Rate-limiting Step Of Reaction Research Articles

Probing the Mechanism of Plasmon-Enhanced Ammonia Borane Methanolysis on a CuAg Alloy at a Single-Particle Level

Plasmon-enhanced ammonia borane (AB) methanolysis, as an efficient, controllable, and safe method for hydrogen release, has attracted increasing attention. However, the mechanism remains controversial since it is difficult to directly observe the interface interaction in the plasmonic field. Here, CuAg alloy nanoparticles (NPs) with controlled compositions are synthesized and exhibit an excellent H2 yield (17.1 μmol min–1) under light illumination. Theories and experiments show that both hot carriers and photoinduced local-field enhancement contribute to the improved catalytic activity under light irradiation. More impressively, plasmon-induced interfacial charge transfer between single CuAg NPs and reactant molecules was explored in situ by a single-particle confocal microscope system, and a complete photoluminescence (PL) quenching phenomenon of CuAg NPs was observed when immersed in a methanol solution, not ammonia borane. The PL quenching indicates the transfer of hot electrons to methanol, which is the rate-limiting step of the AB dehydrogenation reaction. In contrast, charge transfer from the plasmonic NP to AB (the most widely proposed path to date) does not work here. This work provides direct evidence for the hot electron transfer from CuAg to methanol via single-particle PL measurement and provides insights for plasmon-enhanced AB methanolysis.

Carbothermic Reduction and Nitridation Mechanism of Vanadium-Bearing Titanomagnetite Concentrate

In this study, the carbothermic reduction and nitridation mechanism of vanadium-bearing titanomagnetite concentrate are investigated in terms of phase transformation, microstructure transformation, and thermodynamic analyses. The differences in the reaction behavior of titanomagnetite and ilmenite in vanadium-bearing titanomagnetite concentrate, as well as the distribution characteristic of V in the roasted products, are emphatically studied. It is observed that the reaction sequences of titanomagnetite and ilmenite transformations into nitride are as follows: Fe3−xTixO4→Fe2TiO4→FeTiO3→M3O5→(Ti, V)(N, C); FeTiO3→M3O5→Ti(N, C). The reduction of M3O5 to TiN is the rate-limiting step of the entire reaction, and metal iron is an important medium for transferring C for the reduction of M3O5. Titanomagnetite is faster to convert into nitride than ilmenite is, and the reasons for this are discussed in detail. During the entire roasting process, V mainly coexists with Ti and seems to facilitate the conversion of titanium oxides into (Ti, V)(N, C).

Promotion of diphosphine ligands (PPh2(CH2) PPh2, n = 1, 2, 3, 5, 6) for supported Rh/SiO2 catalysts in heterogeneous ethene hydroformylation

• PPh 2 (CH 2 ) n PPh 2 (L n, n = 1, 2, 3, 5, 6) were used as ligands to modify Rh/SiO 2 . • Modifying Rh/SiO 2 by L5 increased activity ~100 times and selectivity to 97%. • CO transient experiments demonstrated activity limitation imposed by H addition. • L5 and L6 exhibited the best promotion while L1 and L2 had only slight effect. Hydroformylation is applied in industry to convert olefin and syngas to value-added products. Rh promoted by phosphine ligands are highly efficient catalysts for this reaction. The promotion mechanism of phosphines has been well studied in homogeneous system. It is important to extend the use of these ligands to heterogeneous system. The dpp* (PPh 2 (CH 2 ) n PPh 2 , n = 1, 2, 3, 5 and 6) ligands were introduced to Rh/SiO 2 and the ethene gaseous hydroformylation reaction was tested. Compared to unmodified Rh/SiO 2 , all the catalysts modified by phosphine showed enhanced activity (~100 times higher for the best ligand) and oxygenate selectivity (from 65% to ~97%). Among the investigation, L5 and L6 ligands exhibited the best performance while L1 and L2 only gave slight promotion. CO cutoff transient experiments were designed to identify the rate-limiting step (RLS) of hydroformylation reaction over the present catalysts. A mechanism was proposed for the change of RLS over the phosphine modified catalysts. Combined with in situ FTIR results, the relationship between electronic state and catalytic activity of the catalyst was verified.

