Dissertação
Avaliação de um modulador a ar comprimido para GC×GC e sua aplicação para determinação de resíduos de pesticidas piretróides em uva
Fecha
2008-02-22Registro en:
FRIGGI, Caroline do Amaral. Evaluation of a compressed air modulator for GC×GC and application to determination of pyrethroid pesticides residues in grape. 2008. 107 f. Dissertação (Mestrado em Química) - Universidade Federal de Santa Maria, Santa Maria, 2008.
Autor
Friggi, Caroline do Amaral
Institución
Resumen
In this study, a new modulator that is simple, robust and presents low operation costs was developed. This modulator uses compressed air to cool two small portions of the second chromatographic column of a GC×GC system. To evaluate the modulation process, solutions of alkanes C7 to C29, and pesticides (bifenthrin, cyfluthrin, cypermethrin, esfenvalerate, fenitrotion, fipronil, trifloxystrobin and trifluralin) were analyzed by GC×GC-FID. The results showed small variations of the peaks areas, between 0.67 and 2.80% for alkanes and
between 0.24 and 5.34% for pesticides. The standard deviation (SD) for the retention time in the first column (1tR) was around 0.05 min, for alkanes and pesticides. For retention times in the second column (2tR), the SD was 0.04 s for
the majority of the compounds, except for cyfluthrin and permethrin (0.08 s). The linear range was between 0.1 and 5.0 mg L-1 with a coefficient of determination (r2)
greater than 0.9945 for pesticides analyzed by GC×GC-FID. The GC×GC system proposed was applied in the determination of pyrethroid pesticides (bifenthrin, cypermethrin, deltamethrin, fenvalerate and esfenvalerate and permethrin cis and trans) in grape samples Italy cultivar spiked at 3 levels (0.02, 0.05 and 0.5 mg kg- 1). Samples were extracted by the mini-Luke modified method (acetone method)
and pesticides were quantified by GC×GC-μECD. The parameters evaluated in the validation of the method were: analytical curve, linearity, limit of detection (LOD), limit of quantification (LOQ), precision (in terms of repetitivity and
intermediate precision) and accuracy (recovery), as well as the matrix effect on the chromatographic response. All analytical curves showed a linear range between 0.02 and 0.5 mg L-1 with r2 greater than 0.9956 and 0.9994 for the curves prepared in solvent (ethyl acetate) and matrix extract (grape), respectively. From the results obtained by calculation of the matrix effect percentage it can be concluded that the pyrethroid pesticides showed a considerable negative matrix effect. The values of
method LOQ were 0.01 to 0.02 mg kg-1 for all pyrethroids. The values of recovery for the 3 spiked levels were between 94.3 and 115.2%, with good precision (RSD<18.4%), demonstrating that the performance of the mini-Luke modified
method employed for the extractions is satisfactory. This study also showed that the GC×GC-μECD system using a modulator with a double jet of compressed air has potential for application in the analysis of pyrethroid pesticide residues in grapes, since it supplies low values of LOD and LOQ, and good accuracy in the analytical response.