Related Degradation Products Research Articles

Identification of mozambioside roasting products and their bitter taste receptor activation

Arabica coffee contains the bitter-tasting diterpene glycoside mozambioside, which degrades during coffee roasting, leading to yet unknown structurally related degradation products with possibly similar bitter-receptor-activating properties.The study aimed at the generation, isolation, and structure elucidation of individual pyrolysis products of mozambioside and characterization of bitter receptor activation by in vitro analysis in HEK 293T-Gα16gust44 cells.The new compounds 17-O-β-d-glucosyl-11-hydroxycafestol-2-on, 11-O-β-d-glucosyl-16-desoxycafestol-2-on, 11-O-β-d-glucosyl-(S)-16-desoxy-17-oxocafestol-2-on, 11-O-β-d-glucosyl-15,16-dehydrocafestol-2-on, and 11-O-β-d-glucosyl-(R)-16-desoxy-17-oxocafestol-2-on were isolated from pyrolyzed mozambioside by HPLC and identified by NMR and UHPLC-ToF-MS. Roasting products 11-O-β-d-glucosyl-(S)-16-desoxy-17-oxocafestol-2-on, 11-O-β-d-glucosyl-15,16-dehydrocafestol-2-on, and 11-O-β-d-glucosyl-(R)-16-desoxy-17-oxocafestol-2-on had lower bitter receptor activation thresholds compared to mozambioside.Molecular docking simulations revealed the binding modes of the compounds 11-O-β-d-glucosyl-15,16-dehydrocafestol-2-on and 11-O-β-d-glucosyl-(R)-16-desoxy-17-oxocafestol-2-on and their aglycone 11-hydroxycafestol-2-on in the two cognate receptors TAS2R43 and TAS2R46.The newly discovered roasting products 17-O-β-d-glucosyl-11-hydroxycafestol-2-on, 11-O-β-d-glucosyl-(S)-16-desoxy-17-oxocafestol-2-on, 11-O-β-d-glucosyl-15,16-dehydrocafestol-2-on, and 11-O-β-d-glucosyl-(R)-16-desoxy-17-oxocafestol-2-on were detected in authentic roast coffee brew by UHPLC-ToF-MS and could contribute to coffee's bitter taste impression.

Analytical method development, validation, and out-of-specification investigations for polyethylene glycol

This work was motivated by the United States Pharmacopeia monograph modernization initiative and European directorate for the quality of medicines and healthcare. An out-of-specification (OOS) occurrence prompted OOS investigations for the cGMP (cGMP refers to the Current Good Manufacturing Practice regulations enforced by the FDA) release testing of residual ethylene oxide in polyethylene glycol (PEG) according to the standards detailed within the United States Pharmacopeia/National Formulary (USP-NF) for polyethylene glycol, and the European Pharmacopoeia (Ph. Eur.) for macrogols. During the OOS root cause investigations, we observed a PEG degradant and identified it as methyl formate, which co-elutes with ethylene oxide using the GC (gas chromatography) methods published in current USP-NF and Ph. Eur. for PEGs. To address this, a novel method utilizing static headspace gas chromatography with flame ionization detection (HS-GC-FID) was developed to test various grades of PEGs for the presence of residual ethylene oxide, along with other process related impurities and degradation products. With this new method, ethylene oxide, a known genotoxic impurity and IARC (International Agency for Research on Cancer) Class 1 human carcinogen, can be well resolved from methyl formate, a newly identified and comparatively innocuous degradant derived from PEG. The currently available official compendial methods are unable to separate the specific impurities in PEGs. However, the new GC method presented in this paper has been shown to have a high and unique selectivity, allowing for baseline separations (chromatographic resolutions greater than 1.5) of all related impurities in PEGs, which is a challenging task. Additionally, this method has been found to be stability-indicating based on a forced degradation study. During stress stability study of PEGs involving acid, alkali, heat, light, and oxidation, some other PEG degradants, including formaldehyde, were identified. It is possible that formaldehyde undergoes a disproportionation reaction known as the Cannizzaro reaction, leading to the formation of formic acid and methanol. The formic acid then undergoes an esterification reaction with methanol to produce methyl formate. To the best of our knowledge, this is the first stability-indicating HS-GC-FID method that accomplishes this separation in a single run, and it was successfully validated as per ICH (the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use) guidelines. Therefore, this method is suitable for the conduct of cGMP batch release and stability testing of PEGs in regulated quality control (QC) laboratories.

