A critical review on the use of modern sophisticated hyphenated tools in the characterization of impurities and degradation products

Development of stability-indicating assay method and liquid chromatography-quadrupole-time-of-flight mass spectrometry-based structural characterization of the forced degradation products of alpelisib

The US Food and Drug Administration and the European Medicines Agency approved alpelisib in 2019 for the treatment of metastatic breast cancer. A thorough literature review revealed that a stability-indicating analytical method (SIAM) is not available for the quantification of alpelisib and its degradation products (DPs). In this study, per the comprehensive stress study recommended by the International Council for Harmonisation (ICH), alpelisib was exposed to hydrolysis, oxidation, photolysis, and thermal stress. Degradation of the drug was observed under hydrolysis, oxidative, and photolysis conditions, whereas the drug was stable under thermal stress condition. We developed a SIAM for the separation of alpelisib and its major DPs that were formed under different stress conditions. The validation of the developed method was performed per ICH Q2(R1) guidelines. Five DPs were identified and characterized. Structure elucidation of all DPs was performed with the modern characterization tool of liquid chromatography-quadrupole time-of-flight mass spectrometer (LC-Q-TOF-MS/MS). The degradation pathway of the drug and its mechanisms were outlined, and in silico toxicity prediction was performed using the ProTox-II tool.

Oxidative treatment of micropollutants present in wastewater: A special emphasis on transformation products, their toxicity, detection, and field-scale investigations

Micropollutants have become ubiquitous in aqueous environments due to the increased use of pharmaceuticals, personal care products, pesticides, and other compounds. In this review, the removal of micropollutants from aqueous matrices using various advanced oxidation processes (AOPs), such as photocatalysis, electrocatalysis, sulfate radical-based AOPs, ozonation, and Fenton-based processes has been comprehensively discussed. Most of the compounds were successfully degraded with an efficiency of more than 90%, resulting in the formation of transformation products (TPs). In this respect, degradation pathways with multiple mechanisms, including decarboxylation, hydroxylation, and halogenation, have been illustrated. Various techniques for the analysis of micropollutants and their TPs have been discussed. Additionally, the ecotoxicity posed by these TPs was determined using the toxicity estimation software tool (T.E.S.T.). Finally, the performance and cost-effectiveness of the AOPs at the pilot scale have been reviewed. The current review will help in understanding the treatment efficacy of different AOPs, degradation pathways, and ecotoxicity of TPs so formed.

Differential role of potential stressors, underlying degradation mechanism, characterization of degradants using LC-MS/MS, and establishment of a stability-indicating analytical method for duvelisib

Duvelisib (DUV) was first approved globally in 2018. An extensive literature search revealed that the differential role of a potential degradation medium in altering the shelf-life of DUV due to its exposure during storage has not been identified till date. Moreover, its degradation impurities and degradation mechanism are not known. In addition, no analytical method has been reported for the quantification of DUV in the presence of its degradation impurities. Therefore, the aim of this study was to identify the impact of different potential degradation media on the stability of DUV, establish the degradation mechanism, and identify its major degradation impurities. The aim was also to establish a stability-indicating analytical method for the quantification of DUV in the presence of its degradation impurities. This study is the first to report the structure of degradation impurities and the step-by-step degradation mechanism of DUV. This information will be useful for the scientific community and manufacturers in optimizing the formulation parameters and/or storage conditions. The validated method can be employed for analysis of stability study and routine quality control samples of newer DUV formulations in pharmaceutical industries. The identified impurities may serve as impurity standards for specifying their limits in the drug after required qualification studies.

A critical assessment on stability behaviour of Vorinostat using LC-MS-QTOF with H/D exchange and NMR

Vorinostat is the first USFDA-approved HDAC inhibitor for the treatment of cutaneous t-cell lymphoma. Vorinostat was exposed to ICH-recommended hydrolytic (acid, base, and neutral), oxidative, thermal, and photolytic stress conditions to understand the degradation behaviour. A Stability indicating LC method was developed and validated for separating and identifying forced degradation products. Under different stress conditions, six degradants were identified and characterized by LC-HRMS, MS/MS, and hydrogen-deuterium exchange mass studies. Vorinostat was found to be highly susceptible to the acidic and basic environment. In contrast, the drug substance was stable in the solid state under thermal and photolytic conditions whereas, it was found moderately stable when photolytic stress was provided to dissolved state of Vorinostat in acetonitrile-water. The degradants were identified as 7-amino-N-phenylheptanamide, 8-hydrazineyl-8-oxo-N-phenyloctanamide, 8-oxo-8-(phenylamino)octanoic acid, 8-oxo-8-(2-(7-oxo-7-(phenylamino)heptyl)hydrazineyl)-N-phenyloctanamide, 8,8'-(1-hydroxyhydrazine-1,2-diyl)bis(8-oxo-N-phenyloctanamide), and N1-((8-oxo-8-(phenylamino)octanoyl)oxy)-N8-phenyloctanediamide. The mechanistic explanation for the formation of each degradant in stability conditions has also been derived. The major degradants were also isolated/synthesized and characterized through 1H NMR for preparing impurity standards. Additionally, in-silico toxicity of the degradants was predicted in comparison to the drug, to identify whether any degradant has any specific type of toxicity and requires special focus to set specification limits during formulation development. The predicted toxicity indicated that the degradants have similar safety profile as that of the drug and specification can be set as per general impurity guideline.

