Related Degradation Products Research Articles

Occurrence of PBDEs and alternative halogenated flame retardants in sewage sludge from the industrial city of Guangzhou, China

This study investigated the prevalence and abundance of halogenated flame retardants (HFRs) in sludge samples from 5 sewage treatment plants in Guangzhou, China. Detection of 18 polybrominated diphenyl ethers (PBDEs), 9 alternative HFRs including Dechlorane Plus (DP), brominated alkylbenzenes, and polybrominated biphenyls, and 2 related degradation products was conducted. Decabromodiphenyl ether (BDE 209) and decabromodiphenyl ethane (DBDPE) were the dominant HFRs, with concentrations ranging from 200 to 2150 ng/g and 680–27,400 ng/g, respectively. The DBDPE detected was the highest level reported so far, exceeding those previously reported by 10–100 times. PBDEs were surpassed as the dominant HFRs in sewage sludge, with mean DBDPE/BDE 209 ratio exceeding 2 in all samples. The review of earlier surveys reveals that DBDPE level was surging while BDE 209 was declining. Annual emissions of BDE 209, DP, and DBDPE were estimated to be 227.9, 10.5, and 979.3 kg/yr, respectively. Although ecological risks assessment suggested low risks for the examined sludge, the key environmental properties and transformation pathways of alternative HFRs remain largely unknown. These findings prompt for further investigations on alternative HFR and sustainable management practices for HFR-laden biosolids. The HFR emission pattern revealed in this study is likely representative of other similarly industrialized regions in the post-PBDE era.

Accumulation of Pesticides in Anaerobic Clayey Till‐Controls and Implications for Groundwater

AbstractPesticide residuals after point‐source pesticide spills in clay‐rich aquitards may potentially affect underlying groundwater for many decades due to slow release of accumulated pollution in the clayey matrix material of the aquitard. In this study, we evaluated factors behind different degrees of accumulation of phenoxy acids (MCPP, dichlorprop, 2,4‐D MCPA) and triazines (simazine and terbutylazine) observed in an old pesticide pollution described by Jørgensen et al. (2016a, this issue). By using leaching experiments, it was shown that a zone of maximum concentrations of MCPP and dichlorprop (mg/L) observed by Jørgensen et al. (2016a, this issue) represented accumulated potentially mobile pollution in anaerobic, however largely immobile pore water of the clayey matrix in the upper few meters of the unoxidized aquitard zone. By using sorption experiments, we determined 9 to16 times higher mobility by diffusion and flow for the phenoxy acids (R = 1 to 2) than for the triazines (R = 9 to 16) in the clayey matrix material of the aquitard. This indicated that more rapid and greater accumulation could occur for the phenoxy acids in the clayey matrix than for the triazines. In contrast, the relative mobility of the phenoxy acids and triazines was much closer in sand‐filled fractures and thin sand layers/lamina in the clay, suggesting that the migration of the same compounds along these textural preferential flow paths into the underlying aquifer was less different. Despite that a greater mass had originally been spilled of 2,4‐D and MCPA having similar mobility as the accumulated MCPP and dichlorprop, these compounds were not accumulated in the zone of maximum concentrations. It is suggested that the controls, which initially allowed for the observed separate accumulation of MCPP and dichlorprop as a zone of maximum pollution, were due to the combination of high persistence and high mobility for these specific pesticides in the clayey till matrix material of the aquitard. The investigation showed that over time the initial high concentrations of the accumulated phenoxy acids (MCPP, dichlorprop) transformed into high concentrations of related mobile degradation products (e.g., 4‐CPP and 2‐CPP), which extended the total time of groundwater pollution beyond the disappearance of the original phenoxyacids.

Quantification of ascorbic acid and acetylsalicylic acid in effervescent tablets by CZE-UV and identification of related degradation products by heart-cut CZE-CZE-MS.

