Formation Of N-nitrosamines Research Articles

Formation of algal-derived nitrogenous disinfection by-products during chlorination and chloramination

Algal cells and algal organic matter (AOM) are a source of high dissolved organic carbon (DOC) and nitrogen (DON) concentrations. This poses a possible health risk due to their potential to form disinfection by-products (DBPs), some of which may be of health concern, after disinfection. While several studies have focussed on the formation of carbonaceous DBPs from AOM, only a few studies have focussed on the formation of nitrogen containing N-DBPs from AOM. Hence, the main aim of this study was to thoroughly investigate the N-DBP formation potential of the AOM from a species of cyanobacteria commonly found in natural waters, Microcystis aeruginosa. Three haloacetonitriles, two halonitromethanes, two haloacetamides, and eight N-nitrosamines were analysed by gas chromatography-mass spectrometry after chlorination and chloramination of the extracted AOM. To provide further insight into the influence of changing DON character on N-DBP formation potential, the AOM from three other species, Chlorella vulgaris, Dolichospermum circinale and Cylindrospermopsis raciborskii, were also tested. Dichloroacetonitrile (DCAN) was the DBP formed in the highest concentrations for both chlorination and chloramination of bulk AOM from all the species. Furthermore, during chlorination and chloramination, the high molecular weight fraction (>1 kDa) of AOM from M. aeruginosa had a greater DCAN formation potential (normalised to DOC or DON) than the AOM in the low molecular weight fraction (<1 kDa) of M. aeruginosa, regardless of growth stage. N-Nitrosamine formation from the bulk AOM of all species occurred only after chloramination. The molar concentration of N-nitrosodimethylamine (NDMA) was lower than the other N-nitrosamines detected. However, NDMA formation increased with culture age for all four species, in contrast to most other N-nitrosamines whose formation remained consistent or decreased with culture age. Overall, algal growth could result in elevated concentrations of N-DBPs due to the increasing concentrations of high molecular weight algal DON in the AOM. It is suggested that the AOM comprises precursors containing long C-chain amine (R1-NH-R2) or cyclic N-containing amine structures. Comparisons to previously measured N-DBP concentrations in drinking water suggest that the AOM from the algae and cyanobacteria examined in this study are not likely to be a major source of precursors for either DCAN or NDMA in real waters. However, AOM may present a major precursor source for other N-nitrosamines.

Effects of rosemary extract, grape seed extract and green tea polyphenol on the formation ofN‐nitrosamines and quality of western‐style smoked sausage

The effects of rosemary extract, grape seed extract (GSE) and green tea polyphenol (GTP) on the physicochemical properties and N-nitrosamines content of western-style smoked sausage were investigated. Among the additives, GTP had the highest total phenol content (109.82 mg GAE/g DW) and the best scavenging capacity on ABTS (IC50 = 0.16 g/ml). Rosemary extract and GTP reduced the hardness of sausage (p < .05). Rosemary extract, GSE and GTP reduced the gumminess and chewiness of sausage (p < .05), but had little effects on the cohesiveness and springiness (p > .05). Rosemary extract increased the a* and b* values of sausage significantly (p < .05), GSE and GTP had little effects on color (p > .05). The additives all decreased the pH values, TBARs values of sausage (p < .05) and increased the moisture content in sausage (p < .05). The additives can significantly reduce the residual nitrite and N-nitrosamines content of western-style smoked sausage. GTP showed the best effect on TBARs (48.29%), residual nitrite (68.87%) and N-nitrosamines (61.29%). Above all, the additives had good antioxidant ability and could inhibit the formation of N-nitrosamines. Compared with other additives, GTP had the best effect. Practical applications Rosemary extract, GSE and GTP have attracted much attention due to their great antibacterial and antioxidant properties. This paper studies the effects of rosemary extract, GSE and GTP on the quality and N-nitrosamines concent of western-style smoked sausage. It has shown that rosemary extract and GTP can increase the moisture content of the products and improve their hardness. Rosemary extract and GSE can improve the color of the product to some extent. Because the three additives have good antioxidant properties, they can be used to extend the shelf life of products. Moreover, the three additives can reduce residual nitrite and inhibit N-nitrosamine formation, which can provide certain theoretical basis for the development of low nitrate products and cancer prevention. However, the inhibition mechanism of the three additives on N-nitrosamine formation needs further study. In addition, the three additives all have specific flavor, which can affect the flavor of the products. This problem also needs to be improved.