Investigation of Unusual N-(Triphenyl-λ5-phosphanylidene) Amide Fragmentation Observed upon MS/MS Collision-Induced Dissociation

A mechanism of unusual tandem (MS/MS) fragmentation of protonated species of N-(triphenyl-λ⁵-phosphanylidene) derivatives, [M + H]⁺ to generate triphenylphosphine oxide (TPPO) within the mass spectrometer has been investigated and reported. Collision-induced dissociation of these molecules resulted in the generation of TPPO as a signature fragment. This fragment suggested the presence of a P-O bond in the structure which was contrary to the structure of the compound identified by nuclear magnetic resonance spectrometry (NMR) and single-crystal X-ray diffractometry (SXRD) techniques with a P═N bond rather than a P-O bond. In order to confirm the generation of the TPPO fragment within the mass spectrometer, 14 different N-(triphenyl-λ⁵-phosphanylidene) derivatives containing amide, ¹⁸O-labeled amide, thiamide, and nonacyl phosphazene derivatives were synthesized and their MS/MS behavior was studied by liquid chromatography-high-resolution mass spectrometry. Fragmentation of these amide derivatives generated TPPO/TPPS or their ¹⁸O-labeled analogues as the major fragment in almost all cases under similar MS conditions. Based on the outcome of these experiments, a plausible mechanism for such fragmentation, involving the intramolecular shifting of oxygen from carbon to phosphorus, has been proposed. DFT calculations for the protonated species at B3LYP-D3/6-31+G(d,p) further supported the proposed mechanism involving a four-membered ring, P-O-C-N, as the transition state. Details of this work are presented here.

Isolation, structural characterization and quantification of impurities in bupivacaine

Bupivacaine was found to be unstable during the accelerated storage condition(40 ℃ and 75% relative humidity), and two degradation impurities with the same protonated molecular ion were observed by high performance liquid chromatography-mass spectrometry (LC-MS). A semipreparative method was used to separate and purify the two impurities, and their structures were elucidated via comprehensive HR-MSMS and NMR spectroscopy analyses. Their stereo structures were characterized through single crystal X-ray diffraction. Meanwhile, an LC-MS method was developed and validated to quantify the two degradation impurities of bupivacaine. Chromatographic separation was performed on a C18 reversed-phase column (4.6 × 150 mm, 5 µm) using an equivalent elution with water and methanol. The limits of quantitation for the two degradation impurities (named RS1 and RS2) were 0.89 and 0.65 ng, respectively, and the average recoveries were in the range of 90∼108% and relative standard deviations were less than 5.0%. The proposed LC-MS method can be used to control the quality of bupivacaine and its formulations. DATA AVAILABILITY: Data will be made available on request.

Hyphenated liquid chromatography - diode array detection - charged aerosol detection - high resolution - multistage mass spectrometry with online hydrogen/deuterium exchange: One stop solution for pharmaceutical impurity profiling

Hyphenation of different analytical techniques has always been advantageous in structural characterization as it saves time, money and resources. In the pharmaceutical sector, chromatography-based impurity profiling, including identification, characterization, and quantification in drug substances or finished products, is of utmost importance to comply with quality, patient safety and regulatory requirements. These impurities are monitored using LC-UV/DAD and identified and/or characterized using HRMS and MS/MS. LC analysis usually yields the area percent purity of the targeted peak, however, this is not sufficient for pharmaceutical purposes; where the regulatory requirement is to report impurities in percent weight by weight. Unfortunately, the non-availability of impurity standards and relative response factors at an early stage of drug development, risks the product quality due to the inability of the method to differentiate percent purity, and percent weight by weight. Hence, there is a need for a distinctive way of determining the relative response factor. In the current study, a unique hyphenation has been employed by integrating LC with DAD, CAD, and HRMSⁿ with hydrogen-deuterium exchange. The LC flow, post-DAD detection has been diverted to CAD with an inverse gradient for relative response factor determination and MS Orbitrap for exact mass, and MSⁿ fragmentation. A separate infusion pump has been incorporated to infuse D₂O on a need basis, which can perform partial hydrogen deuterium exchange for determining the number of labile hydrogens in the impurity structure. This hyphenation has been validated with four model compounds and a total of nineteen chromatographic peaks. The technique provides ample information for their qualitative analysis along with percent weight-by-weight values, which fulfils the regulatory requirements and can be used as one-stop solution for impurity profiling.

Characterization of potential degradation products of brexpiprazole by liquid chromatography/quadrupole-time-of-flight mass spectrometry and nuclear magnetic resonance, and prediction of their physicochemical properties by ADMET Predictor™

RATIONALE

Brexpiprazole (BRZ) was subjected to hydrolytic (acid, base and neutral), oxidative, photolytic and thermal stress degradation in solutions prepared in a mixture of acetonitrile-water (70:30 v/v). The oxidative study was additionally done in methanol-buffer mixture at pH 3, 7 and 11. Also, compatibility of the drug with selected excipients was investigated in the solid state. Additionally, physicochemical and ADMET properties of BRZ and its degradation products (DPs) were predicted using ADMET Predictor™ software. It provides the conditions for quality control of BRZ and its derivatives during manufacturing, processing and storage conditions.

METHODS

The formed DPs were separated from the drug and among themselves on a C-18 column utilizing mobile phase composed of methanol and ammonium formate buffer (10mM, pH 4.0), which was run in a gradient mode. Characterization of DPs was carried out by first establishing the mass fragmentation pathway of the drug based on its liquid chromatography/quadrupole-time-of-flight mass spectrometry (LC/Q-TOF-MS) data, followed by LC/Q-TOF-MS studies of DPs. Three DPs were isolated and, along with the drug, they were subjected to 1D (¹ H, ¹³ C and DEPT-135) and 2D (COSY and HSQC) NMR studies for confirmation of their structures.

RESULTS

BRZ was observed to be susceptible to hydrolytic (neutral, acid and alkali), photolytic and oxidative degradation conditions; it was stable on thermal exposure. A total of 12 DPs (BRZ-1 to BRZ-12) were formed in solution state. Mechanisms of BRZ degradation were postulated.

CONCLUSIONS

The extent of degradation of BRZ in different stress conditions highlights that stability of BRZ in drug formulations can be improved (i) by using excipients that can impart a low-pH microenvironment, (ii) by addition of antioxidants and (iii) through protection from light.