Capillary electrophoresis is commonly applied for the analysis of pharmaceutical products due to its high separation efficiency and selectivity. For this purpose, electrospray-ionization-(ESI)-interfering additives or electrolytes are often required, which complicates the identification of impurities and degradation products by mass spectrometry (MS). Here, a capillary zone electrophoresis (CZE) method with ultraviolet (UV) absorption detection for the simultaneous determination and quantification of ascorbic acid and acetylsalicylic acid in effervescent tablets was developed. Related degradation products were identified via CZE-CZE-MS. Systematic optimization yielded 100 mM tricine (pH = 8.8) as appropriate background electrolyte, resulting in baseline separation of ascorbic acid, acetylsalicylic acid, and related anionic UV-active degradation products. The CZE-UV method was successfully validated regarding the guidelines of the Food and Drug Administration. The validated method was applied to trace the degradation rate of the active pharmaceutical ingredients at defined ambient conditions. A heart-cut CZE-CZE-MS approach, including a 4-port-nL-valve, was performed for the identification of the observed degradation products. This 2D setup enables a precise cutting of accurate sample volumes (20nL) and the independent operation of two physically separated CZE dimensions, which is especially beneficial regarding MS detection. Hence, the ESI-interfering tricine electrolyte components were separated from the analytes in a second electrophoretic dimension prior to ESI-MS detection. The degradation products were identified as salicylic acid and mono- and diacetylated ascorbic acid. This setup is expected to be generally applicable for the mass spectrometric characterization of CZE separated analytes in highly ESI-interfering electrolyte systems. Graphical Abstract A CZE-UV method for the quantification of effervescent tablet ingredients and degradation products was developed and validated. In order to identify unknown degradation products separated in the CZE-UV, a 2D heart-cut approach was performed applying a mechanical 4-port-valve. The unknown substances were transferred from the 1st to the 2nd dimension followed by the separation of ESI-interfering tricine from the analytes prior to mass spectrometric detection.

Monitoring antigenic protein integrity during glycoconjugate vaccine synthesis using capillary electrophoresis-mass spectrometry.

A capillary electrophoresis-mass spectrometry (CE-MS) method was developed for the characterization and integrity assessment of the Mycobacterium tuberculosis (MTB) antigens TB10.4 and Ag85B and their chemically produced glycoconjugates, which are glycovaccine candidates against tuberculosis (TB). In order to prevent protein adsorption to the inner capillary wall and to achieve efficient separation of the antigen proteoforms, a polyionic multilayer coating of polybrene-dextran sulfate-polybrene (PB-DS-PB) was used in combination with 1.5 M acetic acid as background electrolyte (BGE). Coupling of CE to high-resolution time-of-flight MS was achieved by a coaxial interface employing a sheath liquid of isopropanol-water (50:50, v/v) containing 0.1 % formic acid. The MTB antigens were exposed to experimental conditions used for chemical glycosylation (but no activated saccharide was added) in order to investigate their stability during glycovaccine production. CE-MS analysis revealed the presence of several closely related degradation products, including truncated, oxidized and conformational variants, which were assigned by accurate mass. Analysis of synthesized mannose conjugates of TB10.4 and Ag85B allowed the determination of the glycoform composition of the neo-glycoproteins next to the characterization of degradation products which were shown to be partly glycoconjugated. Moreover, the selectivity of CE-MS allowed specific detection of deamidated species (protein mass change of 1.0 Da only), indicating that chemical glycosylation increased susceptibility to deamidation. Overall, the results show that CE-MS represents a useful analytical tool for the detailed characterization and optimization of neo-glycoconjugate products. Graphical Flowchart illustrating Mycobacterium tuberculosis (MTB) antigen glycosylation, glycoconjugate variant and degradation product separation by capillary electrophoresis (CE) and their characterization by intact mass spectrometry (MS) Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-016-9723-5) contains supplementary material, which is available to authorized users.

