Reversed-phase high-performance liquid chromatography, coupled with coulometric electrochemical detection, was successfully applied for the quantification of added folic acid (FA) in fortified fruit juices and cereal products. The method allowed good separation of the 5-HCO-H4 folate and folic acid in cereal samples. The retention times of vitamins were repeatedly determined by isocratic elution using 40 mM sodium phosphate dibasic, heptahydrate buffer, and 8% acetonitrile (v/v) (0.9 mL/min, pH 5.5) as mobile phase with the Supelco LC 18 column 5 μm (25 cm × 4.6 mm). Folate concentrations were measured using a trienzyme (hog kidney folate conjugase, α-amylase, and protease) folate extraction method.
A gold(III)-imprinted thiocyanato-functionalized silica network of type SBA-15 was prepared by co-condensation of tetraethoxysilane (TEOS) with thiocyanatopropyltriethoxysilane (TCTES) in the presence of Pluronic123 and Au(III) ions. Compared to the non-imprinted material, the imprint has a higher selectivity and adsorption capacity for Au(III). The maximum static adsorption capacity for Au(III) is 475 mg·g−1 for the ion-imprinted, and 62 mg·g−1 for the non-imprinted sorbent. The imprint was applied to the sorption of Au(III) from digested geological samples prior to its determination by graphite furnace atomic absorption spectrometry. Adsorption is fast and does not substantially prolong the analytical procedure. Under optimum conditions, the detection limit for Au(III) is 2 ng·g−1. The method was validated by analyzing certified reference materials, and results were in good agreement with certified values. The procedure was successfully applied to the separation and determination of gold in complex geological samples.
Graphical abstractSchematic presentation of the preparation of ion-imprinted thiocyanato-functionalized mesoporous silica and its application for the preconcentration of gold from digested soils before its determination by slurry sampling graphite furnace atomic absorption spectrometry (GF AAS).
Electronic supplementary materialThe online version of this article (10.1007/s00604-018-3106-x) contains supplementary material, which is available to authorized users.
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