Promote reactants activation and key intermediates formation for facilitated toluene photodecomposition via Ba active sites construction

The establishment of active sites can obviously promote photocatalytic efficiency, but its role in activation mechanism and generation of key reaction intermediates during toluene mineralization remains unsolved. We reveal that the benzene ring opening is the rate-limiting step of mineralization reaction, and the inert CC bond in the ring is the crucial reason for the shortage mineralization of previous catalysts. In this work, the Sr1-xBaxTiO3 solid solution was prepared as a model photocatalysts to reveal the mechanism of photocatalytic toluene degradation. The electronic local center was constructed at the substituted Ba sites, which intensified the charge transfer between catalyst surface and adsorbed molecules. The strong oxidative species generated by enhanced activation further facilitated the conversion of toluene to generate benzoic acid as the key reaction intermediate before ring-opening. Through the combined theoretical calculation and in situ characterization methods, it was revealed that efficient degradation and stable mineralization of toluene in photocatalysis can be achieved by activating toluene and promoting the formation of key reaction intermediates. This study could advance a new viewpoint for safe and efficient photocatalytic air purification.

Understanding the enhancement of CaO on water gas shift reaction for H2 production by density functional theory

The water gas shift reaction is an important reaction for H2 production in various industrial applications. The presence of CaO can promote the reactivity of the water gas shift reaction without any catalysts, but the enhancement mechanism of CaO in this reaction is difficult to determine just by the experiment. In this work, the water gas shift reaction along four possible pathways on the CaO surface were studied by density functional theory (DFT) analysis. The energy barriers along the pathways were analyzed to determine the most possible reaction pathway and role of the CaO surface. The DFT calculation results show that the WGS reaction is more prone to proceed along the redox-a pathway probably: H2O dissociates into hydroxyl and atomic H spontaneously when H2O and CO co-adsorb on the CaO surface, then the hydroxyl continues to dissociate and CO is oxidized by the generated atomic O. Afterwards, H2 molecule generates from two atomic H, and then CO2 adsorbs and H2 desorbs simultaneously on the CaO surface. The CaO surface enables the spontaneous dissociation of H2O, which is the rate-limiting step of WGS reaction. The generation of CO2 is facilitated, and the energy barrier is reduced from 2.304 to 0.757 eV on the CaO surface. Besides, the formation of CO32− on the surface avoids the energy barrier for CO2 desorption, while the CO2 also occupies the active site and reduces the enhancement of CaO on WGS reaction. The calculation result reinforces the comprehension on the mechanism of CaO on WGS reaction.

Particle carbonation kinetics models and activation methods under mild environment: The case of calcium silicate

CO2 mineralization is an economical technology with a low carbon footprint and has been considered an effective means to achieve carbon fixation. The slow diffusion and reaction in the gas-solid system of CO2 mineralization is a common issue affecting the normal carbonation depth. The surface water plays a critical role as an ionic mass transferring medium in the reaction systems. By studying the CO2 mineralization of dispersed calcium silicate (CS) particles, this work systematically revealed the kinetics and mechanisms of carbonation under mild environments (below 80°C). It was interesting to find that carbonation of CS particles followed different kinetic mechanisms depending on the temperature and with the migration of surface water. At 20°C, the CO2 mineralization reaction conformed to the unreacted shrinking-core mechanism with the primary reaction rate-limiting step of product layer diffusion. For higher temperatures (40–80°C), the carbonation process was controlled by the surface water coverage. The leaching behavior of CS indicated that electrical double layer (EDL) formed at the particle interface and limited Ca2+ activity in water film might be the mechanism of surface water coverage controlled kinetics. Accordingly, the enhanced CO2 mineralization of CS, 58.16% CO2 uptake increment, was realized at 80°C through rehydration activation. The evolution of mineral micromorphology with process of leaching and carbonation is characterized by semi-quantitative XRD analysis and mercury intrusion porosimetry analysis. CO2 mineralization kinetics and the proposed activation method under mild environment open the door to efficient CO2 mineralization with low energy consumption.

Load CoOx cocatalyst on photoanode by spin coating and calcination for enhanced photoelectrochemical water oxidation: A case study on BiVO4

Water oxidation reaction is the rate-limiting step of the water splitting reaction. Loading water oxidation cocatalyst can effectively improve water oxidation performance. It is challenging to efficiently load water oxidation cocatalyst on photoanodes for photoelectrochemical water oxidation. In this work, CoOx was loaded on BiVO4 by a facile spin coating and calcination method. The photocurrent of the as-prepared CoOx/BiVO4 photoanode reached 2.73 ​mA/cm2 at 1.23 ​V vs RHE, which is comparable to that of CoOx/BiVO4 photoanode prepared using other methods. The H2 and O2 production reach 130.8 and 61.9 ​μmol respectively in 3 ​h test. All experiment results show that the improved photocurrent could be ascribed to enhanced charge separation efficiency and charge injection efficiency.

