Dilute Phosphoric Acid 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.

Approach towards the Purification Process of FePO4 Recovered from Waste Lithium-Ion Batteries

The rapid development of new energy vehicles and Lithium-Ion Batteries (LIBs) has significantly mitigated urban air pollution. However, the disposal of spent LIBs presents a considerable threat to the environment. Recycling these waste LIBs not only addresses the environmental issues but also compensates for resource shortages and generates substantial economic benefits. Current recycling processes primarily focus on the extraction of valuable metals, often overlooking the treatment of residual waste post-extraction. This project targets the iron phosphate (FePO4) derived from waste lithium iron phosphate (LFP) battery materials, proposing a direct acid leaching purification process to obtain high-purity iron phosphate. This purified iron phosphate can then be used for the preparation of new LFP battery materials, aiming to establish a complete regeneration cycle that recovers lithium carbonate and iron phosphate from waste LFP materials for the production of LFP. The study investigates process parameters such as acid types and concentrations, leaching time, and the number of leaching cycles. The results demonstrate that, after purification, the levels of impurity metals decrease while the iron content increases correspondingly. Under optimized experimental conditions, the dilute sulfuric acid leaching rates of Al, Cu, Ca, and Ni reached 36.0%, 51.4%, 89.5%, and 90.9%, respectively. Furthermore, hydrothermal treatment in dilute phosphoric acid achieved leaching rates of 87.9%, 85.8%, 98.4%, and 99.1% for Al, Ca, Cu, and Ni, respectively. The microstructure characterization revealed significant changes in phase and grain morphology during the leaching process in dilute phosphoric acid, which are likely associated with the liberation of impurity atoms from the lattice. These findings indicate that acid leaching is highly effective in removing impurities from the iron phosphate recycled from waste LIBs.

Development and Validation of RP-HPLC Method for Quantitative Analysis of Sulfamethoxazole and Trimethoprim in Liquid Suspension: A Comparative Study with Compendial Method

Co-trimoxazole is a combination of trimethoprim or sulfamethoxazole. It is used to treat common infectious diseases, including the lung disorders, urinary disorders, and gastrointestinal infections. The current study was performed to develop a new RP-HPLC technique. The main purpose was to analyze SMX (Sulfamethoxazole) and TMP (Trimethoprim) in a liquid medium of 60mL. The analyses of SMX and TMP were performed on RP-HPLC with a C18 column (25 cm × 4.6 mm) packed with 5 µm ODS, L1 stationary phase, while the mobile phase consisted of methanol and water with a ratio of 6:4. The pH of the system was adjusted to 2.6 by using dilute phosphoric acid. The injection volume was 20μL having a flow rate of 1 mL/minute and column temperature of 40ºC. The analysis of all chromatograms was performed at a single wavelength of 254 nm. The validation of the method was determined for range, precision, linearity, specificity, accuracy, and system suitability. This method was found to be more environmentally friendly with respect to the other compendial methods, which are used for the TMP and SMX analysis.

Surface reconstruction of copper foil via electrochemical etching to proliferate CH4 production from CO2 electroreduction

Electrocatalytic CO2 reduction (eCO2R) to CH4 is a prospective approach for producing high value-added fuels. In this work, an effective approach was proposed by surface reconstruction using copper foil to facilitate eCO2R to CH4. The copper foil surface reconstruction was achieved via electrochemical etching in dilute phosphoric acid. Comprehensive characterizations suggested that the crystallinity and chemical binding energy states of the copper foil were well preserved after surface reconstruction, but the arrangement of copper atoms on the surface was adjusted. Etching time for 80 s was the most preferable condition, obtaining a uniform valley pattern structure with abundant grain boundaries, reporting the highest CH4 Faraday efficiency of 68.84% which was an order of magnitude higher compared to green foil counterpart. The relevant partial current density, CH4 production rate, and half-cell power conversion energy were measured to be −16.32 mA cm−2, 0.174 μmol s−1 cm−2, and 28.8% respectively from eCO2R at −1.3 V (vs. RHE). The in-situ ATR-IR spectroscopy confirmed that the surface reconstructed copper foil can significantly strengthen the adsorption of the *CO intermediate, facilitating its further hydrogenation to produce CH4 instead of dimerization to give C2 products. This work expanded the method of surface modification for copper foil via electrochemical etching and realized the regulation of geometric morphology on catalyst surface to obtain the desired performance for CO2 electroreduction reaction.