Mechanism of capmatinib degradation in stress conditions including degradation product characterization using ultra-high-performance liquid chromatography-quadrupole-time of flight mass spectrometry and stability-indicating analytical method development

RATIONALE

Capmatinib (CMT) has been recently approved for the treatment of non-small cell lung cancer by the United States Food and Drug Administration (USFDA). Till date, the degradation mechanism of CMT in different stress conditions is not known. Moreover, degradation products (DPs) of the drug are yet to be identified. Characterization study on degradation products of CMT has not been reported before. Furthermore, no previously reported literature is available on the stability-indicating method of CMT.

METHODS

Owing to the lack of such scientific reports, we developed a sensitive, stability-indicating method for CMT which can resolve it from all its degradation products. The method was validated as per the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH Q2 [R1]) guideline. We studied and established the degradation mechanism of CMT in different stress conditions. One degradation product (DP2) was isolated and characterized using ¹ H NMR.

RESULTS

The degradation products (DP1, DP2 and DP3) of the drug have been identified and characterized for the first time by using high-resolution mass spectrometry and ¹ H NMR spectroscopy. CMT was found to become degraded under acidic, basic and photolytic stress conditions in the solution phase to yield three major DPs. The drug was found to be stable in neutral hydrolysis, oxidation and thermal stress conditions.

CONCLUSIONS

DP1 was formed under acidic and basic hydrolytic conditions, whereas DP2 and DP3 were formed under photolytic conditions. Characterization of all the DPs has been carried out to establish their structures and understand the molecular mechanism behind the degradation of the drug. Few studies reported quantitative analysis of CMT and its metabolites in biological fluids. However, this is the first study to identify the unknown DPs of CMT and the mechanism of its degradation. Moreover, this article reports a stability-indicating analytical method for CMT which has not yet been reported in any literature.

Screening of Novel Antimicrobial Diastereomers of Azithromycin-Thiosemicarbazone Conjugates: A Combined LC-SPE/Cryo NMR, MS/MS and Molecular Modeling Approach

A well-known class of antibacterials, 14- and 15-membered macrolides are widely prescribed to treat upper and lower respiratory tract infections. Azithromycin is a 15-membered macrolide antibiotic possessing a broad spectrum of antibacterial potency and favorable pharmacokinetics. Bacterial resistance to marketed antibiotics is growing rapidly and represents one of the major global hazards to human health. Today, there is a high need for discovery of new anti-infective agents to combat resistance. Recently discovered conjugates of azithromycin and thiosemicarbazones, the macrozones, represent one such class that exhibits promising activities against resistant pathogens. In this paper, we employed an approach which combined LC-SPE/cryo NMR, MS/MS and molecular modeling for rapid separation, identification and characterization of bioactive macrozones and their diastereomers. Multitrapping of the chromatographic peaks on SPE cartridges enabled sufficient sample quantities for structure elucidation and biological testing. Furthermore, two-dimensional NOESY NMR data and molecular dynamics simulations revealed stereogenic centers with inversion of chirality. Differences in biological activities among diastereomers were detected. These results should be considered in the process of designing new macrolide compounds with bioactivity. We have shown that this methodology can be used for a fast screening and identification of the macrolide reaction components, including stereoisomers, which can serve as a source of new antibacterials.

Two Validated Chromatographic Methods for Determination of Ciprofloxacin HCl, One of its Specified Impurities and Fluocinolone Acetonide in Newly Approved Otic Solution

Two sensitive, selective and precise chromatographic methods have been established for concomitant quantification of ciprofloxacin HCl (CIP), fluocinolone acetonide (FLU) along with ciprofloxacin impurity A (CIP-imp A). The first method was thin-layer chromatography (TLC-densitometry) where separation was accomplished using TLC silica plates 60 G.F254 as a stationary phase and chloroform-methanol-33%ammonia (4.6:4.4:1, by volume) as a developing system. The obtained plates were scanned at 260 nm over concentration ranges of 1.0-40.0, 0.6-20.0 and 1.0-40.0 μg band-1 for CIP, FLU and CIP-imp A, respectively. The second method was based on high-performance liquid chromatography using a Zorbax ODS column (5 μm, 150 × 4.6 mm i.d.) where adequate separation was achieved through a mobile phase composed of phosphate buffer pH 3.6-acetonitrile (45:55, v/v) at flow rate 1.0 mL min-1 with ultraviolet detection at 254 nm. Linear regressions were obtained in the range of 1.0-40.0 μg mL-1 for CIP, 0.6-20.0 μg mL-1 for FLU and 1.0-40.0 μg mL-1 for CIP-imp A. The suggested methods were validated in compliance with the International Conference on Harmonization guidelines and were successfully applied for determination of CIP and FLU in bulk powder and newly marketed otic solution.

In silico toxicity evaluation for transformation products of antimicrobials, from aqueous photolysis degradation

This study investigates degradation processes of three antimicrobials in water (norfloxacin, ciprofloxacin, and sulfamethoxazole) by photolysis, focusing on the prediction of toxicity endpoints via in silico quantitative structure-activity relationship (QSAR) of their transformation products (TPs). Photolysis experiments were conducted in distilled water with individual solutions at 10 mg L^-1 for each compound. Identification of TPs was performed by means of LC-TOF-MS, employing a method based on retention time, exact mass fragmentation pattern, and peak intensity. Ten main compounds were identified for sulfamethoxazole, fifteen for ciprofloxacin, and fifteen for norfloxacin. Out of 40 identified TPs, 6 have not been reported in the literature. Based on new data found in this work, and TPs already reported in the literature, we have proposed degradation pathways for all three antimicrobials, providing reasoning for the identified TPs. QSAR risk assessment was carried out for 74 structures of possible isomers. QSAR predictions showed that all 19 possible structures of sulfamethoxazole TPs are non-mutagenic, whereas 16 are toxicant, 18 carcinogenic, and 14 non-readily biodegradable. For ciprofloxacin, 28 out of the 30 possible structures for the TPs are mutagenic and non-readily biodegradable, and all structures are toxicant and carcinogenic. All 25 possible norfloxacin TPs were predicted mutagenic, toxicant, carcinogenic, and non-readily biodegradable. Results obtained from in silico QSAR models evince the need of performing risk assessment for TPs as well as for the parent antimicrobial. An expert analysis of QSAR predictions using different models and degradation pathways is imperative, for a large variety of structures was found for the TPs.

