Automated solid-phase extraction and high-performance liquid chromatographic determination of nitrosamines using post-column photolysis and tris(2,2′-bipyridyl) ruthenium(III) chemiluminescence

High performance liquid chromatography coupled with post - Column derivatization methods in food analysis: Chemistries and applications in the last two decades

High performance liquid chromatography coupled with post-column derivatization is used for increasing the sensitivity and selectivity of the desirable analytes after the chromatographic separation. The transformation of the analytes can be conducted through the addition of a suitable reagent in the eluted stream or the ultraviolet irradiation of the eluted analytes, forming detectable derivatives for ultraviolet or fluorescence detectors. This review focuses on the developed methods using high performance liquid chromatography coupled with post-column derivatization for the determination of substances in food samples during the last two decades. The significance of the determination of each analyte in foods and the existing guidelines in each case are discussed. Preparation of the samples and the analytical methods are commented. For each analyte, official methods and commercially available systems and reagents are mentioned, as well.

Nitrosamines crisis in pharmaceuticals - Insights on toxicological implications, root causes and risk assessment: A systematic review

The presence of N-nitroso compounds, particularly N-nitrosamines, in pharmaceutical products has raised global safety concerns due to their significant genotoxic and mutagenic effects. This systematic review investigates their toxicity in active pharmaceutical ingredients (APIs), drug products, and pharmaceutical excipients, along with novel analytical strategies for detection, root cause analysis, reformulation strategies, and regulatory guidelines for nitrosamines. This review emphasizes the molecular toxicity of N-nitroso compounds, focusing on genotoxic, mutagenic, carcinogenic, and other physiological effects. Additionally, it addresses the ongoing nitrosamine crisis, the development of nitrosamine-free products, and the importance of sensitive detection methods and precise risk evaluation. This comprehensive overview will aid molecular biologists, analytical scientists, formulation scientists in research and development sector, and researchers involved in management of nitrosamine-induced toxicity and promoting safer pharmaceutical products.

Current status and prospects of development of analytical methods for determining nitrosamine and N-nitroso impurities in pharmaceuticals

Nitrosamine impurities in pharmaceuticals have recently been concerned for several national regulatory agencies to avoid carcinogenic and mutagenic effects in patients. The demand for highly sensitive and specific analytical methods with LOQs in the ppb and sub-ppb ranges is among the most significant challenges facing analytical scientists. In addition, artifactual nitrosamine formation during sample preparation and injection leading to overestimation of nitrosamines has received considerable attention. Numerous analytical methodologies have been reported for quantifying nitrosamine impurities in active pharmaceutical ingredients and medicinal products at the interim limit criteria as preventive measures. In this review, we meticulously discuss those reported gas and liquid chromatographic methods for nitrosamine determination in pharmaceuticals in aspects of chromatographic conditions and sensitivity of detection. We also introduce the potential of novel fluorescence-based methods recently developed to rapidly screen nitrosamine impurities. In addition, the review assesses the nitrosation assay procedure (NAP test), which is expected to be a future preventive measure for screening potential nitrosation and identifying suspected contamination with N-nitroso or other potential mutagenic impurities during the drug development process.

Degradation of N-Nitrosodiethylamine in aqueous solution by gamma-irradiation

N-Nitrosodiethylamine (NNDEA) is a toxic compound which is affranchised into the medium mostly via industrial wastewater. For the investigation of degradation mechanism of NNDEA, the aqueous solutions of NNDEA were exposed to Advanced Oxidation processes (AOP's) such as gamma-irradiation, ozonation, UV irradiation and UV/Ozone (ozone effect) and UV/H2O2 (hydrogen peroxide effect). Since the structure of NNDEA is small, it is rapidly degraded in all processes except UV-irradiation process but forming acetic acid and formic acid just was seen in gamma and UV/H₂O₂processes. In the other processes, NNDEA is transformed directly to nitrite and nitrate which they can form NNDEA again in the medium. The concentration of NNDEA was decreased from 50 to 21 mg L^-1 after 2.20 kGy gamma-irradiation. After 2.85 kGy gamma irradiation, NNDEA was completely removed from the medium. The results showed that the concentration of NNDEA decreased with UV-irradiation time, the concentration of 50 mg L^-1 NNDEA was 42, 30, 24 and 19 mg L^-1 after 10, 20, 40 and 60 min UV-irradiation, respectively. It has been investigated that the UV-irradiation does not have much effect on the degradation of 50 mg L^-1 NNDEA solution and requires long-term irradiation. In this study, gamma-irradiation was chosen as the best method because of the complete degradation effect and the prevention of the reformation of the NNDEA.