A Chemical Characterization Workflow for Nontargeted Analysis of Complex Extracts from Polymer Based Medical Device Using High Resolution LC/MS.

The chemical characterization of extractables and leachables (E&Ls) is an important aspect of biosafety and biocompatibility assessment in medical device industry. The advent of the body-contact use of medical devices in patient treatment has introduced a potential source for extractables and leachables as these medical devices are comprised of various polymeric materials. Several industry working groups, the FDA and USP, have recognized the guidance for chemical characterizations and nontargeted analysis of medical device extracts, such as ISO 10993-18:2020. The MS application of nontargeted analysis has played a critical role in understanding the E&Ls from medical device extracts. However, there have been very few reports about the MS based workflow with nontargeted analysis for medical device extracts and there is little guidance about the exact methodologies which should be used, even though there is an urgent need for a clearly defined process for the identification of medical device extracts. In this study, we demonstrated an analytical LC/MS (liquid chromatography/mass spectrometry) workflow using high resolution Exploris120 Orbitrap instrument for data acquisition and Compound Discoverer 3.3 intelligent software for data processing to profile the polymer related E&Ls from a balloon dilation catheter device extracted with 40% ethanol. An E&L ID workflow combining LC separation, data-informed MS acquisition strategy, MS information mining (including adduct ions, MS information from both electrospray ionization (ESI) (+) and ESI (-), in-source fragmentation, common fragment ions (CFIs), common neutral losses (CNLs), and in silico MS simulation was described with intelligent software processing and manual data interpretation. The workflow developed in this study was proven to be effective to provide a comprehensive profile of polymer related degradation products, polymer impurities and additives including surfactants, UV curing agent, antioxidants, and plasticizers for the device analyzed. The classification of E&L compounds using CFIs and CNLs was very effective to facilitate the identification of polymer related impurities and extract the polymer related impurities with common structures in a large data result set.

Quantitative Study of Impurities in Bedaquiline Fumarate: Identification and Characterization of Its Three Degradation Products Using HPLC, LC/ESI-MS, and NMR Analyses

The study aimed to establish a high-performance liquid chromatography (HPLC) method for the quantitative analysis of the related substances of bedaquiline fumarate. Nuclear magnetic resonance and mass spectrometry were used for characterization and assay. A chromatographic method was used for separation. The conditions used were: gradient elution system composed of methanol 0.01mol/L KH2PO4 and 0.01 mol/L K2HPO4 (pH = 4.1) with a flow rate of 1 mL/min, at 224 nm as the detection wavelength. In this study, three degradation products of bedaquiline fumarate have been disclosed for the first time. The related impurities and degradation products of the drug were well separated. The method provided linear responses within the concentration range, which varied from 0.20 to 10.08 μg/mL with limits of detection of 0.10 μg/mL and limits of quantification of 0.20 μg/mL. The mean percent recovery varied between 91.64 and 105.89%. The method was validated for other parameters such as specificity, stability, and robustness. This method was validated and worked well for the impurity studies and quality control analysis of the laboratory-prepared samples of bedaquiline fumarate.

A new validated RP-HPLC-UV DAD method for assay of bisoprolol fumarate and related substances in tablets

The research focus of this work was development and validation of an efficient analytical method that can be used for separation and determination of related substances of bisoprolol in finished drug product using reversed-phase HPLC with UV-DAD. In a previous systematic study of various stationary phases and elution conditions it was found that several octadecylsilane phases can be successfully employed for separation of the critical pairs of bisoprolol and its related degradation products. Namely, method development led to conclusions that satisfactory resolution and peak shapes were obtained with gradient elution with water with 0.2% perchloric acid and acetonitrile and the reversed-phase columns: Hypersil 3 BDS C18 (100 x 4 mm, 3 m); Zorbax SB C18 (150 x 4.6 mm, 3.5 m); Acquity UPLC BEH C18 (50 x 2.1 mm, 1.7 m), and Xterra MS C18 (100 x 4.6 mm, 3.5 m). Since regular quality control includes the parameter related substances, which is of great importance for the overall quality of dosage forms, this study was oriented towards widening the available validated analytical methods for determination of this parameter. In this work, the results from the validation of the method for determination of related substances of bisoprolol using Zorbax SB C18 150 x 4.6 mm, 3.5 m, are presented. Validation parameters that were tested (linearity, accuracy, precision, selectivity) confirmed that the method is suitable for its intendance and it was used for characterization of the samples from a forced degradation study of bisoprolol tablets. Keywords: Bisoprolol, RP-HPLC-UV DAD, validation, related substances

Determination and quantification of related substances and degradation products in bictegravir by full factorial design evaluated HPLC and mass spectrometry.