Normal-Phase TLC and Gradient Reversed-Phase HPLC for the Simultaneous Determination of Enrofloxacin and Bromhexine HCl in Presence of Two of Their Official Impurities

In this work, two chromatographic methods are developed and validated for the determination of enrofloxacin and bromhexine (BRM) HCl in the presence of two of their specified impurities, ciprofloxacin and BRM impurity C. The suggested chromatographic methods included the use of thin layer chromatography (TLC-densitometry) and high-performance liquid chromatography (HPLC). In case of TLC-densitometry, good separation was achieved by using mobile phase of n.butanol:acetone:water:glacial acetic acid:triethylamine (10:3:1:0.5:0.5, by volume) on silica gel stationary phase at 254-nm detection. The developed HPLC method used BDS HYPERSIL C18 column with a mobile phase of water:acetonitrile:methanol:triflouroacetic acid. A linear gradient elution of 75-10%, 20-50% and 5-40% for water, acetonitrile and methanol, respectively, was applied in 13 min at a flow rate of 1.5 mL min-1. These methods were sufficient to separate the four substances simultaneously, and they are validated as per International Conference on Harmonization guidelines.

An Overview of Advances in the Chromatography of Drugs Impurity Profiling

A systematic literature survey published in several journals of pharmaceutical chemistry and of chromatography used to analyze impurities for most of the drugs that have been reviewed. This article covers the period from 2016 to 2020, in which almost of chromatographic techniques have been used for drug impurity analysis. These chromatography techniques are important in the analysis and description of drug impurities. Moreover, some recent developments in forced impurity profiling have been discussed, such as buffer solutions, mobile phase, columns, elution modes, and detectors are highlighted in drugs used for the study. This primarily focuses on thorough updating of different analytical methods which include hyphenated techniques for detecting and quantifying impurity and degradation levels in various pharmaceutical matrices.

Recent Progresses in Analytical Perspectives of Degradation Studies and Impurity Profiling in Pharmaceutical Developments: An Updated Review

Forced degradation studies have been used to simplify analytical methodology development and achieve a deeper knowledge about the inherent stability of active pharmaceutical ingredients (API) and drug products. This provides insight into degradation species and pathways. Identification of impurities in pharmaceutical products is closely related to the selection of the most appropriate analytical methods like HPLC-UV, LC-MS/MS, LC-NMR, GC-MS, and capillary electrophoresis. Herein, recent trends in analytical perspectives during 2018-April 14, 2021, are discussed based on forced and impurity degradation profiling of pharmaceuticals. Literature review showed that several methods have been used for experimental design and analysis conditions such as matrix type, column type, mobile phase, elution modes, detection wavelengths, and therapeutic category. Thus, since these factors influence the separation and identification of the impurities and degradation products, we attempted to perform a statistical analysis for the developed methods according to the abovementioned factors.

A study on structural characterization of potential impurities of Sugammadex sodium using LC/ESI/QTOF/MS/MS and NMR

The first selective relaxant binding agent (SRBA), Sugammadex sodium (SGS) is used to reverse anesthesia. A study of the process related and degradation products will help to optimize process parameters and also to develop the analytical methods and set the quality standard for a quality control strategy in pharmaceutical industry. During the manufacture of SGS, all the process related impurities are controlled in every stage and process related and degradation products are controlled in the active pharmaceutical ingredient (API) as per ICH guidelines. A total of nine process related and degradation impurities of SGS (Impurity-A to Impurity-I) were isolated and characterized by using LC/ESI/QTOF/MS/MS and NMR studies.

UHPLC-DAD Method Development and Validation: Degradation Kinetic, Stress Studies of Farnesol and Characterization of Degradation Products Using LC-QTOF-ESI-MS with in silico Pharmacokinetics and Toxicity Predictions

Farnesol (FAR) is a sesquiterpene molecule with high lipophilicity that has antibacterial and other pharmacological properties along with broad nutritional values with high commercial values. Although having potential, FAR stability behavior and degradation kinetics are not available in the literature. Hence, it is very essential to develop a simple, rapid, accurate, precise, robust, cheap UHPLC-DAD method for FAR. It was also proposed to study mechanistic insights into FAR under different degradation conditions. Therefore, we hypothesized to do systematic stability studies along with degradation kinetic and accelerated stability studies. The developed method was validated. FAR was studied for stress studies, degradation kinetics and ADMET prediction of degradants. Degradation products were characterized using LC-QTOF-ESI-MS. Developed method consists of an isocratic mobile phase with a wavelength of 215 nm. The percent recoveries for FAR were observed within the acceptance limit of 98-102%. The eight major degradation products were formed during stress studies. FAR follows first-order degradation kinetics. FAR and all degradants were found to have more than 75% good human oral absorption, and are non-toxic. FAR UHPLC-DAD method was developed, validated and performed stability studies to know the possible degradation pattern along with degradation kinetic studies.

A Tribute to Professor Saranjit Singh - A Critical Thinker, Innovator, Mentor, and Educator

This commentary presents contributions and accomplishments of Professor Saranjit Singh, National Institute of Pharmaceutical Education and Research (NIPER), SAS Nagar, India, to pharmaceutical research and education. Prof. Singh completed his successful tenure in October 2021. Over his 40+ years of illustrious academic career, he trained 147 Masters and 15 PhD students in the fields of drug stability testing, degradation chemistry, impurity and metabolite characterization, and advanced analytical technologies. He has published ∼250 research articles, reviews, editorials, patent, book, and book chapters, and received numerous awards, including the Professor M.L. Khorana Memorial Lecture Award from the Indian Pharmaceutical Association (IPA) and the Outstanding Analyst and Eminent Analyst awards from the Indian Drug Manufacturers' Association (IDMA). This commentary highlights Prof. Singh's inspiring personal and renowned professional journey, including early life, education, career, accomplishments, as well as his services to academia, industry, and regulatory. By sharing the contributions and accomplishments of Prof. Singh, we strongly believe that his story will inspire the next generation of scientists to continue his legacy to advance the field.