An Organic Chemist's Guide to N-Nitrosamines: Their Structure, Reactivity, and Role as Contaminants

N-Nitrosamines are a class of compounds notorious both for the potent carcinogenicity of many of its members and for their widespread occurrence throughout the human environment, from air and water to our diets and drugs. Considerable effort has been dedicated to understanding N-nitrosamines as contaminants, and methods for their prevention, remediation, and detection are ongoing challenges. Understanding the chemistry of N-nitrosamines will be key to addressing these challenges. To facilitate such understanding, we focus in this Perspective on the structure, reactivity, and synthetic applications of N-nitrosamines with an emphasis on alkyl N-nitrosamines. The role of N-nitrosamines as water contaminants and the methods for their detection are also discussed.

Evaluation of a method for the simultaneous quantification of N-nitrosamines in water samples based on stir bar sorptive extraction combined with high-performance liquid chromatography and diode array detection

A simple, sensitive, and reliable procedure based on stir bar sorptive extraction coupled with high-performance liquid chromatography was applied to simultaneously extract and determine three semipolar nitrosamines including N-nitrosodibutylamine, N-nitrosodiphenylamine, and N-nitrosodicyclohexylamine. To achieve the optimum conditions, the effective parameters on the extraction efficiency including desorption solvent and time, ionic strength of sample, extraction time, and sample volume were systematically investigated. The optimized extraction procedure was carried out by stir bars coated with polydimethylsiloxane. Under optimum extraction conditions, the performance of the proposed method was studied. The linear dynamic range was obtained in the range of 0.95-1000 ng/mL (r = 0.9995), 0.26-1000 ng/mL (r = 0.9988) and both 0.32-100 ng/mL (r = 0.9999) and 100-1000 ng/mL (r = 0.9998) with limits of detection of 0.28, 0.08, and 0.09 ng/mL for N-nitrosodibutylamine, N-nitrosodiphenylamine, and N-nitrosodicyclohexylamine, respectively. The average recoveries were obtained >81%, and the reproducibility of the proposed method presented as intra- and interday precision were also found with a relative standard deviation <6%. Finally, the proposed method was successfully applied to the determination of trace amounts of selected nitrosamines in various water and wastewater samples and the obtained results were confirmed using mass spectrometry.

Nitrosamines and water

This paper provides an overview of all current issues that are connected to the presence of nitrosamines in water technology. N-nitrosodimethylamine (NDMA) is the most frequently detected member of this family. Nitrosamines became the hottest topic in drinking water science when they were identified as disinfection by-products (DBPs) in chloraminated waters. The danger that they pose to consumer health seems to be much higher than that from chlorinated DBPs. This review summarizes our contemporary knowledge of these compounds in water, their occurrence, and precursors of nitrosamines in drinking and wastewaters, in addition to attempts to remove nitrosamines from water. The paper also reviews our knowledge of the mechanisms of nitrosamine formation in water technology. The current, commonly accepted mechanism of NDMA formation during chloramination of drinking waters assumes that dichloramine reacts with dimethylamine, forms unsymmetrical dimethylhydrazine and further oxidizes to NDMA. The question to answer is which precursors are responsible for delivering the DMA moiety for the reaction since the presence of DMA in water cannot explain the quantities of NDMA that are formed. There are also reports that other oxidants that are commonly used in water technology may generate NDMA. However, the mechanisms of such transformations are unknown. Methods for the removal of nitrosamines from water are described briefly. However, the research that has been undertaken on such methods seems to be at an early stage of development. It is predicted that photolytic methods may have the greatest potential for technological application.

