Alkaline Degradation Products Research Articles

An eco-friendly first and second derivative synchronous spectrofluorimetry for quantification of florfenicol in presence of its different degradation products. Application to kinetic stability study.

Two rapid, simple, sensitive and selective derivative spectrofluorimetric methods (first and second derivative synchronous spectrofluorimetric (FDSFS and SDSFS) procedures) have been developed for the analysis of florfenicol in the presence of its various degradation products. FDSFS was applied to assay the drug in the presence of its alkaline, oxidative and photolytic degradation products while SDSFS was used to quantify it in the presence of its acidic degradation product. These methods permitted quantification of florfenicol at corresponding λ Em of 288, 287, 279 and 284 nm without interferences from any of its degradation products. Full validation procedures were applied to the suggested method according to International Conference of Harmonization guidelines. Moreover, different degradation kinetic parameters were calculated such as half-life (t 1/2), degradation rate constant (K) and activation energy (E a). Using the analytical eco-scale, green analytical procedure index and analytical greenness metric approach AGREE as greenness assessment tools, the proposed method was found to be environmentally friendly.

Greenness and whiteness assessment of a sustainable voltammetric method for difluprednate estimation in the presence of its alkaline degradation product.

Nowadays, scientists are currently attempting to lessen the harmful effects of chemicals on the environment. Stability testing identifies how a drug's quality changes over time. The current work suggests a first and sustainable differential pulse voltammetry technique for quantifying difluprednate (DIF) as an anti-inflammatory agent in the presence of its alkaline degradation product (DEG). The optimum conditions for the developed method were investigated with a glassy carbon electrode and a scan rate of 100mVs-1. The linearity range was 2.0 × 10-7-1.0 × 10-6M for DIF. DIF was found to undergo alkaline degradation, when refluxed for 8h using 2.0M NaOH, and DEG was successfully characterized utilizing IR and MS/MS. The intended approach demonstrated the selectivity for DIF identification in pure, pharmaceutical, and degradation forms. The student's t-test and F value were used to compare the suggested and reported approaches statistically. The results were validated according to ICH requirements. The greenness of the studied approach was evaluated using the Green Analytical Procedure Index and the Analytical Greenness metric. Additionally, the whiteness features of the proposed approach were examined with the recently released red, green, and blue 12 model, and the recommended strategy performed better than the reported approaches in greenness and whiteness.

Magnesium Hydroxide as a Versatile Nanofiller for 3D-Printed PLA Bone Scaffolds.

Polylactic acid (PLA) has attracted much attention in bone tissue engineering due to its good biocompatibility and processability, but it still faces problems such as a slow degradation rate, acidic degradation product, weak biomineralization ability, and poor cell response, which limits its wider application in developing bone scaffolds. In this study, Mg(OH)2 nanoparticles were employed as a versatile nanofiller for developing PLA/Mg(OH)2 composite bone scaffolds using fused deposition modeling (FDM) 3D printing technology, and its mechanical, degradation, and biological properties were evaluated. The mechanical tests revealed that a 5 wt% addition of Mg(OH)2 improved the tensile and compressive strengths of the PLA scaffold by 20.50% and 63.97%, respectively. The soaking experiment in phosphate buffered solution (PBS) revealed that the alkaline degradation products of Mg(OH)2 neutralized the acidic degradation products of PLA, thus accelerating the degradation of PLA. The weight loss rate of the PLA/20Mg(OH)2 scaffold (15.40%) was significantly higher than that of PLA (0.15%) on day 28. Meanwhile, the composite scaffolds showed long-term Mg2+ release for more than 28 days. The simulated body fluid (SBF) immersion experiment indicated that Mg(OH)2 promoted the deposition of apatite and improved the biomineralization of PLA scaffolds. The cell culture of bone marrow mesenchymal stem cells (BMSCs) indicated that adding 5 wt% Mg(OH)2 effectively improved cell responses, including adhesion, proliferation, and osteogenic differentiation, due to the release of Mg2+. This study suggests that Mg(OH)2 can simultaneously address various issues related to polymer scaffolds, including degradation, mechanical properties, and cell interaction, having promising applications in tissue engineering.