Rapid Structure Determination of Bioactive 4″-Tetrahydrofurfuryl Macrozone Reaction Mixture Components by LC-SPE/Cryo NMR and MS

LC-SPE/cryo NMR and MS methodologies have been developed and employed for a rapid structure determination of 4″-tetrahydrofurfuryl macrozone reaction mixture components. Macrozones, novel conjugates of azithromycin, and thiosemicarbazones have shown very good in vitro antibacterial activities against susceptible and some resistant bacterial strains and are promising agents for further development. The post-column multiple trapping of the chromatographically separated reaction mixture components on the SPE cartridges increased the sensitivity and together with cryogenically cooled NMR probe made it possible to identify and structurally characterize main 4″-tetrahydrofurfuryl macrozone reaction mixture compounds including those present at very low concentration level. This approach has several advantages over a classical off-line procedure, efficiency and low solvent consumption being the two most important ones. All identified components were process-related. It has been demonstrated that two different kinds of compounds with respect to structure were identified, i.e., macrolide-related and thiosemicarbazone-related ones. This methodology can serve as a platform for reliable and effective macrolides reaction components structure profiling, serving as both isolation and identification tools.

Separation and structural elucidation of cefsulodin and its impurities in both positive and negative ion mode in cefsulodin sodium bulk material using liquid chromatography/tandem mass spectrometry

RATIONALE

The structural identification of impurities in cephalosporins has been reported. However, to the best of our knowledge, there was no report on the impurities of cefsulodin sodium, which is necessary for the quality control. Thus, the aim of this study was to separate and characterize the impurities in cefsulodin sodium raw material using liquid chromatography/tandem mass spectrometry (LC/MS/MS).

METHODS

The analytes were separated on a Kromasil 100-5C18 column (4.6 mm × 250 mm, 5 μm) using a gradient elution with a mobile phase consisting of 1% ammonium sulphate aqueous solution and acetonitrile in the first dimension. The separation in the second dimension was carried on a Shimadzu Shim-pack GISS C18 column (50 mm × 2.1 mm, 1.9 μm) with a mobile phase consisting of 10 mM ammonium formate solution and methanol.

RESULTS

The fragmentation behaviors of cefsulodin and its impurities were studied and the structures of the impurities were deduced based on the MSⁿ data. The structures of ten unknown impurities were proposed based on the work carried out in this study. The degradation behaviors of cefsulodin sodium were also studied. This revealed that cefsulodin sodium should be stored in a dry, cool and dark closed container.

CONCLUSIONS

Based on the characterization of impurities, this study not only revealed the mechanism by which impurities were produced, thus providing guidance to pharmaceutical companies for manufacturing process improvement and impurity control, but also provided a scientific basis for further improvement of official monographs in pharmacopoeias.

Characterization of stress degradation products of nintedanib by UPLC, UHPLC-Q-TOF/MS/MS and NMR: Evidence of a degradation product with a structure alert for mutagenicity

Nintedanib is an anti-cancer drug used for the treatment of idiopathic pulmonary fibrosis and non-small cell lung cancer. The purpose of this study was to explore its degradation chemistry under various stress conditions recommended in ICH guidelines Q1A R(2). The drug was subjected to hydrolytic, photolytic, thermal and oxidative (H₂O₂, AIBN, FeCl₃ and FeSO₄) stress conditions. The degradation products formed in stressed solutions were successfully separated on an ACQUITY UPLC CSH C18 (2.1 × 100 mm, 1.7 μm) column, using a gradient UPLC-PDA method, developed with acetonitrile:methanol (90:10) and 0.1 % formic acid (pH 3.0) as the mobile phase. The drug proved to be labile to acidic, neutral and alkaline hydrolytic, and H₂O₂/AIBN oxidative conditions. It was stable to photolytic and thermal stress conditions, and even in oxidative reaction solutions containing FeCl₃ or FeSO₄. Additionally, the drug exhibited instability when its powder with added sodium bicarbonate was stored at 40 °C/75 % RH for 3 months. In total, nine degradation products (DPs 1-9) were formed. To characterize them, a comprehensive mass fragmentation pathway of the drug was first established using UHPLC-Q-TOF/MS/MS data. Similarly, the mass studies were then carried out on the stressed samples using the developed UPLC method. All the degradation products were primarily characterized through comparison of their mass fragmentation profiles with that of the drug. To confirm the structure in one case (DP 3), additional nuclear magnetic resonance (NMR) studies were carried out on the isolated product. Subsequently, mechanisms for their formation were laid down. A significant finding was the formation of a degradation product upon acid hydrolysis having a free aromatic amine moiety, which is considered as a structural alert for mutagenicity. Furthermore, the physicochemical and ADMET properties of the drug and its degradation products were predicted using ADMET predictor™ software.

Separation and characterization of impurities and isomers in cefpirome sulfate by liquid chromatography/tandem mass spectrometry and a summary of the fragmentation pathways of oxime-type cephalosporins

RATIONALE

Although the identification of degradation products of cefpirome sulfate has been reported, there has been no report concerning the impurities in bulk samples of this compound. To meet the requirements of the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use, the structures of impurities whose content are over 0.1% need to be confirmed. Thus, characterization of the impurities in cefpirome sulfate bulk samples is critical for controlling the production of this drug.

