RESUMEN
A rapid and simple method of using solid-phase microextraction was developed for determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in water samples. In this method, the target analyte is extracted from the sample into the polymeric coating of the fused-silica fiber. After exposure, the fiber is thermally desorbed in the heated injection port of the gas chromatograph, and a chromatographic analysis is performed by using low-resolution tandem mass spectrometry. Parameters that may affect the extension of the microextraction process, such as sampling mode, sample volume, temperature, agitation, and sampling time, were studied. Extraction efficiencies for 3 coating fibers were investigated: 100 microm poly(dimethylsiloxane) (PDMS), 65 microm PDMS-divinylbenzene, and 75 microm carboxen-PDMS. Linearity was evaluated (R = 0.999) for a 250-fold concentration range from the fg/mL to the pg/mL level. The 2,3,7,8-TCDD was detected at the fg/mL level when the headspace over the water sample was sampled for 60 min; the limit of detection obtained was better than that of Method 8280B of the U.S. Environmental Protection Agency. The proposed method performed well when applied to the analysis of tap water, lake water, and seawater samples.
Asunto(s)
Contaminantes Ambientales/análisis , Cromatografía de Gases y Espectrometría de Masas/métodos , Dibenzodioxinas Policloradas/análisis , Agua/química , Adsorción , Calibración , Calor , Control de Calidad , Reproducibilidad de los Resultados , Dióxido de SilicioRESUMEN
Solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry has been applied to the extraction of 30 phenol derivatives from water samples. Analytes were in situ acetylated and headspace solid-phase microextraction was performed. Different parameters affecting extraction efficiency were studied. Optimization of temperature, type of microextraction fiber and volume of sample has been done by means of a mixed-level categorical experimental design, which allows to study main effects and second order interactions. Five different fiber coatings were employed in this study; also, extraction temperature was studied at three levels. Both factors, fiber coating and extraction temperature, were important to achieve high sensitivity. Moreover, these parameters showed a significant interaction, which indicates the different kinetic behavior of the SPME process when different coatings are used. It was found that 75 microm carboxen-polydimethylsiloxane and 100 microm polydimethylsiloxane, yield the highest responses. The first one is specially appropriated for phenol, methylphenols and low chlorinated chlorophenols and the second one for highly chlorinated phenols. The two methods proposed in this study shown good linearity and precision. Practical applicability was demonstrated through the analysis of a real sewage water sample, contaminated with phenols.