significantly linearly correlated with the specific anammox activity, which was further validated by the Haldane inhibition kinetic model, suggesting that the Cond curve can be used as an immediate feedback signal on whether anammox activity was inhibited. Overall, this study presents a fast, convenient and accurate strategy based on online real-time monitoring of instrument parameters, which was conducive to tracking the nitrogen removal process dynamics and performing the necessary operations in a timely manner, and to improving the stability of anammox process in wastewater treatment.

Safety of magnetic resonance imaging in patients with cardiac implantable electronic devices with generator and lead(s) brand mismatch.

Magnetic resonance imaging (MRI) is a valuable imaging modality for the assessment of both cardiac and non‐cardiac structures. With a growing population of patients with cardiovascular implantable electronic devices (CIEDs), 50%–75% of these patients will need an MRI. MRI‐conditional CIEDs have demonstrated safety of MRI scanning with such devices, yet non‐conditional devices such as hybrid CIEDs which have generator and lead brand mismatch may pose a safety risk. In this retrospective study, we examined the outcomes of patients with hybrid CIEDs undergoing MRI compared to those patients with non‐hybrid CIEDs. A total of 349 patients were included, of which 24 patients (7%) had hybrid CIEDs. The primary endpoint was the safety of MRI for patients with hybrid CIEDs as compared to those with non‐hybrid devices, measured by the rate of adverse events, including death, lead or generator failure needing immediate replacement, loss of capture, new onset arrhythmia, or power‐on reset. Secondary endpoints consisted of pre‐ and post‐MRI changes of decreased P‐wave or R‐wave sensing by ≥50%, changes in pacing lead impedance by ≥50 ohms, increase in pacing thresholds by ≥ 0.5 V at 0.4 ms, and decreasing battery voltage of ≥ 0.04 V. The primary endpoint of any adverse reaction was present in 1 (4.2%) patient with a hybrid device, and consistent of atrial tachyarrhythmia, and in 10 (3.1%) patients with a non‐hybrid device, and consisted of self‐limited atrial and non‐sustained ventricular arrhythmias; this was not statistically significant. No significant differences were found in the secondary endpoints. This study demonstrates that MRI in patients with hybrid CIEDs does not result in increased patient risk or significant device changes when compared to those patients who underwent MRI with non‐hybrid CIEDs.

Smart Flow Electrosynthesis and Application of Organodisulfides in Redox Flow Batteries.

Electrochemical techniques have been recognized as an environmentally friendly and sustainable synthetic way to form organodisulfides. However, searching for optimum conditions which suffers from time/material‐consuming caused by the uncertainty of reactant consumption has hindered its rapid and large‐scale development. Inspired by advanced nonaqueous redox flow batteries (NARFBs) technology, it is proposed a smart flow electrosynthesis (SFE) method of organodisulfides that the voltage curve of NARFBs can be utilized as a precise indicator to reflect the desired information about reactants and distinguish the end point of reaction automatically. This electrochemical method also exhibits certain universality and scalability. Additionally, organodisulfides generated in electrolytes can be used as active species for NARFBs without further purification, and their electrochemical properties are easily adjusted by changing raw materials, which effectively alleviate the waste in complex synthesis steps for optimizing and designing active materials separately. An organodisulfide dervied from isopropyl alcohol and carbon disulfide shows excellent cycling life (1000 cycles) with low capacity fade rate (0.024% per cycle). Taking advantages of the inherent NARFBs, this work not only proves a SFE strategy, but also supplies a green and low‐cost molecular engineering scheme for designing electroactive materials for energy storage.

