In this study, amino-modified micro-mesoporous silica (NH 2 -MMS) with hierarchical pores was prepared by modifying micro-mesoporous silica ZSM-5 with 3-aminopropyltriethoxysilane and used as an adsorbent in solid-phase extraction to analyze free fatty acids (FFAs) in krill oil during storage for an initial time. The Brunner Emmet Teller adsorption experiment and Fourier transform infrared spectroscopy demonstrate that NH 2 -MMS, with a hierarchical pore structure, was successfully synthesized. The adsorption experiments, especially static adsorption, indicate that the absorption ability of the prepared NH 2 -MMS, with a hierarchical pore structure, toward FFAs was better than that of traditional amino-modified mesoporous silica (SBA-15) with a mesoporous structure at all temperature and concentrations. Fairly low limits of detection (0.06–0.15 μg g −1 ), acceptable recoveries (85.16–94.31%), and precision (0.08–5.26%) were attained under ideal circumstances. Moreover, NH 2 -MMS has the advantages of easy preparation and being environmentally friendly. As a result, this method offers an alternative to the current method for determining FFAs in different kinds of oil specimens.
A rapid, sensitive and wide coverage ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) method has been developed and validated for the simultaneous quantitation of 14 alkylation DNA adducts in cell genomic DNA, RNA and cell contents isolated from the in vitro cultured human kidney cell line 293 T and the human liver cell line L02 exposed to 3 genotoxic reagents: N -methyl -N- nitrosourea (MNU), methyl methanesulfonate (MMS) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). After exposure, DNA was isolated and directly hydrolysed under acid conditions or digested by enzymes to obtain the hydrolysates containing DNA alkylation adducts followed by optimization of the pretreatment method and chromatographic separation conditions. Quantification was performed on a Waters ACQUITY UPLC BEH Amide column (1.7 μm, 2.1 × 150 mm) using an electrospray ionization (ESI) source in positive mode by selective reaction monitoring (SRM) at the precursor to product ion transitions of 14 analytes. The method showed selectivity, good linearity (r＞0.9950), accuracy (82.1%–115%), and intra-day (RSD%＜14%) and inter-day (RSD%＜15%) precision for 14 analytes. The recoveries of two pretreatment methods were all more than 50.5%, and no relative matrix effects were observed. Additionally, the samples were stable after short-term storage at 20 ℃ for 2 h, at 4 ℃ for 48 h or one cycle of freeze-thaw at −80 ℃. The established UHPLC-MS/MS method was used to evaluate the changes in alkylation DNA adducts and epigenetic modification-related methylcytosine after exposure to genotoxic reagents. For the first time, the results demonstrated that 3 genotoxic reagents induced different total amounts of adducts in the following sequence: MMS ＞ NNK ＞ MNU, and showed significant differences in the ratios of 7MeG to 1MeA and 1MeG to 1MeA in the 293 T cell model. Meanwhile, 293 T and L02 cells revealed significantly different DNA adduct formation characteristics in the contents of 1MeG and 1MeA. The DNA adduct formation relationships between DNA, RNA, and cell contents were probed to predict cancer risk and potential genotoxic exposure. This approach could be used to investigate the DNA adducts, their formation and the relationship to the mutagenicity or carcinogenicity of genotoxic reagents in future studies.
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