Genotoxic Impurities in Pharmaceutical Manufacturing: Sources, Regulations, and Mitigation

Modular Construction of Multivariate Metal-Organic Frameworks for Luminescent Sensing

Metal-organic frameworks (MOFs) have played a pivotal role as rapid and effective luminescent sensing materials. Numerous MOFs with diverse characteristics have been meticulously designed for target analytes. Previous studies have highlighted the factors of spectral characteristics, energy levels, interaction forces, and sensor stabilities for the luminescent sensing performance in response to a specific analyte. This conventional "point-to-point" approach necessitates the matching of sensing materials to a specific analyte. Herein, we develop a modular MOF-based luminescent sensing platform by using a mixed-ligand strategy. A luminescent MOF Eu-FDA with 2,5-furandicarboxylic acid can serve as the foundational platform, with partial replacement by nine distinct hexacyclic isophthalic acids as the modules, respectively, to specifically accommodate different analytes with particular structures and properties. This substitution has been meticulously confirmed through single-crystal X-ray diffraction. Confronted with analytes possessing diverse structural or property characteristics, modular isophthalic acid derivatives can enhance the sensing capability to achieve heightened sensitivity.

Supported Nickel Nanoparticles as Catalyst in Direct sp3 C-H Alkylation of 9H-Fluorene Using Alcohols as Alkylating Agent

Herein, we report an inexpensive first-row transition metal Ni heterogeneous catalytic system for the Csp 3-mono alkylation of fluorene using alcohols as alkylating agents via borrowing hydrogen strategy. The catalytic protocol displayed versatility with high yields of the desired products using various types of primary alcohols, including aryl/hetero aryl methanols, and aliphatic alcohols as alkylating agents. The catalyst Ni NPs@N-C was synthesized via high-temperature pyrolysis strategy, using ZIF-8 as the sacrificial template. The Ni NPs@N-C catalyst was characterized by XPS, HR-TEM, HAADF-STEM, XRD and ICP-MS. The catalyst is stable even in the air at room temperature, displayed excellent activity and could be recycled 5 times without appreciable loss of its activity.

Identification and in vitro genotoxicity assessment of forced degradation products of glimepiride and glyburide using HEK cell-based COMET assay

This study focuses on characterizing the forced degradation products of antidiabetic drugs glimepiride (GMD) and glyburide (GBD), with previously unexplored genotoxicity. Drugs underwent stress induced by acid, base, and hydrogen peroxide. For GMD, impurities were profiled and isolated using Hypersil Gold C8 (250 × 10 mm, 5 μ) through semi-preparative HPLC with a fraction collector. For GBD, impurity profiling was performed using semi-preparative HPLC (Hypersil GOLD C18, 250 × 10 mm, 5 μ), and reverse-phase flash chromatography (FP ECOFLEX C18 4 g column) for isolation. Although five GMD and three GBD impurities were detected, only three GMD and two GBD impurities were separated and assessed for purity using analytical RP-HPLC with the purity percentages ranging from 96.6% to 99.9%. LC-Orbitrap MS was used to identify these three GMD impurities (m/z: 408.122, 338.340, 381.160) and two GBD impurities (m/z: 369.065, 325.283). ProTox-II in silico predictions classified all impurities as class 4 and 5, with no positive genotoxicity indications. In vitro comet assays, using HEK cells, indicated that for GMD, impurity 2 and impurity 5 were less genotoxic, whereas impurity 4 exhibited genotoxicity. For GBD, both impurities 1 and 3 were found to be genotoxic, with impurity 3 showing a higher level of genotoxicity than impurity 1.

Deep eutectic solvents as green and sustainable diluents in headspace gas chromatography for the determination of trace level genotoxic impurities in pharmaceuticals

Genotoxic impurities (GTIs) are potential carcinogens that need to be controlled down to ppm or lower concentration levels in pharmaceuticals under strict regulations. The static headspace gas chromatography (HS-GC) coupled with electron capture detection (ECD) is an effective approach to monitor halogenated and nitroaromatic genotoxins. Deep eutectic solvents (DESs) possess tunable physico-chemical properties and low vapor pressure for HS-GC methods. In this study, zwitterionic and non-ionic DESs have been used for the first time to develop and validate a sensitive analytical method for the analysis of 24 genotoxins at sub-ppm concentrations. Compared to non-ionic diluents, zwitterionic DESs produced exceptional analytical performance and the betaine : 7 (1,4- butane diol) DES outperformed the betaine : 5 (1,4-butane diol) DES. Limits of detection (LOD) down to the 5-ppb concentration level were achieved in DESs. Wide linear ranges spanning over 5 orders of magnitude (0.005-100 µg g-1) were obtained for most analytes with exceptional sensitivities and high precision. The method accuracy and precision were validated using 3 commercially available drug substances and excellent recoveries were obtained. This study broadens the applicability of HS-GC in the determination of less volatile GTIs by establishing DESs as viable diluent substitutes for organic solvents in routine pharmaceutical analysis.

Continuous Flow Oxidation of Alcohols Using TEMPO/NaOCl for the Selective and Scalable Synthesis of Aldehydes

A simple and benign continuous flow oxidation protocol for the selective conversion of primary and secondary alcohols into their respective aldehyde and ketone products is reported. This approach makes use of catalytic amounts of TEMPO in combination with sodium bromide and sodium hypochlorite in a biphasic solvent system. A variety of substrates are tolerated including those containing heterocycles based on potentially sensitive nitrogen and sulfur moieties. The flow approach can be coupled with inline reactive extraction by formation of the carbonyl-bisulfite adduct which aids in separation of remaining substrate or other impurities. Process robustness is evaluated for the preparation of phenylpropanal at decagram scale, a trifluoromethylated oxazole building block as well as a late-stage intermediate for the anti-HIV drug maraviroc which demonstrates the potential value of this continuous oxidation method.

