RESUMEN
A sample preparation procedure including a simultaneous microwave-assisted (MA) extraction and derivatization for the determination of chlorophenoxy acids in soil samples is presented. For a selective and sensitive measurement, an analytical technique such as GC coupled with MS needs to be adopted. For GC analyses, chlorophenoxy acids have to be converted into more volatile and thermally stable derivatives. Derivatization by means of microwave radiation offers new alternatives in terms of shorter derivatization time and reduces susceptibility for the formation of artefacts. Extraction and derivatization into methyl esters (ME) were performed with sulphuric acid and methanol. Due to the novelty of the simultaneous extraction and derivatization assisted by means of microwave radiation, a careful investigation and optimization of influential reaction parameters was necessary. It could be shown that the combination of sulphuric acid and methanol provides a fast sample preparation including an efficient clean up procedure. The data obtained by the described method are in good agreement with those published for the reference material. Finally, compared to conventional heating and also to the standard procedure of the EPA, the sample preparation time could be considerably shortened.
Asunto(s)
Cromatografía de Gases y Espectrometría de Masas/instrumentación , Cromatografía de Gases y Espectrometría de Masas/métodos , Herbicidas/análisis , Herbicidas/química , Contaminantes del Suelo/análisis , Contaminantes del Suelo/química , Ácido 2,4,5-Triclorofenoxiacético/análisis , Ácido 2,4,5-Triclorofenoxiacético/química , Ácido 2,4-Diclorofenoxiacético/análisis , Ácido 2,4-Diclorofenoxiacético/química , Ácido 2-Metil-4-clorofenoxiacético/análogos & derivados , Ácido 2-Metil-4-clorofenoxiacético/análisis , Ácido 2-Metil-4-clorofenoxiacético/química , Butiratos/análisis , Butiratos/química , Microondas , Estructura Molecular , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Estereoisomerismo , Temperatura , Factores de TiempoRESUMEN
Contrary to its lower brominated congeners, the flame retardant decabromodiphenylether (DecaBDE) is not banned by the decision 2005/717/EG of the European Union. But the question of the bioavailability and bioaccumulation of this second most used flame retardant worldwide becomes subject of more intense research. In the present study, we developed a microwave-assisted method for the extraction of DecaBDE from polymers. Owing to its main use in electrical and electronic appliances and according to the fire safety standard UL94 V-0, the extraction procedure was carried out for the model compounds polyethylene and polystyrene. Special emphasis has been given to an accurate optimization by an experimental response surface design. Quantification was performed by means of HPLC-DAD. In order to achieve comparable data, extraction was also performed with classic Soxhlet extraction. To compare these results with an independent technique, microwave-induced oxygen combustion and ion chromatography complete this study.
RESUMEN
Microwave radiation is used to speed up chemical derivatization. In the present study, three microwave-assisted techniques for the methylation of chlorophenoxy acid herbicides prior to analysis by gas chromatography coupled with mass spectrometry are compared. Derivatization was performed with the catalysts sulphuric acid and boron trifluoride as well as with trimethylsilyldiazomethane. In order to establish optimized and stable conditions, a screening for statistically significant factors by means of experimental designs was carried out and supplemented by a careful optimization. Special emphasis has been given to an accurate validation to prove the performance of the techniques. Furthermore, all microwave-assisted methods were compared with their conventional analogues. The optimized methods are valid for routine analysis of different matrices such as water, soil, sediment or tissues, especially for high sample throughput since a simultaneous derivatization of up to 64 samples in one run is possible.
Asunto(s)
Herbicidas/análisis , Ácido 2,4-Diclorofenoxiacético/análisis , Ácidos , Boranos , Diazometano/análogos & derivados , Ésteres/síntesis química , Ésteres/química , Cromatografía de Gases y Espectrometría de Masas , Indicadores y Reactivos , Metanol/química , Metilación , Microondas , Control de Calidad , Estándares de Referencia , Solventes , Ácidos Sulfúricos/química , Compuestos de TrimetilsililoRESUMEN
In the present study, the preparation of methyl esters of chlorophenoxy acids with trimethylsilyldiazomethane (TMSD) is reported. TMSD is a mild and safe alternative to the highly toxic, thermally labile, and explosive diazomethane. Due to the novelty of this method, the characteristics of the reaction were investigated and the derivatization procedure was screened for statistically significant factors. The parameters identified as influential are the amount of methanol as well as reaction time and temperature. A careful optimization by a complete factorial response surface design was carried out to generate optimal reaction conditions with respect to maximum recovery and reaction yield. Special emphasis has been given to an accurate validation of the derivatization procedure. LODs were determined between 4.1 and 8.1 ng/mL for the enriched sample and linearity was proofed for more than five orders of magnitude. The applicability of the method was demonstrated by the analyses of quality control material including sample preparation with SPE. Polar herbicides investigated in the study belong to acetic acid (2,4-D, MCPA, and 2,4,5-T), butanoic acid (MCPB), and propanoic acid (mecoprop). An efficient, fast, and high-throughput method for the determination of polar herbicides including the potential for automation is proposed.
