Nitrosodimethylamine Research Articles

NDMA enhances claudin-1 and -6 expression viaCYP2E1/ROS in AGS cells

Carcinogenic N-nitroso compounds, especially N-nitroso dimethylamine, increase the risk of gastric cancer development. Cytochrome P450-2E1 metabolizes this compound, thus generating an oxidant microenvironment. We aimed to evaluate in gastric adenocarcinoma cells if its effect on CYP2E1 and ROS affects signaling pathways associated with gastric cancer oncogenesis. The impact of N- nitroso dimethylamine upon CYP2E1 and ROS activation/secretion was evaluated by the DCFDA assay protocol, TER measurements, Stat3, pSTAT3, ERK1/2, and pERK1/2 expression, claudins-1 and -6 expression, and finally mRNA values of IL-1β IL-6, IL-8 and TNFα. Our results showed that exposure to N- N-nitroso dimethylamine disrupts the regulation of Stat3 and Erk1/2, alters the expression of claudin-1 and claudin-6 tight junction proteins, and increases the secretion of pro-inflammatory cytokines. These alterations induce a continuous local inflammatory process, an event identified as a gastric cancer promoter. In summary, N-nitroso dimethylamine can disrupt cell mechanisms associated with gastric cancer oncogenesis.

Correction: N-Nitrosodimethylamine (NDMA) formation and mitigation in potable reuse treatment trains employing ozone and biofiltration

Correction for ‘N-Nitrosodimethylamine (NDMA) formation and mitigation in potable reuse treatment trains employing ozone and biofiltration’ by Fernanda Bacaro et al., Environ. Sci.: Water Res. Technol., 2019, 5, 713–725, https://doi.org/10.1039/C8EW00926K.

Impact of ozonation on the formation of particulate nitrosodi-methylamine (NDMA) in atmosphere

The contribution of ozonation to the formation of particulate nitrosodi-methylamine (NDMA) in the aqueous aerosol phase was investigated using measurement data from 2018 in Seoul, Republic of Korea and a box model. The correlation between the NDMA concentration and aerosol liquid water content and box model results showed that aqueous aerosol phase reactions, including nitrosation and ozonation, might contribute to the formation of NDMA. The concentration of NDMA and the ratio of O3/dimethylamine exhibited a negative correlation, suggesting that the contribution of ozonation to NDMA formation may not be significant. Furthermore, when the daily concentration of NDMA exceeded 10 ng/m3, the pH was 3.96 ± 0.48, indicating that the impact of ozonation on NDMA concentration might not be significant. To quantitatively investigate the contribution of ozonation, the ozonation mechanism that forms NDMA was included in the box model developed in our previous study. The model results showed that the ozonation contributed to the ambient concentration of NDMA (7.9 ± 3.8% (winter); 1.9 ± 3.0% (spring); 10.0 ± 0.77% (summer); 3.6 ± 7.3% (autumn)). It is estimated that the relatively higher O3/NOx ratio in summer (1.63 ± 0.69; 0.64 ± 0.52 (winter); 1.14 ± 0.92 (spring); 0.52 ± 0.54 (autumn)) could enhance ozonation and that relatively lower pH in summer (2.2 ± 0.4; 5.3 ± 1.2 (winter); 3.9 ± 1.2 (spring); 3.9 ± 0.7 (autumn)) could hinder nitrosation compared to that in other seasons.