Organic Solvent Nanofiltration in Pharmaceutical Applications

Separation and purification in organic solvents are indispensable procedures in pharmaceutical manufacturing. However, they still heavily rely on the conventional separation technologies of distillation and chromatography, resulting in high energy and massive solvent consumption. As an alternative, organic solvent nanofiltration (OSN) offers the benefits of low energy consumption, low solid waste generation, and easy scale-up and incorporation into continuous processes. Thus, there is a growing interest in employing membrane technology in the pharmaceutical area to improve process sustainability and energy efficiency. This Review comprehensively summarizes the recent progress (especially the last 10 years) of organic solvent nanofiltration and its applications in the pharmaceutical industry, including the concentration and purification of active pharmaceutical ingredients, homogeneous catalyst recovery, solvent exchange and recovery, and OSN-assisted peptide/oligonucleotide synthesis. Furthermore, the challenges and future perspectives of membrane technology in pharmaceutical applications are discussed in detail.

Analyzing Alkyl Bromide Genotoxic Impurities in Febuxostat Based on Static Headspace Sampling and GC-ECD

Herein, a sensitive and selective gas chromatography-electron capture detector (GC-ECD) method was developed and validated for the quantification of trace levels of five bromo-containing genotoxic impurities in Febuxostat active pharmaceutical ingredient (API) after headspace sampling (HS). Multivariate experimental designs for the optimization of static headspace parameters were conducted in two stages using fractional factorial design (FFD) and central composite design (CCD). The optimum headspace conditions were 5 min of extraction time and a 120 °C extraction temperature. Baseline separation on the analytes against halogenated solvents was carried out using an Agilent DB-624 (30 m × 0.32 mm I.D., 1.8 μm film thickness) stationary phase under isothermal conditions. The method was validated according to ICH guidelines in terms of specificity, linearity, the limits of detection and quantification, precision and accuracy. The linearity was assessed in the range of 5-150% with respect to the specification limit. The achieved LOD and LOQ values ranged between 0.003 and 0.009 and 0.01 and 0.03 μg mL-1, respectively. The accuracy of the method (expressed as relative recovery) was in the range of 81.5-118.2%, while the precision (repeatability, inter-day) was less than 9.9% in all cases. The validated analytical protocol has been successfully applied to the determination of the impurities in various Febuxostat API batch samples.

Development and validation of a stability-indicating ultra-high-performance liquid chromatography method for the estimation of ibrutinib and trace-level quantification of related substances using quality-by-design approach

A new ultra-high-performance liquid chromatography method was developed using quality-by-design principles for quantifying trace-level impurities of ibrutinib. The method utilized an ACQUITY UPLC BEH C18 column with a mobile phase consisting of equal parts of 0.02 M formic acid in water and 0.02 M formic acid in acetonitrile. The critical method parameters, including mobile phase pH, column temperature, and flow rate, were optimized using the design of experiments. Statistical analysis revealed the impact of these parameters on critical quality attributes. Perturbation and response surface plots illustrated the individual and interactive effects of the parameters. The optimal parameter levels were determined to be pH, 2.5; column temperature, 28°C; and flow rate, 0.55 mL/min. Confirmation experiments demonstrated the method's robustness, with the separation of impurities and unknown degradation products within a 5-min runtime. The optimized ultra-performance liquid chromatography method was validated according to ICH guidelines. The method exhibited linear response within the range of 0.025-100 μg/mL for ibrutinib and 0.0187-0.225 μg/mL for impurities (r2  > 0.9995), with limits of detection/limits of quantification of 0.01/0.025 and 0.015/0.0187 for ibrutinib and four impurities, respectively. Recoveries for the drug and impurities ranged from 92.69 to 102.7%, and precision was below 2% and 8% relative standard deviation for ibrutinib and impurities, respectively.

Methanol recovery: potential of nanolaminate organic solvent nanofiltration (OSN) membranes

Researchers have made a significant breakthrough by merging the energy-saving attribute of organic solvent nanofiltration (OSN) with the remarkable solvent permeance and solute rejection of two-dimensional (2D) laminated membranes. This innovative approach brings forth a new era of sustainable and cost-effective separation techniques, presenting a promising solution to the issue of industrial solvents contaminating the environment. This development paves the way for new opportunities in building a sustainable future. Specifically, our mini-review has cast a spotlight on the separation and recovery of methanol-a solvent abundantly used in industrial processes. We systematically evaluated a diverse array of free-standing 2D nanolaminate OSN membranes. The analysis encompasses the assessment of pure methanol permeance, solute rejection capabilities, and the simultaneous evaluation of methanol permeance and solute rejection performance. Notably, this study sheds light on the considerable potential of 2D laminated OSN membranes in revolutionizing separation processes for the industrial use of methanol.