METHODS

The structures of cefpirome sulfate impurities were investigated using two-dimensional liquid chromatography (LC) coupled to electrospray ionization tandem mass spectrometry. In the first LC dimension, a Kromasil 100-5C18 column (4.6 mm × 250 mm, 5 μm) was used, and the mobile phases were 0.03 M ammonium dihydrogen phosphate solution and acetonitrile. In the second dimension, the column was a Shimadzu Shim-pack GISS C18 column (50 mm × 2.1 mm, 1.9 μm), and the mobile phases were 10 mM ammonium formate solution and methanol. An ion trap time-of-flight mass spectrometer operated in both positive and negative ion mode was employed in this study.

RESULTS

Nine impurities and isomers in cefpirome sulfate, eight of which were previously unknown, were separated and characterized. Structures were proposed for the eight unknown compounds based on the MSn fragmentation data. The degradation behavior of cefpirome sulfate was also studied.

CONCLUSIONS

Based on the characterization of impurities and isomers, this study could be used to improve the quality control of the cefpirome sulfate drug recommended in pharmacopoeias. The degradation behavior of cefpirome sulfate provides a basis for the selection of storage conditions.

Characterization of degradation products of celiprolol hydrochloride using hyphenated mass and NMR techniques

Stress degradation studies were carried out on celiprolol hydrochloride under the ICH prescribed hydrolysis (acidic, basic and neutral), photolytic, oxidative and thermal conditions. Maximum degradation was observed upon hydrolysis, especially in the basic condition. In oxidative condition, the drug degraded only upon severe exposure to H₂O₂, but it remained stable when challenged with AIBN. It also degraded significantly under photolytic conditions. However, the drug was stable to thermal stress. A total of seven degradation products were formed, whose separation was successfully achieved on an Inertsil ODS-3V C-18 HPLC column employing a gradient mobile phase. A comprehensive mass fragmentation pattern of the drug was initially established through the support of high resolution mass spectrometry (HR-MS), multi-stage tandem mass spectrometry (MSⁿ) and on-line H/D exchange MS data. The same approach was then extended to characterization of the degradation products. Additionally, two degradation products were isolated and subjected to 1D/2D NMR studies for their structural confirmation. One of the degradation products showed instability during isolation, therefore, it was subjected to LC-NMR studies for its structural confirmation.

Identification and structural characterization of potential degraded impurities of ribociclib by time of flight -tandem mass spectrometry, and their toxicity prediction

The US FDA and EMA approved Ribociclib (RIBO) to treat metastatic breast cancers in 2017. Formation of impurities during storage of any drug can significantly contribute to its overall toxicity and therapeutic efficacy, which ultimately leads to a safety concern. Over the period, it has been observed that impurities sometimes cause serious unwanted toxicity, which can even lead to withdrawal of a drug from market. Therefore, complete characterization of potential impurities is extremely important to identify molecular hot spots regarding structural changes. To the best of our knowledge, till date, the potential degraded impurities of RIBO are unknown. No study reported in literature on the structural characterization of the degradation impurities of RIBO. In this study, an ICH recommended comprehensive stress study under hydrolytic, oxidative, photolytic and thermolytic conditions was performed on RIBO. The degradation products were characterized by tandem mass spectrometry utilising time of flight mass analyzer majorly after electrospray ionisation. The atmospheric pressure chemical ionisation mode was employed in characterization of the N-oxide degradation products where Meisenheimer rearrangement occurred. A degradation product was synthesized in house and fully characterized with the help of NMR (¹H NMR, ¹³C NMR, DEPT, 2D NMR and D₂O exchange experiments). The source of formylation for the generation of degradation products was investigated employing different solvent systems. The degradation pathways were delineated by explaining the putative mechanism of degradation in various conditions. The in silico toxicity of the degradation impurities was evaluated with the help of ProTox-II toxicity prediction platform.

Stability assessment of tamsulosin and tadalafil co-formulated in capsules by two validated chromatographic methods

The advent of a new pharmaceutical formulation evokes the need for examining the chemical stability of their constituents and establishing proper stability-indicating methods. Herein, the stability of the newly co-formulated Tamsulosin and Tadalafil were examined under different stress conditions. The acidic degradation of Tamsulosin yielded its sulfonated derivative, while Tadalafil was susceptible to both acidic and basic degradation. Two stability-indicating chromatographic methods, namely; high-performance thin-layer chromatography and high-performance liquid chromatography, have been developed. Significant high-performance thin-layer chromatography-fractionation could be achieved by utilizing a stationary phase of silica gel 60 F₂₅₄ and a mobile phase composed of ethyl acetate/toluene/methanol/ammonia (4:2:4:0.6, by volumes) with densitometric recording at 280 nm over a concentration range of 0.5-25 μg/band for both drugs. The HPLC-separation could be reached on XBridge^® C₁₈ column isocraticaly by using a mobile phase having acetonitrile/phosphate buffer, pH 6.0 (45:55, v/v) pumped at a flow rate of 1.7 mL/min and applying diode array ultraviolet-detection at 210 nm over a linearity range of 3-70 μg/mL for each drug. Specificity of the two methods was additionally assured via peak purity assessment. Moreover, the methods were distinctly exploited for evaluating the drugs' stability in accelerated stability-studied samples of Tamplus^® capsules.

Capillary electrophoretic methods for quality control analyses of pharmaceuticals: A review

Capillary electrophoresis represents a promising technique in the field of pharmaceutical analysis. The presented review provides a summary of capillary electrophoretic methods suitable for routine quality control analyses of small molecule drugs published since 2015. In total, more than 80 discussed methods are sorted into three main sections according to the applied electroseparation modes (capillary zone electrophoresis, electrokinetic chromatography, and micellar, microemulsion, and liposome-electrokinetic chromatography) and further subsections according to the applied detection techniques (UV, capacitively coupled contactless conductivity detection, and mass spectrometry). Key parameters of the procedures are summarized in four concise tables. The presented applications cover analyses of active pharmaceutical ingredients and their related substances such as degradation products or enantiomeric impurities. The contribution of reported results to the current knowledge of separation science and general aspects of the practical applications of capillary electrophoretic methods are also discussed.

