Development of an LC-MS method for determination of nitrogen-containing heterocycles using mixed-mode liquid chromatography

Mohammad Sajjad Abdighahroudi,Torsten C Schmidt,Holger V Lutze

doi:10.1007/s00216-020-02665-x

Mohammad Sajjad Abdighahroudi, Torsten C Schmidt + Show 1 more

Open Access

https://doi.org/10.1007/s00216-020-02665-x

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Abstract

N-containing heterocycles (NCHs) are largely used as precursors for pharmaceuticals and can enter the environment. Some NCHs have been shown to be toxic, persistent, and very mobile in the environment. Thus, they have received increasing attention in the past years. However, the analysis of these polar compounds in environmental samples is still a challenge for liquid chromatography. This paper investigates the use of mixed-mode liquid chromatography (MMLC), which has reversed-phase and ion exchange characteristics for measurements of NCHs in water. NCHs with low pKa (i.e., < 2.5) display mainly reversed-phase interactions (neutral species) with the stationary phase and those with higher pKa (i.e., > 5) interact by a mixture of reversed-phase/ion exchange/HILIC mechanism. It was also shown that the presented method performs well in the quantification of the majority of the selected NCHs in surface water with MDLs between 3 and 6 μg/L, a low matrix effect and recoveries in the range of 77–96% except for pyridazine exhibiting 32% were achieved. The method was successfully employed to follow the degradation of NCHs in ozonation.

Highlights

Published in the topical collection Persistent and Mobile Organic Compounds – An Environmental Challenge with guest editors Torsten C
The stronger bases imidazole, pyridine, and Efficiency and asymmetry are almost constant for imidazole, pyridine, and piperidine for all δACN, except for 0.05 in which pyridine and piperidine show somewhat lower efficiency
It appears that the role of selectivity in the calculation of resolution is greater than the retention factor (Fig. 1) and efficiency (ESM Fig. S2)

Summary

Introduction

Published in the topical collection Persistent and Mobile Organic Compounds – An Environmental Challenge with guest editors Torsten C. N-containing heterocycles (NCH) are a group of compounds with wide occurrence in the environment and broad application in chemistry [1,2,3]. They have been detected at industrial and agricultural sites [4, 5], groundwater [6,7,8,9,10], and surface water [11, 12]. The features of chemicals such as pharmaceuticals, industrial solvents, ionic liquids, and pesticides are based on NCH moieties [14,15,16]. Aromatic N-heterocycles such as pyrazole, pyridine, and pyrazine are byproducts of chemical processes such as acrylonitrile manufacturing [18]

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