Analysis Of N-nitrosodimethylamine Research Articles

Quantitative Analysis of NDMA in Drug Products: A Proposed High-Throughput Approach Using Headspace–SIFT-MS

Since the initial 2018 recall of angiotensin receptor blockers due to unacceptable levels of mutagenic N-nitrosodimethylamine (NDMA) impurity, numerous drug products delivering diverse active pharmaceutical ingredients (APIs) have been recalled. Regulators and the industry are working together to understand and address this widescale problem. Conventional analysis of NDMA utilizes liquid or gas chromatography-based procedures that can involve complicated sample preparation and slow sample analysis. Selected ion flow tube mass spectrometry (SIFT-MS) analyses NDMA directly in the gas phase using soft chemical ionization, with an LOQ of 2 ng g−1. Through the novel application of the multiple headspace extraction (MHE) technique, NDMA was quantified directly and rapidly from the drug product without dissolution, at levels well below the regulatory acceptable intake of 96 ng day−1. A comparative analysis of recalled metformin using MHE-SIFT-MS and a conventional liquid chromatography–mass spectrometry/mass spectrometry (LC-MS/MS) method showed good agreement. Use of the novel MHE-SIFT-MS approach may enable a wider screening of drug products to be conducted, since it provides around a three-fold increase in daily sample throughput.

Dispersant-First Dispersive Liquid-Liquid Microextraction (DF-DLLME), a Novel Sample Preparation Procedure for NDMA Determination in Metformin Products

Since December 2019, global batch recalls of metformin pharmaceutical products have highlighted an urgent need to control N-nitrosodimethylamine (NDMA) contamination to demonstrate patient safety and maintain supply of this essential medicine. Due to their formulation, the metformin extended-release products present difficult analytical challenges for conventional sample preparation procedures, such as artefactual (in-situ) NDMA formation, gelling, and precipitation. To overcome these challenges, a new version of dispersive liquid-liquid microextraction (DLLME) termed dispersant-first DLLME (DF-DLLME) was developed and optimized for the analysis of NDMA in metformin extended-release products using a detailed Design of Experiments (DoE) to optimize sample preparation. Gas chromatography-high resolution accurate mass-mass spectrometry (GC-HRAM-MS) combined with automated DF-DLLME were successfully applied to monitor the NDMA levels of two different metformin extended-release AstraZeneca products to ultra-trace levels (parts per billion). The additional benefits associated with DF-DLLME, which include automation, time/costs saving, and greener sample preparation, make this novel technique easier to transfer from a development to Quality Control (QC) environment. In addition, this also offers an attractive candidate for the wider platform analysis of N-nitrosamines in pharmaceutical drug products.

Analysis of N-nitrosodimethylamine in metformin hydrochloride products by high-resolution accurate mass gas chromatography mass spectrometry.

The high resolving power of the Orbitrap mass spectrometer in a high-resolution accurate mass gas chromatography (HRAM-GC-MS) system provides greater selectivity and sensitivity for the identification and quantification of volatile analytes at low parts per billion (ppb) levels. Hence, it can be applied for the analysis of pharmaceutical impurities like N-nitrosodimethylamine (NDMA) in metformin hydrochloride products (METs). Different METs extracted by a dichloromethane/aqueous system were analyzed by HRAM-GC-MS under softer electron ionization (EI) at 30 eV. The accurate masses of NDMA and its internal standard NDMA-d6 were analyzed by full scan and targeted selected ion monitoring modes under 60 000 and 30 000 full width at half maximum at m/z 200, respectively. Data acquisition and processing were managed by Xcalibur and Trace Finder software, respectively. Limits of detection (LOD) and quantification (LOQ) at 10 and 20 ng/g were achieved, which is below the allowed daily intake of 32 ng/g. The mass errors measured from experimental data were within ±2 ppm of the theoretical values over a period of a week. Sample analysis showed that 180 out of 212 samples (85%) were below LOD and 15 out of 212 samples (7 %) were within LOD and LOQ. Only 17 samples (8%) were found to be above LOQ, comprising one active pharmaceutical ingredient (API), five immediate-release METs and 11 extended-released METs. Amongst these, seven extended-release METs and one API exceeded the daily allowed intake, 32 ng/g. The validated method has been successfully applied for NDMA analysis in various forms of METs. The method is rather straightforward without an additional clean-up step. The scope can also be extended to other volatile impurities in finished pharmaceutical products.