Analytical Method Development and Validation of Ubrogepant and their Degradation Studies in Bulk and Pharmaceutical Dosage form by RP-HPLC

An accurate, rapid economical and straight forward, reliable new analytical method was developed and validated for the quantification of Ubrogepant and their degradation studies by using RP-HPLC.In the proposed method efficient chromatographic separation was achieved by using Ammonium aecetate buffer with pH adjusted to 5.0 with dilute Orthophosphoric acid solution and methanol (30:70 v/v) as a mobile phase with a flow of 1 ml/min and Water and Acetonitrile(30:70) is used as a diluent, the wave length was observed at 280 nm with isocratic mode at ambient temperature and run time was approximately 10 min and the retention time (Rt) of Ubrogepant was observed as 4.570 min. The method validated as per ICH guidelines. System suitability parameters were studied by injecting six standard solutions of Ubrogepant and results were well under acceptance criteria. Linearity study was administered between 25% to 150% levels, Regression coefficient value was observed as 0.999. LOD and LOQ were observed as 0.02 ug/ml and 0.2 ug/ml, respectively. Precision was found to be 0.54 for repeatability and 0.33 for intermediate precision. Recovery of the drug was found to be 100.86% indicates that the recovery is in the acceptable limit. Stress conditions of degradation in Acidic, Alkaline, Peroxide and Thermal were studied for Ubrogepant and validation results were found to be satisfactory and the proposed method was suitable for regular analysis and quality control of pharmaceutical preparations.

Enhanced mechanical properties of surface modified and silica reinforced nomex sandwich composites

Nomex cored glass fiber sandwich composites find their use in several aerospace, automotive, and military applications due to their high specific mechanical properties. This study reports a novel procedure to modify/enhance the mechanical properties of Nomex sandwich composites through surface modification as well as surface nano-silica reinforcement. Surface modification of Nomex was conducted in dilute phosphoric acid solution with varying soaking times. In another set of experiments, the surface of Nomex was reinforced with different concentrations of silica particles by dipping in nano-silica suspension (NexSil™ 8). A combination of chemical modification and silica reinforcement treatments were investigated. Scanning Electron Microscopy (SEM) was used for morphological characterizations while Energy Dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM), and Fourier Transform Infrared Spectroscopy (FTIR) were used to analyze the chemical changes at Nomex surfaces. The mechanical properties of the composite samples were investigated using bend tests (i.e., 3-point and 4-point) and flat-wise compression tests. It was observed that the acid treated samples displayed an increase in flexural strength with etch time. Nano-silica reinforced composite samples also led to an enhancement in flexural as well as compressive strengths with each dip. In contrast, it was found that the compression strength values of the composite samples increased only for short acid treatment time (i.e., 30 sec), and decreased thereof for longer duration(s). Enhancement in flexural strength values were attributed mainly to an increase in Nomex-epoxy interfacial physio-chemical changes. This study demonstrates that surface treated Nomex sandwich composites, through the procedures outlined here, possess superior mechanical/structural properties as compared to non-treated ones.

SIMULTANEOUS REVERSE PHASE-HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (RP-HPLC) ESTIMATION OF AZELASTINE HYDROCHLORIDE, FLUTICASONE PROPIONATE, AND PHENYL ETHYL ALCOHOL IN DYMISTA (MEDA) NASAL SPRAY

This work reported a reverse phase-high performance liquid chromatography method for quantitative estimation of Azelastine Hydrochloride, Fluticasone Propionate, and Phenylethyl Alcohol in Nasal Spray formulation. The assay involved an isocratic elution of these components by using Intersil Octadecylsilane (C18) column (25 cm x 4.6 mm x 5 μm) using mobile phase composition of Buffer: Solvent Mixture (40:60 %v/v) and pH adjusted to 6.5 with dilute orthophosphoric acid. The flow rate was 1.4 mLmin-1 and the analytes are monitored at 254 nm. Separation was completed within 20 minutes. Calibration curves were linear with correlation coefficient more than 0.99 over a concentration range of 50%, 75%, 100%, 125%, and 150% for Azelastine Hydrochloride, Fluticasone Propionate and Phenylethyl Alcohol. The method was proven to be accurate between 50 to 150% with 98 to 102 % recovery of the actives from a spiked placebo. The method was shown to be precise yielding acceptable results for the system reproducibility and method repeatability. All the validation parameters were within the acceptance range according to International Conference on Harmonization norms. The developed method is simple and rapid which could be applied for routine estimation of the formulation.