Carcinogenic Effects of Nitrosodimethylamine (NDMA) Contamination in Ranitidine: Defining the Relationship With Renal Malignancies

Purpose: Ranitidine, a medication used to treat gastric ulcers and reflux, was once the highest selling drug in the world with over $1 billion in annual sales. However, in 2020, ranitidine, known more commonly by the brand name Zantac, virtually vanished from the market after multiple regulatory bodies including the US Food and Drug Administration recommended withdrawal. Their concern was based on detection of nitrosodimethylamine (NDMA), a known animal carcinogen, in ranitidine samples. NDMA has been shown to induce multiple tumor types, including renal tumors. The effects of human exposure, however, are not completely understood. This review aims to clarify what is known about NDMA contamination in ranitidine, the carcinogenic mechanisms of NDMA, and possible associations between ranitidine consumption and renal cancers. Materials and Methods: A comprehensive literature review was performed regarding ranitidine and NDMA, carcinogenesis, and associations with malignancy. Data were considered from environmental, preclinical, and clinical studies from various disciplines. Publications from governmental bodies, including the Food and Drug Administration and International Agency for Research on Cancer, were reviewed and included for analysis. Results: Multiple preclinical studies have demonstrated the carcinogenic effects of NDMA in animals with high rates of renal tumor development. NDMA has been detected in industrial, dietary, and pharmacologic sources. Regarding NDMA levels in ranitidine, evidence points to associations with storage conditions at elevated temperatures and/or prolonged duration as well as endogenous production facilitated by physiologic gastric conditions. Once metabolized, NDMA by-products form DNA adducts with established roles in carcinogenesis. Human data on ranitidine consumption and cancer development are derived from large population studies limited by their observational nature and inconsistent measure of NDMA exposure. To date, NDMA associations with renal malignancies—although evident in animal studies—is not clearly delineated in humans. Conclusions: Detection of NDMA in ranitidine has prompted governmental regulatory bodies to recommend withdrawal of ranitidine from US markets. Classification of NDMA as a “probable human carcinogen” is based on decades of animal studies with a notable rate of renal malignancies. Human observational studies do not clearly demonstrate an association with renal malignancies, but the available data have significant limitations and any conclusions drawn from these observational studies, whether supporting or challenging associations between ranitidine use and renal cancer, should be interpreted with caution.

An innovative solid-phase biosensor for rapid on-site detection of N-nitrosodimethylamine incorporating zein film and upconversion nanoparticles

Pickled frequently contains nitrosodimethylamine (NDMA), a mutagenic and carcinogenic substance that is dangerous for the general public's health. This study reports on the fabrication of a fluorescent biosensor using zein film and aptamer functionalized upconversion nanoparticles (UCNPs) for on-site monitoring of NDMA in meat. UCNPs were first prepared followed by aptamer binding and mixing with zein film, which was further conjugated with cDNA of dabcyl modified at 5′. The fluorescence resonance energy transfer (FRET) mechanism between the UCNPs and dabcyl was exploited. The fluorescence signals of the zein film recovered when NDMA was present because it was selectively collected by the particular aptamer and damaged the cDNA structure. The designed functionalized zein film was used for on-site and portable determination of NDMA with a lower limit of detection of 0.017 ng/mL, and possessed a satisfactory recovery ranging from 95.8% to 100.2% with no significant difference compared with the GC–MS method.

Use of the benchmark-dose (BMD) approach to derive occupational exposure limits (OELs) for genotoxic carcinogens: N-nitrosamines.

N-Nitrosamines are potent carcinogens and considered non-threshold carcinogens in various regulatory domains. However, recent data indicate the existence of a threshold for genotoxicity, which can be adequately demonstrated. This aspect has a critical impact on selecting the methodology that is applied to derive occupational exposure limits (OELs). OELs are used to protect workers potentially exposed to various chemicals by supporting the selection of appropriate control measures and ultimately reducing the risk of occupational cancer. Occupational exposures to nitrosamines occur during manufacturing processes, mainly in the rubber and chemical industry. The present study derives OELs for inhaled N-nitrosamines, employing the benchmark dose (BMD) approach if data are adequate and read-across for nitrosamines without adequate data. Additionally, benchmark dose lower confidence limit (BMDL) is preferred and more suitable point-of-departure (PoD) to calculate human health guidance values, including OEL. The lowest OEL (0.2μg/m3 ) was derived for nitrosodiethylamine (NDEA), and nitrosopiperidine (NPIP) (OEL = 0.2μg/m3 ), followed by nitrosopyrrolidine (NPYR) (0.4μg/m3 ), nitrosodimethylamine (NDMA), nitrosodimethylamine (NMEA), and nitrosodipropylamine (NDPA) (0.5μg/m3 ), nitrosomorpholine (NMOR) (OEL = 1μg/m3 ), and nitrosodibutylamine (NDBA) (OEL = 2.5μg/m3 ). Limits based on "non-threshold" TD50 slope calculation were within a 10-fold range. These proposed OELs do not consider skin absorption of nitrosamines, which is also a possible route of entry into the body, nor oral or other environmental sources. Furthermore, we recommend setting a limit for total nitrosamines based on the occupational exposure scenario and potency of components.

