Determinação de carbendazim em suco de laranja, empregando extração na ponteira descartável de micropipeta com sorvente preparado em laboratório

Abstract

Carbendazim is a benzimidazole fungicide with high stability in the environment and very used in the fungi control, having been negative global prominence at the beginning of this decade because it was found at high rates in Brazilian oranges. Due to the carbendazim polarity, its extraction requires procedures with mixtures of polar and nonpolar sorbents, making the process more expensive, poor selective and complex. In this sense, we have developed a new sorbent selective to carbendazim based on the thermal immobilization of poly(glycidoxypropylmethyl-co-dimethylsiloxane) (PGPMS) onto irregular silica particles. The sorbent was characterized morphologically and structurally, presenting as mesoporous irregular particles with high surface area, 250 m2 g-1, high thermal stability and coated by a thin polymeric layer of PGPMS. Si(PGPMS) was used as sorbent for the carbendazim extraction from orange juices into the disposable micropipette tip (DPX). The extraction conditions of carbendazim from orange juices by the DPX method with the sorbent Si(PGPMS) were optimized, using a central composite design. The sample extracts were quantified by high-performance liquid chromatography and diode array detection (HPLCDAD). The DPX HPLC-DAD method for the determination of carbendazim in orange juice was validated according to the SANTE/11813/2017 document, protocol used by the European community, presenting as a method of good accuracy (recoveries between 98- 112 %), good precision (RSD < 16%) and limit of quantification of 100 μg L-1 (below the maximum residue limit for carbendazim in oranges). The DPX method was used in commercial orange juice samples for the determination of carbendazim, and the presence of pesticide residues was not detected. The samples were then fortified with carbendazim standard solution and the DPX method was used for the pesticide recovery, reaching rates of 93 to 108 %, without matrix effects, results that were comparable to a reference method based on QuEChERS extraction recovery rates 77 to 99 %. Summarizing, it can be concluded that the lab-made sorbent was effective in the DPX extraction of carbendazim in orange juice samples, presenting high selectivity, proved by the single extraction cycle in DPX method. In addition, the method is simple and fast, employing small volumes of sample and solvent, small amount of sorbent for the efficient determination of carbendazim.