Development of a method of analysis for profiling of the impurities in phenoxymethylpenicillin potassium based on the analytical quality by design concept combined with the degradation mechanism of penicillins

Accurate analysis of all of the impurities present in a substance is critical for controlling the impurity profiles of drugs. Penicillins can easily yield a formidable array of degradation-related impurities (DRIs) with significantly different polarities and charge properties, which renders identifying each one a complicated matter. In this work, phenoxymethylpenicillin potassium (Pen V) was selected to find a way to quickly establish a robust analysis method for the impurity profiling of penicillin. Based on the analytical quality by design (AQbD) concept and the degradation mechanism of the drug, structures of all of the DRIs were first proposed. Then Pen V and its detected DRIs were separated and identified by liquid chromatography-tandem mass spectrometry method (LC-MS). Characteristic fragment ions and mass fragmentation process of Pen V and its detected DRIs were summarized. In addition, a quantitative structure-retention relationship (QSRR) model was constructed to predict the retention times of undetected impurities and to evaluate whether the chromatographic system can separate them. Finally, a stability-indicating high-performance liquid chromatography (HPLC) method was developed that can separate all of the DRIs of Pen V.

Intrinsic Stability Study and Forced Degradation Profiling of Olopatadine Hydrochloride by RP-HPLC-DAD-HRMS Method

Objectives

Forced degradation determines the intrinsic stability of a molecule by establishing degradation pathways in order to identify the likely degradation products (DPs). The objective of the present research was to establish intrinsic stability and forced degradation profiling of olopatadine hydrochloride.

Materials and Methods

The intrinsic stability of olopatadine hydrochloride was evaluated by RP-HPLC, where a mixture of 0.1% formic acid and organic phase (methanol:acetonitrile; 50:50 % v/v) was used as mobile phase at 1.0 mL/min in gradient mode. Different stress conditions were employed to explore the intrinsic stability of olopatadine hydrochloride.

Results

In acidic condition, five DPs, i.e. OLO1, OLO2, OLO3, OLO4, and OLO5, were observed. OLO5 was the major DP that increased with time and the peak area of OLO was decreased. In addition to OLO3 and OLO5, two more DPs were observed in alkaline condition, i.e. OLO6 and OLO7. OLO5 and OLO6 were two major DPs; OLO5 increased with time while OLO6 had a zigzag pattern of peak area with time. All DPs of neutral condition were also found in acidic condition while OLO3 and OLO5 were common in all three types of hydrolytic degradation.

Conclusion

Thus, OLO has similar pattern of degradation profiling in all hydrolytic conditions (acidic, alkaline, and neutral). No degradation was found in thermal, ultraviolet light, or oxidative conditions over 10 days. OLO-Imp was recognized as an analogue structure of OLO and proposed as 11-[(3-dimethylamino)-propylidene]-6,11-dihydro-dibenz[b,e]oxepin-2-propanoic acid in standard drug. OLO1 was identified as (2-(4-(dimethylamino) butyl) phenyl)methanol, which may be formed by cleavage of the tricyclic ring in neutral condition.

Studies on the characterization and polymorphic stability of Fosamprenavir

Fosamprenavir calcium is an amprenavir prodrug of the protease inhibitors class used in the treatment of patients with acquired immunodeficiency syndrome (AIDS). Different solid forms of this drug are described in patents, in this sense studies on the physico-chemical characterization and stability are relevant for the selection of a solid form with adequate features for pharmaceutical purposes. In the present work form I (commercial) and amorphous of fosamprenavir calcium were characterized by the techniques of Differential Scanning Calorimetry (DSC), Thermogravimetry (TGA), Powder X-ray Diffraction (PXRD), Fourier-Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Furthermore, the chemical and polymorphic stability of the commercial form were evaluated by DSC, PXRD, FTIR and High-Performance Liquid Chromatography (HPLC). In the studies of characterization, thermal analyses allied to spectroscopic methods (PXRD and FTIR) demonstrated that the presence of water in the crystalline structure of Form I is fundamental for maintaining its crystallinity. In studies of accelerated stability the techniques of DSC, PXRD and FTIR showed that Form I does not suffer phase change when submitted to controlled conditions of temperature and humidity. Moreover, HPLC and FTIR proved the chemical stability of this solid form of fosamprenavir, thus demonstrating its suitability for pharmaceutical purposes.

The role of mass spectrometry and related techniques in the analysis of extractable and leachable chemicals

In addition to degradation products, impurities, and exogenous contaminants, industries such as pharmaceutical, food, and others must concern themselves with leachables. These chemicals can derive from containers and closures or migrate from labels or secondary containers and packaging to make their way into products. Identification and quantification of extractables (potential leachables) and leachables, typically trace level analytes, is a regulatory expectation intended to ensure consumer safety and product fidelity. Mass spectrometry and related techniques have played a significant role in the analysis of extractables and leachables (E&L). This review provides an overview of how mass spectrometry is used for E&L studies, primarily in the context of the pharmaceutical industry. This review includes work flows, examples of how identification and quantification is done, and the importance of orthogonal data from several different detectors. E&L analyses are driven by the need for consumer safety. These studies are expected to expand in existing areas (e.g., food, textiles, toys, etc.) and into new, currently unregulated product areas. Thus, this topic is of interest to audiences beyond just the pharmaceutical and health care industries. Finally, the potential of universal detector approaches used in other areas is suggested as an opportunity to drive E&L research progress in this arguably understudied, under-published realm.