Comprehensive computational study on reaction mechanism of N-Nitroso dimethyl amine formation from substituted hydrazine derivatives during ozonation

N- Nitrosodimethyl amine, the simplest member of the N-Nitrosamine family, is a carcinogenic and mutagenic agent that has gained considerable research interest owing to its toxic nature. Ozonation of industrially important hydrazines, such as unsymmetrical dimethylhydrazine (UDMH) or monomethylhydrazine (MMH), has been associated with NDMA formation and accumulation in the environment. UDMH/MMH - ozonation also leads to several other transformation products such as acetaldehyde dimethyl hydrazine (ADMH), tetramethyl tetra azene (TMT), diazomethane, methyl diazene, etc, which can be either precursors or competitors for NDMA formation. However, the relevant chemistry detailing the formation of these transformation products from UDMH/MMH -ozone reaction and their subsequent conversion to NDMA is not well understood. In this work, we explored the formation mechanism of ADMH and TMT from UDMH-ozonation and their further oxidation to NDMA using the second-order Moller Plesset perturbation theory employing the 6-311G(d) basis set. We have also investigated how MMH selectively forms methyl diazene and diazomethane under normal conditions and NDMA in the presence of excess ozone. Our calculations indicate that the reactions proceed via an initial H abstraction from the hydrazine –NH2 group, followed by the oxidation of the generated N-radical species. The formation of ADMH from the UDMH-ozone reaction involves an acetaldehyde intermediate, which then reacts with a second UDMH molecule to generate ADMH. The preferable attack of ozone molecule on N=C bond of ADMH generates DMAN intermediate, which subsequently undergoes oxidation to form NDMA. Unlike other transformation products, TMT formation occurs via the dimerization of DMAN. 1Though there exists an N=N bond in the TMT, which are preferable attacking sites for ozone, experimental studies show the lower yields of NDMA formation, which corroborates with the high activation barrier required for the process (42 kcal/mol). Overall, our calculated results agree well with the experimental observations and rate constants. Computational calculations bring new insights into the electronic nature and kinetics of the elementary reactions of this pathway, enabled by computed energies of structures that are not possible to access experimentally.

Release regularity and cleaning measures of magnetic anion exchange resin during application

Anion exchange resin is responsible for removing harmful anionic contaminants in drinking water treatment, but it may become a significant source of precursors for disinfection byproducts (DBPs) by shedding material during application without proper pretreatment. Batch contact experiments were performed to investigate the dissolution of magnetic anion exchange resins and their contribution to organics and DBPs. Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) released from the resin were highly correlated with the dissolution conditions (contact time and pH), in which 0.7 mg/L DOC and 0.18 mg/L DON were distributed at exposure time of 2 h and pH 7. The formation potential of four DBPs in the shedding fraction was also revealed that trichloromethane (TCM), dichloroacetonitrile (DCAN), nitrosodimethylamine (NDMA), and dichloroacetamide (DCAcAm) concentrations could reach 21.4, 5.1, 12.1 μg/L, and 69.6 ng/L, respectively. Furthermore, the hydrophobic DOC that preferred to detach from the resin mainly originated from the residues of crosslinkers (divinylbenzene) and porogenic agents (straight-chain alkanes) detected by LC-OCD and GC-MS. Nevertheless, pre-cleaning inhibited the leaching of the resin, among which acid-base and ethanol treatments significantly lowered the concentration of leached organics, and formation potential of DBPs (TCM, DCAN, and DCAcAm) below 5 μg/L and NDMA dropped to 10 ng/L.