Determining and quantifying novel impurities and degraded impurities of a drug product is always a continuous challenge to enhancing the drug quality for patients' safety. Herein, our work deals with (i) developing a rapid, accurate, and reliable high-performance liquid chromatographic validation method to quantify the bictegravir drug (integrase inhibitors of antiretroviral drugs) and its novel related impurities at low levels, and (ii) the liquid chromatography-mass spectrometry (LC-MS) method to identify degraded impurities. Separation of bictegravir acid (impurity-I) and methyl bictegravir (impurity-II) impurities which are identified by LC-MS in the bictegravir drug was executed by developing a method and the same method performance evaluated by using full factorial design. This developed analytical technique gave a well-separated peak of bictegravir and related analytes such as bictegravir acid (impurity-I) and methyl bictegravir (impurity-II), adequate with the peak properties as per USP guidelines. The method's sensitivity and linearity are demonstrated by its detection and quantification limits at low levels with a correlation coefficient of 0.998. The method's repeatability, specificity, and accuracy suggest that this developed technique is a reliable determination strategy for the bictegravir drug substance and its related impurities (impurity-I and impurity-II) in a simple, feasible, and affordable way.

Characterization of seven new related impurities and forced degradation products of tetracaine hydrochloride and proposal of degradation pathway by UHPLC-Q-TOF-MS

A rapid and highly sensitive method was developed for separation and identification of the related impurities and degradation products in tetracaine hydrochloride by ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS). The chromatographic separation was achieved on an Agilent Infinity Lab Poroshell 120 EC-C18 column (4.6 ×100 mm, 2.7 µm) using gradient elution with mobiles phase of A (10 mM ammonium acetate buffer containing 0.1% formic acid) and B (acetonitrile) at a flow rate of 1.0 mL/min. Forced degradation experiments were also performed under acidic, alkaline, thermal, photolytic, and oxidative stress conditions following ICH guidance. The result revealed that tetracaine hydrochloride is extremely sensitive to oxidation condition and highly sensitive to alkaline/acidic hydrolysis, and susceptible to light condition. In total, five related impurities and seven degradation products were successfully detected in the positive mode of electrospray ionization. The structures of all these impurities were characterized based on the high-resolution MS data and manufacture process, and the fragmentation pathways of tetracaine and these impurities were constructed and discussed. Seven of them have not been reported before, and two of them were specified impurities described in various pharmacopoeias. The fragmentation pathways and plausible mechanisms for the formation of these impurities were proposed.

Novel Eco-Friendly Stability Indicating Capillary Zone Electrophoresis Method for Determination of Aripiprazole in Tablet Dosage form: DoE Directed Optimization, Development and Method Validation

In this work, a novel environment-friendly stability indicating capillary zone electrophoresis (CZE) method has been developed and validated for assaying the aripiprazole (ARP) in tablet dosage form. The separation of ARP from its degradation products and internal standard was achieved using a fused silica capillary column (30.2 cm x 75 μm ID), a background electrolyte containing 6 mmol L−1 ammonium formate buffer (pH 3) with 5% methanol under a potential of 15 kV and detection at 214 nm. The stability indicating ability of the method was investigated by analyzing ARP after being subjected to acidic, alkaline, thermal, photolytic, and oxidative stress conditions, according to ICH guidelines. Design of experiments was used during forced degradation and method optimization. Oxidation was the main degradation pathway among those evaluated. The drug was separated from its oxidative degradation products in less than 4 min. CZE method was linear between 60 – 140 μg mL−1, R2 = 0.9980, precise (intra-day 0.88% and inter-day 1.30%). The average recovery was 100.93 ± 0.77%. This is the first method in the literature for quantification of ARP in the presence of its related degradation products with high separation efficiency, low operation cost and minimum solvent consumption. This method could be helpful in the routine quality control analysis in the pharmaceutical industries with least harmful effect on the environment. CZE is considered an eco-friendly alternative of conventionally HPLC methods.