Thyme and Clove Essential Oils as Antioxidants and Antimicrobial in Beef Sausage

Sausage is one of the well-liked foodstuffs in many areas. However, its quality is vulnerable to deteriorate owing to the lipid oxidation and microbial contamination. This research aimed to study the influence of thyme and clove essential oils (EOs) with or without nitrite on the chemical composition, microbial growth, and lipid oxidation rate in sausage during frozen storage-18°C for three months. The obtained results showed that the main component in clove EO and thyme EO is eugenol and thymol. Adding sodium nitrite to sausage resulted in declines in moisture and crude lipids and increases in protein and ash contents of sausage. Adding the tested EOs increased nitrite's effect on the chemical composition of sausage. Besides, these EOs lowered TBARS values, residual nitrite, and TBC in sausage. They also resulted in the rise of nitrite's efficacy in reducing TBARS values and TBC in sausage. Proteus was more sensitive than Klebsiella, whereas E. coli showed more resistance when adding nitrite or EO to sausage. The tested EOs increased the inhibitory influence of nitrite on Proteus, Klebsiella, Aspergillus niger, and Candida albicans in sausage. We concluded that the EOs of clove and thyme have antioxidant and antimicrobial efficacies in raw beef sausage during frozen storage. Also, they have a synergistic impact on nitrite. Therefore, it is suggested that these EOs, especially thyme, could be utilized to prolong shelf-life, prevent deterioration of sausage, and lessen the added nitrite's proportion to sausage for avoiding the formation of carcinogenic N-nitrosamines‏.

Role of absorber and desorber units and operational conditions for N-nitrosamine formation during amine-based carbon capture

The formation of carcinogenic N-nitrosamines from reactions between solvent amines and flue gas NOx is an important concern for the application of amine-based processes to capture CO2 post-combustion. Using an advanced test rig with interconnected absorber and desorber units, we evaluated the importance for N-nitrosamine formation of the desorber relative to the absorber, and any synergism between the two units. Variations in desorber temperature and in flue gas composition indicated that N-nitrosamine formation from fresh monoethanolamine (MEA) occurred predominantly in the absorber. N-nitrosamine formation was driven by high NO2 and O2 flue gas concentrations, although NO also contributed. In contrast, N-nitrosamine formation from piperazine (PZ) was driven by reactions with nitrite in the heated desorber, and accelerated concurrent with nitrite accumulation. A complementary experiment simulating aged MEA solvent (high nitrite, 1.5% sarcosine as a proxy of secondary amine degradation products) suggested the desorber becomes an order of magnitude more important than the absorber for N-nitrosamine formation. For fresh MEA solvent, increasing the desorber temperature from 110 °C to 130 °C promoted thermal decomposition of N-nitrosamines, reducing N-nitrosamine accumulation rates two-fold. Compared to the test rig, the prevailing practice of using separate absorber columns and autoclave-like treatments to mimic desorber units predicted the direction, but underestimated the magnitude of N-nitrosamine formation. Because N-nitrosamine accumulation rates are the net result of competing formation and thermal decomposition processes, use of continuously cycling test rigs may be necessary to understand the impacts of different operating conditions.

N-Nitrosamine formation from chloramination of two common ionic liquids

Ionic liquids (ILs) are a class of solvents increasingly used as “green chemicals.” Widespread applications of ILs have led to concerns about their accidental entry to the environment. ILs have been assessed for some environmental impacts; however, little has been done to characterize their potential impacts on drinking water if ILs accidentally enter surface water. IL cations are often aromatic or alkyl quaternary amines that resemble structures of previously confirmed N-nitrosamine (NA) precursors. Therefore, this study has evaluated two common ILs, 1-ethyl-3-methylimidazolium bromide (EMImBr) and 1-ethyl-1-methylpyrrolidinium bromide (EMPyrBr), for their NA formation potential. Each IL species was reacted with pre-formed monochloramine under various laboratory conditions. The reaction mixtures were extracted using liquid–liquid extraction and analyzed for NAs using high performance liquid chromatography tandem mass spectrometry. At low concentration of IL (250 μmol/L), the yields of NAs (NMEA or NPyr) increased with increasing doses of monochloramine from both IL species. The total NA yield was as high as 2.5 ± 0.3 ng/mg from EMImBr, and as high as 8.6 ± 0.8 ng/mg from EMPyrBr. At high concentration of IL (5 mmol/L), the NA yield reached a maximum at 2.5 mmol/L NH2Cl, and then decreased with subsequent increases in the reactant concentrations, demonstrating ILs' solvent effects. This study re-emphasizes the importance of preventing discharge of ILs to water bodies to prevent secondary impacts on drinking water.