A Full Evaporation Static Headspace Gas Chromatography Method with Nitrogen Phosphorous Detection for Ultrasensitive Analysis of Semi-volatile Nitrosamines in Pharmaceutical Products

The recent detection of potent carcinogenic nitrosamine impurities in several human medicines has triggered product recalls and interrupted the supply of critical medications for hundreds of millions of patients, illuminating the need for increased testing of nitrosamines in pharmaceutical products. However, the development of analytical methods for nitrosamine detection is challenging due to high sensitivity requirements, complex matrices, and the large number and variety of samples requiring testing. Herein, we report an analytical method for the analysis of a common nitrosamine, N-nitrosodimethylamine (NDMA), in pharmaceutical products using full evaporation static headspace gas chromatography with nitrogen phosphorous detection (FE-SHSGC-NPD). This method is sensitive, specific, accurate, and precise and has the potential to serve as a universal method for testing all semi-volatile nitrosamines across different drug products. Through elimination of the detrimental headspace-liquid partition, a quantitation limit of 0.25 ppb is achieved for NDMA, a significant improvement upon traditional LC-MS methods. The extraction of nitrosamines directly from solid sample not only simplifies the sample preparation procedure but also enables the method to be used for different products as is or with minor modifications, as demonstrated by the analysis of NDMA in 10+ pharmaceutical products. The in situ nitrosation that is commonly observed in GC methods for nitrosamine analysis was completely inhibited by the addition of a small volume solvent containing pyrogallol, phosphoric acid, and isopropanol. Employing simple procedures and low-cost instrumentation, this method can be implemented in any analytical laboratory for routine nitrosamine analysis, ensuring patient safety and uninterrupted supply of critical medications.Graphical

Determination of N-nitrosodimethylamine in Ranitidine Dosage Forms by ESI-LC-MS/MS; Applications for Routine Laboratory Testing.

A practical high-performance liquid chromatography-mass spectrometry method was developed for the analysis of N-nitrosodimethylamine (NDMA) characterized as an impurity, in combination with reports of the carcinogen found in ranitidine samples. After simple extraction of ranitidine samples, all compounds were analyzed with a high-performance liquid chromatography-mass spectrometry. Sensitivity was enhanced by employing the ten-way valve switching technology, which was examined to allow NDMA to enter the mass spectrometry and cut out the ranitidine samples extremely. A good linear relationship was observed within 3-100 ng·mL−1 (r = 0.9992). The validated approach was effectively used to evaluate the NDMA contents in ranitidine samples in circulation, which revealed a difference among 21 batches. Quantitative determination of NDMA was within the scope of 3.38-57.05 ng·mL-1. Moreover, the contamination levels of NDMA in seven batches of products from six manufacturers were listed to exceed the acceptable daily intake. The sensitive method was verified to be appropriate to determine NDMA, even with low contents of NDMA in ranitidine products; the analysis of the selected samples reveals that some samples exceeded the national limit requirements. Therefore, it is worthwhile to conduct comprehensive quality control of the other drugs containing NDMA.

HS-SPME-GC-MS as an alternative method for NDMA analysis in ranitidine products

N-nitrosodimethylamine (NDMA) is a carcinogenic contaminant that was accidentally discovered in drugs, such as valsartan and ranitidine, and more recently in metformin. Liquid chromatography tandem mass spectrometry (LC–MS/MS) is the method typically used for the analysis of NDMA in ranitidine. It seems that using gas chromatography (GC) for NDMA analysis is problematic as ranitidine is sensitive to high temperatures. In the present study, we assessed the usefulness of solid-phase microextraction (SPME) as a method of extraction and introduction into the GC. When using headspace (HS) and liquid injection modes in GC for NDMA analysis in ranitidine, higher NDMA levels were detected compared to using LC–MS/MS. Interestingly, using HS-SPME-GC–MS was advantageous because we could avoid the high temperature utilized in the liquid injection and HS modes. Moreover, the results obtained using HS-SPME-GC–MS provided a good match with those achieved using LC–MS/MS. The feasibility of using HS-SPME-GC–MS to successfully analyze NDMA in ranitidine opens new opportunities for the analysis of this contaminant in pharmaceuticals, specifically those that are heat-labile.

N-Nitrosodimethylamine Formation from Treatment of Seasonally and Spatially Varying Source Water

N-nitrosodimethylamine (NDMA) is a disinfection by-product (DBP) that has been classified as a probable human carcinogen in multiple risk assessments. NDMA presence in drinking water is widespread and dependent on source water, disinfectant type, precursors, and water treatment strategies. The objectives of this study were to investigate NDMA formation potential in a modeled monochloramine water treatment plant (WTP) fed by seasonally and spatially varying source water; and to optimize DBP precursor removal by combining conventional and additional treatment techniques. After NDMA analysis, it was found that NDMA formation was significantly dependent on source water type and monochloramine contact time (CT); e.g., at 24 h CT, Cork Brook produced 12.2 ng/L NDMA and Bailey Brook produced 4.2 ng/L NDMA, compared with 72 h CT, Cork Brook produced 4.1 ng/L NDMA and Bailey Brook produced 3.4 ng/L NDMA. No correlations were found between traditional DBP precursors such as total organic carbon and total nitrogen, and the formation of NDMA. The laboratory bench-top treatment system was highly effective at removing traditional DBP precursors, highlighting the need for WTPs to alter their current treatment methods to best accommodate the complex system of DBP control.