Simultaneous Determination of Prasugrel and its Process Related Impurities and Degradation Products in Bulk Drug Substances by RPLC-UV

Aims: This study aims to determine the quantitative prasugrel (PG) and its all possible process-related impurities. Background: To the best of our knowledge, very few analytical methods are available in the literature for monitoring process related impurities and degradation products of PG in bulk drug substance/ active pharmaceutical ingredient (API). Objective: The objective of this study is the separation of Prasugrel and its all possible process-related impurities viz., desacetyl prasugrel-tautomeric forms, intermediates including desacetyl impurity existing in its keto-enol form and positional tautomer impurities with degradation products. Method: A simple and robust HPLC-UV method having Zorbax XDB C18 column (15 cm x 4.6 mm) 3.5μm particle size column was used. Result: Prasugrel and its process related impurities were separated as well as analyzed in pharmaceutical samples' biological matrices. Conclusion: RP-LC method was developed for quantitative determination of PG and related substantial impurities were found to be highly specific, sensitive and precise. The major oxidative degradant was identified as PG desacetyl IMPs (keto-enol and positional tautomer) and hydroxyl IMP.

Ultraviolet photodissociation facilitates mass spectrometry-based structure elucidation with pyrrolidine and piperidine containing compounds

In pharmaceutical development, structural elucidation of small molecules from process related impurities and degradation products is an essential component. As one of the most important methods in the toolbox, high resolution mass spectrometry (HRMS) and specifically tandem mass spectrometry (MS/MS) often provide fast and informative structural insights. However, many small molecule drugs containing certain biological relevant pharmacophores result in limited numbers of fragments when using traditional collision based fragmentation techniques, such as higher energy collisional dissociation (HCD), due to its inherent preference of cleaving the weakest bond first. As an alternative, ultraviolet photodissociation (UVPD), which irradiates the precursor ion with high energy photons, can lead to more extensive fragmentation from the readily UV absorbing small molecules. Here, we showcase the advantage of UVPD over HCD on pyrrolidine and piperidine containing molecules derivatized from a model compound, telmisartan. While HCD only yielded a single, highly abundant ion resulting from the pyrrolidine and pipieridine ring cleavage, UVPD generated rich and structurally informative fragment ions. UVPD is an attractive and powerful alternative for traditional fragmentation techniques for small molecule structural elucidation.

Simultaneous determination of ivermectin, clorsulon and their related substances in an injectable finished product by a stability-indicating RP-HPLC method

A reversed-phase high performance liquid chromatography (RP-HPLC) method has been developed for the determination of ivermectin and clorsulon, including the identification and estimation of their related impurities in an ivermectin and clorsulon injectable finished product. Chromatographic separation was achieved using a gradient elution on a Supelco Ascentis® Express C18 column (150 mm × 4.6 mm i.d., 5 µm particle size) maintained at 55 °C. Mobile phase-A is composed of water and mobile phase-B is composed of acetonitrile/methanol (65/35, v/v). Analytes were monitored by UV detection at 245 nm. The stability-indicating capability of this method has been demonstrated by the adequate separation of all the process related impurities and degradation products of ivermectin and clorsulon from the stress degraded samples of the injectable product. This method was also successfully validated as per the current ICH guidelines with respect to specificity, linearity (R2> 0.999), limit of detection (0.3 μg/mL), limit of quantitation (1.0 μg/mL), accuracy, precision, and robustness for both APIs. This proposed method can significantly benefit the end-users in QC laboratories with laboratory efficiency and throughput during routine analysis and stability monitoring of the injectable product.

NanoUPLC-QTOF-MS/MS Determination of Major Rosuvastatin Degradation Products Generated by Gamma Radiation in Aqueous Solution.

Rosuvastatin, a member of the statin family of drugs, is used to regulate high cholesterol levels in the human body. Moreover, rosuvastatin and other statins demonstrate a protective role against free radical-induced oxidative stress. Our research aimed to investigate the end-products of free radical-induced degradation of rosuvastatin. To induce the radical degradation, an aqueous solution of rosuvastatin was irradiated using different doses of gamma radiation (50–1000 Gy) under oxidative conditions. Rosuvastatin and related degradation products were separated on nanoC18 column under gradient elution, and identification was carried out on hyphenated nanoUPLC and nanoESI-QTOF mass spectrometer system. Elemental composition analysis using highly accurate mass measurements together with isotope fitting algorithm identified nine major degradation products. This is the first study of gamma radiation-induced degradation of rosuvastatin, where chemical structures, MS/MS fragmentation pathways and formation mechanisms of the resulting degradation products are detailly described. The presented results contribute to the understanding of the degradation pathway of rosuvastatin and possibly other statins under gamma radiation conditions.