Proposal of the reaction environment for effective use of structured catalyst

Micro-partition (MP) is a structure with microscale fins and holes, and Micro-partition structured catalyst (MPC) was applied to water-gas shift (WGS) and catalytic hydrogen combustion (CHC) reactions. The use of MPC led to an improvement of the reactivity of both reactions owing to its characteristic structure mixed the reactants fluid, while the effect of MPC stacking on the reactivity improvement was different. The effects of MPC structure and stacking on the reactivity were evaluated for these reactions focusing on a rate-limiting step. The rate-limiting step for WGS and CHC reactions were a chemical reaction and an external mass transfer, respectively. It was suggested that the factors that improved the reactivity owing to the structure of MPC differed from one rate-limiting step to another. And, the ratio of the turnover frequency of each MPC stacking condition to that of the plate-type catalyst was calculated to quantitatively evaluate the effect of reactivity improvement. Furthermore, the effect was almost temperature-independent for CHC, while it was larger at lower temperatures for WGS. That was, the reactivity improvement was enhanced by appropriate MPC stacking at lower temperatures under a rate-limiting step of a chemical reaction.

A catalytic reaction scheme for NO reduction by CO over Mn-terminated LaMnO3 perovskite: A DFT study

LaMnO3 perovskite has been regarded as a promising catalyst for the selective catalytic reduction of NOx with CO. The relationship between the active sites and CO-SCR activity of LaMnO3 perovskite was investigated through density functional theory calculations. All possible reaction steps were proposed to comprehend the CO-SCR catalytic mechanism of NO on LaMnO3 catalyst. The results show that the Mn site at LaMnO3 surface is the dominant active site of NO reduction. The adsorption of reactants (NO and CO) on LaMnO3 surface is controlled by the chemisorption mechanism. N2O2* produced from NO coupling reaction is a crucial reaction intermediate of SCR reaction. N2O2* further reacts with the chemisorbed CO to form CO2 and N2O* intermediate with an activation energy barrier of 50.20 kJ/mol. The activation energy barrier of NO decomposition on LaMnO3 surface is larger than that of N2O2* formation, which suggests that the bimolecular mechanism is responsible for the CO-SCR of NO over LaMnO3 catalyst. The reaction pathway of CO-SCR on LaMnO3 surface contains three steps: 2NO* → N2O2*, N2O2* + CO* → N2O* + CO2 and N2O* + CO* → N2 + CO2*. The rate-limiting step of CO-SCR reaction on LaMnO3 surface is the reduction of N2O.

A cobalt-free bismuth ferrite-based cathode for intermediate temperature solid oxide fuel cells

High catalytic activity of cathode material is one of the key requirements for the practical application of solid oxide fuel cells (SOFC). Here we designed and evaluated a novel non-metal P-doped (Bi, Sr)FeO3−δ, i.e., Bi0.5Sr0.5Fe0.95P0.05O3−δ (BSFP) oxide, as cathode material. BSFP with a cubic structure presents excellent chemical compatibility with Ce0.9Gd0.1O1.95 (GDC) electrolyte after sintering at 1100 °C. Impedance analysis reveals its polarization resistance (Rp) is as low as 0.18 Ω cm2 at 700 °C. Further kinetics study suggests the low-frequency process is the rate-limiting step of the oxygen reduction reaction (ORR). An anode-supported single cell delivers attractive power output of 0.56 W cm−2 at 700 °C. The electroactivity is superior to undoped (Bi, Sr)FeO3−δ, indicating that BSFP perovskite could be a promising cathode for SOFC operating at intermediate temperatures.

Kinetics and mechanistic aspects of removal of heavy metal through gas-liquid sulfide precipitation: A computational and experimental study

The production of fine particles from extremely high supersaturation has challenged the application of sulfide precipitation in treating heavy metal wastewater due to the difficulty of solid-liquid separation. To this end, a gas-liquid sulfide precipitation reactor for the removal of Cu2+ was designed by controlling the mass transfer and supersaturation levels during sulfidation processes. Particularly, a computational fluid dynamics (CFD) model of the reactor, integrating sulfidation reaction kinetics with two-phase flow hydrodynamics, was first built, followed by examining the effects of H2S(g) bubble diameter and flow rate. Based on the CFD simulation, the rate-limiting step of the gas-liquid sulfide precipitation reaction is the gas-liquid mass transfer process. Either reducing H2S(g) bubble diameter or increasing H2S(g) flow rate can result in the control of reaction rate and supersaturation level in the system. In order to validate the CFD simulations, we measured Cu2+ concentrations during the sulfidation process with the batch experiments. The agreement between computational and experimental results indicated that our mechanistic model can provide a protocol for the design and optimization of the reaction system, allowing one to visualize the time-dependent reaction process and evaluate the performance of a reactor.