Oxone-sodium nitrite mediated N-nitrosamines formation under mild conditions from secondary amines

Herein, we report an efficient synthesis of N-nitrosamines from cyclic, aliphatic, benzylic, and aromatic secondary amines via a novel straightforward, efficient, and mild chemical process using sodium nitrite and Oxone in methanol as a solvent at 0–5 °C. The demonstrated methodology accounts well for the parameters like cost-effective, short reaction time, clean and safe handling along with good to excellent yields.

Decomposition of N-nitrosamines formed in CO2 capture systems through electrochemically-mediated reduction on carbon xerogel electrode

N-nitrosamines, as a class of compounds, have been reported to be mutagenic, cytotoxic, genotoxic and carcinogenic. N-nitrosamine formation and emission are a major concern for amine-based CO2 capture systems. A process using a stationary carbon electrode inside an electrochemical cell was developed and tested in this study to adsorb and decompose two N-nitrosamines, N-nitrosopyrrolidine and N-nitrosodiethylamine, from an aqueous amine solution. The carbon xerogel electrode material has a high N-nitrosamine adsorption capacity and can initiate an electrochemically-mediated reduction of N-nitrosamines to a secondary amine. A greater than 80% reduction of N-nitrosodiethylamine and 90% of N-nitrosopyrrolidine was observed from a simulated amine-based waterwash solution using an applied current up to 300 mA. N-nitrosamine decomposition was effective in solutions with relatively high amine or salt concentrations.

Rapid determination of trace level N-nitrosamine precursors in secondary-treated wastewater by using two dimensional-ion chromatography

Nowadays, drinking water treatment involves large usage of chloramines making control of N-nitrosamines formation very challenging. Detecting and removing N-nitrosamine precursors in water is the most effective method to reduce N-nitrosamine formation. Therefore, it is essential to develop methods to detect N-nitrosamine precursors. In this paper, a method based on two-dimensional ion chromatography (2D-IC) is presented for detecting the trace levels of N-nitrosamines precursors, including dimethylamine, trimethylamine, diethylamine, methylethylamine, morpholine and piperidine, in relatively short time with minimized sample preparation. The 2D-IC method exhibits better sensitivity for analytes suffering from matrix interference, by eliminating interfering sample matrix ions, than conventional one-dimensional (1D) IC. Detection limits of the six amines were within the range of 0.035 μg/L to 0.1 μg/L. Excellent linearity was achieved for all the target amines with the method developed. The proposed method in this study was applied in the analysis of real wastewater samples. High recoveries ranging from 91.7 to 109.8% and relative standard deviation of less than 5.3% were obtained. The fully automated and simple method shows high selectivity against interfering metal ions and low detection limits, making routine detection of N-nitrosamines precursors practical.

Formation of N-nitrosamines during the analysis of municipal secondary biological nutrient removal process effluents by US EPA method 521

US EPA Method 521 employs activated carbon-based solid phase extraction (SPE) cartridges for analyzing N-nitrosamines. The analysis of N-nitrosamines and their chloramine-reactive and ozone-reactive precursors in nitrified municipal secondary effluent revealed the potential for NDMA to form as an artefact during the analysis. As samples passed through the SPE cartridge, the activated carbon mediated the reaction of nitrite with dimethylamine to form NDMA. The reaction was not significant with tertiary amines. Artefactual NDMA formation was important for nitrite concentrations >0.2 mg/L as N in the Biological Nitrogen Removal (BNR) process effluent. However, it is difficult to define a general threshold for nitrite concentrations, because the importance of the reaction also depends on secondary amine concentrations, which are usually poorly characterized. Pre-treatment of samples with sulfamic acid to destroy nitrite mitigated the artefact. This artefact did not affect NDMA analysis in a nitrified effluent from another facility, likely due to low dimethylamine concentrations. This artefact also did not affect the analysis of primary effluent, due to the lack of nitrite, or the analysis of other N-nitrosamines, likely due to the lack of their secondary amine precursors. Because chloramination does not significantly degrade nitrite, this artefact could affect the analysis of chloramine-reactive N-nitrosamine precursors. Because ozonation rapidly degrades nitrite, it should not affect the analysis of ozone-reactive precursors. However, ozonation at 0.8 mg ozone/mg dissolved organic carbon resulted in significant degradation of all N-nitrosamines, even though simultaneous NDMA formation from ozone-reactive precursors resulted in a net increase in NDMA concentration.