LNAPL source zone delineation using soil gases in a heterogeneous silty-sand aquifer

Source delineation of hydrocarbon contaminated sites is of high importance for remediation work. However, traditional methods like soil core extraction and analysis or recent Membrane Interface Probe methods are time consuming and costly. Therefore, the development of an in situ method based on soil gas analysis can be interesting. This includes the direct measurement of volatile organic compounds (VOCs) in soil gas taken from gas probes using a PID (Photo Ionization Detector) and the analysis of other soil gases related to VOC degradation distribution (CH4, O2, CO2) or related to presence of Light Non-Aqueous Phase Liquid (LNAPL) as 222Rn. However, in widespread heterogeneous formations, delineation by gas measurements becomes more challenging. The objective of this study is twofold: (i) to analyse the potential of several in situ gas measurement techniques in comparison to soil coring for LNAPL source delineation at a heterogeneous contaminated site where the techniques might be limited by a low diffusion potential linked to the presence of fine sands and silts, and (ii) to analyse the effect of vertical sediment heterogeneities on the performance of these gas measurement methods. Thus, five types of gases were analysed: VOCs, their three related degradation products O2, CO2 and CH4 and 222Rn. Gas measurements were compared to independent LNAPL analysis by coring. This work was conducted at an old industrial site frequently contaminated by a Diesel-Fuel mixture located in a heterogeneous fine-grained aquifer.Results show that in such heterogeneous media migration of reactive gases like VOCs occurs only across small distances and the VOC concentrations sampled with gas probes are mainly related to local conditions rather than the presence of LNAPL below the gas probe. 222Rn is not well correlated with LNAPL because of sediment heterogeneity. Oxygen, CO2, and especially CH4, have larger lengths of diffusion and give the clearest picture for LNAPL presence at this site even when the gas probe is somewhat distant.

Isolation and characterization of related substances in alogliptin benzoate by LC-QTOF mass spectrometric techniques

A highly specific and efficient LC-QTOF mass spectrometric method was developed for the separation and characterization of process related substances and the major degradation products in alogliptin benzoate and its tablets. The separation was performed on Phenomenex Gemini-NX C18 column (250mm×4.6mm, 5μm) using 0.2% formic acid-0.2% ammonium acetate in water as mobile phase A, acetonitrile and methanol (60:40, v/v) as mobile phase B in linear gradient elution mode. Forced degradation studies were also conducted under ICH prescribed stress conditions. Alogliptin benzoate and its tablets were tending to degrade under acid, alkaline, oxidative and thermal stresses, while relatively stable to photolytic stress. A total of seven related substances were detected and characterized through liquid chromatography-high resolution QTOF mass spectrometry techniques, including process related substances and degradation products, and two of them were further synthesized and characterized by NMR spectroscopy. Based on the related substances elucidation and the plausible formation mechanisms, efficient approaches were proposed to reduce or eliminate related substances, and in consequence the quality of alogliptin benzoate and its tablets have been promoted obviously. Therefore, the impurity profiles obtained are critical to the quality control and manufacturing processes optimization and monitoring of alogliptin benzoate and its tablets.

Stability-Indicating RP-UPLC Method Development and Validation for the Process Related Impurities of Nebivolol and Structural Characterization of Its Forced Degradation Products by LC-MS/MS

The present study reports the development and validation of a stability-indicating reverse phase ultra performance liquid chromatographic method for the determination of nebivolol (NEB) in the presence of its process related impurities in bulk drugs and also demonstrates the structural characterization of forced degradation products (DP) of nebivolol by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Forced decomposition study of nebivolol was carried out and studied under acidic, basic, aqueous, oxidative, photolytic and thermal conditions according to the ICH guidelines. Nebivolol was found to be stable under photolytic, thermal and aqueous conditions applied in our study. However, nebivolol degradation was observed under basic and acidic conditions. Successful chromatographic separation of the drug and its process related impurities and degradation products were achieved on a waters acquity BEHC18 stationary phase (50 × 2.1 mm, 1.7µm) with a gradient elution of 10 mM ammonium acetate and acetonitrile at a flow rate of 0.3 mL min-1. Detection of analytes was carried out using a PDA detector with its wavelength set at 222 nm. The developed UPLC method was validated for all validation parameters according to the ICH guidelines. The degradation products were characterized by LC-MS/MS study and the most possible degradation and fragmentation pathways were proposed.