Galvanic corrosion of zero-valent iron to intensify Fe2+ generation for peroxymonosulfate activation

Zero-valent iron (ZVI) usually activates peroxymonosulfate (PMS) through the generation of Fe2+ from the self-corrosion of ZVI in a Fenton-like reaction. However, the generation rate of Fe2+ forms the reaction rate-limiting step. Against this, a microscopic Fe-graphitic carbon galvanic cell array (GCA) was created to intensify the PMS activation process. The synergistic effect between a ZVI anode and a graphitic carbon cathode accelerated the generation of Fe2+ via ZVI galvanic corrosion to significantly increase the PMS activation performance. Distinctive short-circuiting of the anode and cathode in GCA effectively enhanced the galvanic corrosion. The electrochemical behavior of GCA was characterized in detail to elucidate the PMS activation mechanism. The microscopic Fe-graphitic carbon galvanic cell array provided a promising pathway for pollutant remediation.

Isotope-reinforced polyunsaturated fatty acids improve Parkinson\u2019s disease-like phenotype in rats overexpressing \u03b1-synuclein

Lipid peroxidation is a key to a portfolio of neurodegenerative diseases and plays a central role in α-synuclein (α-syn) toxicity, mitochondrial dysfunction and neuronal death, all key processes in the pathogenesis of Parkinson’s disease (PD). Polyunsaturated fatty acids (PUFAs) are important constituents of the synaptic and mitochondrial membranes and are often the first molecular targets attacked by reactive oxygen species (ROS). The rate-limiting step of the chain reaction of ROS-initiated PUFAs autoxidation involves hydrogen abstraction at bis-allylic sites, which can be slowed down if hydrogens are replaced with deuteriums. In this study, we show that targeted overexpression of human A53T α-syn using an AAV vector unilaterally in the rat substantia nigra reproduces some of pathological features seen in PD patients. Chronic dietary supplementation with deuterated PUFAs (D-PUFAs), specifically 0.8% D-linoleic and 0.3% H-linolenic, produced significant disease-modifying beneficial effects against α-syn-induced motor deficits, synaptic pathology, oxidative damage, mitochondrial dysfunction, disrupted trafficking along axons, inflammation and DA neuronal loss. These findings support the clinical evaluation of D-PUFAs as a neuroprotective therapy for PD.

The Role of Local Heating and Phosphate Poisoning during the Oxygen Reduction Reaction in Solid Acid Fuel Cells

With the ongoing effort to decarbonize and decentralize the electricity infrastructure by shifting to renewable energy sources, fuel cells and in particular intermediate temperature fuel cells receive a growing interest as a promising technology for a highly efficient, on demand transformation of chemical into electrical energy. Since the 2000s, fuel cells have cycled from high expectations to disillusion, caused by the high production cost an insufficient stability. High temperature polymer electrolyte membrane fuel cells (HT PEM FC) are a prominent and well investigated candidate for the intermediate temperature range. However, the usage of concentrated, highly corrosive phosphorous acid as membrane dopant required expensive production materials and causes deterioration of the catalyst over time. Changing from a liquid to a solid electrolyte can simultaneously improve the long term stability and reduce the construction price. A suitable solid acid is CsH2PO4. It is a non-toxic and less corrosive electrolyte with a proton conductivity of 2*10-2 S/cm at 240°C.[1] Since first demonstrated for fuel cell fabrication in 2003,[2] the platinum utilization and power densities have been improved ever since.[3,4] Solid acid fuel cells (SAFC) are already used in industry in a small scale, but the development has been hampered by the poor stability of the cathode electrode. The rate limiting reaction step is the complex oxygen reduction reaction (ORR) at the cathode side. During operation, it is the largest source of overpotential and hence waste heat generation.[5] For an active site, the current collector, electrolyte and gas phase need to be in direct contact with each other to provide all necessary reactants, thereby the interface resistance between the current collector and the catalyst is crucial for the performance.In the work we are going to present, we investigated electrodes based on a platinum thin film catalyst layer.[6,7] These electrodes enable us to investigate degradation effects on a reasonable time scale. We will show that only a few areas close to the current collectors meet the requirements for active sites and consequently generating most of the measured current, leading to a localized heating. We observed a current density depended morphology chance of CsH2PO4 during operation at these active sites, located close to the current collector. While a variety of degradation processes can result from this process, we determined a phosphate adsorption on the catalyst as the most pronounced one. Similar to HT PEM FC, phosphate species from the electrolyte can adsorb at the platinum surface and act as catalyst poison.[8–10] We will present, that these poisoning effects can be reversed but not prevented by cyclic voltammetry (CV) measurements. After reactivating the cell by CV measurements, the cell performance increased to the initial value before degrading again. The reversibility of the process was shown for five reactivations over a period of 50 h. Overall, we identified the cause and nature of the main degradation mechanism in solid acid fuel cells with platinum thin film electrodes and will present different design optimizations for a stable, high performance fuel cell which arise from our findings.