Protective effects of epicatechin on the oxidation and N-nitrosamine formation of oxidatively stressed myofibrillar protein

ABSTRACT The present study investigated the protective effects of the polyphenol epicatechin on the protein structural changes, gel properties and N-nitrosodiethylamine (NDEA) formation of oxidatively stressed myofibrillar protein (MP). Results showed that oxidation treatments to MP significantly increased their carbonyl content and surface hydrophobicity as compared to the control groups (p < 0.05). Epicatechin inhibited protein carbonyl content and surface hydrophobicity, especially treated with 2 mM epicatechin. Under oxidative conditions, the fluorescence intensity of tryptophan gradually decreased with the increase of epicatechin concentrations from 0 to 2 mM. The storage modulus (G’) was increased gradually after oxidation and epicatechin treatment. Epicatechin reduced the loss of P 22 and water holding capacity (WHC), promoted the hydration of the proteins. Under oxidative conditions, epicatechin had a concentration dependent effect on the formation of NDEA; low concentrations of epicatechin promoted NDEA formation, while high concentrations inhibited NDEA production. In conclusion, an appropriate quantity of polyphenols can inhibit the oxidation of MP and formation of N-nitrosamines.

QUANTITATIVE PARAMETERS OF NITRATES IN URINE AND N-NITROSODIMETHYLAMINE IN BLOOD AS MARKERS OF THE ORAL EXPOSURE TO NITRATES INTRODUCED WITH DRINKING WATER

Introduction. The nitrate entry into the body with drinking water might lead to endogenous nitrotyrosine and N-nitrosamine formation. The study aims to prove quantitative measurement of N-nitrosodimethylamine in blood and nitrates in urine as markers of the exposure to nitrates entering the body with drinking water. Material and methods. Analysis of blood samples for N-nitrosodimethylamine was carried out using Agilent gas chromatograph with quadrupole mass spectrometric detector. When preparing blood samples, an automatic system for solid extraction Sepaths was used. Studies of urine samples for nitrates were carried out using the system of capillary electrophoresis “Kapel”. The target audience includes two groups. Children consuming drinking water with nitrate level exceeding hygienic norm by 1.2 times and N-nitrosodimethylamine level exceeding by 1.6 times. The second group included children consuming drinking water of satisfactory quality. The establishment of cause-effect relationships is carried out using the package of applied programs Statistica 6.0. Results. The nitrate level in drinking water of target area was 51.7 mg/dm3, what is by 4.7 times higher than in comparison area of 10.9 mg/dm3. The N-nitrosodimethylamine level was at the level of 0.016 mg/dm3, which is by 2.5 higher than in the comparison area of 0.0065 mg/dm3. Discussion. The long-term exposure to nitrate and N-nitrosodimethylamine in the drinking water was found out to form in the children’s blood of first group the N-nitrosodimethylamine accounted of 0.0045±0.0014 mg/dm3 i.e. by 1.5 times higher in comparison with the second group (0.003±0.0009 mg/dm3). In the urine of children from the first group, the nitrates were by 1.5 times more than in the urine of children in the second group. Experimental studies proved that the concentration of nitrates in the urine and N-nitrosodimethylamine in the blood might be considered as markers of the oral exposure and correspond to the permitted level for nitrates in the urine of 43.7 mg/dm3 and N-nitrosodimethylamine in the blood of 0.003 mg/dm3 when nitrate concentration in drinking water is from of 45-51.7 mg/dm3 and N-nitrosodimethylamine from of 0.01-0.016 mg/dm3.

