Determination of mononitrophenols in water by gas-chromatography

Nitrophenols are highly toxic hydrophilic organic compounds. Nitrophenols prevalence in the biosphere is associated with both human industrial activity and with natural processes in the atmosphere and hydrosphere. Nitrophenols determination using gas chromatography requires chemical modification in order to reduce the hydrophilicity and polarity of the analytes. The derivatization must be carried out before the extraction concentration stage, but in most methods of the nitrophenols determination in water this approach is not implemented. The method of determination of mononitrophenols (2-, 3-, and 4-nitrophenols) in water was developed. It involved the nitrophenols bromination directly in the water, bromoderivatives liquid extraction with toluene, silylation by N-tert-Butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) extract and gas chromatographic determination with the electron-capture detector ( GC-ECD ). The nitrophenols bromination conditions in aqueous solutions were optimized (pH value, bromination duration, bromide-ions concentration). In order to reduce the oxidizing activity of bromine, the nitrophenols bromination was recommended in the presence of bromide anions. The extraction (degree of extraction) and gas chromatographic (retention indices, ECD relative molar responses) properties and nitrophenols bromoderivatives properties were studied. It was shown that the degree of extraction of brominated nitrophenols in the toluene/water system exceeded 80% and the subsequent silylation of the bromoderivatives significantly improved their chromatographic properties. The analytical range of nitrophenols in water was 0.02-10 µg/dm 3 with an error of 10-35%, the detection limits were 0.05-0.07 μg/dm 3 , the sample volume for analysis was 50 cm 3 , the analysis duration was 90 min. Key words : mononitrophenols, chemical modification, gas-chromatography, electron-capture detector DOI: http://dx.doi.org/10.15826/analitika.2020.24.2.006 I.V. Gruzdev, B.M. Kondratenok, E.I. Lyu-Lyan-Min Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences (IB FRC Komi SC UB RAS), Kommunisticheskaya st., 28, Syktyvkar, 167982, Russian Federation