Architecture‐controlled synthesis of redox‐degradable hyperbranched polyglycerol block copolymers and the structural implications of their degradation

ABSTRACTWe have successfully synthesized a series of redox‐degradable hyperbranched polyglycerols using a disulfide containing monomer, 2‐((2‐(oxiran‐2‐ylmethoxy)ethyl)disulfanyl) ethan‐1‐ol (SSG), to yield PSSG homopolymers and hyperbranched block copolymers, P(G‐b‐SSG) and P(SSG‐b‐G), containing nondegradable glycerol (G) monomers. Using these polymers, we have explored the structures of the hyperbranched block copolymers and their related degradation products. Furthermore, side reaction such as reduction of disulfide bond during the polymerization was investigated by employing the free thiol titration experiments. We elucidated the structures of the degradation products with respect to the architecture of the hyperbranched block copolymer under redox conditions using 1H NMR and GPC measurements. For example, the degradation products of P(G‐b‐SSG) and P(SSG‐b‐G) are clearly different, demonstrating the clear distinction between linear and hyperbranched block copolymers. We anticipate that this study will extend the structural diversity of PG based polymers and aid the understanding of the structures of degradable hyperbranched PG systems. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1752–1761

Fractionation and analysis of veterinary antibiotics and their related degradation products in agricultural soils and drainage waters following swine manure amendment

The fate of antimicrobial active compound residues in the environment, and especially antibiotics used in swine husbandry are of particular interest for their potential toxicity and contribution to antibiotic resistance. The presence of relatively high concentrations of bioactive compounds has been reported in agricultural areas but few information is available on their degradation products. Veterinary antibiotics reach terrestrial environments through many routes, including application of swine manure to soils. The objectives of this project were first, to develop an analytical method able to quantify and identify veterinary antibiotics and their degradation products in manure, soil and water samples; and second, to study the distribution of these target compounds in soils and drainage waters. A brief evaluation of their potential toxicity in the environment was also made. In order to achieve these objectives, liquid chromatography coupled to high-resolution mass spectrometry was used for its ability to quantify contaminants with sensitivity and selectivity, and its capacity to identify degradation products. Samples of manure, soil and water came from a long-term experimental site where swine manure containing veterinary antibiotics has been applied for many years. In this study, tetracycline antibiotics were found at several hundred μgL−1 in the swine manure slurry used for fertilization, several hundred of ngL−1 in drainage waters and several ngg−1 in soils, while degradation products were sometimes found at concentrations higher than the parent compounds.

Accurate quantification of impurities in pure peptide material - angiotensin I: Comparison of calibration requirements and method performance characteristics of liquid chromatography coupled to hybrid tandem mass spectrometry and linear ion trap high-resolution mass spectrometry.

The prohormone angiotensin I (ANG I) [amino acid sequence: DRVYIHPFHL] and other structurally related peptide hormones play an essential role in the regulation of the water and electrolyte balance in the human body as well as blood pressure. ANG I is a biomarker for hypertension and diabetes. Therefore, well-characterized pure reference materials and comparable and SI-traceable analytical characterization methods are required to establish reference measurement systems (RMS) for laboratory medicine. Two analytical characterization methods based on liquid chromatography/mass spectrometry (LC/MS) systems with electrospray ionization have been developed and validated in-house. Both high-resolution MS (hrMS) and hybrid-tandem MS/MS were used for the identification and quantification of the major structurally related peptide impurities of ANG I. The impurities were quantified by use of external calibrations with original impurity standards. Mass fraction impurity values and corresponding expanded measurement uncertainties were calculated. Five structurally related degradation products were detected as major impurities in a 'pure' ANG I material. The peptides ANG (2-10) [RVYIHPFHL], ANG II [DRVYIHPF] and three ANG I isomers [DRVYLHPFHL, DRVYIHPFHI and DRVYLHPFHI] were identified and corresponding mass fraction values calculated that range from 0.66 to 4.86 mg/g. The mass fraction values for the major related peptide impurities in the ANG I material obtained with both LC/hrMS and LC/MS/MS systems are in excellent agreement. This study emphasizes the importance of mass spectrometric techniques for application to mass balance approaches for mass fraction value and uncertainty assignment of impurities in 'pure' substance reference materials for peptides.