Liquid chromatography-tandem mass spectrometry determination of N-nitrosamines released from rubber or elastomer teats and soothers

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method as an alternative to a gas chromatography-thermal energy analyser (GC-TEA) method recommended by the European Committee on Standardization (CEN) was validated for the simultaneous determination of eight N-nitrosamines released into artificial saliva from rubber or elastomer teats and soothers. N-nitroso-dipropylamine-d₁₄ (NDPA-d₁₄) was used as internal standard for accurate quantification. The method was validated with relatively good analytical results, including sufficiently low limits of detection (0.1-2 µg kg⁻¹) of sample) and good linearity (r²> 0.99) throughout the studied concentration ranges. Intra- and inter-day precisions expressed with the relative standard deviation (RSD, %) were 3.4-8.0% and 4.4-11.3%, which were below the performance criteria based on one-half of the value derived from the Horwitz value. It was also found that the LC-MS/MS method is sufficiently rugged and successfully applicable to its routine analysis for the compliance test of Commission Directive 93/11/EEC.

Fullerenes for aromatic and non-aromatic N-nitrosamines discrimination

The detection of N-nitrosamines (NAms) in water supplies is an environmental and public health issue because many NAms are classified as probable human carcinogens. Non-aromatic (aliphatic and cyclic) NAms are more toxic than aromatic ones as their maximum admissible concentration is limited in drinking water (20-2000ngL(-1)). From that premise, a simple and novel method to discriminate between both fractions of NAms according to their toxicity was proposed. An automatic solid-phase extraction unit containing two sequential sorbent columns was constructed. A sample volume of 25mL was passed through a C(60) fullerene column in which only the aromatic fraction was retained, and the effluent was then passed through a Merck LiChrolut EN column where the non-aromatic fraction was retained. Following elution of the non-aromatic NAms with 150microL of ethyl acetate-acetonitrile (9:1), 1microL of the extract was injected into a GC/MS. A comparative study of C(60) and C(70) fullerenes and nanotubes revealed C(60) fullerene to be the best choice to selectively retain the aromatic fraction. The method exhibits a linear range of 15-20,000ngL(-1); limits of detection of 4-15ngL(-1); and an RSD of approximately 5%. Recoveries throughout the whole method were between 95% and 102% for six non-aromatic NAms spiked into several types of waters. Our study demonstrates that a simple and fast SPE system (10min per sample) with a customary GC-MS instrument permits the quantification of these amines in complex matrices with considerable sensitivity and selectivity.

Gas chromatographic determination of N-nitrosamines in beverages following automatic solid-phase extraction

A semiautomatic method for the determination of seven N-nitrosamines in beverages by gas chromatography with nitrogen-phosphorus detection is proposed. Beverage samples are aspirated into a solid-phase extraction module for preconcentration and cleanup. The influence of the experimental conditions was examined by using various sorbents among which LiChrolut EN was found to provide quantitative elution and the highest preconcentration factors of all. The proposed method is sensitive, with limits of detection between 7 and 33 ng/kg, and precise, with relative standard deviations from 4.3% to 6.0%. The recoveries of N-nitrosamines from beverage samples spiked with 0.5 or 1 microg/kg concentrations of these compounds ranged from 95% to 102%. The method was successfully applied to the determination of residues of the studied N-nitrosamines in beverages including beer, wine, liquor, whisky, cognac, rum, vodka, grape juice, cider, tonic water, and soft drinks. The analytes were only detected in beer samples, positives being confirmed by gas chromatography coupled with impact ionization mass spectrometry.