Determination of N-nitrosodimethyl amine impurity in valsartan by HPLC and LC-MS/MS methods

In this study, two novel, rapid, sensitive, and specific chromatographic methods were developed and validated for the determination of N -nitrosodimethylamine (NDMA) impurity in the valsartan drug substance. The first method is a high-performance liquid chromatography method with a diode array detector (HPLC-DAD). The method was validated according to ICH Q2 (R1) guidelines and was used for the determination of NDMA in valsartan drug substances from different suppliers. Satisfactory validation results were obtained in terms of linearity with a range from 9.10 to 29.5 µg L −1 and R 2 = 0.994, precisions with a coefficient of variation of 1.2%, accuracy with recovery between 94.5% and 103.1%, limit of detection (LOD) and limit of quantitation (LOQ) were 0.0027 and 0.0091 mg kg −1 , respectively. Assay of NDMA in valsartan drug substances using the developed HPLC-DAD method showed that samples from Zhejiang Huahai supplier, obtained between 2012 and 2017, contained high levels of NDMA that exceed the acceptable limits with an average concentration of 59.3 mg kg −1 . On the other hand, the new Zhejiang Huahai samples, obtained after November 2018, did not show significant contamination with NDMA. For confirmation of our results, a second method was developed which is the liquid chromatography method with tandem mass spectrometry detection (LC-MS/MS). The new LC-MS/MS method was developed and validated for confirmation of the results of the NDMA assay in the new valsartan samples obtained from Zhejiang Huahai after November 2018. The new LC-MS/MS method has been more selective than the HPLC-DAD method with LOD and LOQ values of 0.0021 and 0.0070 mg kg −1 , respectively. The results of LC-MS/MS show good agreement with those obtained with the HPLC-DAD method.

Contribution of liquid water content enhancing aqueous phase reaction forming ambient particulate nitrosamines

Contribution of liquid water content (LWC) to the levels of the carcinogenic particulate nitro(so) compounds and the chemistry affecting LWC were investigated based on the observation of seven nitrosamines and two nitramines in rural (Seosan) and urban (Seoul) area in South Korea during October 2019 and a model simulation. The concentrations of both the total nitrosamines and nitramines were higher in Seosan (12.48 ± 16.12 ng/m3 and 0.65 ± 0.71 ng/m3, respectively) than Seoul (7.41 ± 13.59 ng/m3 and 0.24 ± 0.15 ng/m3, respectively). The estimated LWC using a thermodynamic model in Seosan (12.92 ± 9.77 μg/m3) was higher than that in Seoul (6.20 ± 5.35 μg/m3) mainly due to higher relative humidity (75 ± 9% (Seosan); 62 ± 10% (Seoul)) and higher concentrations of free ammonia (0.13 ± 0.09 μmol/m3 (Seosan); 0.08 ± 0.01 μmol/m3 (Seoul)) and total nitric acid (0.09 ± 0.07 μmol/m3 (Seosan); 0.04 ± 0.02 μmol/m3 (Seoul)) in Seosan while neither fog nor rain occurred during the sampling period. The relatively high concentrations of the particulate nitrosamines (>30 ng/m3) only observed probably due to the higher LWC (>10 μg/m3) in Seosan. It implies that aqueous phase reactions involving NO2 and/or uptake from the gas phase enhanced by LWC could be promoted in Seosan. Strong correlation between the concentrations of nitrosodi-methylamine (NDMA), an example of nitrosamines, simulated by a kinetic box model including the aqueous phase reactions and the measured concentration of NDMA in Seosan (R = 0.77; 0.37 (Seoul)) indicates that the aqueous phase reactions dominantly enhanced the NDMA concentrations in Seosan. On the other hand, it is estimated that the formation of nitrosamines by aqueous phase reaction was not significant due to the relatively lower LWC in Seoul compared to that in Seosan. Furthermore, it is presumed that nitramines are mostly emitted from the primary emission sources. This study implies that the concentration of the particulate nitrosamines can be promoted by aqueous phase reaction enhanced by LWC.