A rapid and reliable technique for N-nitrosodimethylamine analysis in reclaimed water by HPLC-photochemical reaction-chemiluminescence

A fast and reliable analytical technique was evaluated and validated for determination of N-nitrosodimethylamine (NDMA) formation and rejection by reverse osmosis (RO) membranes in potable water reuse applications. The analytical instrument used in this study is high-performance liquid chromatography (HPLC), photochemical reaction (PR) and chemiluminescence (CL) – namely HPLC-PR-CL. Results reported here show that HPLC-PR-CL can be used to measure NDMA with a similar level of accuracy compared to conventional and more time-consuming techniques using gas chromatography and tandem mass spectrometry detection in combination with solid phase extraction. Among key residual chemicals (i.e. monochloramine, hydrogen peroxide and hypochlorite) in reclaimed wastewater, hypochlorite was the only constituent that interfered with the determination of NDMA by HPLC-PR-CL. However, hypochlorite interference was eliminated by adding ascorbic acid as a reducing agent. Direct injection of ultrafiltration (UF)-treated wastewater samples into HPLC-PR-CL also resulted in an underestimation of the NDMA concentration possibly due to interference by organic substances in the UF-treated wastewater. Accurate determination of NDMA concentrations in UF-treated wastewater was achieved by reducing the sample injection volume from 200 to 20 μL, though this increased the method detection limit from 0.2 to 2 ng/L. In contrast, no interference was observed with RO permeate. These results suggest that RO membranes could remove part of substances that interfere with the NDMA analysis by HPLC-PR-CL. In addition, RO treatment experiments demonstrated that HPLC-PR-CL was capable of evaluating near real-time variation in NDMA rejection by RO.

Compound-specific carbon, nitrogen, and hydrogen isotope analysis of N-nitrosodimethylamine in aqueous solutions.

Mitigation of N-nitrosodimethylamine (NDMA) and other hazardous water disinfection byproducts (DBP) is currently hampered by a limited understanding of DBP formation mechanisms. Because variations of the stable isotope composition of NDMA can potentially reveal reaction pathways and precursor compounds, we developed a method for the compound-specific isotope analysis (CSIA) of (13)C/(12)C, (15)N/(14)N, and (2)H/(1)H ratios of NDMA by gas chromatography coupled to isotope ratio mass spectrometry (GC/IRMS). Method quantification limits for the accurate isotope analysis of NDMA, N-nitrosodiethyl-, -dipropyl-, and -dibutylamine as well as N-nitrosopyrrolidine were between 0.18 to 0.60 nmol C, 0.40 to 0.80 nmol N, and 2.2 to 5.8 nmol H injected on column. Coupling solid phase extraction (SPE) to GC/IRMS enabled the precise quantification of C, N, and H isotope ratios of NDMA in aqueous samples at concentrations of 0.6 μM (45 μg L(-1)). We validated the proposed method with a laboratory experiment, in which NDMA was formed with stoichiometric yield (97 ± 4%) through chloramination of the pharmaceutical ranitidine (3 μM). δ(13)C and δ(2)H values of NDMA remained constant during NDMA formation while its δ(15)N increased due to a reaction at a N atom in the rate-limiting step of NDMA formation. The δ(2)H value of NDMA determined by SPE-GC/IRMS also corresponded well to the δ(2)H value of the N(CH3)2-group of ranitidine measured by quantitative deuterium nuclear magnetic resonance spectroscopy. This observation implies that the N(CH3)2-moiety of ranitidine is transferred to NDMA without being chemically altered and illustrates the accuracy of the proposed method.

Picogram determination of N-nitrosodimethylamine in water

N-nitrosodimethylamine (NDMA) persistence within surface waters is a major concern for downstream communities exploiting these waters as drinking water supplies. The objective of this study is to develop a novel and efficient analytical method for NDMA via different technologies: pulsed splitless gas chromatography-nitrogen phosphorus detector (GC-NPD), large volume injection (LVI) gas chromatography-mass spectrometry (GC/MS) via programmable temperature vaporizer (PTV) inlet or PTV-gas chromatography-triple quadruple mass spectrometry (GC-MS/MS) and continuous liquid-liquid extraction. It was found that the sensitivity required for NDMA analysis by GC-NPD can only be achieved when the NPD bead is extremely clean. LVI via PTV can greatly improve GC-MS system sensitivity for analyzing NDMA. With the help of DB-624 (25 m x 200 microm x 1.12 microm) connected with DB-5MS (30 m x 250 microm x 0.25 microm) in series, PTV-GC/MS could overcome the matrix interference for the trace analysis of NDMA. Variable instrument conditions were studied in detail, with the optimized process being validated via precision and accuracy studies. PTV- triple quadruple GC-MS/MS system could efficiently remove the interference on a single DB-5MS (30 m x 250 microm x 0.25 microm) column with good sensitivity and selectivity. The developed methods have been successfully applied to test NDMA in different types of water samples with satisfactory results.