Different spectrophotometric methods for simultaneous quantitation of Vericiguat and its alkaline degradation product: a comparative study with greenness profile assessment

Investigations concerning novel drugs and their induced degradation products are necessary for clinical research and quality control in the pharmaceutical industry. Four spectrophotometric techniques have been performed for simultaneous quantitation of Vericiguat (VER) and its alkali-induced degradation product (ADP) without prior separation. Method A is a dual wavelength method (DW) that estimates the absorbance difference at 314–328 nm, and 246–262 nm for VER and ADP; respectively. Method B uses a ratio difference method (RD) to estimate the ratio spectrum’s amplitude difference (DP318-342) and (DP284-292) for VER and ADP; respectively. Method C uses a first derivative ratio method (1DD) to estimate the peak ratio spectrum amplitude of the first derivative at 318 and 275 nm for VER and ADP; respectively. Method D uses the mean centering of the ratio spectra (MCR) to estimate amplitude values for VER and ADP at 337 and 292 nm; respectively. In a concentration range of 5.00–50.00 µg/mL for VER and 5.00–100.00 µg/mL for ADP, the methods were validated following ICH criteria and utilized to estimate VER in bulk and its dosage form. The methods’ greenness was assessed via three tools: the green analytical procedure index (GAPI), analytical eco-scale, and analytical greenness assessment (AGREE).

Stability indicating LC-MS/MS method and validation of Selexipag impurities and identification of its force degradation products

Selexipag belongs to a class of medicines known as IP prostacyclin receptor agonists used to treat pulmonary arterial hypertension.A simple and sensitive LC-MS/MS method has been developed for the identification of process related impurities in Selexipag API. The method was developed using a Zorbax C18 15 × 0.46 cm, 5μ column with a gradient program at 35 0C and flow rate of 1.0 mL/min. Detection was carried out by MS/MS with an ESI detector. Stress conditions were established by exposing the drug to acidic, alkaline, oxidative, thermal and photolytic stress condition. Identified and unidentified impurity was found when the fractions of acid and alkaline degradation product was analyzed by LC-MS/MS. The suggested methodology can be used to test the quality of Selexipag and identify the process-related impurities in pharmaceutical products.

The first validated stability-indicating HPLC/DAD method for quantitation of Vericiguat in its pharmaceutical formulation; Application to degradation kinetic studies

The stability of innovative drug formulations and the development of appropriate stability-indicating methods remain major focuses of recent pharmaceutical analysis. In the present study, an efficient stability-indicating HPLC-DAD technique has been described and validated for the determination of Vericiguat (VER); a novel oral soluble guanylate cyclase (sGC) stimulator used in heart failure. VER's stability under various stress conditions was examined. It was shown that VER was sensitive to alkaline, oxidative and thermal degradation. Mass spectrometry (MS) in electrospray ionization mode was performed to figure out the structure of the alkaline and oxidative degradation products. Efficient separation of VER and its induced degradation products was accomplished using isocratic elution mode on the Inertsil ODS-C18 column. The mobile phase composed of water: acetonitrile (70:30 v/v) with 0.1% O-phosphoric acid; pH was adjusted to 2.22 and a flow rate of 0.80 mL/min. VER was detected at 332 nm over a concentration range of 2.00–20.00 μg/mL. The retention time was 4.500 ± 0.005 min and the correlation coefficient was 0.9996. Following the International Conference of Harmonization's guidelines, the analysis was validated to be specific, fast, simple, precise and accurate for utilization in routine analysis and quality control of VER in its pharmaceutical formulation. Additionally, the suggested technique was expanded to investigate the kinetics of alkaline, oxidative and dry heat degradation.

Removal of high-molecular-weight hexose alkaline degradation products by rosin-based anion adsorbent: Kinetics, thermodynamics, and mechanisms

The dark pigments of beet juice (mainly high-molecular-weight hexose alkaline degradation products , HHADPs) negatively affect the quality of white sugar and should therefore be removed during processing, e.g., through adsorption. Herein, we developed a rosin-based anion adsorbent (RAA) as an effective, regenerable, and green decolorization agent for the removal of HHADPs from beet juice, achieving an equilibrium HHADP adsorption capacity of 6.50 mg/g and a removal efficiency of 89.36%. The investigations of adsorption kinetics, isotherms, thermodynamics, and mechanisms revealed that the adsorption was a spontaneous endothermic multilayer process and mainly corresponded to chemisorption driven by the interactions between the positively charged protonated tertiary amine groups of RAA and the negatively charged carboxylate groups of HHADPs. Our results pave the way to the development of cost-effective and practical adsorbents for an important industrial process, namely beet sugar production. • Rosin-based anion adsorbent (RAA) for beet juice decolorization was developed. • High-molecular-weight hexose alkaline degradation products were used as pigment model. • Equilibrium adsorption capacity of 6.50 mg/g (removal degree = 89.36%) was achieved. • Several adsorption parameters were optimized to improve adsorption performance. • Adsorption was spontaneous and endothermic, mainly corresponding to chemisorption.

