pH Variation Research Articles

Advanced, Cutting-Edge RP-HPLC Methodology for the Comprehensive Quantitative Analysis of Assay of Bictegravir, Emtricitabine, and Tenofovir Alafenamide in Co-Formulated Pharmaceutical Products.

In the current study, a simple and economic stability-indicating RP-HPLC method development and validation was carried out to estimate the bictegravir, emtricitabine and tenofovir from the pharmaceutical dosage form. 0.1M ammonium acetate in 0.5% v/v acetic acid solution and 1g of 1-octane sulfonic acid and adjustment of pH to 4.2 with dilute orthophosphoric acid done and methanol (40:60 v/v) was utilized as the mobile phase. The analysis was done using Inertsil ODS 3V (250 x 4.6 mm x 5 µm) column with column temperature kept at 30°C with an injection volume of 20 μL, flow rate of 1.0 ml/ minute and detection was carried out at 260 nm. The method was developed and it was validated according to ICH Q2 (R1) guidelines. The RT of bictegravir, emtricitabine and tenofovir were determined to be 12.23, 3.0 and 8.5 minutes, providing a reliable marker for its identification. The method was found linear from about 50 To 150% Of the target concentration of bictegravir emtricitabine and tenofovir with of 0.999. Significant degradation was observed in acidic, basic and peroxide stress conditions. Hence, it can be concluded that tablets are sensitive to acidic, basic and oxidation stress conditions. RSD for the peak area responses of emtricitabine, 0.03 and 0.03, respectively, indicating that the system is precise. The testing procedure was accurate from about 50 to 150%. Of the target concentration of emtricitabine, tenofovir alafenamide and bictegravir. The method was robust In relation to flow variation, column oven temperature variation, mobile phase variation and pH variation. In conclusion, our proposed RP-HPLC method provides a sensitive, accurate, and precise means of analyzing emtricitabine, tenofovir alafenamide and bictegravir from pharmaceutical dosage forms.

Exploring the influence of pH on structural and magnetic properties of lead-free double perovskite, La2CoFeO6 nanoparticles

Lead free perovskite is at the center of the present study due to its multifunctional properties. In the present work, pH (0–5) of the solution during the synthesis of La2CoFeO6 (LCFO) nanoparticles has been varied to study its impact on structural and magnetic properties. X-ray diffraction(XRD) pattern confirms the formation of LCFO nanoparticle with pH variation. Rietveld refinement of the XRD patterns indicates that the LCFO is formed in mixed phase of orthorhombic and rhombohedral structure. The percentage contribution of orthorhombic phase decreases with an increase in the pH value. Morphological studies show the increment in the particle size with pH value (from ∼16 nm to ∼32 nm). Structural and morphological investigations indicate that LCFO prepared at pH 0 are highly agglomerated and may have some amorphous phases. Magnetization curves indicate the ferromagnetic response for the LCFO nanoparticles at pH-0. The maximum magnetization (M S ) is found to decrease whereas coercivity (H C ) increases with the increase in pH value. This could be attributed to the structural changes incorporated and presence of anti-site disorder due to the variation of pH. A large exchange bias effect has also been noticed at 60 K for all the LCFO samples.

Physico-Chemical and Structural Characterization of Mixed Natural Polymer Hydrogels Under Simulated Gastrointestinal Fluid

The gastrointestinal track has a varied pH, from an acidic pH in the stomach to a slightly basic pH in the intestine. The pH difference creates problems for the delivery of drugs and nutrients, as the active compounds may not survive the changing pH. Incorporating active ingredients into hydrogels can protect the compounds from degradation. Natural polymer hydrogel is preferable because of its safety and compatibility. However, a suitable formula should be optimized to facilitate suitable delivery in the gastrointestinal track. In this study, we produced hydrogels with 10 different formulas of mixed natural polymers: CMC (C), alginate (A), chitosan (X), and/or guar gum (G). The resulting hydrogels were characterized using swelling performance tests at pH 2 and 6.8, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Hydrogels with the formula of C50A25X25, C25A50X25, C25A50G25, C25A25G50, C25A50X12.5G12.5, and C25A25X25G25 are not digested at pH 2, but those hydrogels are digested at pH 6.8. The FTIR spectra of the hydrogels show functional groups of O–H, C=O, C–O, and C–H. Meanwhile, the SEM results show cracking phenomena on the surface of the hydrogels C50A25X12.5G12.5, C25A50X12.5G12.5, and C25A25X25G25. This study offers a general guide for the development of a natural polymer hydrogel as a suitable nutrient vehicle in the gastrointestinal track. Formulation of each type of nutrient should be optimized for optimum delivery to the designated part of the gastrointestinal track.