Assay of afoxolaner and determination of its related substances in commercial bulk batches of afoxolaner by reversed-phase HPLC method based on a short octadecyl column

Afoxolaner is a new insecticidal and acaricidal active pharmaceutical ingredient (API) belonging to the isoxazoline family, widely prescribed for the control of fleas and ticks in dogs. A stability-indicating reversed-phase high performance liquid chromatography (RP-HPLC) method has been developed for the assay of afoxolaner and determination of its related compounds in bulk API lots of afoxolaner. The chromatographic separation of afoxolaner and its related compounds was achieved by gradient elution on a Zorbax-SB C18 column (50 mm × 4.6 mm i.d., 5 µm particle size) maintained at 40 °C. Mobile phase-A is composed of water and mobile phase-B is composed of acetonitrile/methanol (50/50, v/v). Analytes were monitored by UV detection at 225 nm with a flow rate of 2.0 mL/min. The stability-indicating capability of the method has been demonstrated by adequate separation of all the process related impurities and degradation products of afoxolaner generated by stress degradation of afoxolaner bulk drug substance under various stress conditions. This method was also successfully validated as per the current ICH guidelines for afoxolaner and Q6S07 (afoxolaner related substance) with respect to specificity, linearity (R2 > 0.999), detection limit (∼0.21 µg/mL), quantitation limit (∼0.70 µg/mL), accuracy, precision, and robustness. Due to its speed, high degree of selectivity, and accuracy, the proposed method is suitable and highly desirable in quality control laboratories for routine analysis of afoxolaner.

Stability Indicating RP-HPLC Method for the Analysis of Dacomitinib and its Related Impurities in Bulk and Oral Solid Dosage Formulations

Dacomitinib is an epidermal growth factor receptor inhibitor prescribed for the treatment of metastatic non small-cell lung carcinoma. There are no reported significant official of HPLC methods that resolve the impurities and degradation products generated during stability studies. Therefore, an isocratic RP-HPLC-UV method was developed for the determination of Dacomitinib in the presence of its related impurities and degradation products. The separation of Dacomitinib, impurity 1 and 2 was achieved on Agilent ZORBAX Eclipse (250×4.6 mm; 5 µ id) column as stationary phase, 0.1M sodium perchlorate at pH 5.6, acetonitrile as mobile phase in the ratio of 20:80 (V/V) at a flow rate of 1.0 mL/min in isocratic condition as mobile phase and UV detection was carried at 253 nm. In the optimised conditions, well resolved and retained peaks were observed at a retention time of 5.8 min, 4.0 min and 7.7 min for Dacomitinib, impurity 1 and 2 respectively. In the developed method, a very sensitive detection limit of 0.06 and 0.025 µg/mL was observed for impunity 1 and 2 respectively. The calibration was observed to be within the concentration range of 20 – 200 µg/mL for Dacomitinib and 0.2 – 2 µg/mL for impurity 1 and 2. The proposed method was used to investigate the effective separation of impurities along with degradation compounds formed under different degradative conditions and confirms that the method is stability indicating. Hence it can be concluded that the method was found to be simple, sensitive, specific, accurate, linear, precise, rugged, robust, and useful for estimation and characterizing the stability of Dacomitinib, impurity 1 and 2.

Characterization of Forced Degradation Products & Related Substances of Bilastine by Online LC-Q-TOF-MS and In-silico Study of Characterized Compounds

This manuscript is about the identification of degradation products and four related substances of a novel antihistaminic drug Bilastine by LC-Q-TOF-MS/MS. A selective stability-indicating RP-HPLC method was developed for the separation of Bilastine, its 4 related substances and degradation products. Separation was done through Inertsil ODS-3® column (150 x 4.6 mm, 5 µm) using 10 mM ammonium acetate (pH 6.00) and methanol as eluent in a gradient at 1.0 mL/min flow rate. The chromatogram was extracted at 275 nm wavelength. Two degradation products and four related substances were identified and their structures were proposed on the basis of data obtained from LC-Q-TOF-MS/MS experiments. The developed method was validated in accordance with ICH Q2 and USP <1225> guidelines and it was found to be specific, precise, accurate and robust for the intended use. The method was linear in the range of 160-240 µg/mL for drug and 1.15-4.5 µg/mL for related substances with R2 value greater than 0.999 and 0.997 for drug and RS respectively. Percentage of relative standard deviation for validated parameters was less than 2. Structures of the drug, its degradation products and related substances were subjected to in silico studies for prediction of physicochemical, pharmacokinetic and toxicological properties with the help of QikProp module of Schrödinger suite 2017-1 software. Predicted in silico values suggested that they are safe and lie within the recommended range of parameters.