Prediction of the refractive index and speed of sound of biodiesel from its composition and molecular structure

The refractive index and speed of sound can be applied in many biodiesel studies, such as the characterization of biodiesels, their feedstocks, diesel/biodiesel blends, and their adulteration with vegetable oils. They have also been used to monitor the progress and endpoint of the transesterification reaction and the level of oxidation of biodiesel. About 350 oils are considered with potential for the production of biodiesel, and, for most of them, no experimental values of their refractive index and speed of sound are yet available. Regression models allowing an estimation of these two properties can be very useful. Thus, this study proposes regression models to determine the refractive index and speed of sound of biodiesel as a function of its composition and molecular structure (carbon chain length and unsaturation level). Experimental values of the refractive index for several oil-based biodiesels were measured. A regression study was conducted using our results and available experimental databases including a total of 47 data for the refractive index at 313 K and 263 data for the speed of sound in the range of 288-343 K. The equations, which were obtained using multiple linear regression analysis, correctly reproduced the dependencies of these biodiesel properties on carbon chain length and unsaturation level. The results obtained using the regression models proposed were compared with measured and available experimental data, showing very good agreement. The RMSE values of the refractive index and speed of sound models using all the data were lower than 0.0008 and 1.84 m/s, respectively.

High Sensitivity Graphene Field Effect Transistor‐Based Detection of DNA Amplification

AbstractEnzymatic DNA amplification‐based approaches involving intercalating DNA‐binding fluorescent dyes and expensive optical detectors are the gold standard for nucleic acid detection. As components of a simplified and miniaturized system, conventional silicon‐based ion sensitive field effect transistors (ISFETs) that measure a decrease in pH due to the generation of pyrophosphates during DNA amplification have been previously reported. In this article, Bst polymerase in a loop‐mediated isothermal amplification (LAMP) reaction combined with target‐specific primers and crumpled graphene field effect transistors (gFETs) to electrically detect amplification by sensing the reduction in primers is used. Graphene is known to adsorb single‐stranded DNA due to noncovalent π–π bonds, but not double‐stranded DNA. This approach does not require any surface functionalization and allows the detection of primer concentrations at the endpoint of reactions. As recently demonstrated, the crumpled gFET over the conventional flat gFET sensors due to their superior sensitivity is chosen. The endpoint of amplification reaction with starting concentrations down to 8 × 10−21 m in 90 min including the time of amplification and detection is detected. With its high sensitivity and small footprint, this platform will help bring complex lab‐based diagnostic and genotyping amplification assays to the point‐of‐care.

Timesaving, High-Efficiency Approaches To Fabricate Aramid Nanofibers

Aramid nanofibers (ANFs) have become promising nanoscale building blocks due to their extraordinary performance. However, there are numerous challenges related to the preparation of ANFs, such as the lengthy preparation cycle (7-10 days), low preparation concentration (0.2 wt %), and high difficulty in quantitatively judging the end point of the deprotonation reaction. Herein, we report three time-saving and high-efficiency strategies (fibrillation, ultrasonication, and proton donor-assisted deprotonation) to prepare ANFs with excellent performance. The fiber micromorphology during the deprotonation and protonation recovery processes was first investigated. Then the end point of the deprotonation reaction was detected by Raman spectra and the cationic demand of the ANF/DMSO system. Finally, the size, preparation cycle, and performance of the corresponding ANFs and ANF films fabricated by different approaches were investigated in detail. The results showed that proton donor-assisted deprotonation significantly shortened the traditional preparation cycle from 7 days to 4 h, and is the most efficient method reported thus far. It is noteworthy that a high concentration of ANFs (4.0 wt %) could also be achieved within 12 h. Interestingly, the fabricated ANFs exhibit rigid morphology and a small diameter with a narrow size distribution (10.7 ± 1.0 nm). The resultant ANF film displays desired characteristics of high strength and toughness. The work offers a timesaving, feasible and effective strategy to realize the large-scale production for ANFs, which will facilitate the application of ANFs in the production of advanced nanomaterials.