Green Chemometric Determination of Cefotaxime Sodium in the Presence of Its Degradation Impurities Using Different Multivariate Data Processing Tools; GAPI and AGREE Greenness Evaluation

Four eco-friendly, cost-effective, and fast stability-indicating UV-VIS spectrophotometric methods were validated for cefotaxime sodium (CFX) determination either in the presence of its acidic or alkaline degradation products. The applied methods used multivariate chemometry, namely, classical least square (CLS), principal component regression (PCR), partial least square (PLS), and genetic algorithm-partial least square (GA-PLS), to resolve the analytes' spectral overlap. The spectral zone for the studied mixtures was within the range from 220 to 320 nm at a 1 nm interval. The selected region showed severe overlap in the UV spectra of cefotaxime sodium and its acidic or alkaline degradation products. Seventeen mixtures were used for the models' construction, and eight were used as an external validation set. For the PLS and GA-PLS models, a number of latent factors were determined as a pre-step before the models' construction and found to be three for the (CFX/acidic degradants) mixture and two for the (CFX/alkaline degradants) mixture. For GA-PLS, spectral points were minimized to around 45% of the PLS models. The root mean square errors of prediction were found to be (0.19, 0.29, 0.47, and 0.20) for the (CFX/acidic degradants) mixture and (0.21, 0.21, 0.21, and 0.22) for the (CFX/alkaline degradants) mixture for CLS, PCR, PLS, and GA-PLS, respectively, indicating the excellent accuracy and precision of the developed models. The linear concentration range was studied within 12-20 μg mL-1 for CFX in both mixtures. The validity of the developed models was also judged using other different calculated tools such as root mean square error of cross validation, percentage recoveries, standard deviations, and correlation coefficients, which indicated excellent results. The developed methods were also applied to the determination of cefotaxime sodium in marketed vials, with satisfactory results. The results were statistically compared to the reported method, revealing no significant differences. Furthermore, the greenness profiles of the proposed methods were assessed using the GAPI and AGREE metrics.

Ratiometric fluorescence for ultrasensitive detection of chlortetracycline in milk matrix based on its blue alkaline degradation product and red-emitting cyclodextrin stabilized gold nanocluster

As an emerging fluorescent nanomaterial, gold nanoclusters are of increasing interest in sensing and imaging because of their stable luminescence properties, large Stokes shift and low toxicity. Here, red-emitting gold nanoclusters stabilized by 6-Deoxy-6-mercapto-β-cyclodextrin (6-SH-CD@Au NCs) were successfully synthesized based on photo-reduction method for the detection of chlortetracycline. Under alkaline conditions, chlortetracycline transforms into iso-chlortetracycline (iso-CTC), which has a distinct blue fluorescence at 415 nm. The fluorescence intensity at 415 nm changed with increasing concentration of chlortetracycline and inner filter effect (IFE) of 6-SH-CD@Au NCs, while the fluorescence of the gold nanocluster at 670 nm decreased due to the IFE of iso-CTC. This fluorescent system detected chlortetracycline with good linearity in the concentration range of 5 nM-1 μM, and the limit of detection is 2.7 nM. The developed fluorescence sensor and test paper assay had been successfully applied for the detection of chlortetracycline in milk samples. The results demonstrated that the ratiometric sensor has advantages of simplicity, high sensitivity and specificity, cost-effectiveness and ease of operation.

Isolation, Characterization, and Toxicity Study of Stress Degradation Products of Pranlukast Hydrate.