Simultaneous opto-electrochemical monitoring of carbamazepine and its electro-oxidation by-products in wastewater

The growing human impact on aquatic environments deriving from the extensive use of pharmaceuticals and the release of persistent pollutants necessitates the implementation of new, widespread methods for characterising and quantifying such contaminants and their related degradation products. Carbamazepine, 5 H-dibenzo[b,f]azepine-5-carboxamide, (CBZ) is a widely used anti-epileptic drug characterised by limited removal by conventional wastewater treatments and high persistency in the environment. In this work, CBZ detection and quantification was performed in phosphate buffer, as well as in samples of complex matrix-like landfill leachates and treated wastewater originating from a medical facility, and simultaneously by optical and electrochemical methods using a novel transparent carbon-based nanostructured electrode.Coupling electrochemical (differential pulse voltammetry) with optical (UV–visible spectroscopy) methods, it has been possible to reach the limit of detection (LOD) for CBZ at the levels of 4.7 μM for the electrochemical method, 10.3 μM for the spectroscopic method, and 3.6 μM for the opto-electrochemical method. Raman spectroscopy and ultra-high performance liquid chromatography coupled with tandem mass spectrometry techniques were employed to support and validate the combined technique. The novel developed technique showed high selectivity to carbamazepine and its by-products, even in environmental samples. Thus, this environmentally friendly, fast and accurate detection method is believed to be successfully implementable in investigating other pharmaceutical and chemical contaminates of concern.

Sulfenamides as Standalone Flame Retardants for Polystyrene

Efficient standalone sulfenamide based flame retardants consisting of N-benzothiazol-2-ylsulfanyl-N-tert-butyl-benzothiazole-2-sulfenamide (SF-201) or N-cyclohexylthiophthal-imide (SF-205) have been developed for bulk and expanded polystyrene (EPS). In the first set of experiments the sulfenamides were mixed with general purpose polystyrene (GPPS) in a Haake Rheocord melt blender, and in the second set of experiments suspension polymerizations of styrene were carried out in the presence of either of the sulfenamides. Under these experimental conditions SF-201 was deemed to be a more effective flame retardant than SF-205. The third set of experiments involved all the relevant steps for industrial production of EPS: Preparation of polystyrene beads containing pentane as blowing agent and SF-201 as the sole flame retardant, subsequent pre-expansion of the beads at 120 °C with steam and in the last step molding with steam to produce large EPS blocks. The prepared EPS blocks were cut into desired dimensions for EN ISO 11925-2 fire tests. The obtained beads containing SF-201 had a spherical shape and their particle size distribution as well as molecular weights were rather similar to the reference polystyrene beads. Thus, it seems that SF-201 did not have a notably negative influence in the process of breakage and coalescence of monomer/polymer droplets. In addition, the molecular weight distribution remained narrow and a slight decrease in polystyrene molecular weights were observed in comparison to neat polystyrene prepared under similar conditions. The flame retardant efficacy of SF-201 as a standalone flame retardant in EPS was high, as at 2.5 % loading of SF-201 in EN ISO 11925-2 ignitability test the EN 13501-1 E class with no flammable droplets was obtained. The thermogravimetric analysis (TGA) carried out under inert atmosphere revealed enhanced and earlier onset of polystyrene degradation in the presence of sulfenamides. The enhanced polystyrene degradation led to a lowering of melt viscosity that facilitated an effective mass transfer of fuel and heat away from the fire zone. The pyrolysis gas chromatography-mass spectrometry (PyGCMS) measurements of blends showed a lower level and number of polystyrene related degradation products (styrene, multiple dimer and trimer species) and evidence of parent SF-201 flame retardant molecule was no longer visible. Whereas new volatile amine species such as tert-butylamine and N-tert-butyl-2-benzothiazolesulfenamide were detected which relate to flame retardant activity in the condensed phase and potentially radical scavenging of key combustion radicals (H., .OH) in gas-phase.