Isolation and characterization of acid and base degradation products in Atenolol and Hydrochlorothiazide and a validated selective stability-indicating HPLCUV method for their quantification

Atenolol (( RS )-2-{4-[2-Hydroxy-3-(propan-2-ylamino)propoxy]phenyl}acetamide) and Hydrochlorothiazide (6-chloro-1,1-dioxo-3,4-dihydro-2 H -1,2,4-benzothiadiazine-7-sulfonamide) are beta 1 (? 1 ) receptor blocker and diuretic drug respectively; however the combination dosage regime are used for cardiovascular therapy. Thus a forced degradation study was carried out upon this combination drug regime under acidic and basic environment in order to deconvolute the possible degradation product under specified stressed conditions. Under acidic conditions atenolol and hydrochlorothiazide were cleaved into 2-(4-(3-amino-2- oxopropoxy) phenyl) acetamide and 6-sulphamido benzothiazide. However, under basic conditions, the drugs were spliced into 2-(4-(2-hydroxypropoxy) phenyl) acetamide and 2-chloro 4-amino 1, 6-dihydro benzene sulphonamide respectively. The degradant peaks were elucidated by HPLC using C18 column with methanol: phosphate buffer (70:30 v/v) with a flow rate of 0.5ml/min (UV detection at 226nm).. For quantitative method validation, linearity was observed over product concentration range 2g/ml - 100 g/ml (r 2 0.9992) with regression equation y=43432x. The products were first identified by LC-MS and further confirmed by FT-IR and 1 H 1 NMR. A specific and sensitive stability-indicating assay method for the simultaneous determination of the drugs, its process related impurities and degradation products was developed.

Development and validation of a stability indicating method for S-carboxymethyl-l-cysteine and related degradation products in oral syrup formulation

A stability-indicating method for the determination of S-carboxymethyl-l-cysteine and related degradation impurities in Exputex® 250mg/5mL syrup was developed in anion-exchange liquid chromatography mode. A forced degradation study supported the method development to ensure stability indicating conditions. Aqueous solutions of the active pharmaceutical ingredient and syrup samples at different pH-values were stress-tested in different thermal, light exposure and headspace conditions. One degradation product was detected in thermal stress studies at 60°C and 80°C in the pH range 5.0–7.0 and was identified by mass spectrometry as 5-oxo-thiomorpholine-3-carboxylic acid (lactam of carbocysteine). A second degradation product was only generated in moderately strong oxidizing conditions (0.5% H2O2 aqueous solution) and was identified as S-carboxymethyl-l-cysteine-(R/S)-sulphoxide (carbocysteine sulphoxide).The method was developed on a Zorbax SAX column, in isocratic mode. The mobile phase consisted of 200mM phosphate solution at pH 4.0 and acetonitrile (50:50 v/v) and UV detection was performed at a wavelength of 205nm. The method was linear for carbocysteine (R>0.9982) over a concentration range of 2.5–50μg/mL and 0.4–0.6mg/mL. Linearity for the impurities was shown from the LOQ to 50μg/mL. Specificity was verified and accuracy demonstrated for the active ingredient and its degradation products in syrup samples at 3 levels around their respective specification limits. Repeatability, intermediate precision and inter-laboratory reproducibility were assessed on three commercial batches, analyzed in triplicate by two operators at both the transferring and the receiving site and demonstrated a successful method transfer to the manufacturing quality control laboratory.