Brazilian bentonite/MgO composites for adsorption of cationic and anionic dyes.

Industrial effluents, especially those containing dyes, have become the main cause of contamination of water resources. In this context, Brazilian bentonite/MgO composites, with excellent adsorptive properties, were prepared and investigated for their effectiveness in removing cationic and anionic dyes from aqueous solutions. The new adsorbents were obtained using Brazilian bentonites and MgO using the mechanochemical method followed by heat treatment (at 700°C for 4h). Different characterization techniques were used for the chemical, mineralogical, thermal, surface, and morphological analysis of the raw clays and the composites. The experimental adsorption isotherms were quantified under different conditions of initial concentration, contact time, pH, adsorbent dosage, and temperature variation to interpret the adsorption mechanism of the crystal violet (CV) and Congo red (CR) dyes. The modeling results were obtained from the empirical Sips equation and Pseudo Second Order (PSO) kinetics, indicating that the adsorption of molecules is a heterogeneous phenomenon that occurs in a monolayer on the surface (ns > 1), with the adsorption rate determined by chemisorption. The composites showed the best removal efficiency performance compared to the raw bentonites, with an increase of 12% for the CV dye and 46% for the CR dye. In addition, the qmax values obtained were 423.02mg/g and 479.86mg/g (AM01). This research underscores the potential of Brazilian bentonite/MgO composites as a promising solution for the removal of cationic and anionic dyes from water, offering hope for future applications in the field of environmental engineering and materials science.

Gigartina skottsbergii Setchell & N.L.Gardner (Rhodophyta) Incorporated Organic@Inorganic Hybrid Cu3(PO4)2 Nanoflowers with an Intrinsic Antioxidant and Catalytic Activities

AbstractIn this study, the extract of one of the red algae, Gigartina skottsbergii was used for synthesis of organic@inorganic hybrid nanoflower (hNFs) for the first time. hNFs were sytematically synthesized with different concentrations of algal extract (from 0.5 to 1.65 ml) and Cu2+ in different pHs (7.4 and 9) of PBS. Hierarchical synthesis of hNFs in the PBS buffer did not occur in the acidic medium (pH: 5). The morphological structures of hNFs were detailed with FE-SEM images. hNFs synthesized in morphology closest to the ideal flower structure with variable algal extract concentrations and pH were determined by FE-SEM. Organic and inorganic groups (structural components of hNFs), crystallinity of optimum synthesized hNFs were detailed by FT-IR, EDX and XRD analysis, respectively. It has been recorded that synthesized hNFs have antioxidant properties. hNFs have captured catalytic dyes with peroxidase-like activity. The ability of hNFs in destroying the dye in the presence of H2O2 has been attributed to the Fenton reaction. As a result, an easily applicable, inexpensive, one-step catalyst was synthesized using the Fenton mechanism. It is foreseen that the study data can be applied for nanotechnology field and basic sciences.

Orange Peels as Activated Carbon Charcoal For Cu (II) Ions Elimination From Water Sources

Objectives: The goal of this work is to create inexpensive Orange Peel Activated Carbon (OPAC) for the environmentally friendly to eliminate of Cu (II) from its aqueous solution. Methods: activated carbon made by calcining orange peels at 500°C to cause them to burn. Methods: The samples were characterized using FTIR, transmission electron microscopy, and nitrogen adsorption-desorption. Cu (II) was adsorbed in a batch procedure utilizing 0.25 g of (OPAC) and 100 mL of solution with varying beginning concentrations ranging from 20–80 mg/L. The investigation focused on the effects of variables pH, temperatures, concentrations, dosages, and times on the adsorption capacity. Thermodynamic parameters were computed, adsorption kinetics were assessed using pseudo-first and pseudo-second-order were computed models, and the adsorption isotherms were fitted using the Langmuir and Freundlich models. Findings: The stretching of the hydroxyl groups is shown by peaks at 3100 and 4000 cm-1 as well as the 3300–3800 cm-1 region in the FTIR. Findings: the functionalized (OPAC). N2 adsorption isotherm revealed a hysteresis loop in the p/p0 region between 0.2 and 1. The surface area of obtained mesoporous OPAC was 0.99 nm. The maximum adsorption capacity (79.056 mg/g). Removal of Cu (II) was 99%. The adsorption process was spontaneous and less random, as indicated by the negative values of thermodynamic parameters (∆S° -14.0, ∆H°-54.76, and ∆G°-60.36 kJ.mol-1). According to the findings, orange peel has a high surface area and is highly porous, which allows it to effectively remove over 99% of harmful heavy metals from water sources. Novelty: The study proves that orange peel can be effectively used as one of the best-quality, reasonably priced, readily available, eco-friendly bio-sorbents that is also beneficial to the economy in the long run. Keywords: Orange peel, Cu (II), Adsorption, Kinetic, Thermodynamic, IFTR