Development and Validation Method for Simultaneous Investigation of Ambroxol Hydrochloride and N-Acetyl Cysteine In Bulk And Pharmaceutical Formulation By RP-HPLC.

A simple, precise and rapid reverse phase HPLC- SPD 20-Amethod has been developed and validated for the simultaneous investigation of Ambroxol Hydrochloride (AMB) and N-Acetyl Cysteine (NAC) in tablet dosage form. The mixture of (AMB) and (NAC) was separated on C18 5µm.column (4.5 µm × 25 cm). All separation were monitored with a SPD-20A UV-Vis detector on 210 – 400 nm wavelength at ambient temperature and flow rate of 1 ml/min. The mobile phase was phosphate buffer: acetonitrile (75:25) and pH 2.5 adjusted with dilute ortho-phosphoric acid. The retention time of AMB and NAC were found to be 8.4024 and 3.35088 respectivelythe resolution was 9.86346. The method was mean recoveries in the range of 100.4 to 100.15 for all components. The developed method can be use for the routine analysis of AMB and NAC in tablet dosage form.

Selective and noncontaminated surface polishing of medical Ti-6Al-4V titanium alloy by laser chemical processing

Selective and noncontaminated surface polishing of titanium alloy implants is crucial in the biomedical field. We employed a pulsed laser as a localized and selective heat source and dilute phosphoric acid as a corrosion solution for laser chemical polishing (LCP) of medical Ti-6Al-4V titanium alloy surface. The effect of laser fluence on the removal groove morphology of titanium alloy surfaces was systematically studied, and the characteristics and mechanisms of material removal were further discussed. The results show that the groove morphology of the workpiece surface at different laser fluences can be classified into three categories, depending on the two-dimensional removal profile. The removal mechanism of LCP is a combination of laser etching and chemical corrosion, and chemical etching can completely remove the residues and melts produced by laser ablation. Finally, selective polishing of medical Ti-6Al-4V titanium alloy was achieved by setting appropriate process parameters. Moreover, the energy-dispersive x-ray spectroscopy analysis showed that there was no detectable chemical impurity contamination on the polished surface.

Purification of industrial wet phosphoric acid solution by sulfide precipitation in batch and continuous modes: Performance analysis, kinetic modeling, and precipitate characterization

The purification of wet-process phosphoric acid has always been a challenge for both academic and industrial researchers. A treatment unit was developed to mitigate metallic impurities, such as cadmium, from industrial dilute wet phosphoric acid solution (25% P2O5) by NaHS precipitation in batch and continuous modes. The effects of operating parameters on the purification performance were evaluated: namely Sulfur/Cd2+ molar ratio, the presence of other metallic ions besides Cd2+, temperature, and hydraulic residence time. In the batch mode, equilibrium was attained in less than 20 min; augmenting Sulfur/Cd2+ molar ratio increased the CdS precipitation effectiveness up to 86%, but temperature increment had an adverse effect. In the continuous mode, a hydraulic residence time of 40 min was necessary to reach the same yield as in the batch mode at 25 °C. Sulfidation was found to eliminate simultaneously other metallic impurities (especially Cu and As) originally present in the wet-produced phosphoric acid. Finally, NaHS precipitation was able to reduce the concentration of cadmium from 65.95 mg Cd/kg P2O5 to 11.15 mg Cd/kg P2O5 from untreated industrial WPA solution (25% P2O5) at 25 °C, which outperforms most of the published data based on alternative treatment processes.

Effects of Inhibitors Generated by Dilute Phosphoric Acid Plus Steam-Exploded Poplar on Saccharomyces cerevisiae Growth

The pretreatment of lignocellulosic biomass is important for efficient bioethanol conversion, but causes undesirable by-products that inhibit microbial growth, conversely affecting the bioconversion efficiency. In this study, the main inhibitors derived from dilute phosphoric acid plus steam-exploded poplar wood were identified as 0.22 g/L furfural, 3.63 g/L acetic acid, 0.08 g/L syringaldehyde, etc., indicating the green nature and low toxicity of the pretreatment process. The effects of the three typical inhibitors (furfural, acetic acid, and syringaldehyde) on Saccharomyces cerevisiae 1517RM growth were analyzed and shown to prolong the lag phase of microbial growth to different degrees. In all the inhibitor groups, the ergosterol secretion was boosted, indicating low cell membrane fluidity and robustness of the strain to an adverse environment. The cell electronegativity and morphology of S. cerevisiae 1517RM also changed under different growth conditions, which was helpful for monitoring the physicochemical properties of cells. Furfural, acetic acid, and syringaldehyde had a synergistic effect on each other, providing an important reference to improving the subsequent ethanol fermentation process.