Pranlukast hydrate (PRN), a cysteinyl leukotriene receptor antagonist (CysLT1), is used to treat bronchial asthma. The objective of this study is to perform the isolation, characterization, and toxicity analysis of stress degradation products of PRN. In high-performance liquid chromatography (HPLC), the separation was achieved using a Phenomenex Gemini C18 (250 × 4.6 mm, 5 μ) column; the ammonium format buffer (50 mM), pH 4, with formic acid: acetonitrile (50:50, v/v) was used as a mobile phase at a flow rate of 1.25 mL/min; and the photodiode array detector was used for detection at 230 nm. The drug was subjected to stress degradation as per ICH Q1A (R2) and ICH Q1B guidelines. The drug was found to be labile in alkaline (62.48% degradation) and photolytic (liquid state) (7.67% degradation) conditions, whereas the drug was found to be stable in acidic, peroxide, photolytic (solid state), and thermal conditions. The characterization of the drug and its degradation products was achieved using liquid chromatography-electrospray ionization-quadrupole time of flight tandem mass spectrometry (LC-ESI-QTOF-MS/MS), and the degradation mechanism was proposed. There were two degradation products observed in alkaline conditions (DP6 and DP9), whereas six novel degradation products were observed in photolytic degradation products (DP1, DP3, DP4, DP5, DP7, and DP10). The developed method was successfully validated as per the ICH Q2 (R1) guideline. The isolation of the alkaline degradation product DP9 was performed using preparative HPLC, and it was found to be 96.8% pure degradation product. The characterizations of the isolated degradation product (DP9) and procured impurity were performed using MS/MS, NMR, and FTIR. The mass of the procured impurity and DP9 were observed to be 404 and 500 Da, respectively. The in vitro cytotoxicity study of the procured impurity and DP9 was conducted using a 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay using an A549 cell line, and they were found to be cytotoxic at concentrations above 62.5 and 250 μg/mL, respectively. Furthermore, an in silico toxicity study was performed to predict the toxicity of all the major characterized degradation products of PRN using admetSAR software version 2.0. DP1, DP2, DP6, and DP10 were found to be hepatotoxic, mutagenic according to the micronucleus test, and aquatic toxic. We can conclude that the drug should be kept away from the direct exposure of light and the toxicity levels of DP1, DP2, DP6, and DP10 should be reduced below 0.1% to avoid their toxic effect.

Eco-friendly stability-indicating HPTLC micro-determination of the first FDA approved SARS-CoV-2 antiviral prodrug Remdesivir: Study of degradation kinetics and structural elucidation of the degradants using HPTLC-MS

The worldwide spread coronavirus (covid-19) pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) represents a global health crisis. The world was forced to face a great challenge to control and overcome this health disaster through various containment measures including efficient vaccination side by side with effective medication. Remdesivir (RMD) is the first FDA approved antiviral agent for treatment of covid-19 pandemic and hence regarded as the first-in-class medication of this highly contagious respiratory disease. The current study represents the first stability indicating HPTLC method for the estimation of RMD in bulk form and pharmaceutical formulation. The method employed TLC silica gel aluminum plates 60 F254 as stationary phase and green mobile phase composed of ethyl acetate and ethanol (96: 4, v/v) with densitometric detection at 245 nm. Comprehensive validation of the adopted method was accomplished according to the ICH guidelines regarding linearity, ranges, detection and quantification limits, precision, accuracy and robustness. The developed method offered a neat separation of the drug in presence of pharmaceutical excipients as well as in presence of acidic, alkaline, neutral hydrolytic, oxidative and photolytic degradants. Additionally, structural elucidation of alkaline and hydrolytic oxidation degradation products was carried out using HPTLC-MS. Furthermore, for the first time the acidic and alkaline degradation kinetics of RMD were studied and its degradation rate constants and half-lives were calculated. Moreover, greenness appraisal of the developed method as well as comparison with previously published stability indicating HPLC methods were performed using analytical Eco-scale, GAPI and AGREE metrics.

DETERMINATION OF TOLTRAZURIL IN PRESENCE OF COMPLETE ALKALINE DEGRADATION PRODUCT BY RP-HPLC AND TLC-DENSITOMETRIC METHODS