NDMA formation during ozonation of metformin: Roles of ozone and hydroxyl radicals

Metformin, a high-consumed pharmaceutical for diabetes, has been reported to generate carcinogenic nitroso-dimethylamine (NDMA) during treatment of its containing wastewater. However, whether it would produce NDMA during ozonation or not is unclear, let alone discriminate roles of ozone (O3) and hydroxyl radicals (OH). In this paper, effects of ozonation on NDMA formation from metformin were investigated, roles of O3 and OH were also distinguished by adding tert-butyl alcohol (tBA) as OH scavenger. Moreover, various influencing factors and reaction mechanisms were demonstrated. The results indicated that NDMA could be directly formed from metformin during ozonation, the addition of OH scavenger significantly enhanced its formation (0–46.2 ng/L vs 0–139.1 ng/L). The formation of NDMA by O3 and OH was more affected by bromide and HCO3− than those with only O3; while the impacts of pH and sulphate on the latter were more notable. No matter without/with tBA in the solution, the formed NDMA during ozonation of metformin increased with raising pH (from 5 to 9) and achieved the maximum 69.6 ng/L and 235.9 ng/L at pH 9, respectively; small amount of bromide (0.1 μM) promoted NDMA production, high levels of bromide (10 μM) inhibited its formation; the existence of HCO3− enhanced the amounts of NDMA from 44.5 to 73.5 ng/L (raised by 65.2%) by O3 and OH and from 102.9 to 130 ng/L with only O3 (raised by 26.3%); with the addition of sulphate, NDMA concentration raised by 43.8% by O3 and OH, while the value was high up to 134.6% with only O3. Based on the result of UPLC-Q-TOF and density functional theory, the oxidation intermediates were identified and possible transformation pathways of metformin during ozonation were proposed. The findings in this paper would provide reference when treating metformin-containing water in future.

The occurrence of volatile N-nitrosamines in heat-treated sucuk in relation to pH, aw and residual nitrite.

In this study, the occurrence of volatile nitrosamines were investigated in heat-treated sucuk, a kind of semi-dry fermented sausage. The pH, aw and residual nitrite of the samples were also determined. In addition, a principal component analysis (PCA) was also performed in order to elucidate the relationship between nitrosamine and these variables. Significant differences between brands were found in terms of NDMA (N- Nitrosodimethylamine), NPYR (N-Nitrosopyrolidine) and NPIP (N-Nitrosopiperidine) (p<0.05). NDMA and NPYR varied from 1.71 to 3.57µg/kg and 1.65 to 7.29µg/kg, respectively. Higher levels were found for NPIP (5.19 to 16.40µg/kg). NDEA (N-Nitrosodiethylamine) and NDBA (N- Nitrosodibutylamine) were not found in any of the heat-treated sucuk samples. The residual nitrite content was under 10mg/kg in all samples. The aw and pH values varied between 0.913 and 0.940 and between 4.28 and 5.47, respectively. In PC1 explaining 72% of the variance, NDMA and NPYR were placed on the negative side, NPIP on the positive side. Residual nitrite and aw were more effective for NPIP, while pH was an important parameter for NDMA and NPYR.