Advantages and limitations of on-line solid phase extraction coupled to liquid chromatography–mass spectrometry technologies versus biosensors for monitoring of emerging contaminants in water

On-line solid phase extraction (SPE) coupled to liquid chromatography-mass spectrometry (LC-MS) and biosensors are advanced technologies that have found increasing application in the analysis of environmental contaminants although their application to the determination of emerging contaminants (previously unknown or unrecognized pollutants) has been still limited. This review covers the most recent advances occurred in the areas of on-line SPE-LC-MS and biosensors, discusses and compares the main strengths and limitations of the two approaches, and examines their most relevant applications to the analysis of emerging contaminants in environmental waters. So far, the on-line configuration most frequently used has been SPE coupled to liquid chromatography-(tandem) mass spectrometry. Sorbents used for on-line SPE have included both traditional (alkyl-bonded silicas and polymers) and novel (restricted access materials (RAMs), molecularly imprinted synthetic polymers (MIPs), and immobilized receptors or antibodies (immunosorbents) materials. The biosensor technologies most frequently applied have been based on the use of antibodies and, to a lesser extent, enzymes, bacteria, receptors and DNA as recognition elements, and the use of optical and electrochemical transducing elements. Emerging contaminants investigated by means of these two techniques have included pharmaceuticals, endocrine disrupting compounds such as estrogens, alkylphenols and bisphenol A, pesticides transformation products, disinfection by-products, and bacterial toxins and mycotoxins, among others. Both techniques offer advantageous, and frequently comparable, features such as high sensitivity and selectivity, minimum sample manipulation, and automation. Biosensors are, in addition, relatively cheap and fast, which make them ideally suited for routine testing and screening of samples; however, in most cases, they can not compete yet with on-line SPE procedures in terms of accuracy, reproducibility, reliability (confirmation) of results, and capacity for multi-analyte determination.

Comparison of the sensitivities of seven N-nitrosamines in pre-screened waters using an automated preconcentration system and gas chromatography with different detectors

A simple, expeditious procedure for confirming the presence of N-nitrosamines in previously screened positive water samples was proposed. Water samples were continuously aspirated into a photometric flow system for screening. Positive samples were then confirmed and N-nitrosamines were identified by gas chromatography using different detectors (mass spectrometry, flame ionization and nitrogen-phosphorus). The system for the screening purpose was based on the preconcentration of the analytes onto a sorbent column, elution, and derivatization to form nitrite, then formation of a coloured product (Griess reaction) and photometric detection. The detection limits of the gas chromatographic method for 100 ml of sample were 2.0-3.5 microg/l, 20-80 and 3-13 ng/l for flame ionization, nitrogen-phosphorus and mass spectrometric detectors, respectively. The precision as RSD was similar for all detectors (3.0-6.5%). The screening of different types of water showed that wastewaters contain levels of N-nitrosamines that can be detected only using MS as a detector.

New method for the photo-chemiluminometric determination of benzoylurea insecticides based on acetonitrile chemiluminescence

The viability of tandem photochemical reaction-chemiluminescence detection has been studied for the determination of five benzoylurea insecticides, namely, diflubenzuron, triflumuron, hexaflumuron, lufenuron and flufenoxuron. The 'on-line' photochemical reaction of benzoylurea pesticides provides an enhanced chemiluminescence response of the pesticides during their oxidation by potassium hexacyanoferrate(III) and sodium hydroxide, whose signal increases with the percentage of acetonitrile in the reaction medium. The determination was performed using a photoreactor consisting of a PFA (perfluoroalkoxy) tube reactor coil (5 mx1.6-mm O.D. and 0.8-mm I.D.) and an 8-W xenon lamp. As the yield of the photoderivatization process and the chemiluminescent signals depend on the percentage of acetonitrile, the chromatographic column (a Gemini C18, Phenomenex 150 mmx4.6 mm, 5-microm particle size) was chosen with the aim of using high percentages of this organic solvent in the mobile phase. Previous studies showed that the rate of the chemiluminescent reaction was very fast. Therefore, a modification was carried out in the detector in order to mix the analytes and reactants as near as possible to the measure cell. The optimised method was validated with respect to linearity, precision, limits of detection and quantification accuracy. Under the optimised conditions, linear working range extends three orders of magnitude with the relative standard deviation of intra-day precision below 10% and detection limits between 0.012 and 0.18 microg mL-1, according to the compound. The proposed method has been successfully applied to the determination of benzoylureas in cucumber with good results.