Role of various factors affecting the photochemical treatment of N-nitrosamines related to CO2 capture

ABSTRACT Post-combustion CO2 capture using amine solvents is the most feasible method of reducing anthropogenic CO2 emissions, which are the largest contributor to global warming. The formation of carcinogenic N-nitrosamines (i.e. by-products) can hinder the industrial application of this technology. In this study, the effects of direct UV photolysis (N-nitrosamine concentration and amines) and advanced oxidation processes (UV/H2O2 and UV/O3) on the three specific N-nitrosamines that are commonplace in amine-based CO2 capture (i.e. N-nitrosodiethylamine (NDEA), N-nitrosodiethanolamine (NDELA), and N-nitrosomorpholine (NMOR)) were examined. A significant decrease in the photodegradation rate constants was observed for NDEA (1.02 × 100 to 2.94 × 10−1 min−1), NDELA (1.52 × 100 to 3.32 × 10−1 min−1), and NMOR (1.93 × 100 to 2.20 × 10−1 min−1) as their concentrations increased within 1–50 mg/L. This is the first report of a significant increase in the degradation rate constants of N-nitrosamine with an increase in amine concentrations (i.e. monoethanolamine, diethanolamine, and morpholine) within 10–200 mM. The photodegradation rate constants increased as the molar ratio of H2O2 to N-nitrosamine increased to 20, but then decreased at molar ratios beyond this. O3 had a negligible effect on the photodegradation of N-nitrosamines.

Effect of drying temperature and presalting methods on the quality and N-nitrosamine formation of dried mud carp (Cirrhinus molitorella )

Effect of drying temperature and presalting methods on the quality and N-nitrosamine formation of dried mud carp (<i>Cirrhinus molitorella</i> )

Risk assessment of N-nitrosodiethylamine (NDEA) and N-nitrosodiethanolamine (NDELA) in cosmetics

ABSTRACTN-nitrosamines and their precursors found in cosmetics may be carcinogenic in humans. Thus the aim of this study was to carry out risk assessment for N-nitrosamines (N-nitrosodiethanolamine [NDELA], N-nitrosodiethylamine [NDEA]) and amines (triethanolamine [TEA], diethanolamine [DEA]) levels in cosmetics determined using validated liquid chromatography–tandem mass spectrometry (LC–MS/MS) procedures. NDELA and NDEA concentrations were present at levels of “not detected” (N.D.) to 596.5 μg/kg and N.D. to 40.9 μg/kg, respectively. TEA and DEA concentrations ranged from N.D. to 860 μg/kg and N.D. to 26.22 μg/kg, respectively. The nitrite concentration (3–2250 mg/l), number of nitrosating agents to a maximum 5, and pH (3.93–10.09) were also assessed. The impact of N-nitrosamine formation on the levels of TEA, DEA, nitrite, and other nitrosating agents was also examined. N-nitrosamine concentrations correlated with the number of nitrosating agents and nitrite concentrations. Data demonstrated that higher nitrite concentrations and a greater number of nitrosating agents increased NDELA and NDEA yields. Further, the presence of TEA and DEA exerted a significant influence on N-nitrosamine formation. Risk assessments, including the margin of exposure (MOE) and lifetime cancer risk (LCR) for N-nitrosamines and margin of safety (MOS) for amines, were calculated using product type, use pattern, and concentrations. Exposure to maximum amounts of NDELA and NDEA resulted in MOE > 10,000 (based upon the benchmark dose lower confidence limit 10%) and LCR <1 × 10−5, respectively. In addition, TEA and DEA concentrations in cosmetic samples resulted in MOS values >100. Therefore, no apparent safety concerns were associated with cosmetic products containing NDELA, NDEA, TEA, and DEA in this study. However, since amines and nitrosating agents produce carcinogenic nitrosamines, their use in cosmetics needs to be minimized to levels as low as technically feasible.

Specific and total N-nitrosamines formation potentials of nitrogenous micropollutants during chloramination