Application of SECM to detect a local electrolyte acidification due to the hydrogen flux desorption from a cathodic charged stainless steel

This work aims to estimate local pH variations of a hydrogen charged sample using Scanning ElectroChemical Microscopy (SECM). For that purpose, the microelectrode is polarized in the cathodic domain, where the proton reduction takes place. An initial calibration suggests that cathodic current of the platinum tip is sensitive to pH variations. Then, this system was applied near the surface of stainless steel previously charged with hydrogen. Coupling this result with the analysis of the uncharged samples at two different pH, it appears that hydrogen desorption induces a local acidification which could explain the increase in dissolution kinetics after hydrogen absorption, which has been reported in many studies.

Assessing the nutrient removal performance from rice-crayfish paddy fields by an ecological ditch-wetland system

Agricultural drainage from catchments significantly impacts aquatic ecosystems due to high nitrogen and phosphorus concentrations in runoff. While original ecological ditches and wetlands have demonstrated effectiveness in nutrient load removal, the overall impact of an ecological ditch-wetland system (EDWS) on agricultural nutrient removal has received limited attention. This study conducted a field experiment to investigate the physicochemical conditions and nutrient removal efficiency of an EDWS for purifying nutrient discharge from rice-crayfish paddy fields. Variations in water temperature (WT), dissolved oxygen (DO), pH, and total suspended solids (TSS) within the EDWS were assessed. Nutrient concentrations—including total nitrogen (TN), ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), total phosphorus (TP), and soluble reactive phosphorus (SRP)—were monitored from the tillering to the ripening stage of the rice growth cycle. The evaluation of nutrient removal efficiencies in the EDWS revealed that ecological ditches exhibited higher removal efficiencies compared to wetlands. The average total removal efficiencies for TN, NH4-N, NO3-N, TP, and SRP were 37.50 %, 39.38 %, 38.62 %, 37.94 %, and 39.51 %, respectively, with peak removal efficiencies observed at specific growth stages of the rice crop. Furthermore, the study explored the influence of hydraulic retention time on nutrient removal efficiency in the EDWS, indicating higher nutrient discharge removal efficiencies under low water discharge rates. Linear regression analysis identified water discharge, influent nutrient loads, and TSS as significant factors affecting nutrient removal efficiency in the EDWS. This study provides valuable insights into the effectiveness of EDWS in purifying nutrient discharge from rice-crayfish paddy fields, highlighting their potential as sustainable solutions for nutrient management in agricultural landscapes.

A transformation and auxiliary extraction of Cr during electrokinetic removal of Cr-contaminated multilayer composite soil chamber.

Multilayer composite soil chamber was proposed to extract the Cr of contaminated site soil and insight into transformation of Cr fractionation associated with valence states. The variations of current, soil pH and moisture content were explored, as well as the migration of Cr fractionation and redistribution of Cr. Results indicated that duration of half peak current could be used to adjust treatment time and it varied among different composite ways. Moreover, extraction efficiency of Cr in soil near cathode was relatively higher and reached 60% when citric acid was used. Citric acid could promote the transformation between different Cr fractionations or different valence states. It could also improve the desorption of Cr, and could prevent excessive fluctuations of moisture content at the same time. Cr redistributed acrossed the soil chamber after extraction. When deionized water was used, Cr(VI) significantly migrated toward anode mainly in the form of exchangeable fractionation (EXC) while Fe-Mn oxides fractionation (Fe-Mn) which may be in the form of cationic Cr(III) hydroxides migrated toward cathode. When using citric acid, fractionations that were difficult to migrate of Cr, especially for Fe-Mn in site soils could be activated and became EXC and carbonate fractionation (CAR), then migrated to the anode or cathode. The migration of exchangeable Cr(III) was dramatically enhanced. But the use of citric acid could cause Cr(VI) transformation to Cr(III) near anode. In addition, during the migration process, EXC could go back to Fe-Mn again or transform to residue fractionation (RES).