Characterization of new nitrosamines in drinking water using liquid chromatography tandem mass spectrometry

N-Nitrosodimethylamine (NDMA), a member of a group of probable human carcinogens, has been detected as a disinfection byproduct (DBP) in drinking water supplies in Canada and the United States. To comprehensively investigate the occurrence of possible nitrosamines in drinking water supplies, a liquid chromatography-tandem mass spectrometry technique was developed to detect both thermally stable and unstable nitrosamines. This technique consisted of solid-phase extraction (SPE), liquid chromatography (LC) separation, and tandem quadrupole linear ion trap mass spectrometry (MS/MS) detection. It enabled the determination of sub-ng/L levels of nine nitrosamines. Isotope-labeled N-nitrosodimethylamine-d6 (NDMA-d6) was used as the surrogate standard for determining recovery, and N-nitrosodi-n-propylamine-dl4 (NDPA-dl4) was used as the internal standard for quantification. The method detection limits were estimated to be 0.1-10.6 ng/L, and the average recoveries were 41-111% for the nine nitrosamines; of these, NDMA, N-nitrosopyrrolidine (NPyr), N-nitrosopiperidine (NPip), and N-nitrosodiphenylamine (NDPhA) were identified and quantified in drinking water samples collected from four locations within the same distribution system. In general, the concentrations of these four nitrosamines in this distribution system increased with increasing distance from the water treatment plant, indicating that the amount of formation was greater than the amount of decomposition within this time frame. The identification of NPip and NDPhA in drinking water systems and the distribution profiles of these nitrosamines have not been reported previously. These nitrosamines are toxic, and their presence as DBPs in drinking water may have toxicological relevance.

Determination of nine pyrethroid insecticides by high-performance liquid chromatography with post-column photoderivatization and detection based on acetonitrile chemiluminescence

An HPLC method was developed to determine pyrethroids, including fenpropathrin, beta-cyfluthrin, lambda-cyhalothrin, deltamethrin, fenvalerate, permethrin, acrinathrin, tau-fluvalinate, and bifenthrin, by coupling HPLC, post-column irradiation with UV light and chemiluminescence detection of the resulting photoproducts. It is based on the observation that photolyzed pyrethroids take part in a chemiluminescent reaction in presence of K3Fe(CN)6 and NaOH, whose signal increases with the percentage of acetonitrile in the reaction medium. As the yield of the photoderivatization process and the chemiluminescent signals depend on the percentage of acetonitrile, the chromatographic column (a Gemini C18, Phenomenex 150 mm x 4.6 mm, 5 microm particle size) was chosen with the aim of using high percentages of this organic solvent in the mobile phase. Previous studies showed that the rate of the chemiluminescent reaction was very fast. Therefore, a modification was carried out in the detector in order to mix the analytes and reactives as near as possible to the measure cell. The optimised method was validated with respect to linearity, precision, limits of detection and quantification accuracy. Under the optimised conditions, linear working range extends three orders of magnitude with the relative standard deviation on intra-day precision below 10% and detection limits between 0.013 and 0.049 microg mL(-1), according to the compound. The proposed method has been successfully applied to the determination of pyrethroids in tomato with good results.

Tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence

This paper critically reviews analytical applications of the chemiluminescence from tris(2,2'-bipyridyl)ruthenium(II) and related compounds published in the open literature between mid-1998 and October 2005. Following the introduction, which summarises the reaction chemistry and reagent generation, the review divides into three major sections that focus on: (i) the techniques that utilise this type of detection chemistry, (ii) the range of analytes that can be determined, and (iii) analogues and derivatives of tris(2,2'-bipyridyl)ruthenium(II).