Circulating Branched Chain Amino Acids are Associated with Body Composition and Physical Function in Older Adults

Identification of mechanisms underlying age‐related alterations in body composition and decreases in physical function will be important for addressing the growing challenge of providing health care to the rapidly expanding aging population. The goal of the current study was to use mass spectrometry‐based metabolic profiling in combination with principal components analysis (PCA) and multivariable‐adjusted linear regression to provide insight into biologic mechanisms that may underlie body composition and physical function in older adults (N=73). Branched chain amino acids (BCAA: leucine, isoleucine, valine) or their related degradation products were negatively associated with total fat mass, positively associated with thigh muscle cross sectional area (CSA) and the fat‐free mass index (total lean mass/height2), but were both positively and negatively associated with mobility (400 meter gait speed; 400‐m). Collectively these data suggest a role for BCAA metabolism in mechanisms related to body composition and physical function in older adults. Future studies aimed at validation of these results in a larger cohort, and, that test the causative role of these associations are of interest. Component Loadings β ± SE p‐value Total Fat AA Factor 5: Valine, Leucine, Isoleucine 0.80, 0.77, 0.76 ‐1.5 ± 0.4 0.001 Muscle CSA AA Factor 2: 4‐methyl‐2‐oxopentanoate, 3‐methyl‐2‐oxovalerate, 3‐methyl‐2‐oxobutyrate 0.87, 0.83, 0.83 6.2 ± 2.0 0.003 AA Factor 5: Valine, Leucine, Isoleucine 0.80, 0.77, 0.76 6.9 ± 1.9 0.0004 FFMI AA Factor 5: Valine, Leucine, Isoleucine 0.80, 0.77, 0.76 0.6 ± 0.2 0.0002 400‐m AA Factor 4: α‐hydroxyisovalerate, 2‐hydroxy‐3‐methylvalerate, α‐hydroxyisocaproate 0.87, 0.78, 0.78 0.1 ± 0.0 0.02 AA Factor 5: Valine, Leucine, Isoleucine 0.80, 0.77, 0.76 ‐0.0 ± 0.0 0.04

Development and Validation of UPLC Method for the Determination of Duloxetine Hydrochloride and Its Impurities in Active Pharmaceutical Ingredient

A suitable, rapid, sensitive and accurate ultra-performance liquid chromatography (UPLC) method was developed for the quantitative determination of Duloxetine hydrochloride and its impurities in active pharmaceutical ingredient. Chromatographic separation was achieved on shim-pack XR-ODS II (3.0 × 100 mm, 2.2 μm), and the gradient eluted within a period of time, that is, 15 minutes. The eluted compounds were monitored at 230 nm. The flow rate was 0.9 ml/min and the column oven temperature was maintained at 40oC. The resolution of Duloxetine hydrochloride and 12 impurities (potential impurity, process related impurity and degradation products) were greater than 1.3. The correlation coefficient (r2>0.99) values indicated clear correlations between the investigated compound concentrations and their peak areas within the quantitation limit to 200% level. The performance of the method was validated according to the present ICH guidelines for specificity, quantitation limit, detection limit, linearity, accuracy, precision, ruggedness and robustness. The recoveries obtained (93.28-102.41%) ensured the accuracy of the developed methods.

Simultaneous Analysis of Losartan Potassium and its Related Impurities and Degradation Products in Tablets Using HPLC

A simple, sensitive, precise and reliable gradient HPLC method was developed and validated for simultaneous quantitative determination of losartan potassium and its eleven related impurities and degradation products in a tablet formulation. Among them B, C, D, E, F, I and G were related impurities and J, K, L and M were degradation products. Optimum chromatographic separation was carried out on an ACCHROM ODS-C18 (250 mm×4.6 mm, 5 µm) column using mobile phases consisting of acetonitrile and 0.1% phosphoric acid under a gradient elution program. The UV detection wavelength was performed at 220 nm with a flow rate of 1.0 mL/min. The column temperature was maintained at 35 °C. All standard curves obtained exhibited good linear regression (r > 0.9995) within the tested range. All the average recovery rates were in the range of 97.00-103.00% and RSD was less than 2.00% (n = 3). Limits of detection and quantification were determined in the level of ng/mL. The results demonstrated that the validated method was suitable for the simultaneous quantification of losartan potassium and its eleven related impurities and degradation products in a tablet formulation. Keywords: HPLC, losartan potassium, related impurities and degradation products, simultaneous quantitative determination.