Treatment of Domestic Wastewater Using Membrane Bioreactor (MBR) Pilot Plant: A Case Study of Wastewater from Kklung Hok’s Treatment Pond and The Environmental Research and Training Centre (ERTC), Pathumthani, Thailand

This research performant of Membrane Bioreactor (MBR) pilot plant for treatment of Wastewater from Khlung Hok’s treatment pond volume of 250 liter and The Environmental Research and Training Centre (ERTC) volume of 100 liter, both wastewater was mix on MBR. Aeration was fed at air flow rate 150 l/min over two hours to provide the oxygen for microorganisms. Further, Aeration was fed continuously for 6 hours. sample were collected every one hour. Result found that: the wastewater variation of pH, DO, BOD, COD, NH4+, NO2– concentration of the feed tank from Khlung Hok’s treatment pond were 7.16, 0.60 mg/l, 95mg/l, 157 mg/l, 34.96 ppm and NO2 not found and from ERTC’s wastewater were 6.87, 0.41 mg/l, 93 mg/l, 160 mg/l, 21.23 ppm and 0.043 ppm, respectively. After air flow in MBR over 2 hour the concentration of influent was found 6.64, 0.60 mg/l, 48 mg/l, 105.67 mg/l, 22.30 ppm and 0.031 ppm, respectively. And during the whole process effluent pH concentration were between 6.64-7.46, DO were between 1.11-5.8 mg/l. The removal BOD efficiency were over 89.58% (on 5th hour), COD were over 75.39% (on 4th hour), NH4 were over 53.61% of (on first hour) and were over NO2 48.71% of (on 2nd hour), respectively. Result indicated that effective removal BOD, COD, NH4+ and NO2– by MBR could be achieved and increased in scale for use in the fieldwork or the treatment of wastewater in the environment.

Spatiotemporal Variation and Influences of Acidification in the North Pacific, 1995–2019

The continuous rise in atmospheric CO2 levels has led to persistent ocean acidification, which negatively impacts marine environments crucial for marine life and alters the chemical composition of seawater. This phenomenon carries significant implications for human society. Utilizing surface seawater pH data from the North Pacific spanning 1995 to 2019, this study investigates the overall and localized spatiotemporal variations in pH within the region, as well as the factors influencing these variations. Additionally, it conducts a quantitative analysis of the different influencing factors. The findings reveal a consistent downward trend in surface seawater pH in the North Pacific, decreasing from 8.073 to 8.029, with notable seasonal variations. The highest pH values are recorded in winter, followed by spring, with lower values in autumn and summer. Spatially, the pH values are higher in the northwest and lower in the southeast, with the most pronounced acidification occurring in the central and western regions, while other areas exhibit more uniform acidification levels. Spatial correlation analysis indicates that surface seawater pH in the North Pacific generally shows a negative correlation with sea surface temperature (SST), salinity (SSS), and chlorophyll-a concentration (chl a) and a positive correlation with dissolved oxygen (DO). Among these factors, SST exerts the greatest influence on seawater pH, followed by DO and SSS. The degree of acidification varies across different regions, and the dominant influencing factors differ accordingly. In the equatorial central region (A), the primary factors are chl a and SST; in the eastern regions of China and Japan (B) and the western region of Canada (C), DO and SSS are the main controlling factors. An interaction analysis of each pair of dominant factors using the geodetector shows that their respective contributions to regions A, B, and C are 70%, 90%, and 50%, respectively. Understanding the primary factors driving acidification in different regions can aid in comprehending the biological and environmental impacts of acidification in those areas and provide valuable insights for mitigating marine acidification.