Simultaneous and trace-level quantification of four benzene sulfonate potential genotoxic impurities in doxofylline active pharmaceutical ingredients and tablets using high-performance liquid chromatography with ultraviolet detection

In the production of doxofylline, the common occurrence of toxic p-toluene sulfonate generation prompted the development and validation of a method using HPLC with ultraviolet detection (HPLC-UV). This method is designed for detecting four potential genotoxic impurities (PGIs) present in both doxofylline drug substance and tablets, with a focus on the UV-absorbing group p-toluene sulfonate. The four impurities were methyl 4-methylbenzenesulfonate (PGI-1), ethyl 4-methylbenzenesulfonate (PGI-2), 2-hydroxyethyl 4-methylbenzenesulfonate (PGI-3), and 2-(4-methylphenyl)sulfonyloxyethyl 4-methylbenzenesulfonate (PGI-4). In this method, chromatographic separation was achieved using a Waters Symmetry C18 column (250 mm × 4.6 mm, 5 μm). The mobile phases consisted of 20% acetonitrile as mobile phase A and pure acetonitrile as mobile phase B, operating in gradient elution mode at a flow rate of 1.0 mL/min. According to the guidelines of the International Conference on Harmonization, it was determined that this method could quantify four PGIs at 0.0225 μg/mL in samples containing 60 mg/mL. The validated approach demonstrated excellent linearity (R2 > 0.999) across the concentration range of 30%-200% (relative to 0.075 μg/mL doxofylline) for the four PGIs. The accuracy of this method for the four PGIs ranged from 94.8% to 100.4%. The reverse-phase-HPLC-UV analytical method developed in this study is characterized by its speed and precision, making it suitable for the sensitive analysis of benzene sulfonate PGIs in doxofylline drug substances and tablets.

A new stability-indicating HPLC-UV method for determination of amlodipine besylate and its impurities in drug substance

A new fast stability-indication high performance liquid chromatography method was developed and validated for the determination of amlodipine besylate and its organic impurities in drug substance. The separation of amlodipine and its seven impurities was achieved on a core shell C18 column, 100 mm × 4.6 mm; 2.6 μm, within 15 min. The mobile phase comprised of 0.4% ammonium hydroxide in water and methanol delivered in a gradient mode; the method detection wavelength is 237 nm. The selected column is stable at high pH and provided a good peak shape for basic compounds. Amlodipine besylate was subject to acid, base, oxidative, thermal, and photolytic stress conditions. The degradation products were well resolved from the amlodipine peak and its impurities. Major degradants were analyzed by liquid chromatography coupled with single-quadrupole mass detector. Amlodipine peak was shown to be free of co-elution by mass spectral analysis in all stress conditions. The method was validated in terms of specificity, linearity, accuracy, precision, and robustness. The developed method could be applied for routine quality control analysis of amlodipine besylate drug substance.

DNA Repair-Responsive Engineered Whole Cell Microbial Sensors for Sensitive and High-Throughput Screening of Genotoxic Impurities

Genotoxic impurities (GTIs) occurred in drugs, and food and environment pose a threat to human health. Accurate and sensitive evaluation of GTIs is of significance. Ames assay is the existing gold standard method. However, the pathogenic bacteria model lacks metabolic enzymes and requires mass GTIs, leading to insufficient safety, accuracy, and sensitivity. Whole-cell microbial sensors (WCMSs) can use normal strains to simulate the metabolic environment, achieving safe, sensitive, and high-throughput detection and evaluation for GTIs. Here, based on whether GTIs causing DNA alkylation required metabolic enzymes or not, two DNA repair-responsive engineered WCMS systems were constructed including Escherichia coli-WCMS and yeast-WCMS. A DNA repair-responsive promoter as a sensing element was coupled with an enhanced green fluorescent protein as a reporter to construct plasmids for introduction into WCMS. The ada promoter was screened out in the E. coli-WCMS, while the MAG1 promoter was selected for the yeast-WCMS. Different E. coli and yeast strains were modified by gene knockout and mutation to eliminate the interference and enhance the GTI retention in cells and further improved the sensitivity. Finally, GTI consumption of WCMS for the evaluation of methyl methanesulfonate (MMS) and nitrosamines was decreased to 0.46-8.53 μg and 0.068 ng-2.65 μg, respectively, decreasing 2-3 orders of magnitude compared to traditional methods. This study provided a novel approach to measure GTIs with different DNA damage pathways at a molecular level and facilitated the high-throughput screening and sensitive evaluation of GTIs.

Strategy of Choosing Templates in Molecular Imprinting to Expand the Recognition Width for Family-Selectivity

The class-selective molecular-imprinted polymers (MIPs) have shown the recognition ability to multiple targeted molecules through using one or multiple templates. However, choosing the right templates, the core problem, still lacks a systemic guide and decision-making. In this work, we propose a strategy of selecting templates through expanding the recognition width for the improvement of class-selectivity. First, three families of genotoxic impurity (GTI) were selected as model objects, and the spatial size and binding energy of each GTI-monomer complexes were obtained and compared by computational simulation. The two indexes of energy width (W_E) and size width (W_L) were introduced to compare the similarity and differences on the two recognition factors, binding strength and spatial size, among these GTIs in each family. Through shortening the width to increase similarity on binding energy and size, the dual templates in the aromatic amines (AI) family and sulfonic acid esters (SI) family were successfully selected. Correspondingly, the prepared dual-template MIPs in the two GTI families can simultaneously recognize all the GTIs comparing with that of single template MIP, respectively. Meanwhile, through comparing the adsorption capacity of the selected template and its analogues in one GTI family, the recognition efficiency of the dual-template MIPs was higher than that of the single-template MIP. This indicates that though using the selected right templates, the higher class-selectivity and the larger recognition width can be realized. Thus, this work can solve the problem of blind template selection, and provide the useful theoretical guidance for designing family-selective molecular imprinting.

