Retention of nitramines on silica-based reversed phase materials and UiO-66 MOF materials

Abstract

Capturing and storing of CO2 can reduce the emissions of CO2 in the atmosphere. However, such facilities may emit amines that can be transformed into the potentially carcinogenic nitramines dimethylnitramine (DMA-NO2), monoethanolnitramine (MEA-NO2) and monomethylnitramine (MMA-NO2) which may be released into the environment. Presently, methods for trace determination of these compounds are lacking. The goal of the study was to find a material that can give sufficient retention to provide an enrichment of the nitramines before liquid chromatography electrospray ionization-mass spectrometry determination. The retention of the nitramines was examined on various C18 materials and the metal-organic frameworks UiO-66 and UiO-66 1,4-benzenedicarboxylate-NH2 (UiO-66-NH2), which were packed in 100 µm inner diameter columns. Of the tested materials, UiO-66-NH2 showed the highest retention factors for the nitramines. UiO-66-NH2 with 0.1% formic acid adjusted to pH 7 as mobile phase gave the best compromise of retention factors for DMA-NO2 and MEA-NO2, as the intended liquid chromatography-mass spectrometry method was evaluated for DMA-NO2 and MEA-NO2 only. MMA-NO2 had the highest retention factor on UiO-66-NH2 with 0.05% dibutylamine in the mobile phase. In conclusion, the retention factors achieved were in general higher on the UiO-66 materials than on the C18 materials. However, the retention obtained is probably not large enough to give limit of quantification down to 4 ng/L, albeit, not tested, due to extraordinary circumstances.