This is accomplished by first raising the potential to a level sufficient to oxidize the gold surface. This cause desorption of the carbohydrate oxidation products. The electrode potential is then lowered to reduce the electrode surface back to gold (Dionex, 2012). The association of analytical techniques using experimental design, with principal component analysis (Barros Neto, Scarminio, & Bruns, 2003),
has been increasingly applied, facilitating the establishing of correlations between various raw materials, based on their chromatographic profiles (Garcia et al., 2009). This study aims to evaluate the performance and correlation between two different chromatographic systems: HPLC–HPAEC-PAD and post-column derivatization HPLC-UV–Vis, applied for carbohydrate determination (method ISO 11292), following simplex-centroid design, to verify the ability to Selleck SRT1720 distinguish a mixture of triticale and acai in arabica coffee. The samples of arabica coffee, triticale, and acai seeds were provided by the Agronomic Institute of Parana (Londrina, Parana State, Brazil). The samples were roasted and ground to achieve a colour
similar to that of commercial selleck chemicals roasted and ground coffee, presenting a medium roast. For the adulterant study, sampling followed the simplex-centroid experimental design, represented by an equilateral triangle, with a total of 10 different compositions coded from 1 to 10. The vertices of which, corresponded to the pure matrices. The edges corresponded to the binary mixes of the same proportion; the central point – to the ternary mix with equal proportions; and the three axial points – to the proportions 4:1:1, 1:4:1, Mannose-binding protein-associated serine protease 1:1:4. All samples of arabica coffee-triticale-acai were prepared in duplicate for both systems, except for the central point, that samples were prepared in triplicate. The preparation was given by weighing different proportions of the matrices in order to always reach on a dry weight basis 0.3000 g for the analysis by HPLC–HPAEC-PAD, and 0.2000 g for the analysis by post-column derivatization reaction HPLC-UV–Vis.
In sequence, samples with the respective weights, according to each method, were hydrolyzed, by transferring to a 500 mL Erlenmeyer with screw-cap, with adding 50 mL of 1.00 mol L−1 hydrochloric acid, and by placing in a water bath thermostated at 85 °C for 180 min, stirring every 30 min manually. After, the solution was cooled down with tap water until room temperature, filtered with a blue-stripe pleated paper into a 100 mL volumetric flask that was completing up to the mark with ultrapure water. An aliquot of 10.0 mL of the solution was passed through a C18 cartridge (Sep Pak, Waters) preconditioned with methanol and water, and in a 0.22 μm nylon membrane (Millipore), collecting the filtrate in vials that were injected into the respective chromatographic systems.