Colunas capilares extratoras à base de grafeno e derivados ancorados em sílica para a determinação de Xantinas e Ocratoxina em amostras de café

Abstract

Given the increasing need to analyze natural constituents or contaminating compounds in complex food matrices in a simple and automatized way, it has become frequent the use of miniaturized preparation techniques coupled with the analytical system. In-tube solid-phase microextraction (in-tube SPME) is a sensitive technique that allows its direct coupling to LC systems. Here we present a series of graphenebased materials supported on silica as sorbents used in an in-tube SPME system coupled on-line with Ultra Performance Liquid Chromatography and tandem Mass Spectrometry (UPLC-MS/MS) for the extraction of xanthines and ochratoxin A (OTA) in coffee samples. The synthesized materials were characterized by Infrared Spectroscopy (IR) and Scanning Electron Microscopy (SEM). Aminopropyl silica particles coated with graphene oxide functionalized with C18 and end-capping (SiGOC18ecap) showed the best extraction performance. Consequently, on-line intube SPME-UPLC-MS/MS was successfully implemented employing a microcolumn (0,5 mm i.d x 100 mm) packed with SiGOC18ecap particles. Extraction parameters and detection conditions were optimized. The validated method for xanthines showed low detection (0.1-0.2 µg L-1) and quantification (0.3-1.0 µg L-1) limits, linearity over the range 0.5-500 µg L-1 and recoveries of the individual xanthines from 57 to 110%). High extraction efficiency was determined by the enrichment factors obtained (5.6-7.2). Caffeine was determined in all roasted and soluble coffee samples analyzed at levels from 12.1 to 36.8 mg g-1. Small amounts of theobromine < 0.10 mg g-1 and theophylline < 0.07 mg g-1 were also detected in several samples. The method for OTA analysis in soluble coffee beverage, presented limits of detection and quantification of 0.20 and 0.35 μg L-1 , respectively, linearity over the range 0.35-2.0 μg L-1 , besides being a simple and economical procedure for OTA evaluation. This work demonstrated that graphene-based materials represent a promising new sorbent for in-tube SPME. The high pre-concentration factor obtained showed a great extraction capacity. The methods were efficient, simple and fast, showing a good potential to be applied for the xanthines and ochratoxin analysis in other matrices.

Determinação de pesticidas em alimentos derivados da cana-de-açúcar por LC-MS/MS empregando DPX como técnica de preparo de amostra

“…presentes no C18, sugerindo a ligação do C18 às partículas de SiGO efetivamente ocorreu. 82 Além disso, observa-se uma redução do estiramento O-H (3420 cm -1 ), uma vez que os grupos silanóis são funcionalizados com C18, e no caso do material SiGOC18endcap, essa redução é ainda maior, uma vez que na etapa de encapping, o TMS reduz os grupos silanóis remanescentes. 82 Figura 4 -Espectros FT-IR dos materiais sintetizados…”