N-nitrosamines are a group of potent human carcinogens that can be formed during oxidative treatment of drinking water and wastewater. Many tertiary and quaternary amines present in consumer products (e.g., pharmaceuticals, personal care and household products) are known to be N-nitrosodimethylamine (NDMA) precursors during chloramination, but the formation of other N-nitrosamines has been rarely studied. This study investigates the specific and total N-nitrosamine (TONO) formation potential (FP) of various precursors from nitrogen-containing micropollutants (chlorhexidine, metformin, benzalkonium chloride and cetyltrimethylammonium chloride) and tertiary and quaternary model amines (trimethyl amine, N,N-dimethylbutyl amine, N,N-dimethylbenzyl amine and tetramethyl ammonium). All the studied nitrogenous micropollutants displayed quantifiable TONO FP, with molar yields in the range 0.04–11.92%. However, the observed TONO pools constituted mostly of uncharacterized species, not included in US-EPA 8270 N-nitrosamines standard mix. Only the quaternary ammonium compound benzalkonium chloride showed quantifiable NDMA FP (0.56% molar yield), however, explaining only a minor fraction of the observed TONO FP. The studied model amines showed molar NDMA yields from 0.10% (trimethyl amine) to 5.05% (N,N-dimethylbenzyl amine), very similar to the molar TONO yields. The comparison of the FPs of micropollutants and model compounds showed that the presence of electron donating functional groups (such as a benzyl group) in tertiary and quaternary amine precursors leads to a higher formation of NDMA and uncharacterized N-nitrosamines, respectively. LC-qTOF screening of a list of proposed N-nitrosamine structures has enabled to identify a novel N-nitrosamine (N-nitroso-N-methyldodecylamine) from the chloramination of benzalkonium chloride. This finding supports the hypothesis that different functional groups in quaternary amines can act as leaving groups during chloramination and form differing N-nitrosamine structures at significant yield. Molar TONO yields determined for micropollutants were finally validated under experimental conditions closer to real water matrices, confirming their representativeness also for lower concentration ranges.

“NITROSAMINE SAFE” THIURAM DISULFIDE

ABSTRACT An investigation into the technological performance of a new nitrosamine safe thiuram disulfide, tetraisononylthiuramdisulfide (TINTD), in natural rubber was undertaken. Initially, TINTD was synthesized from di(3,5,5-trimethylhexyl)amine. It was then demonstrated to function as a sulfur donor, a primary accelerator, and as a secondary accelerator when combined with sulfenamides. These investigations found that the long-branched alkyl chain on the nitrogen of TINTD and of its vulcanization breakdown product zinc diisononyldithiocarbamate (ZDNC) makes both chemical species very soluble in the elastomer. This high solubility of TINTD and ZDNC in the rubber makes TINTD highly attractive for use in soluble efficient vulcanization systems. In addition, the nature of the long-branched alkyl chain means that the formation of carcinogenic N-nitrosamine is difficult, and if formed, it is toxicologically much less hazardous in terms of both acute toxicity and metabolic activity. Thus, concerns of accelerator toxicity, irritant dermatitis from thiuram and dithiocarbamate, and type IV allergy may be reduced or totally eliminated. The curing efficiency of various thiuram disulfides was also investigated as a function of alkyl chain length and the degree of chain branching. The cure performance was found to be determined by both chain length and chain branching.

Formation of N-nitrosamines by micelle-catalysed nitrosation of aliphatic secondary amines.

N-Nitrosamines are an important class of potent human carcinogens and mutagens that can be present in water and wastewater. For instance, N-nitrosamines can be formed by reaction of nitrosating agents such as NO+ or N2O3 formed from nitrite under acidic conditions with secondary amine precursors by an acid-catalysed nitrosation pathway. This study investigates the catalytic effect of cationic and anionic micelles on the nitrosation of secondary aliphatic amines in the presence of nitrite at different pH values. The results of this study demonstrate that the nitrosation of hydrophobic secondary amines (e.g., dipropylamine and dibutylamine) by nitrite was significantly enhanced in the presence of micelles of the cationic surfactant cetyltrimethylammonium chloride whereas anionic micelles formed by sodium dodecylsulfate did not significantly enhance the formation of N-nitrosamines. Rate enhancements of up to 100-fold were observed for the formation of N-nitrosodibutylamine in the presence of cetyltrimethylammonium chloride. The magnitude of the catalytic effect of cationic micelles on the nitrosation reaction depended mainly of the hydrophobicity of the amine precursors (i.e., alkyl chain length), the stability and the charge of the micelles and pH. One important enhancement factor is the lowering of the pKa of the precursor alkylammonium ion due to the electrical potential at the micelle-water interface by up to ∼2.5 pH units. These results suggest that cationic micelle-forming surfactants might play a role in the formation of N-nitrosamines in wastewater, consumer products and in industrial processes using high concentrations of cationic surfactants.