Enhanced anaerobic digestion of food waste by the addition of cobalt iron oxide

In this study, the impact of cobalt iron oxide(CoFe2O4) on the anaerobic digestion (AD) of food waste (FW) was investigated including the variations in pH, VFAs, ORP, Fe2+/Fe3+ concentrations, SCOD, dehydrogenase activity, methane production and microbial community structure. The results showed that CoFe2O4 had a positive effect on the anaerobic digestion of food waste. CoFe2O4 could promote the release of SCOD, increase the dehydrogenase concentration and reduce ORP resulting in an increase of methane production. At a CoFe2O4 concentration of 200 mg/L, the cumulative methane production reached to 414.75 mL/(gVS) which was increased by 79.1% compared to the control group(231.59 mL/(gVS)). Meanwhile, the variation of microbial community showed that CoFe2O4 could increase the relative abundance of Methanobacterium and the methane production pathway in the AD was shifted from acetoclastic to hydrogenotrophic.

Repairment of carbon steel oxide scale using Ce³⁺ and Ni²⁺ doped sol-gel technique

Corrosion of carbon steel rebars in concrete structures significantly compromises their safety, reliability, and environmental performance. This work focuses on enhancing rebar corrosion resistance by repairing the defects of oxide scale. Here, sol-gel was employed as a carrier, by which Ce3+ and Ni2+ were transferred to the oxide scale defects based on the isoelectric point theory, and deposited at these defects with the pH variation as temperature. The repaired oxide scale showed enhanced uniform elemental distribution and improved electrochemical properties, maintaining integrity even under prolonged exposure to Cl−-rich environments. Notably, the impedance modulus at 0.01 Hz (|Z | 0.01Hz) of treated samples was six times higher than untreated ones, indicating superior performance against high electric fields. This strategy shows great potential for enhancing the durability of concrete structures.

Exploring sustainable solutions: Utilizing recycled coffee grounds as a new bio‐adsorbent material for removal of Pb(II) ions from water

AbstractThis study investigates the potential of utilizing spent coffee grounds (SCG) treated with Ca(OH)2 as an adsorbent for the removal of lead (Pb(II)) ions from aqueous solutions. The SCG was subjected to sequential treatments, including washing, drying, sieving, and immersion in Ca(OH)2 solutions of varying concentrations. Adsorption experiments were conducted under different conditions to evaluate the efficiency of the adsorbent, including variations in contact time, solution pH, adsorbent dosage, temperature, and initial Pb(II) ion concentration. Characterization of the SCG before and after treatment was performed using Fourier transform infrared spectroscopy. The results revealed significant changes in the structural properties of the SCG after treatment with Ca(OH)2, leading to enhanced adsorption performance. The adsorption experiments demonstrated that the efficiency of Pb(II) ion removal was influenced by factors such as contact time, solution pH, adsorbent dosage, temperature, and initial Pb(II) ion concentration. Optimal conditions for maximum adsorption efficiency were identified as a contact time of 270 min, pH 6, adsorbent dosage of 1 g, and temperature of 313 K, resulting in a maximum adsorption capacity qmax of 18.69 mg g−1. The highest desorption rate was observed using HNO3, measured at 90.6%. The reusability efficiency of the adsorbent material was 87.98% in the first use, decreased to 75.41% after five reuses, and further reduced to 39.96% after ten reuses, indicating a decline in performance with repeated use. These findings highlight the potential of SCG as an effective and environmentally friendly adsorbent for the removal of potentially toxic elements from aqueous solutions.

Effective remediation of mercury (II) from aqueous solutions using CS-MnFe2O4-CoS-MWCNTs: Box-Behnken design optimization and adsorption isotherm, kinetics, and thermodynamics evaluation.

