LC–MS/MS Method for Simultaneous Determination of Monoethanol- and Dimethylnitramine in Aqueous Soil Extracts

Monoethanol (MEA)- and dimethyl (DMA)-nitramines are by-products of amine-based post-combustion CO2 capture (PCCC) processing, and are potentially carcinogenic. The compounds are challenging to measure, also with LC–tandem mass spectrometry (MS/MS), attributed to their high polarity and extreme proneness to matrix effects. In contrast to related methods, the MEA- and DMA-nitramines were simultaneously determined in aqueous soil extracts in less than 10 min using a 1 mm × 150 mm Atlantis® T3 (3 µm) C18 column. A mobile phase of water/methanol (90/10, v/v) and 2 mM acetic acid allowed for electrospray ionization (ESI) of both analytes [in contrast to the need for both ESI and atmospheric pressure chemical ionization (APCI) in related methods]. Polarity switching electrospray was required for the simultaneous detection of the analytes, and concentration limits of detection (LODs) in the aqueous soil extracts were ≤5.0 µg L−1 using an injection volume of 20 μL and no prior enrichment step. Matrix effects were compensated for using isotope-labelled internal standards, and satisfactory precision and linearity were obtained (within- and between-day precisions ≤19%, r 2 ≥ 0.995 for concentrations up to 500.0 µg L−1). To avoid signal decrease over time when measuring DMA-nitramine alone, the use of polarity switching was beneficial, in addition to frequent cleaning of the ion transfer capillary. The validated method can be used to determine nitramines in aqueous soil extracts, which is of importance as soil sorption is a determinant of the compounds’ environmental fate.