Toward N-nitrosamines free water: Formation, prevention, and removal

ABSTRACTThis study elucidates the recent trends in the formation, prevention, and removal of N-nitrosamines such as N-nitrosodimethylamine (NDMA) from wastewater or drinking water. Reports are rife on the occurrence of NDMA in areas such as amine degradation during postcombustion CO2 capture (PCC), chlorinated/chloraminated and ozonated drinking water, smoked or cooked foods personal care, tobacco and pharmaceutical products. The major routes responsible for the formation of NDMA in portable waters include chlorination/chloramination and ozonation. The major NDMA precursors are secondary, tertiary, and quaternary amines such as dimethylamine, diethanolamine, and triethanolamine. Due to the environmental and public health concerns posed by this contaminant, a proactive approach is necessary towards suppressing their occurrence, as well as their removal. Consequently, this study critically reviewed the formation, prevention, and removal of N-nitrosamines. The study discussed NDMA prevention techniques, such as physical adsorption, pre-oxidation, and biological activated carbon. The removal techniques discussed here include physicochemical (such as combined adsorption and microwave irradiation and UV photolysis), bioremediation, catalytic reduction, and dope technology. Irrespective of the effectiveness and seemingly economic viability of some of these technologies, preventing the occurrence of NDMA right from the outset is more potent because the treatments consume more energy.

Evaluation of the Nitric Oxide and Nitrite Scavenging Capability, N-Nitrosamine Formation Inhibitory Activity, and Optimization of Ultrasound-Assisted Aqueous Two-Phase System Extraction of Total Saponins from Coreopsis tinctoria Flowering Tops by Response Surface Methodology.

Coreopsis tinctoria flowering tops (CTFs) is a popular health product as herbal tea or as a traditional medicinal herb that is rich in saponins and exerts substantial biological activity. In this study, an ultrasound-assisted aqueous two-phase system (ATPS) was utilized to extract total saponins from CTFs and optimize the extraction process by response surface methodology. Moreover, the nitric oxide and nitrite scavenging capability, and N-nitrosamine formation inhibitory activity of total saponins were evaluated. Results showed that the optimal conditions for total saponins were 37.76% (w/w) ammonium sulfate and 35.62% (w/w) ethanol in ATPS coupled with ultrasonic-assisted extraction. Under the optimal conditions, the maximum yield of total saponins of 33.4g/kg can be obtained from the CTFs raw material. The nitric oxide radical scavenging, nitrite scavenging, and N-nitrosamine inhibitory activities (SC50) were 287.92±7.42, 191.63±7.69, and 1787.4±51.26μg/mL, respectively. The total saponins has a certain nitric oxide and nitrite scavenging capability, and N-nitrosamine formation inhibitory activity in vitro. Given these activities, research on saponins from CTFs provides profound and lasting implications for the novel applications of C. tinctoria.

Influence of pH on the UV photolysis of N-nitrosamines in water: Kinetics and products

Amine-based post-combustion CO2 capture is recognized as a promising technique for abating CO2 emissions from anthropogenic sources. A severe drawback of this technique, however, is the formation of carcinogenic N-nitrosamines as a by-product. In this study, the effect of pH was investigated on the UV photodegradation of N-nitrosamines (N-nitrosodiethanolamine (NDELA), N-nitrosodiethylamine (NDEA), and N-nitrosomorpholine (NMOR)) which are closely related to the amine-based CO2 capture technology. A decrease in pseudo-first-order degradation rate constants was observed for NDELA (2.49×10−2–6.48×10−3L/W-min), NDEA (1.56×10−2–5.25×10−4L/W-min), and NMOR (1.68×10−2–7.00×10−4L/W-min) with an increase in pH2−10. The formation of NO2− was more prevalent than that of NO3− at pH4−10, while under strong acidic condition (pH2) NO3− formation was more prevalent. The concentration of secondary amines (diethanolamine, diethylamine, and morpholine) increased from basic (pH10) to weakly acidic conditions (pH4) and then decreased at pH2. Whereas, the concentration of primary amines (monoethanolamine and ethylamine) followed the opposite trend. Furthermore, mechanistic pathways were revealed for N-nitrosamine photodegradation based on the degradation products. A good total nitrogen (TN) balance over the irradiation period confirmed that all the main degradation products were quantified.