Otimização de condições cromatográficas para quantificação de teor de ativo de Acefato por cromatografia gasosa com detector por ionização em chama (FID)

Abstract

The use of pesticides in agriculture has become even more frequent with technological advances, with the search for faster work aimed at mitigating losses in plantations due to pest attacks. However, inadequate and excessive management poses dangers to humans related to exposure to pesticides. In this context, there is an increasing demand for pesticide quantification techniques that aim at better applicability and sensitivity in the results. Thus, this work aimed to optimize parameters for the determination of acephate by gas chromatography coupled to the flame ionization detector (FID), with a lower cost alternative when compared to techniques coupled to mass spectrometry. To optimize the chromatographic parameters, the acephate samples were prepared at concentrations of 100% active, 4 and 10 g L-1, according to RDC No. 166, dated July 24, 2017 and ABNT 14029:2016, with acetone and isopropanol solvents. Adjustments of column, injection and detector temperatures, air and hydrogen flows, injection volumes, sample concentration and chromatographic column were adapted according to the need to improve resolutions, in order to accentuate the chromatographic peak. As a result, the oven temperature set at 195 °C provided better retention time, without interference from background noise. The injector temperature at 180 °C became ideal, since temperatures of 270°C would possibly degrade the sample. Detector temperature at 250 °C and injection volumes of 1 µL brought a narrowing of the peak, when compared to lower temperatures. Higher sample concentrations increased the peak height, and the best concentration evaluated was 10 g L-1. Subtle changes in air and hydrogen flow did not bring major changes, and the use of the HP-5 column brought excellent resolution of the results, with a theoretical number of plates of 1,708.45, a value that shows excellent column efficiency, in addition to obtaining the analytical signal with good resolution (symmetrical peak). The realization of the calibration curve yielded a linear correlation coefficient R equal to 0.99785, and quantification limit (QL) and determination (DL) equal to 0.0800 and 0.0300 mg kg⁻¹, respectively, and the QL met the quantification conditions of acephate in crops such as cotton, garlic, onion, carrot, citrus and melon, according to the maximum residue limit (MRL) established by the National Health Surveillance Agency (ANVISA).