Objective: Toltrazuril is veterinary medicine, which is extensively used as an antiprotozoal drug. This drug can be analyzed by two sensitive chromatographic, accurate, and reproducible methods that have been developed and validated for the determination of toltrazuril in the presence of its alkaline degradation product. Methods: The first method involves an RP–HPLC separation of the two components, successfully achieved using Eclipse XDB-C18 Column (4.6 x 150 mm, 5 µm), using a mixture of acetonitrile and water (60:40, v/v) as a mobile phase at a flow rate of 1.4 ml/min. quantification was done with UV detector at a wavelength 242 nm UV detection. The second method is based on the separation and quantification of toltrazuril and its alkaline degradation product by TLC-densitometry on TLC silica gel aluminum plates GF254, using dichloromethane: methanol (9.5:0.5, v/v) as the developing system followed by densitometric measurement at 242 nm UV detection. Results: For RP-HPLC linearity of toltrazuril over the concentration range of 12.5–75 µg/ml, the components were well resolved from each other with significant diverse Rt values of 6.17 and 8.62 min for toltrazuril and its degradation product, respectively. While in TLC-densitometry method, the linearity of toltrazuril over the concentration range 0.2-6 µg/spot and the studied components were well resolved from each other with significant different Rf values of 0.33 and 0.52 for toltrazuril and its alkaline degradation product, respectively. For both the developed and validated methods the %RSD was found to be less than 2% and the % recovery was found to be between [98-102 %]. Conclusion: Fortunately, effective separation of the drug from its degradation product was established, along with the determination of toltrazuril as a raw material and the marketed pharmaceutical formulation, such as suspension without any interference. Hence it can be used for routine analysis in various pharmaceutical industries.

Green hydrogen production via electrochemical conversion of components from alkaline carbohydrate degradation

Water electrolysis is a promising approach for the sustainable production of hydrogen, however, the unfavorable thermodynamics and sluggish kinetics of oxygen evolution reaction (OER) are associated with high anodic potentials. To lower the required potentials, an effective strategy is proposed to substitute OER with partial oxidation of degradation products of carbohydrate origin from the waste stream of a chemical pulping industry. In this work, two different catalytic materials – PdNi and NiO are investigated comparatively to understand their catalytic performance for the oxidation of carbohydrate alkaline degradation products (CHADs). PdNi can catalyze CHADs with low potential requirements (−0.11 V vs. Hg/HgO at 150 mA cm−2) but is limited to current densities <200 mA cm−2. In contrast, NiO can operate at very high current densities but required relatively higher potentials (0.53 V vs. Hg/HgO at 500 mA cm−2). The performance of this non–noble metal catalyst compares favorably with that of Pd-based catalysts for hydrogen production from CHADs at high conversion rates. This work shows the potential to utilize waste streams from a large-scale process industry for sustainable hydrogen production, and also opens up opportunities to study earth-abundant electrocatalysts to efficiently oxidize biomass-derived substances.

Forced Degradation Studies of Drospirenone: Isolation and Characterization of Degradation Products

Abstract: Aim and Objectives: To remain safe for further processing or human consumption, study of stressed degradation for the identification of feasible degradants is required. The stability indicating high performance thin layer chromatographic method was developed with Camag HPTLC system. Materials and Methods: Silica C60F254 precoated TLC plates were used as stationary phase for separation of degradation products. The optimized mobile phase system consist of toluene: methanol: diethylamine (7:3:0.1) at 280 nm. Results: From the mass details and IR, NMR interpretation, the plausible structure of alkaline degradation product of drospirenone could be 17α (3-hydroxy propyl)-6β, 7β, 15β, 16β-dimethylene-5β-androstane-3β,5,17β triol and acidic degradation product of drospirenone could be 3-oxo-15α,16α-dihydro-3’H-cyclopropa[15,16]-17α-pregna-4,6- diene-21,17-carbolactone. Also In silico toxicity studies of the degradation products were performed to assess the toxicity profile of the products using Protox online sever. Conclusion: This analytical method can be considered as an alternative practical and inexpensive method for simple, accurate and efficient quantitative detection of drospirenone in the presence of its degraded products. Key words: Drospirenone, Characterization, Forced degradation studies, In silico toxicity study, Degradation products of drospirenone.

High-performance quaternary ammonium-functionalized chitosan/graphene oxide composite aerogel for remelt syrup decolorization in sugar refining