Surfactant‐Assisted Dilute Phosphoric Acid Plus Steam Explosion of Poplar for Fermentable Sugar Production

AbstractIn this work, a fatty alcohol polyoxyethylene ether based nonionic surfactant named JFC−M was introduced into a dilute phosphoric acid plus steam explosion of poplar for the enhancement of fermentable sugar production. Factors influenced the pretreatment efficiency such as JFC−M, phosphoric acid, steam explosion pressure, and residence time were optimized by single factor and orthogonal test. An 86.3 % cellulose recovery rate was achieved. Besides, an 85.7 % enzymatic saccharification rate was obtained under the optimized parameters as follows: 1 : 2.5 solid/liquid rate, 2 h pre‐soaking time, 1.0 v/v% JFC−M, 2.0 wt% phosphoric acid, 2.2 MPa steam explosion pressure, 120 s residence time. The morphological and structural characteristics of samples before and after pretreatment were characterized by scanning electron microscopy, X‐ray diffraction, and Fourier transform infrared techniques, showing that the adding of JFC−M was of a notable influence on overcoming the biomass recalcitrance of feedstock and boosting cellulose digestion.

Development and Validation of Stability Indicating RP-UPLC Method for the Estimation of Pomalidomide in Bulk and Pharmaceutical Dosage Form

The present research work is mainly focussed on development of a novel, rapid, accurate and stability indicating UPLC method by using an advanced separation technique called Ultra Performance Liquid Chromatography, for the quantitative analysis of Pomalidomide in bulk and pharmaceutical dosage forms. This is a modified form of HPLC technique in which there is a significant increase in sensitivity, resolution and rapidity. The operation was carried out on a Waters Acquity UPLC instrument. Data acquisition and processing was done using Empower 2 software. The drug was eluted on an Acquity BEH C18 (50×2.1mm id, 1.7µm) analytical column with mobile phase containing 0.01M Potassium dihydrogen orthophosphate (adjusted to pH 3.5 using 0.1% dilute orthophosphoric acid (30%): Acetonitrile (70%). 0.3ml min-1 flow rate was maintained and the study was performed at 225nm using TUV detector. The drug was found to be retained at 1.682min. The number of theoretical plates and asymmetry was also found to be within the acceptance criteria. Method validation was carried out according to the ICH guidelines and the parameters namely- accuracy, precision, linearity, robustness, ruggedness, specificity, LOD and LOQ were studied. It was found that 5-30µg/ml was the linearity range and all other parameters result were found to be within the limits. Pomalidomide drug was stressed to acid, alkali, oxidative, thermal, hydrolytic and photolytic degradation and the results revealed that the developed method was capable to segregate all the degraded products from the active pharmaceutical ingredient. Hence this method can be used for routine quality estimation of drug analysis.

Exploitation of olive tree pruning biomass through hydrothermal pretreatments

The conversion of lignocellulosic materials into renewable products is performed through a process including pretreatment, enzymatic hydrolysis and fermentation, being the first one a key step in both technical and economic terms. As two of the most widely used pretreatment methods, liquid hot water (LHW) and steam explosion (SE) were compared in this work using olive tree (Olea europaea L.) pruning biomass (OTPB), an especially relevant lignocellulosic residue, largely available at low cost with no practical applications. Moreover, to achieve the best results in terms of bioproducts (e.g., antioxidants, bioethanol, oligosaccharides and the most complete use of the material) previous steps of aqueous extraction and dilute phosphoric acid treatment were added. Results show that LHW and SE performed similarly, although the former yielded the highest overall sugar recovery, 92%, at lower operation temperature (180 °C) versus 80.4% for SE at 220 °C. Ethanol production in selected conditions was however slightly better in the case of SE-pretreated samples, resulting in 72% yield compared with 63% in LHW-samples, but at different temperatures (220 °C versus 200 °C) although both pretreatments resulted in an ethanolic solution of about 4.4% (v/v).