Assessment by HPLC of the degradation behavior of acitretin under hydrolytic, oxidative, photolytic and thermal stress conditions

Acitretin is a photosensitive oral retinoid with very limited data available on its degradation. The official HPLC method for acitretin determination was insufficient to resolve the degradation products generated during stability studies. Therefore, an isocratic RP-HPLC–UV method was developed for the determination of acitretin in the presence of its related impurities and degradation products. Efficient chromatographic separation was achieved on a Thermo beta-basic column C18 (100mm×4.6mm, 5μm) with mobile phase containing 0.3% (v/v) glacial acetic acid with acetonitrile (ACN) and isopropyl alcohol (IPA) in an isocratic ratio of 70:30 at a flow rate of 1.0mL/min with the eluent monitored at 360nm. The method was validated for specificity, linearity, precision, accuracy and robustness. The calibration plot was linear over the concentration range of 50–150μg/mL with a correlation coefficient (r2) of 0.999. The proposed method was used to investigate the degradation kinetics of acitretin under the different degradative conditions. The degradation rate constant (K), half-life (t1/2), and t90 were calculated. Degradation of acitretin followed pseudo-first-order kinetics. The drug was found to be less stable under acidic and photolytic degradation conditions: the photolytic degradation constants for acitretin in sunlight and UV light were 0.002698% and 0.0008402%min−1, respectively. The LOD for acitretin and the known impurities were at a level below 0.02%. The method shows consistent recoveries for ACTR (99.8%–101.2%) and also for its known impurities (97.2–101.3%). The method was found to be accurate, precise, linear, specific, sensitive, rugged, robust, and useful for characterizing the stability of this chemical.

A novel automated hydrophilic interaction liquid chromatography method using diode-array detector/electrospray ionization tandem mass spectrometry for analysis of sodium risedronate and related degradation products in pharmaceuticals

A simple, sensitive and fast hydrophilic interaction liquid chromatography (HILIC) method using ultraviolet diode-array detector (UV-DAD)/electrospray ionization tandem mass spectrometry was developed for the automated high performance liquid chromatography (HPLC) determination of sodium risedronate (SR) and its degradation products in new pharmaceuticals. The chromatographic separations were performed on Ascentis Express HILIC 2.7μm (150mm×2.1mm, i.d.) stainless steel column (fused core). The mobile phase consisted of formate buffer solution (pH 3.4; 0.03M)/acetonitrile 42:58 and 45:55 (v/v) for granules for oral solution and effervescent tablet analysis, respectively, at a flow-rate of 0.2mL/min, setting the wavelength at 262nm. Stability characteristics of SR were evaluated by performing stress test studies. The main degradation product formed under oxidation conditions corresponding to sodium hydrogen (1-hydroxy-2-(1-oxidopyridin-3-yl)-1-phosphonoethyl)phosphonate was characterized by high performance liquid chromatography-electrospray ionization-mass tandem mass spectrometry (HPLC-ESI-MS/MS). The validation parameters such as linearity, sensitivity, accuracy, precision and selectivity were found to be highly satisfactory. Linear responses were observed in standard and in fortified placebo solutions. Intra-day precision (relative standard deviation, RSD) was ≤1.1% for peak area and ≤0.2% for retention times (tR) without significant differences between intra- and inter-day data. Recovery studies showed good results for all the examined compounds (from 98.7 to 101.0%) with RSD ranging from 0.6 to 0.7%. The limits of detection (LOD) and quantitation (LOQ) were 1 and 3ng/mL, respectively. The high stability of standard and sample solutions at room temperature means an undoubted advantage of the method allowing the simultaneous preparation of many samples and consecutive chromatographic analyses by using an autosampler. The developed stability indicating method is suitable for the quality control of SR in new and commercial pharmaceutical formulations.