Green stability-indicating capillary electrophoretic method for simultaneous determination of Lesinurad and Allopurinol in tablet dosage form: Degradation kinetics investigation

A binary mixture of Lesinurad (LES) and Allopurinol (ALP) is a newly marketed anti-gout combination where no stability indicating methods have been reported for its analysis. In this work, a simple, green stability indicating capillary zone electrophoretic method coupled with a diode array detector (CZE-DAD) has developed and validated for analyzing this mixture in their combined dosage form. Separation was achieved using fused silica capillary (55 cm × 50 μm id) using 50 mM borate buffer adjusted to pH 10 with 0.5 M NaOH. The linearity concentration ranges were 5–50 and 10–100 μg/mL for LES and ALP, respectively. The stability indicating ability of the proposed method was investigated by analyzing the two drugs after being subjected to several stress conditions as per ICH guidelines. The developed method was able to separate the two intact drugs from their degradation products formed under different stress conditions (acidic, basic, oxidation). In addition, the developed method has been applied to investigate the degradation kinetics of LES and ALP under acidic, basic and oxidative conditions. The degradation of the two drugs was found to follow pseudo-first order kinetics and degradation half-lives were also calculated for both drugs under different stress conditions. The developed CZE method is the first in the literature for determination of both LES and ALP in the presence of their related degradation products with high separation efficiency, minimum solvent consumption, enhanced method greenness and low operation cost. Thus, the proposed method is an efficient simple eco- friendly analytical tool for the routine analysis of LES and ALP in their combined dosage form in presence of their degradation products in quality control laboratories.

New stability indicating RP-HPLC method for the determination of Abiraterone acetate, its related substances and degradation products in bulk and dosage form

A robust, specific, sensitive and precise reverse-phase HPLC method has been developed for the quantitative determination of an atypical anticancer drug Abiraterone acetate and its eighteen potential impurities in drug substances. Chromatographic separation was achieved on a Kinetex C18 (4.6 mm × 150 mm, 5µ) column, using buffer (1 g of KH2PO4 in 1000 ml water and adjusting the pH 3.1 with ortho phosphoric acid) and acetonitrile in gradient elution mode. The flow rate was kept at 0.8 ml/min and thermostated at 40 °C with runtime of 65 min. The optimized method was found to produce symmetric and sharp peaks with good separation between the processes related impurities and degradation impurities. Quantification is achieved with photodiode array detection at 205 nm over the concentration range of 0.2–3.0 mg/mL. Forced degradation study was carried out under acidic, alkaline, oxidative, photolytic and thermal conditions to demonstrate the stability-indicating capability of the developed HPLC method. Developed method is validated as per ICH guidelines and found to be linear, accurate, specific, selective, precise, robust and useful during the process development as well as quality check in bulk drug manufacturing.

Computational Investigation into the Oxidation of Guanine to Form Imidazolone (Iz) and Related Degradation Products.

Imidazolone (Iz) is one of the many products resulting from oxidative damage to DNA. Three pathways for the formation of Iz and related degradation products have been studied by density functional theory using the ωB97XD functional with the 6-31+G(d,p) basis set and SMD implicit water solvation plus a small number of explicit water molecules positioned to help stabilize charged species and facilitate reaction steps. The first pathway starts with guanine radical and the addition of superoxide at C5. Endoperoxide formation was calculated to have slightly lower barriers than diol formation. The next steps are pyrimidine ring opening and decarboxylation. Ring migration then proceeds via an acyclic intermediate rather than a bicyclic intermediate and is followed by formamide loss to yield Iz. The second pathway starts with 8oxoG and proceeds via C5 superoxide addition and diol formation to a relatively stable intermediate, oxidized guanidinohydantoin (Ghox). The barriers for hydroxide ion addition to Ghox are much lower than for water addition and should yield more Iz and parabanic acid at higher pH. The third pathway starts with 8-hydroxy guanine radical formed by hydroxyl radical addition to C8 of guanine or water addition to C8 of guanine radical. Superoxide addition at C5 is followed by diol formation, ring opening and decarboxylation similar to pathways 1 and 2, subsequently leading to Iz formation. The calculated pathways are in good agreement with experimental observations.