The decolorization of remelt syrup is the most critical step in the sugar refining process as it directly affects the quality of refined sugar. Adsorption is a useful method that can be applied to decolorize the syrup. A quaternary ammonium-functionalized chitosan/graphene oxide composite aerogel (GO-QACSA) was developed as an effective adsorbent for the removal of high-molecular-weight reducing sugar alkaline degradation products (HRSADPs), the main class of colorants in remelt syrup. The advantages of GO-QACSA to remove HRSADPs can be attributed to its well-connected 3-D network-like porous structure, nontoxicity, high hydrophilicity, and the richness of quaternary ammonium groups. The equilibrium adsorption capacity of GO-QACSA for HRSADPs reached 364.09 mg/g and the removal rate was > 90%. GO-QACSA exhibited an ultra-fast adsorption rate. Recycling experiments indicated that GO-QACSA exhibited good renewability and reusability. The interaction mechanism for the adsorption of HRSADP on GO-QACSA was studied, and the results revealed that two layers of HRSADPs adhered to the surface of GO-QACSA via electrovalent bonds formed between the quaternary ammonium and carboxylate groups. On average, 2–3 carboxylate ions in one HRSADP molecule bonded with the quaternary ammonium cations of GO-QACSA. Four phenomenological mathematical models, namely, External mass transfer resistance (EMTR), Internal mass transfer resistance (IMTR), combined EMTR–IMTR, and Adsorption on active sites (AAS), were presented based on the best-fit equilibrium isotherms. These models could be used to provide new insights into the adsorption mass transfer behaviors of the system.

A stability-indicating HPLC method for estimation of doxylamine succinate in tablets and characterization of its major alkaline stress degradation product

BackgroundA new selective rapid RP-HPLC-DAD method was developed and evaluated for the quantification of doxylamine succinate (DOX) in bulk and pharmaceutical dosage form. The separation of DOX at different degradation conditions was achieved with a Kromasil C18 (4.6 × 250 mm, 5-μm particle size). The mobile phase employed comprised of phosphate buffer (pH 3.5) and methanol in the ratio of 45:55 v/v. The flow rate was kept maintained at 1.0 ml/min and eluents were detected at 262 nm. The drug was subjected to different stress conditions like acid, base, neutral, hydrolysis, oxidation, photolysis, and thermal degradation. The analytical performance of the proposed HPLC method was thoroughly validated in terms of linearity, precision, accuracy, specificity, robustness, detection, and quantification limits.ResultsThe method produces linear responses that were found in the range of 10–50 μg/ml. The regression equation was found to be Y = 42984x − 10260. The correlation coefficient was found to be 0.9998. The LOD and LOQ for DOX were found to be 0.96 and 3.28 μg/ml, respectively. The short-term solution stability of DOX (100 μg/ml) was evaluated under (25 ± 2°C) storage condition and found to be 98.82 to 101%. The percentage recovery for DOX was in the range of 99.73 to 99.91%. The obtained results of the stress degradation study and peak purity data indicate the potential of the developed HPLC method to resolve degradants from DOX peak. The major alkaline degradation product was isolated using preparative chromatographic technique and extensive FT-IR was performed to ascertain the structure of the alkaline degradant.ConclusionIt was concluded that the proposed method was simple, sensitive, accurate, cost-effective, and less time-consuming for the quantification of DOX. This method was successfully utilized for stability testing of commercially available DOX tablets. Hence, the proposed method can be applied for routine quality control of DOX in bulk drug as well as in marketed formulations.

Quaternary ammonium-functionalized magnetic chitosan microspheres as an effective green adsorbent to remove high-molecular-weight invert sugar alkaline degradation products (HISADPs)

• We elucidated the structural properties of HISADPs. • QAMCM was creatively synthesized and systematically characterized. • In vitro cytotoxicity tests were conducted to evaluate the food safety of QAMCM. • QAMCM adsorbed HISADPs well and exhibited good regenerability. • PFO–PSO and FPMT models described the adsorption mechanisms well. Quaternary ammonium-functionalized magnetic chitosan microspheres (QAMCM) were fabricated for the removal of high-molecular-weight invert sugar alkaline degradation products (HISADPs), the main class of colorants in beet juice. The equilibrium adsorption capacity of QAMCM for HISADP was 98.03 mg/g at 0.6 mg/mL QAMCM dosage, 333 K temperature, pH 7, and 60 mg/L initial HISADP concentration, and the corresponding removal rate reached 98.03%. The adsorption kinetics were studied by using a pseudo-first-order and pseudo-second-order (PFO–PSO) combined model. Results revealed that HISADP adsorption by QAMCM is a complex process because of the involvement of both chemisorption and physisorption instead of only one mechanism. However, chemisorption (electrostatic attraction and electron sharing) is the dominant kinetic mechanism. Analysis of the mass transfer mechanisms showed that the dynamic characters of the adsorption capacities of the liquid film around QAMCM and the pores of QAMCM could be well described using a film–pore mass transfer model, which could be used to provide insights into the adsorption mass transfer behaviors of the system. Additionally, HISADPs with smaller sizes were preferentially adsorbed by QAMCM compared with larger ones. Research on the isotherms and thermodynamics showed that HISADP adsorption by QAMCM occurred via an endothermic multi-layer process and was spontaneous. Overall, QAMCM was found to be an efficient, green, and recyclable decolorization adsorbent for beet juice.