Direct Amination of α-Triaryl Alcohols via Vanadium Catalysis

α-Triaryl amines have been used as pharmaceuticals and pharmaceutical intermediates for antifungal and anticancer applications. Current methods to synthesize such compounds require at least two steps, and no direct amination of tertiary alcohols has been reported. Herein, we disclose efficient catalytic conditions for the direct amination of α-triaryl alcohols to access α-triaryl amines. VO(OⁱPr)₃, a commercially available reagent, has been identified as an effective catalyst for the direct amination of several α-triaryl alcohols. This process is scalable, as demonstrated by a gram-scale synthesis, and the reaction still works at as low as a 0.01 mol % catalyst loading with the turnover number reaching 3900. Moreover, commercial pharmaceuticals including clotrimazole and flutrimazole have been successfully prepared rapidly and efficiently using this newly developed method.

Confined Target-Triggered Hot Spots for In Situ SERS Analysis of Intranuclear Genotoxic Markers

The γH2AX is a type of confined target in nuclei which is highly expressed around the damaged DNA during genotoxicity and has therefore been identified as a marker of genotoxicity. Convenient and intuitive in situ real-time detection of γH2AX is crucial for an accurate assessment of genotoxicity. Selective and nondestructive surface-enhanced Raman spectroscopy (SERS) is suitable to achieve this goal. However, the detection of substances in the nucleus by SERS is still limited due to the contradiction of probes between the nuclei entry efficiency and signal enhancement. This study utilized the characteristics of γH2AX as a confined target and constructed a γH2AX immunosensor based on gold nanoprobes with a small size (15 nm), which was modified with the TAT nuclear targeting peptide to ensure high nuclei entry efficiency. Once DNA damage was induced, the local overexpression of γH2AX further recruited the probe through immune recognition, so that hot spots could be assembled in situ to generate strong Raman signals, which were applied to evaluate the genotoxicity of drug impurities. This study proposed a novel SERS detection strategy, characterized by confined target-induced size conversion and hot spot formation, for in situ real-time analysis of intranuclear targets at the single-living-cell level, which intelligently simplified the structure of SERS probes and the operation process.

A fluorescent probe for alkylating agents and its quantification of triflate as a genotoxic impurity

The responses of a reaction-based fluorescent probe BI-Py towards alkyl halide, epoxide, carbonate, sulfate, sulphonate and triflate were evaluated and the probe achieved selective detection of ethyl triflate in acetonitrile with a LOD of 1.08 μM. BI-Py exhibited great potential for detecting triflate as a genotoxic impurity in drug substances.

Development and Validation for Quantification of 7-Nitroso Impurity in Sitagliptin by Ultraperformance Liquid Chromatography with Triple Quadrupole Mass Spectrometry

The purpose of this research study was to develop an analytical method for the quantification of 7-nitroso-3-(trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4] triazolo [4,3-a] pyrazine (7-nitroso impurity), which is a potential genotoxic impurity. Since sitagliptin is an anti-diabetic medication used to treat type 2 diabetes and the duration of the treatment is long-term, the content of nitroso impurity must be controlled by using suitable techniques. To quantify this impurity, a highly sensitive and reproducible ultraperformance liquid chromatography with triple quadrupole mass spectrometry (UHPLC-MS/MS) method was developed. The analysis was performed on a Kromasil-100, with a C18 column (100 mm × 4.6 mm with a particle size of 3.5 µm) at an oven temperature of approximately 40 °C. The mobile phase was composed of 0.12% formic acid in water, with methanol as mobile phases A and B, and the flow rate was set to 0.6 mL/min. The method was validated according to the current International Council for Harmonisation (ICH) guidelines with respect to acceptable limits, specificity, reproducibility, accuracy, linearity, precision, ruggedness and robustness. This method is useful for the detection of the impurity at the lowest limit of detection (LOD), which was 0.002 ppm, and the lowest limit of quantification (LOQ), which was 0.005 ppm. This method was linear in the range of 0.005 to 0.06 ppm and the square of the correlation coefficient (R2) was determined to be > 0.99. This method could help to determine the impurity in the regular analysis of sitagliptin drug substances and drug products.

Determination of Three Alkyl Camphorsulfonates as Potential Genotoxic Impurities Using GC-FID and GC-MS by Analytical QbD

Camphorsulfonic acid salts are commonly used in the manufacturing production of active pharmaceutical ingredients (APIs) and have the potential to form alkyl camphorsulfonates, which can be considered as potential genotoxic impurities (PGIs). Alkyl camphorsulfonates should be controlled using the Threshold of Toxicological Concern (TTC) when detected in APIs due to their genotoxicity. An in silico study utilizing the ICH M7 guideline was performed in order to classify the alkyl camphorsulfonates that can be produced from the reaction of camphorsulfonic acid salts with methanol, ethanol, and isopropyl alcohol, which are commonly used solvents in API manufacturing processes. Two sensitive, reproducible, and accurate analytical methods using GC-FID and GC-MS were developed using the analytical Quality By Design (QbD) approaches for the quantitation of three alkyl camphorsulfonates in APIs satisfying the control limit of PGIs according to the TTC. The detection limits of the GC-FID method were found to be between 1.5 to 1.9 ppm, and the detection limits of the GC-MS method were found to be between 0.055 to 0.102 ppm. The method was validated in terms of accuracy, linearity, precision, detection limit, quantitation limit, specificity and robustness.

Synthesis and Characterization of Related Substances of Torasemide

Torasemide, a pyridine-3-sulfonylurea derivative, is a high-efficiency loop diuretic. During the process development of torasemide, five process-related substances, which have been specified in the pharmacopeia, would be produced. In this study, all these related substances, including compounds A–E, were synthesized via simple procedures and subsequently characterized by 1H nuclear magnetic resonance (NMR), 13C NMR, and mass spectrometry. Particularly, a simple synthetic method for compound A has not been found in previous literature. It is worth noting that other related substances could be prepared from compound B in one or two steps. The availability of these related substances could allow for quality control in the process of torasemide.