Rapid and in-situ detection of fecal indicator bacteria in water using simple DNA extraction and portable loop-mediated isothermal amplification (LAMP) PCR methods

Contamination of water by fecal matter and potential human enteric pathogens is a serious health concern. Microbiological water quality has been assessed by conventional culture-based methods of fecal indicator bacteria (FIB). Recently, molecular techniques for FIB have been introduced as alternative tools for rapid detection. However, such molecular techniques require a modern laboratory setting, expensive equipment, and skilled personnel. In this study, we developed a simple and rapid DNA extraction method based on a syringe filter without any specialized equipment. Furthermore, loop-mediated isothermal amplification (LAMP) PCR for fecal indicator bacteria (FIB) (i.e. E. coli and E. faecalis) was carried out using the DNA extracts from the syringe-filter based DNA extraction method. The efficiency of the extracted DNA from the syringe-filter based method was comparable to the results of the commercial kit method. We also tested fresh and marine-water collected directly from different locations in Singapore that were spiked with E. coli or E. faecalis. The LAMP assays combined with our DNA extraction method showed higher sensitivity and more tolerance to PCR inhibitors than that of conventional PCR methods. We further developed a portable LAMP device to conduct isothermal PCR reactions for rapid on-site measurement of FIB. As the color changes in the end point of the LAMP reaction can be observed with the naked eye, the portable LAMP device was easily operated and quick, obtaining results in 30 min. The simple, portable and user-friendly platform can be used as an initial screening for the rapid detection of the presence FIB in lower-resource settings. In conclusion, the portable LAMP device coupled with a syringe-filter based DNA extraction method enables us to detect the presence of FIB for assessing microbial water quality within 1 h without any sophisticated laboratory equipment or highly trained personnel.

Coupled equilibria in H-bond donating ring-opening polymerization: The effective catalyst-determined shift of a polymerization equilibrium

In the classic view of catalysis, a catalyst cannot alter the thermodynamically-determined endpoint of a reversible reaction. This conclusion is predicated on the assumption that the catalyst does not perturb the energy of product or reactant or does so to an equal extent. In the H-bond mediated ring-opening polymerization (ROP) of lactone monomers, the strength of the interactions of thiourea with product and reactant are not equal, and the magnitudes of these interactions are of similar energy to the free energy of reaction. The total monomer concentration at equilibrium in the thiourea/base cocatalyzed ROP of lactones is shown to be a function of the initial concentration of thiourea. Because the binding of thiourea to monomer and the polymerization reaction itself are both reversible, the application of varying amounts of thiourea catalyst directly alters the total amount of monomer in the reaction solution at equilibrium, which can be recovered at the end of the reaction.

Synthesis of a water-soluble thiourea-formaldehyde (WTF) resin and its application to immobilize the heavy metal in MSWI fly ash

Because of the high concentrations of heavy metals, municipal solid waste incineration (MSWI) fly ash is classified as a hazardous waste, which need to be treated to avoid damaging the environment. A novel water-soluble thiourea-formaldehyde (WTF) resin was synthesized by two step reactions (hydroxymethylation reaction and condensation reaction) in the laboratory. Synthetic conditions, removal of free formaldehyde in the resin and the ability of immobilization heavy metals in the MSWI fly ash were studied. The possible molecular structure of the resin was also discussed by elemental analysis and FTIR spectra. Experimental results showed that the synthesis conditions of WTF resin were the formaldehyde/thiourea (T/F) mole ratio of 2.5:1, hydroxymethylation at pH 7.0–8.0 and 60 °C for 30min, and condensation of at pH 4.5–5.0 and 80 °C. In addition, the end point of condensation reaction was measured by turbidity point method. The result of elemental analysis and FTIR spectra indicated that thiourea functional group in the WTF resin chelated the heavy metal ions. Melamine can efficiently reduce the free formaldehyde content in the resin from 8.5% to 2%. The leaching test showed that the immobilization rates of Cr, Pb and Cd were 96.5%, 92.0% and 85.8%, respectively. Leaching concentrations of Cr, Pb and Cd in the treated fly ash were decreased to 0.08 mg/L, 2.44 mg/L and 0.23 mg/L, respectively. The MSWI fly ash treated by WTF resin has no harm to the environment.