Validation of the promotion mechanism between bromide and UDMH to form NDMA during ozonation

Unsymmetrical dimethylhydrazine (UDMH) is found to generate substantial carcinogenic nitroso-dimethylamine (NDMA) during ozonation, moreover, its formation is promoted by ubiquitous bromide ions (Br−) in water matrixes, but the mechanism is still unclear. In this study, effects of Br− on NDMA formation during ozonation of UDMH were studied, meanwhile, its promotion pathways were also determined. The results demonstrated that Br− promoted NDMA formation from UDMH during ozonation, the formation rate constant with Br− is over 7 times of that without Br−. NDMA amount raised from 142.5 to 327.5 μg/L when Br− dosages increased from 0 to 100 μM. No matter with or without Br−, the augment of O3 dosages facilitated NDMA formation; the maximum value was achieved at pH 8. NDMA decreased dramatically from 173.8 to 123.5 μg/L with HCO3− raising from 0 to 160 μM, while increasing remarkably to 222.5 μg/L with SO42− dosing. In addition, NOM inhibited NDMA formation from UDMH during ozonation. The mass spectrum of LC-MS/MS verified that the generation of Br-UDMH was main cause for promoting NDMA formation. Moreover, hypobromous acid (HBrO) was confirmed to be responsible for Br-UDMH formation. In addition, the position that oxidants and Br− attacked was demonstrated based on Gaussian calculation. The results of this study could provide theoretical basis for the application of ozonation in bromine-containing water matrixes.

Particulate Nitrosamines and Nitramines in Seoul and Their Major Sources: Primary Emission versus Secondary Formation.

Seven nitrosamines and three nitramines in particulate matter with an aerodynamic diameter of less than or equal to 2.5 μm (PM2.5) collected in 2018 in Seoul, South Korea, were quantified. Annual mean concentrations of the sum of nitrosamines and nitramines were 9.81 ± 18.51 and 1.12 ± 0.70 ng/m3, respectively, and nitrosodi-methylamine (NDMA) and dimethyl-nitramine (DMN) comprised the largest portion of nitrosamines and nitramines, respectively. Statistical analyses such as non-parametric correlation analysis, positive matrix factorization, analysis of covariance, and orthogonal partial least squared discrimination analysis were carried out to identify contribution of the atmospheric reactions in producing NDMA and DMN. In addition, kinetic calculation using reaction information obtained from the previous chamber studies was performed to estimate concentrations of NDMA and DMN that might be produced from the atmospheric reactions. It was concluded that (1) the atmospheric reactions contributed to the concentrations of NDMA more than they did for those of DMN, (2) the contribution of atmospheric reactions to the concentrations of NDMA and DMN was significant due to high NO2 concentrations in winter, and (3) primary emissions predominantly affected the ambient concentrations of NDMA and DMN in spring, summer, and autumn.

Nitrosodimethylamine Impurities in Metformin Drug Products

Metformin is a high-dose antidiabetic drug and most widely used first-line therapeutic agent for the management of type 2 diabetes mellitus (T2DM). Medicines regulatory agencies discovered contamination of genotoxic nitrosamine impurity in certain medications containing angiotensin receptor blocking (ARB) agents. This resulted in screening for nitrosamine impurities in a number of probable drug products. In November 2019, the Singapore government withdrew metformin drug products, due to the contamination of nitrosamine impurity, called nitrosodimethylamine (NDMA). The regulatory agencies from different geographies started investigation and subsequently, many products withdrew from the international market due to the presence of an unacceptable limit of NDMA in metformin tablets. Both pharmaceutical companies and regulatory agencies responded to mitigate this emerging issue. USV Private Limited (USV) has adopted a proactive quality risk management program to investigate the presence of genotoxic impurities in metformin products. The presence of NDMA impurities were tested in 425 batches of drug substances and drug products. Threshold toxicological concern (TTC) of all the batches was found to be ≤30 ng/day, when compared to the regulatory limit of 96 ng/day. Hence, USV metformin products are safe and can be continuously prescribed for the management of T2DM.