A colorimetric and fluorometric probe for phenylhydrazine and its application in real samples

A fluorescent probe for phenylhydrazine detection was developed with aldehyde as the recognition group and good selectivity towards phenylhydrazine over hydrazine, hydroxylamine and other amines was observed. Its application in real water samples and fast visualization of phenylhydrazine using a probe-loaded paper strip were demonstrated.

Blue-Light-Induced Iron-Catalyzed α-Alkylation of Ketones

We report a visible-light-induced iron-catalyzed α-alkylation of ketones. The photocatalytic system is based on the single diaminocyclopentadienone iron tricarbonyl complex. Two catalytic intermediates of this complex are able to harvest light, allowing the synthesis of substituted aromatic and aliphatic ketones at room temperature using the borrowing hydrogen strategy in the presence of various substituted primary alcohols as alkylating reagents. Preliminary mechanistic studies unveil the role of light for both the dehydrogenation and reduction step.

Analytical Method Development for 19 Alkyl Halides as Potential Genotoxic Impurities by Analytical Quality by Design

Major issues in the pharmaceutical industry involve efficient risk management and control strategies of potential genotoxic impurities (PGIs). As a result, the development of an appropriate method to control these impurities is required. An optimally sensitive and simultaneous analytical method using gas chromatography with a mass spectrometry detector (GC–MS) was developed for 19 alkyl halides determined to be PGIs. These 19 alkyl halides were selected from 144 alkyl halides through an in silico study utilizing quantitative structure–activity relationship (Q-SAR) approaches via expert knowledge rule-based software and statistical-based software. The analytical quality by design (QbD) approach was adopted for the development of a sensitive and robust analytical method for PGIs. A limited number of literature studies have reviewed the analytical QbD approach in the PGI method development using GC–MS as the analytical instrument. A GC equipped with a single quadrupole mass spectrometry detector (MSD) and VF-624 ms capillary column was used. The developed method was validated in terms of specificity, the limit of detection, quantitation, linearity, accuracy, and precision, according to the ICH Q2 guideline.

Photo-tailored heterocrystalline covalent organic framework membranes for organics separation

Organics separation for purifying and recycling environment-detrimental solvents is essential to sustainable chemical industries. Covalent organic framework (COF) membranes hold great promise in affording precise and fast organics separation. Nonetheless, how to well coordinate facile processing—high crystalline structure—high separation performance remains a critical issue and a grand challenge. Herein, we propose a concept of heterocrystalline membrane which comprises high-crystalline regions and low-crystalline regions. The heterocrystalline COF membranes are fabricated by a two-step procedure, i.e., dark reaction for the construction of high-crystalline regions followed by photo reaction for the construction of low-crystalline regions, thus linking the high-crystalline regions tightly and flexibly, blocking the defect in high-crystalline regions. Accordingly, the COF membrane exhibits sharp molecular sieving properties with high organic solvent permeance up to 44-times higher than the state-of-the-art membranes.

Covalent organic frameworks (COF) hold great promise in filtration and separation but combining facile processing, high crystallinity and high separation performance remains challenging. Here, the authors demonstrate that heterocrystalline COF membranes in which high-crystalline regions are tightly linked by low-crystalline regions can improve molecular sieving properties at high solvent flux.

Comparative study of performances of UHPLC-MS/MS and HPLC/UV methods for analysis of ziprasidone and its main impurities

Ziprasidone is the second generation antipsychotic drug with unique multipotent G-protein-coupled (GPCR) receptor binding profile. Since ziprasidone is a highly lipophilic and unstable compound, development of efficient method for a concurrent assay of ziprasidone and its main impurities was a very challenging task.

The UHPLC-MS/MS method that we developed for simultaneous determination of ziprasidone and its main impurities (BITP, Chloroethyl-chloroindolinone, Zip-oxide, Zip-dimer, and Zip-BIT) was compared with some other related HPLC-UV methods of our own and other authorship. An increase of the mobile phase pH value from 2.5 to 4.7 units in the examined analytical methods influenced elution order of the investigated compounds. It was found out that the UHPLC-MS/MS method is more selective and sensitive than the earlier developed HPLC-UV method. Similar to our earlier HPLC-UV method, the UHPLC-MS/MS method is linear with a correlation coefficient (r) above 0.99 for all the analysed compounds, but with a negligibly lower precision and accuracy. Finally, with shorter analysis time, smaller column size and reduction of solvent consumption, UHPLC-MS/MS is assumed as a greener method than HPLC-UV for the ziprasidone purity assay.

After transfer of the UHPLC-MS/MS method to the UHPLC-DAD system, suitability of the UHPLC-DAD method for routine control of ziprasidone and its main impurities is examined and confirmed based on the retained good selectivity, resolution and short analysis time.

Ligand-Controlled Ruthenium-Catalyzed Borrowing-Hydrogen and Interrupted-Borrowing-Hydrogen Methodologies: Functionalization of Ketones Using Methanol as a C1 Source

Herein we report simple, highly efficient, and phosphine-free N,C-Ru and N,N-Ru catalysts for ligand-controlled borrowing-hydrogen (BH) and interrupted-borrowing-hydrogen (I-BH) methods, respectively. This protocol has been employed on a variety of ketones using MeOH as a green, sustainable, and alternative C1 source to form a C-C bond through the BH and I-BH methods. Reasonably good substrate scope, functional group tolerance, and good-to-excellent yields at 70 °C are the added highlights of these methodologies. Controlled experiments reveal that an in situ formed formaldehyde is one of the crucial elements in this ligand-controlled selective protocol, which upon reaction with a ketone generates an enone as an intermediate. This enone in the presence of the N,C-Ru catalyst and N,N-Ru catalyst through the BH and I-BH pathways yields methylated ketones and 1,5-diketones, respectively.