Chemometrics Approaches in Forced Degradation Studies of Pharmaceutical Drugs

Chemometrics is the chemistry field responsible for planning and extracting the maximum of information of experiments from chemical data using mathematical tools (linear algebra, statistics, and so on). Active pharmaceutical ingredients (APIs) can form impurities when exposed to excipients or environmental variables such as light, high temperatures, acidic or basic conditions, humidity, and oxidative environment. By considering that these impurities can affect the safety and efficacy of the drug product, it is necessary to know how these impurities are yielded and to establish the pathway of their formation. In this context, forced degradation studies of pharmaceutical drugs have been used for the characterization of physicochemical stability of APIs. These studies are also essential in the validation of analytical methodologies, in order to prove the selectivity of methods for the API and its impurities and to create strategies to avoid the formation of degradation products. This review aims to demonstrate how forced degradation studies have been actually performed and the applications of chemometric tools in related studies. Some papers are going to be discussed to exemplify the chemometric applications in forced degradation studies.

Adenosine Derivates as Antioxidant Agents: Synthesis, Characterization, in Vitro Activity, and Theoretical Insights

In this work, we present results about the synthesis and the antioxidant properties of seven adenosine derivatives. Four of these compounds were synthesized by substituting the N6-position of adenosine with aliphatic amines, and three were obtained by modification of the ribose ring. All compounds were obtained in pure form using column chromatography, and their structures were elucidated by infrared spectroscopy (IR) and Nuclear Magnetic Resonance (NMR). All adenosine derivatives were further evaluated in vitro as free radical scavengers. Our results show that compounds 1c, 3, and 5 display a potent antioxidant effect compared with the reference compound ascorbic acid. In addition, the absorption, distribution, metabolism and excretion (ADME) calculations show favorable pharmacokinetic parameters for the set of compounds analyzed, which guarantees their suitability as potential antioxidant drugs. Furthermore, theoretical analyses using Molecular Quantum Similarity and reactivity indices were performed in order to discriminate the different reactive sites involved in oxidative processes.

A comprehensive study on rearrangement reactions in collision-induced dissociation mass spectrometric fragmentation of protonated diphenyl and phenyl pyridyl ethers

RATIONALE

Recently, we have reported a forced degradation study of a pharmaceutical drug regorafenib which contains a phenyl pyridyl ether derivative as building block. We observed interesting rearrangements in two of its degradation products in tandem mass spectrometry (MS/MS) experiments. As diphenyl ether derivatives are also molecular building blocks of biological importance and used as herbicides and flame retardants, we decided to investigate specifically the fragmentation behavior of these compounds along with phenyl pyridyl derivatives in detail using high-resolution electrospray ionization (ESI) MS/MS.

METHODS

To understand the fragmentation reactions of protonated substituted diphenyl ethers and phenyl pyridyl ethers, ESI-MS/MS experiments were performed using a quadrupole time-of-flight (QTOF) mass spectrometer.

RESULTS

In contrast to radical cations of diphenyl ether derivatives which do not eliminate CO, the [M + H]⁺ ions of substituted diphenyl ethers undergo rearrangement reactions after loss of neutral molecules (H₂ O, HCl, etc.) to form a bicyclic structure containing a keto group and do eliminate CO. Similar rearrangement followed by fragmentation was observed for protonated phenyl pyridyl ethers and the degradation products formed from regorafenib and sorafenib.

CONCLUSIONS

The protonated ions of substituted diphenyl ethers and phenyl pyridyl ethers on collision-induced dissociation have exhibited interesting rearrangement reactions, despite the nature of the substituent on both the aryl moieties. The proposed fragmentation patterns of these compounds give an insight into the understanding of gas-phase reactions in mass spectrometric studies of diphenyl ether and phenyl pyridyl ether derivatives.

A study on structural characterization of degradation products of cangrelor using LC/QTOF/MS/MS and NMR

A complete degradation study was performed on cangrelor drug substance as per the ICH guidelines. The study reveals that a total of six degradation products (DP-1 to DP-6) were found and out of these, three unknown degradation products (DP-1, DP-5 and DP-6) were not reported in the literature. Based on the degradation study, the drug substance cangrelor was found to be sensitive towards acidic, basic and oxidative conditions. Besides, it was stable under thermal and photolytic stress conditions. The degradation products were characterized by using advanced LC/QTOF and MS/MS analysis. Further, the structures were characterized by NMR studies. The identified degradation products of cangrelor are valuable for cangrelor manufacturing process and quality control.

Identification of new process-related impurity in the key intermediate in the synthesis of TCV-116

Development of safe and effective drugs requires complete impurity evaluation and, therefore, knowledge about the formation and elimination of impurities is necessary. During impurity profiling of a key intermediate during synthesis of candesartan cilexetil (1-(((cyclohexyloxy)carbonyl) oxy)ethyl 1-((2'-(2H-tetrazol-5-yl)-[1,1'-biphenyl]-4-yl) methyl)-2-ethoxy-1H-benzo[d]imidazole-7-carboxylate, TCV-116), a novel compound, which had not been reported previously, was observed. Structural elucidation of impurity was achieved by liquid chromatography hyphenated to different high resolution mass analyzers. Based on exact mass measurements and fragmentation pattern, a chloro alkyl carbonate ester analogue of the intermediate was identified. Structure of the impurity was confirmed by mass spectro-metric and NMR analyses of the target substance. Identified impurity could represent a hazard if it is transferred to the final API stage and its presence should be kept below allowed limits. Further investigation could reveal whether bis(1-chloroethyl) carbonate is a precursor to impurity formation. Therefore, synthesis should be regulated so as to minimize impurity production. Analysis of the final product indicated that the amount of impurity did not exceed 50 mg L-1, which represents the detection limit, determined according to the signal/noise ratio.

Identification and structural characterization of the stress degradation products of omeprazole using Q-TOF-LC-ESI-MS/MS and NMR experiments: evaluation of the toxicity of the degradation products

Omeprazole (OMP), a prototype proton pump inhibitor used for the treatment of peptic ulcers and gastroesophageal reflux disease (GERD), was subjected to forced degradation studies as per ICH guidelines Q1A (R2).