Validated RP-HPLC Method for the Estimation of Amiloride and Hydrochlorothiazide in Combined Tablet Dosage Form

The aim of this work is to build up a rapid, exact, precise and accurate reverse phase liquid chromatographic method for the simultaneous analysis of amiloride and hydrochlorothiazide in tablet dose structure. The chromatographic strategy was normalized utilizing Hypersil ODS coulmn (250×4.6mm, 5μm molecule size) with UV detection at 210nm and flow rate of 1ml/min. The mobile phase includes phosphate buffer (pH acclimated to 2.5 with dilute Ortho Phosphoric acid) and acetonitrile in the proportion of 60:40 v/v. The linearity of proposed technique was found in the range of 5-30μg/ml (R²=0.999) for amiloride and 50-300μg/ml (R²=0.999) for Hydrochlorothiazide appropriately. The limit of detection (LOD) was discovered to be 0.10μg/ml and 0.40μg/ml for Amiloride and Hydrochlorothiazide appropriately. The limit of quantitation (LOQ) was discovered to be 0.30μg/ml and 1.20μg/ml for Amiloride and Hydrochlorothiazide separately. The retention times of Amiloride and Hydrochlorothiazide were found to be 3.258min and 2.383min separately. The technique was truly recommended and %RSD was found to be under 2 demonstrating high degree of exactness and accuracy. Subsequently proposed strategy can be effectively evaluated for the simultaneous estimation of Amiloride and Hydrochlorothiazide in promoted formulations.

Purification of recovered phosphoric acid by extracting aluminium with di-2-ethylhexyl phosphoric acid

The extraction of aluminium from dilute phosphoric acid with di-2-ethylhexyl phosphoric acid (DEHPA) was optimized using response surface methodology. The optimization was based on the experimental three-level central composite face-centred design (CCF) and was conducted on real-life samples. The three variables included were pH, extractant concentration and aqueous to organic phase ratio (AO). Under the optimized conditions (pH 2.5, 0.6 M DEHPA and AO ratio 1:2), extraction efficiency of 99% for aluminium in four extraction stages is achieved. The purified phosphoric acid solution can then be utilized by the fertilizing industry. Stripping tests for organic phase loaded with aluminium were conducted with sulphuric acid. Extremely high stripping efficiency was obtained with 0.9 M sulphuric acid resulting in the recovery rate of 88% in one stage. After stripping, the aluminium sulphate solution can be reused as a precipitation agent for phosphorus in the wastewater treatment process.

Validated RP-HPLC method for the estimation of Amiloride and hydrochlorothiazide in combined tablet dosage form

The aim of this work is to build up a fast, exact, precise and touchy reverse phase liquid chromatographic method for the synchronous assessment of amiloride and hydrochlorothiazide in tablet dose structure. The chromatographic strategy was normalized utilizing Hypersil ODS segment (250×4.6mm, 5μm molecule size) with UV discovery at 210nm and stream pace of 1ml/min. The portable stage includes phosphate buffer (pH acclimated to 2.5 with dilute Ortho Phosphoric acid) and acetonitrile in the proportion of 60:40 v/v. The linearity of proposed technique was examined in the scope of 5-30μg/ml (R²=0.999) for amiloride and 50-300μg/ml (R²=0.999) for Hydrochlorothiazide appropriately. The limit of detection (LOD) was discovered to be 0.10μg/ml and 0.40μg/ml for Amiloride and Hydrochlorothiazide appropriately. The limit of quantitation (LOQ) was discovered to be 0.30μg/ml and 1.20μg/ml for Amiloride and Hydrochlorothiazide separately. The retention times of Amiloride and Hydrochlorothiazide were found to be 3.258min and 2.383min separately. The technique was truly recommended and %RSD was found to be under 2 demonstrating serious level of exactness and accuracy. Subsequently proposed strategy can be effectively evaluated for the synchronous assessment of Amiloride and Hydrochlorothiazide in promoted formulations.