Effective monitoring of the electro-Fenton degradation of phenolic derivatives by differential pulse voltammetry on multi-walled-carbon nanotubes modified screen-printed carbon electrodes

This work illustrates a fast, sensitive and selective electroanalytical methodology for simultaneous determination of phenolic derivatives. Optimization of differential pulse voltammetry (DPV) conditions and electrochemical study by cyclic voltammetry (CV) of phenolics are included. Differential pulse voltammetry at screen-printed carbon electrodes (SPCE) was selected for the sensitive detection of m-Cresol and Tert-butylhydroquinone. The introduction of Multi-walled Carbon-Nanotubes with acid groups, MWCNT-COOH, as modifier on working SPCE enhances the performance of electrode surface with a highly catalytic activity on it, allowing a 5-fold higher sensitive analysis than unmodified SPCE, with a limit of detection as low as about 1μM. This simple and low-cost methodology has been applied, for first time, to monitoring the electro-Fenton degradation of m-Cresol, giving selective information of the reactant loss and products formation. Aromatic intermediates (monohydroxy, polyhydroxy and quinone phenolic derivatives) have been identified and followed during the electrolysis process. The electro-Fenton with iron on activate carbon is 4-fold faster than with other catalyst. The results are validated by chromatographic (HPLC) technique. The electroanalytical methodology described, in conjunction with the use of small SPCE as sensor transducer, can be implemented for continuous monitoring of end-point of the electro-Fenton reaction at industrial level in wastewater remediation plants, indicating the two main stages of electro-Fenton during the electrolysis.

Decoloration of wine and subsequent enzymatic quantification of histamine

We would like to present a simple decoloration procedure for (red) wine and the subsequent enzymatic method for the specific quantification of histamine. The test kit for sample preparation contains three solutions that are used to decolorate wine by two simple precipitation steps within 15 min. The enzymatic test kit consists of a microtiter plate coated with two substrates and ready to use reagents (buffer, calibrators and enzyme histamine dehydrogenase). The determination is performed within 15 min and the measurement wavelength is 450 nm which is the common wavelength for ELISA procedures. The linear range is from 1 to 20 mg/L in the extracted sample (corresponding to 2.4–48 mg/L in wine) and the recovery is >85% in red wines and more than 90% in white and rose wines. The limit of quantification is calculated to 1 mg/L. Wines at this low histamine levels showed CVs of less than 7%. The assay shows a high precision with a relative within-lab reproducibility standard deviation of less than 7%. A method comparison between HPLC and the new enzymatic system revealed a very high degree of agreement. The enzymatic procedure contains no dilution steps, no washing steps like for an ELISA, and a clear defined end-point of the enzymatic reaction.

Using PAT To Understand, Control, and Rapidly Scale Up the Production of a Hydrogenation Reaction and Isolation of Pharmaceutical Intermediate

The development of a hydrogenation process and subsequent isolation for an intermediate in the manufacture of an active pharmaceutical ingredient is described. In-line process analytical technology (PAT) approaches were applied to gain process understanding and control. First, a calibration-free, qualitative, scale-independent approach using in situ mid-infrared (MIR) spectrometry to determine the end point of a hydrogenation reaction in real time is described. A curve-fitting algorithm was developed using MATLAB software to allow the reaction rate to be calculated at any given time during the reaction on the basis of the consumption of an intermediate species. The algorithm, coupled with understanding of the process, allowed the end point to be correctly identified in triplicate during scale-up of the process from 0.2 to 20 L scale. Second, a quantitative partial least-squares (PLS) regression model was developed using near-infrared (NIR) spectrometry to determine the solvent composition during the subse...