Intermolecular Interactions in the Membrane Filtration of Highly Alkaline Steeping Lye.

The reuse of steeping lye is crucial for the sustainable production of viscose fibers. Steeping lye contains hemicellulose and many alkaline degradation products, such as organic acids, so that its purification can be evaluated in terms of total organic carbon removal. When considering purification by membrane filtration, intermolecular interactions between hemicellulose and organic acids can strongly affect their retention efficiency. Herein, we give more insights into the ultrafiltration and nanofiltration of steeping lye and corresponding model solutions. Furthermore, we studied the impact of total organic carbon concentration, hemicellulose concentration and sodium hydroxide concentration on the membrane performance. Hydrogen bonds between hemicellulose and certain types of hydroxy acids increased the retention of the latter. In contrast, charge based repulsion forces led to a decreased retention of a certain type of hydroxy acids. It can be clearly shown that taking intermolecular interactions into account is highly important for the description of complex multicomponent mixtures. In addition, the results can be extended to other, highly alkaline process streams with organic content, such as Kraft pulping liquors.

Synthesis, Isolation and Characterization of three acid and alkaline hydrolytic products of Nimodipine and Development of a valid RP-HPLC method for simultaneous determination of Nimodipine and Citicoline sodium in the presence of Nimodipine degradation products in Bulk and Tablets

Impurity profiling of active pharmaceutical ingredients is a crucial step in assessing their quality. Moreover, the chemical nature of nimodipine makes it susceptible easily to acidic and alkaline hydrolysis. On the other hand, nimodipine is co-formulated with citicoline sodium pharmaceutically as tablets to treat cerebral ischemia. In this study, three degradation products of nimodipine were synthesized, isolated and characterized with aid of FTIR spectroscopy, 1H-NMR as well as LC-MS/MS after exposing to drastic acidic and alkaline conditions. Subsequently, a simple, selective and valid RP-HPLC method was developed for simultaneous estimation of nimodipine and citicoline in the presence of nimodipine acid and alkaline degradation products in bulk and tablets. Chromatographic separation was achieved using an isocratic mobile phase consisting of acetonitrile: 0.02 M KH2PO4 (containing 0.2% v/v, triethylamine and adjusted to pH 3.0 with orthophosphoric acid) (70:30, v/v) at a flow rate 1.0 mL min-1 at ambient temperature (25 ºC) on a Eurospher II C18 (250 mm × 4.6 mm, 5 µm) column with UV detection at 270 nm for citicoline and 235 nm for nimodipine and its acidic and alkaline hydrolytic products. Linearity, accuracy and precision were found to be acceptable over a concentration range of (4.5–120 μg mL-1) for nimodipine and (15–400 μg mL-1) for citicoline. The proposed method could be successfully applied for the routine analysis of the studied drugs in their pharmaceutical preparation in the presence of nimodipine common degradation products without any preliminary separation step.

Development of Advanced Chemometric-Assisted Spectrophotometric Methods for the Determination of Cromolyn Sodium and Its Alkaline Degradation Products.

Advanced and sensitive spectrophotometric and chemometric analytical methods were successfully established for the stability-indicating assay of cromolyn sodium (CS) and its alkaline degradation products (Deg1 and Deg2). Spectrophotometric mean centering ratio spectra method (MCR) and chemometric methods, including principal component regression (PCR) and partial least square (PLS-2) methods, were applied. Peak amplitudes after MCR at 367.8 nm, 373.8 nm and 310.6 nm were used within linear concentration ranges of 2–40 µg mL−1, 5–40 µg mL−1 and 10–100 µg mL−1 for CS, Deg1 and Deg2, respectively. For PCR and PLS-2 models, a calibration set of eighteen mixtures and a validation set of seven mixtures were built for the simultaneous determination of CS, Deg1 and Deg2 in the ranges of 5–13 µg mL−1, 8–16 µg mL−1, and 10–30 µg mL−1, respectively. The authors emphasize the importance of a stability-indicating strategy for the investigation of pharmaceutical products.