Trace Level Quantification of 4-Methyl-1-nitrosopiperazin in Rifampicin Capsules by LC-MS/MS

Rifampicin is a first-line anti-tuberculosis drug. However, in August 2020, the presence of 1-methyl-4-nitrosopiperazine (MNP), a nitrosamine impurity, was detected by the United Stated Food and Drug Administration (US FDA) in rifampicin capsules. Consequently, the development of efficient methods for the detection of MNP is an important objective. In this study, the MNP present in rifampicin capsules was detected using LC-MS/MS. A total of 27 batches from nine manufacturers in the Chinese market were tested, with MNP (0.33–2.36 ppm) being detected in all samples at levels exceeding the maximum acceptable intake limit of 0.16 ppm initially set by the FDA. However, after considering the associated benefits and risks, the FDA-approved limit was revised to 5 ppm; hence, all the samples examined herein exhibited MNP levels well below the required limit. Furthermore, the results of forced degradation experiments suggest that MNP is formed by the thermal degradation of rifampicin.

Micronized cellulose from citrus processing waste using water and electricity only

Along with a water-soluble fraction rich in pectin, the hydrodynamic cavitation of citrus processing waste carried out in water demonstrated directly on semi-industrial scale affords an insoluble fraction consisting of micronized cellulose of low crystallinity ("CytroCell"). Lemon and grapefruit CytroCell respectively consist of 100-500 nm wide cellulose nanorods, and of 500-1000 nm wide ramified microfibrils extending for several μm. These findings establish a technically viable route to low crystallinity micronized cellulose laying in between nano- and microcellulose, using water and electricity only.

Recent Applications of Derivatization Techniques for Pharmaceutical and Bioanalytical Analysis through High-performance Liquid Chromatography

Background:

Derivatization of analytes is a quite convenient practice from an analytical perspective. Its vast prevalence is accounted by the availability of distinct reagents, primarily pragmatic for obtaining desired modifications in an analyte structure. Another reason for its handiness is typically to overcome limitations such as lack of sensitive methodology or instrumentation.The past decades have witnessed various new derivatization techniques including in-situ, enzymatic, ultrasound-assisted, microwave-assisted, and photochemical derivatization which have gain popularity recently.

Methods:

The online literature available on the utilization of derivatization as prominent analytical tools in recent years with typical advancements is reviewed. The illustrations of the analytical condition together with the structures of different derivatizing reagents (DRs) are provided to acknowledge the vast capability of derivatization to resolve analytical problems.

Results:

The derivatization techniques have enabled analytical chemists throughout the globe to develop an enhanced sensitivity method with the simplest of the instrument like High-Performance Liquid Chromatography (HPLC). The HPLC, compared to more sensitive Liquid chromatography coupled to tandem mass spectrometer, is readily available and can be readily utilized for routine analysis in fields of pharmaceuticals, bioanalysis, food safety, and environmental contamination. A troublesome aspect of these fields is the presence of a complex matrix with trace concentrations for analyses. Liquid chromatographic methods devoid of MS detectors do not have the desired sensitivity for this. A possible solution for overcoming this is to couple HPLC with derivatization to enable the possibility of detecting trace analytes with a less expensive instrument. Running cost, enhanced sensitivity, low time consumption, and overcoming the inherent problems of analyte are critical parameters for which HPLC is quite useful in high throughput analysis.

Conclusion:

The review critically highlights various kinds of derivatization applications in different fields of analytical chemistry. The information primarily focuses on pharmaceutical and bioanalytical applications in recent years. The various modes, types, and derivatizing reagents with brief mechanisms have been ascribed briefly Additionally, the importance of HPLC coupled to fluorescence and UV detection is presented as an overview through examples accompanied by their analytical conditions.

Synthesis of Antipsychotic Drug, Cariprazine: An Improved and Commercially Viable Synthetic Approach

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The novel synthetic route to an antipsychotic drug Cariprazine was developed and demonstrated on a commercial scale. The synthesis of Cariprazine is achieved from N-(4-oxocyclohexyl) acetamide by using various reactions such as Wittig-Horner reaction, reduction of alkene, hydrolysis of ester, deacylation, amidation, reduction of weinreb amide to yield the corresponding aldehyde, and finally reductive amination of aldehyde in presence of the corresponding amine to form Cariprazine. In this article, we report a novel intermediate 2-[trans-4-(3,3-Dimethylureido)cyclohexyl]-N-methoxy-N-methylacetamide by avoiding potentially genotoxic substances/intermediates, tedious, drastic reaction conditions.

Selective Plate-Based Assay for Trace EDTA Analysis via Boron Trifluoride-methanol Derivatization UHPLC-QqQ-MS/MS Enabling Biologic and Vaccine Processes

The employment of ethylenediaminetetraacetic acid (EDTA) across several fields in chemistry and biology has required the creation of a high number of quantitative assays. Nonetheless, the determination of trace EDTA, especially in biologics and vaccines, remains challenging. Herein, we introduce an automated high-throughput approach based on EDTA esterification in 96-well plates using boron trifluoride-methanol combined with rapid analysis by ultra-high-performance liquid chromatography-triple quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS). Derivatization of EDTA to its methyl ester (Me-EDTA) serves to significantly improve chromatographic performance (retention, peak shape, and selectivity), while also delivering a tremendous enhancement of sensitivity in the positive ion mode electrospray ionization (ESI+). This procedure, in contrast to previous EDTA methods based on complexation with metal ions, is not affected by high concentration of other metals, buffers, and related salts abundantly present in biopharmaceutical processes (e.g., iron, copper, citrate, etc.). Validation of this assay for the determination of ng·mL^-1 level EDTA in monoclonal antibody and vaccine products demonstrated excellent performance (repeatability, precision, and linear range) with high recovery from small sample volumes while also providing an advantageous automation-friendly workflow for high-throughput analysis.