Stability-indicating assay method for determination of actarit, its process related impurities and degradation products: Insight into stability profile and degradation pathways☆

The stability of the drug actarit was studied under different stress conditions like hydrolysis (acid, alkaline and neutral), oxidation, photolysis and thermal degradation as recommended by International Conference on Harmonization (ICH) guidelines. Drug was found to be unstable in acidic, basic and photolytic conditions and produced a common degradation product while oxidative stress condition produced three additional degradation products. Drug was impassive to neutral hydrolysis, dry thermal and accelerated stability conditions. Degradation products were identified, isolated and characterized by different spectroscopic analyses. Drug and the degradation products were synthesized by a new route using green chemistry. The chromatographic separation of the drug and its impurities was achieved in a phenomenex luna C18 column employing a step gradient elution by high performance liquid chromatography coupled to photodiode array and mass spectrometry detectors (HPLC–PDA–MS). A specific and sensitive stability-indicating assay method for the simultaneous determination of the drug actarit, its process related impurities and degradation products was developed and validated.

LC-MS/MS characterization of forced degradation products of ambrisentan: development and validation of a stability-indicating RP-HPLC method

The current study reports the characterization of degradation products of ambrisentan by liquid chromatography-tandem mass spectrometry, and development and validation of a stability-indicating reversed phase high performance liquid chromatographic method for determination of ambrisentan in the presence of its process related impurities in bulk drugs. The drug was subjected to various stress conditions such as hydrolysis, oxidation, photo- and thermal degradations to investigate the stability-indicating ability of the method. Significant degradation was observed during acidic and oxidative stresses. Ambrisentan was well resolved from its process related impurities and degradation products formed under stress conditions. The chromatographic separation was accomplished on an Agilent XDB C18 column (150 × 4.6 mm; 5 μm) with the mobile phase consisting of 10 mM NH4OAc (pH = 5.2) and CH3CN in a gradient elution mode at a flow rate of 1.0 ml min−1. The eluents were monitored by a photodiode array detector at 215 nm and quantitation limits were obtained in the range of 0.07–0.25 μg ml−1 for ambrisentan and all its process related impurities. The developed liquid chromatographic method was validated with respect to accuracy, precision, linearity, robustness and limits of detection and quantitation. The degradation products were characterized by comparing their collision induced dissociation mass spectral data with that of ambrisentan and the most possible degradation and fragmentation pathways were proposed.

Development and validation of a stability indicating LC-PDA-MS/MS method for separation, identification and characterization of process related and stress degradation products of rivaroxaban

An isocratic reversed phase high-performance liquid chromatography coupled with a photo diode array and electrospray ionization tandem mass spectrometry (LC-PDA-ESI-MS/MS) method was developed for the identification and characterization of stress degradation products (DPs) and an unknown process related impurity (PR) of rivaroxaban (RVR) in bulk drugs. RVR, a selective and direct factor Xa inhibitor, was subjected to hydrolysis (acidic, alkaline and neutral), photolysis, thermolysis, and oxidation as per ICH guidelines and found susceptible to acid and base hydrolytic stress conditions. In total, three DPs (DP-1, DP-2, and DP-3) were formed. All the DPs, PR and RVR were well separated on a Kinetex C18 (150 × 4.6 mm, 5 μm) column using a mobile phase consisting of 20 mM ammonium acetate and acetonitrile (65 : 35 v/v) at a flow rate of 1.0 ml min−1. To elucidate the structures of PR and DPs, MS/MS experiments were carried out to study the molecular ion fragmentation of RVR, PR, and DPs. The product ions of PR and DPs were compared with those of the RVR molecular ion to assign most possible structures. Potential impurities were isolated by semi-preparative HPLC and subjected to NMR spectroscopy. The LC-PDA method was validated with respect to specificity, linearity, accuracy, precision and robustness as per ICH guidelines.