Mercury (Hg) is a hazardous heavy metal, non-biodegradable and toxic, posing a serious threat to aquatic life and human health. Therefore, the removal of Hg ions from contaminated water using effective and eco-friendly adsorbents is necessary. In the present study, three magnetic chitosan-based organic-inorganic nanocomposites, such as CS-MnFe2O4, CS-MnFe2O4-CoS, and CS-MnFe2O4-CoS-MWCNTs, were designed and constructed to investigate their capacity for adsorbing Hg ions from aqueous solutions. The physicochemical properties of prepared composites were characterized by various analyses. The BET analyses indicated their high surface area and porous structure, and the N2 adsorption-desorption showed that the modification of CS in three stages by MnFe2O4 and crosslinking reaction, CoS preparation, and MWCNT incorporation resulted in increased N2 adsorption. The XRD confirms the synthesis of MnFe2O4 and CoS in the CS matrix and also the distinct peaks of MWCNTs. The CS-MnFe2O4-CoS-MWCNTs showed acceptable thermal stability with 45% char yields and superparamagnetic properties with magnetic saturation (Ms) of 16 emu g-1. The interactive impacts of independent variables (pH, contact time, and adsorbent dosage) on the removal percentage of Hg(II) onto three prepared adsorbents, as well as the process optimization, were assessed by the Box-Behnken design. The optimum conditions were identified, and the data from the analysis of variance showed that the three independent factors (pH, contact time, and adsorbent dosage) significantly influenced the adsorption of Hg(II). The adsorption isotherm and thermodynamics analysis investigation showed that at low concentrations of Hg(II), the adsorption process was both endothermic and spontaneous for the studied adsorbents.

Statistical physics insights in the Allura Red adsorption on chitosan: Effects of adsorbents features, and experimental conditions

This study presents an innovative approach using statistical physical modeling to analyze the effect of experimental conditions and adsorbent features on removing Allura Red dye by chitosan. Five models based on statistical physics were employed to understand the removal mechanism under different experimental conditions, including variations in pH, particle sizes, chitosan deacetylation degrees, and temperatures. The best models were determined through rigorous statistical analysis and a detailed evaluation of the estimated parameters, considering their physical meaning and standard deviations. The models demonstrated high predictive capacity (coefficients of determination greater than 0.9 and low mean squared error values < 110). Analysis of the effects of experimental conditions revealed that a pH of 6.6, particles smaller than 0.10 mm, a high degree of deacetylation (84 %), and temperatures of 298 K and 308 K present the greatest potential for dye removal by chitosan. Furthermore, it was observed that, in general, the dye removal mechanism involves the formation of a double layer with two adsorption energies under the best experimental conditions, and the process occurs predominantly by physical forces (adsorption energy below 35 kJ/mol). This work contributes significantly to understanding how experimental conditions influence the mechanism of dye adsorption by chitosan, offering valuable and new insights for future applications and optimizations in the treatment of effluent-containing dyes.

Natural light driven plastic leaching effects on carbon chemistry in the tropical coastal waters of eastern Arabian sea: An experimental study

This study examined the effects of solar light driven plastic degradation on carbon chemistry in the coastal waters of eastern Arabian Sea along the west coast of India. The research was conducted through experimental incubations exposed to natural sunlight at multiple locations between December 2023–February 2024. Photodegradation induced a significant pH decrease (up to 0.38 ± 0.02) between controls and plastic incubations ranging from 8.17 ± 0.01 to 7.54 ± 0.02 with the highest variation in the Mumbai coast ranging from 8.13 ± 0.01 to 7.75 ± 0.03. pH variations are primarily caused by the leaching of organic acids and CO2 release during solar irradiated incubation. Plastic leaching due to natural light irradiation and subsequent changes in the water chemistry is of prime significance with dissolved organic carbon (DOC) leaching of 0.002–0.03% of plastic weight into the coastal waters. Our estimations suggest 15–75 metric tonnes (MT) of DOC release per year by plastic pollution in the eastern Arabian Sea coastal waters. Further, the fluorescent dissolved organic matter (FDOM) fragmentation, a part of DOC, may act as an organic source of synthetic contaminants and would promote heterotrophic microbial action in the coastal waters. Photodegradation of plastic and the interaction of natural DOC and plastic-derived DOC resulted in longer wavelengths FDOM, which may affect the penetration of photosynthetically active radiation in the water column, thereby impacting primary production. Finally, future research work focussing on the role of plastic pollution in coastal ocean acidification and vice-versa is essential and will be increasingly intense in the upcoming decades.