Design and application of cotranscriptional non-enzymatic RNA circuits and signal transducers

Nucleic acid circuits are finding increasing real-life applications in diagnostics and synthetic biology. Although DNA has been the main operator in most nucleic acid circuits, transcriptionally produced RNA circuits could provide powerful alternatives for reagent production and their use in cells. Towards these goals, we have implemented a particular nucleic acid circuit, catalytic hairpin assembly, using RNA for both information storage and processing. Our results demonstrated that the design principles developed for DNA circuits could be readily translated to engineering RNA circuits that operated with similar kinetics and sensitivities of detection. Not only could purified RNA hairpins perform amplification reactions but RNA hairpins transcribed in vitro also mediated amplification, even without purification. Moreover, we could read the results of the non-enzymatic amplification reactions using a fluorescent RNA aptamer ‘Spinach’ that was engineered to undergo sequence-specific conformational changes. These advances were applied to the end-point and real-time detection of the isothermal strand displacement amplification reaction that produces single-stranded DNAs as part of its amplification cycle. We were also able to readily engineer gate structures with RNA similar to those that have previously formed the basis of DNA circuit computations. Taken together, these results validate an entirely new chemistry for the implementation of nucleic acid circuits.

Monitoring the conversion of soybean oil to methyl or ethyl esters using the refractive index with correlation gas chromatography

A simple method (refractive index) was applied to monitor the progress and the end point of the transesterification reaction of soybean oil to biodiesel (methyl or ethyl esters). Additionally, the same method may be used to determine the methyl or ethyl ester content during the transesterification reaction progress. To do so, blends of biodiesel and soybean oil were prepared at different wt.% to obtain a simple linear correlation with the refractive index and a correlation coefficient (R2) of 0.9997 and 0.9996 for the FAMEs and FAEEs, respectively. The transesterification process of soybean oil with methanol and ethanol was performed to determine how the refractive index properties change due to the ratio of conversion. It was concluded that in the reaction kinetics of the methanolysis reaction, the efficiency was over 90% in 8h. Compared with existing chromatographic techniques, the refractive index method for monitoring the transesterification of vegetable oils presented good results. Additionally, the method was rapid, inexpensive and especially suitable for process control applications.

Calibration of nanowatt isothermal titration calorimeters with overflow reaction vessels

Obtaining accurate results with nanowatt titration calorimeters with overflow cells requires mass calibration of the buret injection volume, chemical calibration of the reaction vessel effective volume, and chemical calibration of the calorimetric factor used to convert the measured electrical signal to heat rate. Potential errors in electrical calibration of power compensation calorimeters require validation of the calorimetric factor with chemical reactions with accurately known stoichiometries and enthalpy changes. The effective volume of the reaction vessel can be determined from the endpoint of a quantitative reaction with known stoichiometries. Methods for calibration and potential calibration errors to be avoided are described. Publication of results obtained must include data on calibrations and sufficient raw data to assess precision and accuracy of the results.

Influence of ethylene glycol on CaCO 3 particles formation via carbonation in the gas–slurry system

Calcium carbonate precipitation was investigated in the gas–slurry system in the reaction of calcium hydroxide and carbon dioxide. The precipitation process was occurred in the presence of ethylene glycol (EG). The used organic additive changed the viscosity of reactive mixture, the solubility of carbon dioxide and the solubility of calcium carbonate which influence CaCO 3 precipitation conditions. The course of reaction was monitored by conductivity probe. The increase concentration of ethylene glycol in the reactive mixture caused higher CO 2 usage to achieve the end point of reaction. Calcium carbonate was precipitated as calcite and produced CaCO 3 particles formed agglomerates in all experiments. The size of obtained CaCO 3 particles decreased when the EG concentration increased from 0% to 15% (by vol.). The further increase of EG concentration in solution up to 20% resulted in an increase of the size of CaCO 3 particles.

Monitoring the transesterification reaction with laser spectroscopy

The production of biodiesel is rapidly expanding around the world, making it more important to produce this fuel with more energy efficiency. In this paper, we observed a series of transesterification reactions of soy bean oil and methyl alcohol catalyzed by potassium hydroxide. The observations were made using a non-invasive optical technique. This technique is useful to indicate the endpoint of a transesterification reaction or to determine when this reaction is reaching the state of chemical equilibrium. This study made it possible to improve the follow-up of the transesterification reaction, by optimizing the reaction time with a better monitoring system.