Inhibitory effect of alkyl groups on N-nitrosamine formation from secondary and tertiary alkylamines with monochloramine

N -nitrosamines are contaminants of emerging concern, and controlling these chemicals in potable water and recycled water for potable reuse has become important for protecting public health. This study aimed to evaluate the influence of the alkyl chain lengths of N -nitrosamine precursors (secondary and tertiary amines) on the formation of N -nitrosamines via chloramination. The molar conversion efficiency from dimethylamine, an N -nitrosodimethylamine (NDMA) precursor, to NDMA (0.67%) was greater than that from diethylamine, an N -nitrosodiethylamine (NDEA) precursor, to NDEA (0.38%). Similarly, the molar conversion efficiency from trimethylamine to NDMA (0.92%) was greater than from triethylamine to NDEA (0.33%). Interestingly, a considerable difference in molar conversion efficiencies were observed for tertiary amines with the N , N -dialkyl- α -arylamine structure: the molar conversion efficiencies from N , N -dimethylbenzylamine and N , N -diethylbenzylamine to NDMA and NDEA were 50.2% and 1.7%, respectively. These results indicate that amines with ethyl groups have lower potentials for producing the corresponding N -nitrosamines than those with methyl groups. These differences in yields between amines with methyl and ethyl groups can be explained by the difference in electron density in the nitrogen atom of the amine, which influences the protonation of the amine and stabilization of intermediate species. These findings could be useful for enhancing source control of water and wastewater by regulating runoff or industrial wastewater containing high concentrations of specific N -nitrosamine precursors. • Formation of four N -nitrosamines from the secondary and tertiary amines were tested. • The molar conversion of amines having ethyl group were lower than those of methyl group. • Benzylamines had higher molar conversion values in comparison with simple alkylamines. • Longer alkyl chains in amines suppressed N -nitrosamine formation reactions.

Presence of nitrosamine impurities in medicinal products

In 2018, some sartan medicinal products were reported to be contaminated with nitrosamine compounds, which are potent mutagenic carcinogens. Two nitrosamines received particular attention: N -nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA). These have since been confirmed in different types of medicinal products, including ranitidine and metformin. Consequently, the European Medicines Agency (EMA) started an investigation into the cause of contamination and an assessment of the risk to patients taking contaminated medicinal products. The main source of contamination were changes in production, which involves combinations of amines and nitrogen compounds and the use of specific catalysts and reagents. Withdrawals of medicinal products that took place in Croatia did not lead to a shortage of sartan- or metformin-containing medicines. Moreover, ranitidine had been preventively withdrawn all over the EU, including Croatia, creating shortages at the time, but was subsequently replaced with therapeutic alternatives.

Isolation of N-Nitrosodimethylamine (NDMA) from Drug Substances Using Solid-Phase Extraction-Liquid Chromatography-Tandem Mass Spectrometry

N -nitrosodimethylamine (NDMA) contamination in several drugs has been reported since 2018, and there is also a potential risk of the NDMA contamination in various other drug substances and their pharmaceutical products. To quantitate NDMA in various drugs having diverse physicochemical properties, a specific, sensitive and durable analytical method is required, in addition to methods that can be applied to a class of nitrosamines. We aimed to develop an off-line isolation method for NDMA in drug substances using solid-phase extraction (SPE) for quantification using high-performance liquid chromatography (HPLC)–atmospheric pressure chemical ionization (APCI)–tandem mass spectrometry (MS/MS).Impediments to accurate quantitation of NDMA in drug substances using LC–MS/MS and insufficient durability of the system is due to the extremely large amounts (≈ 10 8 times) of active pharmaceutical ingredients (APIs) in sample solutions in comparison to the trace amount of NDMA. It is occasionally possible to encounter a reduced retention of NDMA and/or decreased separation from other substances in LC, matrix effect in MS detection, and undesirable contamination of instruments with API and other substances, which consequently results in deterioration of system performance and generation of unreliable data even in the cases where divert valve is configured between the column and ion source of the MS instrument.To address the problems, an off-line isolation methodology for NDMA from APIs having diverse physicochemical properties, namely ranitidine hydrochloride (ranitidine), metformin hydrochloride (metformin), nizatidine, valsartan, and telmisartan , was developed. The applicability of the method was confirmed by batch analysis of metformin and ranitidine. Furthermore, contrary to previous reports, NDMA was found to be stable over a wide pH range. The methodology and information would contribute the control of NDMA concentration in various drugs to realize the safe delivery of pharmaceuticals to patients.