HPLC-MS Analysis of Four Potential Genotoxic Impurities in Alogliptin Pharmaceutical Materials

BACKGROUND

Pyridine, 3-aminopyridine, 4-dimethylaminopyridine, and N, N-dimethylaniline are reactive bases that may be used in preparing of alogliptin (ALO) pharmaceutical ingredient. They are considered as potentially genotoxic impurities since they contain electrophilic functional groups. Therefore, they should be monitored at the allowed limits in ALO.

OBJECTIVE

The aim of this study was to develop a novel liquid chromatography mass spectrometry (LC-MS) method to estimate quantities of pyridine, 3-aminopyridine, 4-dimethylaminopyridine, and N, N-dimethylaniline impurities in ALO drug material.

METHODS

The separation was performed on KROMASIL CN (250 mm × 3.9 mm, 3.5 µm) column in reversed phase mode. The mobile phase was a mixture of water-methanol (55:45, v/v) containing 2.5 mM ammonium acetate and 0.1% formic acid.The mass spectrometer was used to detect the amount of impurities with selected ionization monitoring mode at m/z = 80, 95, 122, and 123 for pyridine, 3-aminopyridine, N, N-dimethylaniline and 4-dimethylaminopyridine, respectively. Flow rate of the method was 0.5 mL/min.

RESULTS

Sensitivity of the method was excellent at levels very less than allowed limits. The method had excellent linearity in the concentration ranges of QL-150% of allowed limits and coefficients of determination were above 0.9990. The recovery ratios were in the range of 93.56-110.28%.

CONCLUSIONS

Results showed good linearity, precision, accuracy, sensitivity, selectivity, robustness, and solution stability. The studied method was applied to test two samples of raw materials and one sample of tablets.

HIGHLIGHTS

The method discussed here could be very useful for controlling of potentially genotoxic impurities levels in ALO during its synthesis and for testing ALO raw materials as quality control tests before using them in preparing of pharmaceutical products.

Application of in vitro PAMPA technique and in silico computational methods for blood-brain barrier permeability prediction of novel CNS drug candidates

Permeability assessment of small molecules through the blood-brain barrier (BBB) plays a significant role in the development of effective central nervous system (CNS) drug candidates. Since in vivo methods for BBB permeability estimation require a lot of time and resources, in silico and in vitro approaches are becoming increasingly popular nowadays for faster and more economical predictions in early phases of drug discovery. In this work, through application of in vitro parallel artificial membrane permeability assay (PAMPA-BBB) and in silico computational methods we aimed to examine the passive permeability of eighteen compounds, which affect serotonin and dopamine levels in the CNS. The data set was consisted of novel six human dopamine transporter (hDAT) substrates that were previously identified as the most promising lead compounds for further optimisation to achieve neuroprotective effect, twelve approved CNS drugs, and their related compounds. Firstly, PAMPA methods was used to experimentally determine effective BBB permeability (P_e) for all studied compounds and obtained results were further submitted for quantitative structure permeability relationship (QSPR) analysis. QSPR models were built by using three different statistical methods: stepwise multiple linear regression (MLR), partial least square (PLS), and support-vector machine (SVM), while their predictive capability was tested through internal and external validation. Obtained statistical parameters (MLR- R²_pred=-0.10; PLS- R²_pred=0.64, r²_m=0.69, r^/2_m=0.44; SVM- R²_pred=0.57, r²_m=0.72, r^/2_m=0.55) indicated that the SVM model is superior over others. The most important molecular descriptors (H₀p and SolvEMt_3D) were identified and used to propose structural modifications of the examined compounds in order to improve their BBB permeability. Moreover, steered molecular dynamics (SMD) simulation was employed to comprehensively investigate the permeability pathway of compounds through a lipid bilayer. Taken together, the created QSPR model could be used as a reliable and fast pre-screening tool for BBB permeability prediction of structurally related CNS compounds, while performed MD simulations provide a good foundation for future in silico examination.

Development and Validation of a UPLC-MS/MS Method for Ultra-Trace Level Determination of Acyl Chloride Potential Genotoxic Impurity in Mezlocillin

3-Chlorocarbonyl-1-methanesulfonyl-2-imidazolidinone (CMI) is a critical intermediate used in the synthesis of mezlocillin drug substance and also a potential genotoxic impurity with acyl chloride moiety. The content of CMI in mezlocillin should be <0.16 ppm to avoid the carcinogenicity and mutagenicity threats to patients. Therefore, a workable determination of CMI was critically crucial for ensuring the safety of mezlocillin drug products. However, the conventional HPLC method is insufficient for detection limits at ppm or lower levels. Besides, the high activity of acyl chloride also raises a challenge to the direct measurement of CMI. Thus, we explored a simple esterification approach, which converts CMI into methyl 3-(methylonyl)-2-oxoimidazolidine-1-carboxylate completely by optimizing the reaction temperature and time. Furthermore, the selected reaction monitoring model of triple quadrupole mass spectrometer optimized by the Box-Behnken design significantly enhanced the sensitivity of ultra-trace level determination. The limit of detection and limit of quantification of the method were reached 0.014 and 0.02 ppm, respectively, in the following validation study. A sensitive and specific ultra-performance liquid chromatography tandem mass spectrometry method for ultra-trace level determination of acyl chloride potential genotoxic impurity in mezlocillin drug substance has been successfully established in this study, which will provide a practical quality control tool of mezlocillin.