Impacts of the East Asia monsoon on the PM2.5 acidity in Hanoi

This study investigates the acidity of particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) in Hanoi, the capital city of Vietnam, and its influencing factors by analyzing measured concentrations of water-soluble inorganic ions (WSIIs) in 107 24-h samples collected between June 2021 and February 2022. The average sulfate, nitrate, and ammonium concentrations were 5.79, 3.55, and 5.46 μg m−3, respectively. Among the samples, 83 exhibited alkaline aerosols characterized by elevated ammonium-to-sulfate molar concentration ratios (ASMCR) ranging from 2.3 to 9.6, while 24 showed acidic characteristics with ASMCR ranging from 0.5 to 2.5. By employing the Extended Aerosol Inorganic Model E-AIM III, with major WSIIs as the input parameters, the estimated aerosol acidity pH ranged from 8.6 to 10.9 for alkaline aerosols and below 4.5 for acidic aerosols. These variations in ASMCR and aerosol pH highlight the distinct acidic and alkaline aerosol source regions affecting Hanoi's PM2.5 by the monsoon air masses. The Potential Source Contribution Function (PSCF) maps of NH4+ and SO42− revealed the Northeast and Southeast monsoon upwind sources of acidic aerosols over China's Guangdong coastal region and Vietnam's offshore, respectively. Alkaline aerosols were observed during the Northeast and Southwest monsoons, with upwind sources originating in South China, Thailand, and Cambodia. The emergence of the ammonium-rich source areas in South China may be attributed to China's sustained emission control measures, targeting acidic SO2 and NOx emissions while leaving alkaline NH3 emissions largely unaffected. This research provided insights into the intricate relationships between regional emissions, long-range transport, and local meteorological-driven emissions, offering valuable guidance for effective air quality management in urban environments.

Analysis of phosphofructokinase-1 activity as affected by pH and ATP concentration

A key player in energy metabolism is phosphofructokinase-1 (PFK1) whose activity and behavior strongly influence glycolysis and thus have implications in many areas. In this research, PFK1 assays were performed to convert F6P and ATP into F-1,6-P and ADP for varied pH and ATP concentrations. PFK1 activity was assessed by evaluating F-1,6-P generation velocity in two ways: (1) directly calculating the time slope from the first two or more datapoints of measured product concentration (the initial-velocity method), and (2) by fitting all the datapoints with a differential equation explicitly representing the effects of ATP and pH (the modeling method). Similar general trends of inhibition were shown by both methods, but the former gives only a qualitative picture while the modeling method yields the degree of inhibition because the model can separate the two simultaneous roles of ATP as both a substrate of reaction and an inhibitor of PFK1. Analysis based on the model suggests that the ATP affinity is much greater to the PFK1 catalytic site than to the inhibitory site, but the inhibited ATP-PFK1-ATP complex is much slower than the uninhibited PFK1-ATP complex in product generation, leading to reduced overall reaction velocity when ATP concentration increases. The initial-velocity method is simple and useful for general observation of enzyme activity while the modeling method has advantages in quantifying the inhibition effects and providing insights into the process.

Development of analytical methods and method validation for the qualitative and quantitative determination of Carboxymethyl Cellulose (CMC) in yogurt and ayran

This study presents the development and validation of analytical methods for the qualitative and quantitative determination of Carboxymethyl Cellulose (CMC) in yogurt and ayran. The methods were evaluated for their detection limit (LOD), quantification limit (LOQ), and method detection limit (MDL) across multiple samples, demonstrating robust sensitivity with MDL and LOD values of 0.03% for both yogurt and ayran. Recovery studies showed high accuracy, with recovery rates between 98% and 100%, and consistent recovery within the acceptable range of 97–103%, reinforcing the methods' reliability. The quantitative analysis exhibited strong repeatability and reproducibility, with low relative standard deviations (RSDr and RSDR), confirming minimal intra-day and inter-day variability. The calibration curves for CMC analysis demonstrated excellent linearity with high coefficients of determination (R2 = 0.9985 for yogurt and 0.9951 for ayran), ensuring accurate quantification over a wide concentration range. Measurement uncertainty analysis further validated the methods' precision and accuracy, showing low relative uncertainties for trueness, repeatability, and reproducibility. Robustness evaluations indicated that the methods maintained consistent recovery rates despite variations in pH, heating time, and sample quantity, highlighting their reliability under different conditions. For qualitative analysis, the visual images method showed exceptional performance with perfect sensitivity and specificity, accurately identifying all positive and negative samples without any false positives or negatives. This high level of accuracy makes the visual images method a valuable tool for ensuring product safety and compliance with quality standards in the dairy industry. Overall, the validated analytical methods for CMC detection in yogurt and ayran demonstrated high precision, accuracy, and reliability, making them essential for quality control and regulatory compliance in dairy production.