Partial Reactions of the Na,K-ATPase: Determination of Activation Energies and an Approach to Mechanism

Kinetic experiments were performed with preparations of kidney Na,K-ATPase in isolated membrane fragments or reconstituted in vesicles to obtain information of the activation energies under turnover conditions and for selected partial reactions of the Post-Albers pump cycle. The ion transport activities were detected with potential or conformation sensitive fluorescent dyes in steady-state or time-resolved experiments. The activation energies were derived from Arrhenius plots of measurements in the temperature range between 5 °C and 37 °C. The results were used to elaborate indications of the respective underlying rate-limiting reaction steps and allowed conclusions to be drawn about possible molecular reaction mechanisms. The observed consequent alteration between ligand-induced reaction and conformational relaxation steps when the Na,K-ATPase performs the pump cycle, together with constraints set by thermodynamic principles, provided restrictions which have to be met when mechanistic models are proposed. A model meeting such requirements is presented for discussion.Graphic

Reaction mechanism of Ca2Fe2O5 oxygen carrier with CO in chemical looping hydrogen production

The CO adsorption behavior, CO oxidation and oxygen anion diffusion of Ca2Fe2O5(010) surface were systematically investigated to deeply understand the reaction mechanism of Ca2Fe2O5 oxygen carrier with CO based on density functional theory (DFT) calculations. The results indicate that the activity of CO adsorption on four terminations of Ca2Fe2O5(010) surface follows the order: FeO2- terminated > FeO-terminated > CaO-terminated > OCa-terminated. Four reaction pathways for CO oxidation were proposed. It was found that CO oxidation reaction is very easy to proceed, and that both types of surface oxygen (O1 and O2) could exhibit high activity. The oxygen diffusion in Ca2Fe2O5 is inherently a high-temperature process. In addition, the energy barrier of oxygen diffusion is much higher than that of CO oxidation, implying that oxygen diffusion is the rate-limiting step for the entire reaction between Ca2Fe2O5 oxygen carrier and CO. The superior reactivity of Ca2Fe2O5 oxygen carrier is attributed to its excellent surface oxygen activity and good oxygen diffusion ability.

Insights of the mechanisms for CO oxidation by N2O over M@Cu12 (M = Cu, Pt, Ru, Pd, Rh) core-shell clusters

Catalytic conversion of N2O and CO to the nonharmful gases can relieve many environmental problems caused by them. A density functional theory study is performed to investigate the CO oxidation by N2O over the M@Cu12 (M = Cu, Pt, Ru, Pd, Rh) core-shell clusters. The stability of clusters and the adsorption of N2O are enhanced with the doping of noble metals which act as the electron collectors according to the NBO analysis. Two mechanisms (the stepwise adsorption mechanism and the co-adsorption mechanism) with adsorption of N2O on metallic clusters by N end and O end are well-established. On these clusters, the highest activation energy for the N2O decomposition to yield N2 is predicted to be 7.7 kcal/mol. The average barrier for the subsequent CO oxidation is about 14 kcal/mol, which is the rate-limiting step for the overall reaction. Overall, this oxidation process is both thermodynamically and kinetically favorable on Cu-based core-shell clusters. By comparison, the alloy clusters exhibit superior catalytic activities compared to pure Cu cluster for the rate-limiting step.

Kinetic and Spectroscopic Characterization of the Catalytic Ternary Complex of Tryptophan 2,3-Dioxygenase.