Ru-Catalyzed Selective Catalytic Methylation and Methylenation Reaction Employing Methanol as the C1 Source

Methanol can be employed as a green and sustainable methylating agent to form C-C and C-N bonds via borrowing hydrogen (BH) methodology. Herein we explored the activity of the acridine-derived SNS-Ru pincer for the activation of methanol to apply it as a C1 building block in different reactions. Our catalytic system shows great success toward the β-C(sp³)-methylation reaction of 2-phenylethanols to provide good to excellent yields of the methylated products. We investigated the mechanistic details, kinetic progress, and temperature-dependent product distribution, which revealed the slow and steady generation of in situ formed aldehyde, is the key factor to get the higher yield of the β-methylated product. To establish the environmental benefit of this reaction, green chemistry metrics are calculated. Furthermore, dimerization of 2-naphthol via methylene linkage and formation of N-methylation of amine are also described in this study, which offers a wide range of substrate scope with a good to excellent yield.

Lopinavir/Ritonavir: A Review of Analytical Methodologies for the Drug Substances, Pharmaceutical Formulations and Biological Matrices

Lopinavir/ritonavir is a potent coformulation of protease inhibitors used against HIV infection. Lopinavir is the main responsible for viral load suppression, whereas ritonavir is a pharmacokinetic enhancer. Both of them have recently gained relevance as candidate drugs against severe coronavirus disease (COVID-19). However, significant beneficial effects were not observed in randomized clinical trials. This review summarizes the main physical-chemical, pharmacodynamic, and pharmacokinetic properties of ritonavir and lopinavir, along with the analytical methodologies applied for biological matrices, pharmaceutical formulations, and stability studies. The work also aimed to provide a comprehensive impurity profile for the combined formulation. Several analytical methods in four different pharmacopeias and 37 articles in literature were evaluated and summarized. Chromatographic methods for these drugs frequently use C8 or C18 stationary phases with acetonitrile and phosphate buffer (with ultraviolet detection) or acetate buffer (with tandem mass spectrometry detection) as the mobile phase. Official compendia methods show disadvantages as extended total run time and complex mobile phases. HPLC tandem-mass spectrometry provided high sensitivity in methodologies applied for human plasma and serum samples, supporting the therapeutic drug monitoring in HIV patients. Ritonavir and lopinavir major degradation products arise in alkaline and acidic environments, respectively. Other non-chromatographic methods were also summarized. Establishing the impurity profile for the combined formulation is challenging due to a large number of impurities reported. Easier and faster analytical methods for impurity assessment are still needed.

Rhenium(I)-Catalyzed C-Methylation of Ketones, Indoles, and Arylacetonitriles Using Methanol

A ReCl(CO)₅/MeC(CH₂PPh₂)₃ (L2) system was developed for the C-methylation reactions utilizing methanol and base, following the borrowing hydrogen strategy. Diverse ketones, indoles, and arylacetonitriles underwent mono- and dimethylation selectively up to 99% yield. Remarkably, tandem multiple methylations were also achieved by employing this catalytic system.

Development and validation of an analytical method for quantitative determination of three potentially genotoxic impurities in vildagliptin drug material using HPLC-MS

A novel high-performance liquid chromatography-mass spectrometry method was developed to determine the quantities of pyridine, 4-dimethylaminopyridine, and N, N-dimethylaniline impurities in vildagliptin drug material. These impurities are reactive bases that may be used in synthesis of vildagliptin pharmaceutical ingredients. They are considered as potentially genotoxic impurities since they contain electrophilic functional groups. Therefore, these impurities should be monitored at the allowed limits in vildagliptin. Hence a high-performance liquid chromatography-mass spectrometry method was developed to quantify the amounts of these impurities in vildagliptin. The column was KROMASIL CN (250 mm × 3.9 mm, 3.5 μm) in reversed-phase mode. The mobile phase was a mixture of water-methanol (55:45) containing 2.5 mM ammonium acetate and 0.1% formic acid. The mass spectrometer was used to detect the amounts of impurities using selected ionization monitoring mode at m/z = 80, 122, and 123 for pyridine, N, N-dimethylaniline, and 4-dimethylaminopyridine, respectively. The flow rate was 0.5 mL/min. The sensitivity of the method was excellent at levels very less than the allowed limits. The method had excellent linearity in the concentration ranges of limit of quantification-150% of the permitted level with coefficients of determination above 0.9990. The recovery ratios were in the range of 93.70-108.63%. Results showed good linearity, precision, accuracy, sensitivity, selectivity, robustness, and solution stability.

Critical Analysis of Drug Product Recalls due to Nitrosamine Impurities

A product recall is the outcome of a careful pharmacovigilance; and it is an integral part of drug regulation. Among various reasons for product recall, the detection of unacceptable levels of carcinogenic impurities is one of the most serious concerns. The genotoxic and carcinogenic potential of N-nitrosamines raises a serious safety concern, and in September 2020, the FDA issued guidance for the pharmaceutical industry regarding the control of nitrosamines in drug products. The FDA database shows that >1400 product lots have been recalled from the market due to the presence of carcinogenic N-nitrosamine impurities at levels beyond the acceptable intake limit of 26.5 ng/day. The drugs that were present in recalled products include valsartan, irbesartan, losartan, metformin, ranitidine, and nizatidine. This perspective provides a critical account of these product recalls with an emphasis on the source and mechanism for the formation of N-nitrosamines in these products.