http://dx.doi.org/10.4322/sc.2014.016

Trace analysis in the field using gas chromatography-mass spectrometry

Truong, Tai V.; Sadowski, Charles S.; Rands, Anthony D.; Richter, Bruce E.; Brande, Tiffany; Later, Douglas W.; Lee, Milton L.

Palavras-chave: Field detection, Trace analysis, Sample preparation, GC-MS, SPME, SPE, Needle trap, Purge-and-trap, Thermal desorption.

ResumoTrace analysis of samples in the field, including air, headspace, and water (i.e., drinking and waste), as well as solid matrices and surfaces, for volatile organic compounds (VOCs) and semi-VOCs is a growing demand. Detection of target analytes, such as pesticides, polycyclic aromatic hydrocarbons (PAHs) and the natural compounds geosmin and 2-methyl isoborneol at ppb and ppt levels can be accomplished using simple sample preparation methods and gas chromatography-mass spectrometry (GC-MS). Solid phase micro extraction (SPME), solid phase extraction (SPE), thermal desorption, needle trap and purge-and-trap have become indispensable methods for field sampling when GC-MS is used for separation and detection. Sensitivity, selectivity, speed of analysis and simplicity of advanced in-field sample preparation devices have improved on-site trace analysis. Example analyses reported in this work involving approximately 54 VOCs were shorter than 20 min for drinking water, waste water and solid waste samples at the ppt to ppb concentration levels. Geosmin and 2-methyl isoborneol were detected at less than 10 ppt in water samples within 20 min. Pesticides including lindan, endrin, heptachlor, heptachlor epoxide, methoxychlor, malathion, carbaryl, benfluralin and chlorthal dimethyl, as well as PAHs such as naphthalene, fluorene, phenanthrene, acenaphthalene, acenaphthylene, anthracene, pyrene and chrysene were sampled and detected at concentrations in the low ppb in water samples within 15-20 min. Other organo-chlorine and organo-phosphorus pesticides in fresh tea-like leaves were also detected at ppb levels. VOCs can be detected at low ppb concentrations using a needle trap, and even lower with a higher flow thermal desorption tube. Dimethyl sulfide in water was determined at low ppb concentration. These analytical methods are generally applicable to other target analytes in environmental samples.


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