The first step of the kynurenine pathway for l-tryptophan (l-Trp) degradation is catalyzed by heme-dependent dioxygenases, tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase. In this work, we employed stopped-flow optical absorption spectroscopy to study the kinetic behavior of the Michaelis complex of Cupriavidus metallidurans TDO (cmTDO) to improve our understanding of oxygen activation and initial oxidation of l-Trp. On the basis of the stopped-flow results, rapid freeze-quench (RFQ) experiments were performed to capture and characterize this intermediate by Mössbauer spectroscopy. By incorporating the chlorite dismutase-chlorite system to produce high concentrations of solubilized O2, we were able to capture the Michaelis complex of cmTDO in a nearly quantitative yield. The RFQ-Mössbauer results confirmed the identity of the Michaelis complex as an O2-bound ferrous species. They revealed remarkable similarities between the electronic properties of the Michaelis complex and those of the O2 adduct of myoglobin. We also found that the decay of this reactive intermediate is the rate-limiting step of the catalytic reaction. An inverse α-secondary substrate kinetic isotope effect was observed with a kH/kD of 0.87 ± 0.03 when (indole-d5)-l-Trp was employed as the substrate. This work provides an important piece of spectroscopic evidence of the chemical identity of the Michaelis complex of bacterial TDO.

Modeling and Optimization of Aqueous Mineral Carbonation for Cement Kiln Dust Using Response Surface Methodology Integrated with Box-Behnken and Central Composite Design Approaches

Carbon capture and storage (CCS) is an attractive area of research in such fields as CO2 mineral carbonation, global warming and sustainable energy systems. In this study, carbonation efficiency for aqueous mineral carbonation (MC) was achieved through two steps, which include leaching of calcium from cement kiln dust (CKD) followed by the reaction of pure CO2 with the calcium hydroxide precipitates formed by the hydroxylation using NaOH. Response surface methodology (RSM) with a Box-Behnken design (BBD) was applied to optimize the calcium leaching yield, while the carbonation efficiency from CKD was assessed using RSM with central composite design (CCD). Optimization of calcium leaching is highly important, as it is a rate-limiting reaction step in MC and also influences and enhances carbonation efficiency. Different parameters including acid concentration (HNO3), leaching temperature, leaching time, and dose of CKD sample were considered in order to optimize the maximum yield of Ca leaching from the CKD sample. In addition, different CO2 flow rates and temperatures were used as parameters for optimizing carbonation efficiency. Two quadratic regression models were developed for each process, i.e. calcium leaching and carbonation. For calcium leaching, a maximum of 98.55% calcium was extracted under the optimal set of acid concentration 4.13 M, 90 °C, 28 min leaching time, and 13.8 g of CKD sample. For carbonation, the maximum carbonation efficiency of 89.2% was achieved for a CO2 flow rate of 1163 cm3/min at 90 °C. Calcium leaching results indicate that the leaching yield was significantly affected by all the input parameters except leaching time. For carbonation, both factors affected the carbonation efficiency, with the effect temperature shown to be greater than that of the CO2 flow rate. Additionally, the predicted results agreed well with the experimental values for both calcium leaching and carbonation processes, with errors of less than 1% and 5%, respectively.

Simple Method for the Assessment of Peroxiredoxin Activity in Biological Samples

Abstract The current study describes a simple spectrophotometric protocol for the assessment of peroxiredoxin (Prx) activity and demonstrates its reproducibility, accuracy, and precision. The dissociation of organic or inorganic peroxide represents the rate-limiting step for reactions regulated by the Prx enzyme. In the current protocol, Prx enzyme activity was assessed by incubating enzyme samples with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer, containing suitable concentrations of the substrates, organic or inorganic peroxide and 1,4-dithio-DL-threitol (DTT). At the end of the incubation period, a solution containing sulfosalicylic acid (SSA) and ammonium ferrous sulfate was added to stop the enzymatic reaction. SSA acts as a ligand to link the ferric ion formed by the reaction between ferric ammonium sulfate (FAS) and residual peroxide, producing a maroon-colored ferrisulfosalicylate complex, which was spectrophotometrically measured at 500 nm. This method does not require the use of strong acids at high concentrations to stop the enzymatic reaction. Also, the novel method was validated against a Bland–Altman plot analysis of Prx activity using the thiocyanate method in matched samples. The comparison between the sulfosalicylate and thiocyanate methods resulted in a correlation coefficient equal to 0.9976, demonstrating that the novel sulfosalicylate method is on par with the reference method.