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

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 pK a (i.e., < 2.5) display mainly reversedphase interactions (neutral species) with the stationary phase and those with higher pK a (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. Keywords Nitrogen-containing heterocycles. Liquid chromatography. Reversed-phase. Cation exchange. Mixed-mode chromatography Published in the topical collection Persistent and Mobile Organic Compounds-An Environmental Challenge with guest editors Torsten C.

Reaction of Chlorine Dioxide with Saturated Nitrogen-Containing Heterocycles and Comparison with the Micropollutant Behavior in a Real Water Matrix

“…Yet, it is likely that although the sum formulas are the same, the structures are not. The detection of two compounds with the same sum formulas at different retention times can be due to cation exchange properties of the mixed mode column in which the p K a of a compound plays a role in retention . In that, if 3-piperidone (p K a of conjugated amine = 7.19) is formed instead of 2-piperidone (p K a of acidic amine = 14.89), it will show higher retention compared to 2-piperidone and 2,5-piperidinedione (p K a of acidic amine = 12.13), which also has been detected.…”