DEVELOPMENT AND VALIDATION OF STABILITY INDICATING RP-HPLC METHOD FOR THE SIMULTANEOUS ESTIMATION OF ETHINYL ESTRADIOL AND GESTODENE IN BULK AND PHARMACEUTICAL DOSAGE FORMS

Objective: The principal objective of this study is to develop and validate a simple, new, fast, selective, precise, and economic stability-indicating the RP-HPLC method for the simultaneous estimation of Ethinyl estradiol and Gestodene in a bulk and pharmaceutical dosage form.
 Methods: The present method was developed and validated on a Waters HPLC system using Phenomenex Gemini C18(250 mm × 4.6 mm i.d., 5 µm particle size) column and mobile phase composition of phosphate buffer: Acetonitrile (75:25 v/v) and the pH was adjusted to 3.6 using dilute orthophosphoric acid. The system was regulated at 1.0 ml/min flow rate at 237 nm UV detection.
 Results: The two drugs Ethinyl Estradiol and Gestodene, were eluted at 1.788 min and 3.475 min retention time, respectively. The analytical parameters such as accuracy, precision, linearity, LOD, LOQ, ruggedness, and robustness were used for validating the developed method according to International Conference on Harmonisation [ICH] guidelines. Linearity was exhibited over the concentration range of 10-50µg/ml and 25-125µg/ml for Ethinyl Estradiol and Gestodene, respectively. The method revealed the Limit of Detection and Quantitation values for Ethinyl Estradiol and Gestodene were 1.399µg/ml, 3.909µg/ml and 4.24µg/ml, 11.85µg/ml, respectively. The stress testing was carried out to give rise to degradation products by exposing the drugs to acid, alkali, thermal, oxidative, photolytic, and hydrolytic degradation. The obtained data showed that the content of Active pharmaceutical ingredients and the degradation products were successfully separated without any interference, which confirmed the stability-indicating nature of the developed method.
 Conclusion: The new, simple, rapid, selective, precise, and economic stability-indicating RP-HPLC method has been successfully developed and validated. It can be satisfactorily applied for the periodic laboratory quantitative estimation of Ethinyl Estradiol and Gestodene in formulations and active pharmaceutical ingredients.

Validated RP-HPLC method for the estimation of nebivolol hydrochloride and valsartan in combined tablet dosage form

The intention of this work is to develop a rapid, precise, accurate and sensitive reverse phase liquid chromatographic technique for the simultaneous estimation of Nebivolol and Valsartan in tablet dosage form. The chromatographic method was standardized using Inertsil ODS column (250×4.6mm, 5μm particle size) with UV detection at 278nm and flow rate of 1ml/min. The mobile phase comprises of ACN: Buffer (pH adjusted to 3.5 with dilute Ortho Phosphoric acid) in the fraction of 60:40 v/v. The linearity of proposed method was investigated in the range of 12.5-62.5μg/ml (R²=0.999) for Nebivolol and 200-1000μg/ml(R²=0.999) for Valsartan duly. The limit of detection (LOD) was found to be 0.05μg/ml and 0.81μg/ml for Nebivolol and Valsartan duly. The limit of quantification (LOQ) was found to be 0.15μg/ml and 2.44μg/ml for Nebivolol and Valsartan respectively. The retention time of Nebivolol and Valsartan were ground in to be 4.400min and 2.568min respectively. The method was authentically suggested and % RSD was ground in to be less than 2 indicating high degree of accuracy and precision. Hence proposed method can be successfully graded for the simultaneous estimation of Nebivolol and Valsartan in marketed formulation.

Understanding the Role of Concentrated Phosphoric Acid Solutions as High-Temperature Silicon Nitride Etchants

The ongoing demands for increased storage capacity flash memory in 2D-NAND structures resulted in their replacement by more advanced 3D-NAND structures, with the memory cells made of multiple, vertically stacked silicon oxide/silicon nitride layers. A critical step is selectively etching the silicon nitride films involving a wet etch technique using concentrated phosphoric acid at high temperatures. Concentrated phosphoric acid solutions demonstrate unique behaviors and have particularly high electrical conductivity, but the etching mechanism remains poorly understood. This study investigates the fundamental role of phosphoric acid in the silicon nitride etching and proposes complex active species for the silicon nitride surface protonation and hydroxylation. Characterization methods include 31P-NMR, XPS, FTIR, conductometry, viscometry and ellipsometry. We conclude that the unique performance of concentrated phosphoric acid as silicon nitride etchant results from an anomalously fast proton transport via the Grotthuss diffusion mechanism based on an intramolecular proton transfer driven by easily polarizable, hydrogen bond rearrangements between dissociated molecules as dimers, trimers and triple ions. By contrast, dilute phosphoric acid solutions and other strong protic acids (methanesulfonic acid, sulfuric acid, nitric acid), at both high and low concentrations exhibit protonic conductivity based on molecular diffusion of the H3O+/H2O/anions as separate entities (classical vehicle mechanism).