In recent years the increasing interest in water-soluble organic compounds (WSOCs) in the atmosphere is fuelled by their potential role in affecting the global climate, since they alter the hygroscopic properties of atmospheric particle, affecting their ability to act as cloud condensation nuclei and can also contribute to higher atmospheric absorption of solar radiation and atmospheric heating. In addition, some WSOCs – such as dicarboxylic acids and saccharides – are potentially useful molecular tracers, since they can have several different sources including primary emissions from biomass burning and fossil fuel combustion, as well as photochemical oxidation of organic precursors of both biogenic (e.g. pinonic acid) and anthropogenic precursors (e.g. phthalic and benzoic acids). GC–MS is the most widely applied technique for the characterization of organic aerosols since it yields excellent separation efficiency, sensitivity and high number of species analyzed. Due to their high polarity, hydrophilicity and low volatility, carboxylic acids and saccharides have to be converted into volatilizable and stable derivatives — i.e., trimethylsilyl derivatives using BSTFA(N,Obis(trimethylsilyl)-trifluoroacetamide) as silylation reagent. Indeed, multi-residue analytical methodologies, that achieve simultaneous analysis of several compounds, are useful for reducing the complexity and time required for sample preparation and analysis in order to provide a large amount of reliable data. With this aim, the proper selection of the extraction operating conditions is a critical step, since they are essential to achieve the highest yield for several target analytes with a wide range of water solubility and volatility. This paper describes the optimization of the extraction operating conditions to develop a GC-MS procedure for the simultaneous analysis of carboxylic acids and saccharides in atmospheric aerosols, providing the low detection limits and the high reproducibility required by environmental monitoring. The factors considered were the solvent type (characterized by polarity p’ parameter) and extraction volume (10-20 ml). The response surface methodology (RSM) including central composite design (CCD) was applied to fully investigate the experimental domain of the operative parameters using a limited number of experiments. The response surface computed by the RSM model shows the simultaneous dependence of the extraction yield on the combination of the two variables, solvent polarity and volume.

GC-MS method for the simultaneous analysis of water-soluble organic compounds in PM: response surface methodology for optimizing solvent extraction.

PIETROGRANDE, Maria Chiara;BACCO, Dimitri;CHIEREGHIN, Sara;
2012

Abstract

In recent years the increasing interest in water-soluble organic compounds (WSOCs) in the atmosphere is fuelled by their potential role in affecting the global climate, since they alter the hygroscopic properties of atmospheric particle, affecting their ability to act as cloud condensation nuclei and can also contribute to higher atmospheric absorption of solar radiation and atmospheric heating. In addition, some WSOCs – such as dicarboxylic acids and saccharides – are potentially useful molecular tracers, since they can have several different sources including primary emissions from biomass burning and fossil fuel combustion, as well as photochemical oxidation of organic precursors of both biogenic (e.g. pinonic acid) and anthropogenic precursors (e.g. phthalic and benzoic acids). GC–MS is the most widely applied technique for the characterization of organic aerosols since it yields excellent separation efficiency, sensitivity and high number of species analyzed. Due to their high polarity, hydrophilicity and low volatility, carboxylic acids and saccharides have to be converted into volatilizable and stable derivatives — i.e., trimethylsilyl derivatives using BSTFA(N,Obis(trimethylsilyl)-trifluoroacetamide) as silylation reagent. Indeed, multi-residue analytical methodologies, that achieve simultaneous analysis of several compounds, are useful for reducing the complexity and time required for sample preparation and analysis in order to provide a large amount of reliable data. With this aim, the proper selection of the extraction operating conditions is a critical step, since they are essential to achieve the highest yield for several target analytes with a wide range of water solubility and volatility. This paper describes the optimization of the extraction operating conditions to develop a GC-MS procedure for the simultaneous analysis of carboxylic acids and saccharides in atmospheric aerosols, providing the low detection limits and the high reproducibility required by environmental monitoring. The factors considered were the solvent type (characterized by polarity p’ parameter) and extraction volume (10-20 ml). The response surface methodology (RSM) including central composite design (CCD) was applied to fully investigate the experimental domain of the operative parameters using a limited number of experiments. The response surface computed by the RSM model shows the simultaneous dependence of the extraction yield on the combination of the two variables, solvent polarity and volume.
2012
atmospheric aerosol; analysis of water-soluble organic compounds; GC-MS method optimization; solvent extraction.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/1700509
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