Nitrogen–phosphorus detection and nitrogen chemiluminescence detection of volatile nitrosamines in water matrices: Optimization and performance comparison

Two nitrogen-specific detection methods, nitrogen–phosphorus detection (NPD) and nitrogen chemiluminescence detection (NCD), were investigated as low cost alternatives to mass spectrometry (MS) with chemical ionization (CI) for analysis of nitrosamines in aqueous samples. NCD showed greater sensitivity to N-nitrosodimethylamine (NDMA) and seven other volatile nitrosamines than did NPD. Instrument detection levels for NDMA were established at 2.6 μg/L and 4.0 μg/L in solvent with 3 μL splitless gas chromatograph (GC) injection for NCD and NPD, respectively. Using a dual-column confirmation method, both NCD and NPD compared favorably with CI-MS results for NDMA analysis in a variety of water sample types. For seven other nitrosamines, both detectors showed excellent accuracy in analyzing high concentrations (greater than 300 ng/L) in complex wastewater matrices, while the accuracy of spike recoveries of very low levels (less than 15 ng/L) in clean matrices varied for each nitrosamine and detection method.

Solid-phase microextraction of N-nitrosodimethylamine in beer

N-nitrosodimethylamine (NDMA) is a highly active carcinogen that has been detected in trace levels in beers. Solid-phase microextraction (SPME) was used to develop a method for the extraction of NDMA from beer using headspace sampling and gas chromatography with mass spectrometry detection. Polydimethylsiloxane/divinylbenzene (PDMS–DVB) fibres were used to evaluate the influence of equilibrium time, ionic strength, extraction time and temperature by means of a factorial design. The method was validated calculating the linearity, reproducibility, limit of detection and limit of quantification. The method was applied to the quantitative analysis of NDMA combining the standard addition method with an internal standard method.

Alternative Methods For The Analysis Of Ndma And Other Nitrosamines In Water

N‐nitrosodimethylamine (NDMA) and other nitrosamines have been reported in drinking and recycled water at low parts‐per‐trillion levels, both as contaminants and disinfection byproducts. Many of these nitrosamines cause cancer in animals and are probable human carcinogens. In this study, three existing analytical methods were expanded, refined, and validated for the analysis of NDMA and seven other nitrosamines in potable, waste, and recycled water. Method detection limits for a solid‐phase extraction (SPE) method and a cartridge SPE (CSPE) coupled with gas chromatography–tandem mass spectrometry were 0.7–0.8 ng/L for NDMA and 0.3–1.4 ng/L for other nitrosamines. The micro‐liquid–liquid extraction (MLLE) method that was developed used less volume and was effective at analyzing the different sample matrixes but yielded higher detection limits (2–4 ng/L). NDMA was the only nitrosamine detected in potable water; however N‐nitrosodiethylamine, N‐nitrosomorpholine, N‐nitrosopiperidine, N‐nitrosodi‐N‐butylamine, and N‐nitrosopyrrolidine were present in other matrixes tested. The SPE methods and the MLLE method have been submitted for inclusion in the next revision of Standard Methods for the Examination of Water and Wastewater, and the CSPE method will be submitted for approval in the future.

InternationalN‐nitroso compounds check sample programme: Report on the performance in the second study dedicated to their determination in beer and malt

The second check sample survey for the determination of N-nitrosamines in beer and malt has been initiated. Each laboratory received four samples: two beer, from the same batch, spiked respectively with 0.5 microgram/l N-nitrosodimethylamine (NDMA) and 4 micrograms/l NDMA plus 30 micrograms/l N-nitrosoproline (NPRO) and two naturally contaminated malts. Sixteen laboratories sent their results and two apologized in view of analytical problems. Results from this have been statistically evaluated. Comparison to those from the previous study demonstrated a distinct improvement in the results from the analysis of NDMA in beer and malt. Little has been achieved for the other two common contaminants of beer and malt, N-nitrosopyrrolidine (NPYR) and NPRO. For this latter compound in beer, however, some hope came from the data produced by the method of Sen et al. (1983), but the number of results is insufficient to allow firm conclusions to be drawn.