Preparation of flower-like molybdenum disulfide for solid-phase extraction of N-nitrosoamines in environmental water samples

Fluorescent paper-based sensor integrated with headspace thin-film microextraction for the detection of acyclic N-nitrosamines following in situ photocatalytic decomposition

BACKGROUND

In this work, a novel analytical approach based on the photocatalytic decomposition of N-nitrosamines combined with headspace thin-film microextraction of the generated nitrogen oxides such as NO has been developed for the determination of the acyclic N-nitrosamine fraction in drinking water samples. A hydrophilic cellulose substrate modified with fluorescent silver nanoclusters (Ag NCs) was used both as extractant and sensing platform. A quenching effect of Ag NCs fluorescence occurs as the concentration of N-nitrosamines increases. Front-face fluorescence spectroscopy with a solid sample holder was employed for directly measuring the fluorescence quenching onto the cellulose substrate.

RESULTS

In order to achieve an optimal analytical response, different parameters involved in the photocatalytic reaction as well as those concerning the microextraction step were fully investigated. It is demonstrated that the photodegradation rate of cyclic N-nitrosamines at acidic pH is much lower than that of acyclic ones, which can be the basis for the determination of the later fraction in waters. Under optimal conditions, a detection limit for the acyclic N-nitrosamine fraction around 0.08 μg L^-1 using N-nitrosodimethylamine (NDMA) as model compound for calibration was obtained. Several drinking waters were spiked with acyclic N-nitrosamines showing recoveries in the range of 98-102% with a relative standard deviation of 3-4% (N = 3).

SIGNIFICANCE AND NOVELTY

N-nitrosamines generated as by-products during disinfection processes applied to water cause multiple adverse effects on human health being classified as potential human carcinogens. This study highlights the suitability of a fluorescent paper-based sensor for the rapid analysis of the acyclic N-nitrosamine fraction (i.e. the most abundant fraction) as a total index in drinking water, being useful as screening tool before exhaustive chromatographic analysis, which saves costs, time and reduces waste generation.

Development and validation of rapid ultra high performance liquid chromatography with tandem mass spectroscopic method for the quantification of N-Nitrosodimethyl amine and N-Nitrosodiethyl amine in sitagliptin and metformin hydrochloride immediate and extended-release formulations

A simple, effective LC-MS based method is developed and validated to determine N-Nitrosodimethylamine and N-Nitrosodiethylamine in pharmaceutical formulations of Sitagliptin and Metformin hydrochloride combination dosage forms. Atlantis T3 (100 × 3 mm, 3 μm) column and eluent-A (0.1% formic acid in water), and eluent-B (0.1% formic acid in methanol) were used to achieve chromatographic separation. A gradient program time (min)/%B: 0.01/3, 2/3, 4/55, 5/55, 5.5/90, 6.0/90, 6.5/3 and 7/3, and column flow rate: 0.75 mL/min was employed. The column oven and auto sample cooler temperatures were 40°C and 10°C, respectively. Atmospheric Pressure Ionisation +ve mode with corona discharge potential as 4.0 volts, drying gas (N₂ ) flow as 110 mL/min, and nebulizer gas (N₂ ) flow as 350 mL/min. Employing PerkinElmer triple quadrupole mass spectrometer, QSight 200 series, the source temperature was 450°C, and hot surface-induced desolvation temperature was 250°C. Under optimized conditions, diluent-1 and diluent-2 offered better recovery and improved peak shapes. The required method sensitivity of Nitrosodimethylamine (Limit of Quantitation 0.74 ng mL^-1 ) and Nitrosodiethylamine (Limit of Quantitation 0.37 ng mL^-1 ) for the nitrosamine impurities were achieved using an optimized test concentration of Metformin hydrochloride at 45.7 mg mL^-1 . This article is protected by copyright. All rights reserved.