Insight into the formation of N-nitrosodimethylamine in metformin products

An effective analytical method for the quantification of N-nitrosodimethylamine (NDMA) using a liquid chromatography coupled with tandem mass spectrometry was developed and applied to a process optimization study of the production of metformin film coated tablets in order to identify the key factors behind the NDMA formation in metformin products. The method uses a linear gradient elution with mobile phases 0.1 % formic acid in water for chromatography and methanol for chromatography and a column Acquity UPLC HSS T3 1.8 μm. The use of the tandem mass spectrometry in a positive ion mode with an atmospheric pressure chemical ionization allows for the use of an isotopically labelled internal standard and an external calibration standard. The method was validated according to the guidelines of International Council for Harmonization in terms of limit of detection and quantification, linearity, precision, accuracy and method selectivity. To further justify the effectiveness of the method, a comparison between two laboratories was performed using a linear regression testing. Both methods give comparable results. 469 samples of both metformin active pharmaceutical ingredient and film coated tablets were analysed and the key factors behind NDMA formation were identified. Hypotheses explaining the mechanism were formulated and confronted with measurements and scientific literature. Protective measures to prevent NDMA contamination in metformin products were drawn.

THMs, HAAs and NAs production from culturable microorganisms in pipeline network by ozonation, chlorination, chloramination and joint disinfection strategies

Disinfection is an indispensable process to inactivate pathogens, while unexpected disinfection by-products (DBPs) would also be formed between the reaction of residual disinfectants and microorganisms in the water distribution system (WDS). However, there are few studies referring to the formation of DBPs and DBPs-associated toxicity under various disinfection methods based on microorganisms in the real WDS. In addition, the main contributors of bacterial communities or components that generate DBPs are unclear. In this study, the formation of trihalomethanes (THMs), halo-acetic acids (HAAs), nitrosamines (NAs) from culturable microorganisms in pipeline network by ozonation(O3), chlorination (Cl2), chloramination (NH2Cl) and joint disinfection methods were compared, meanwhile, their calculated toxicities under different oxidation scenarios were also discussed. Moreover, 16S ribosomal ribonucleic acid (rRNA) gene sequencing was used to identify the main microbial communities. The results demonstrated that THMs and HAAs increased with increasing disinfectant dosages, while the quantity of NAs (mainly nitroso dimethylamine (NDMA)) was not significantly related to disinfectant dosages for each disinfection strategy. Chloroform (TCM) and dichloroacetic acid (DCAA) were the dominant THMs and HAAs species, respectively. NDMA existed in the samples before disinfections, which may due to the metabolic activity of microorganisms. Pre-O3 increased THMs formation during subsequent Cl2 and NH2Cl treatment. However, pre-O3 effectively reduced HAAs produced by subsequent chlorination. O3/Cl2 disinfection had the highest DBPs formation potential (DBPFP) (883.6 nM), while its calculated toxicity was similar to that in Cl2 disinfection treatment. Pseudomonas was the most abundant bacterial genus in biofilm of WDS pipeline. This study can aid in an optimal disinfection strategy for water treatment plants to reduce the toxicity of DBPs caused by biomass in pipelines and ensure water quality safety.