Mesoporous substrates with ion-exchange functionalities for the removal of sugar matrices

Sugars can be present in food products as native components or as added components during production processes. From an analytical chemistry point of view, the presence of sugars can make difficult the routine safety control of food products (e.g. analysis of pesticides or other contaminants), whereas from an environmental chemistry point of view, sugars contribute to the increase of the biochemical oxygen demand (BOD) of wastewaters of food industrial processes. Analysis of contaminants in food products is usually preceded by a sample pre-treatment to eliminate matrix interference and to separate analytes of interest from other components. QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) technique is one of the most used approach in food analysis. In this technique, sugar interference is removed by d-SPE using a commercial sorbent named PSA (primary, secondary amine). The aim of this work is to prepare mesoporous substrates that can be used both as alternative sorbents to PSA in analytical chemistry applications and as adsorption substrates for the removal of sugar contribution to BOD. For this purpose, a SBA-15 substrate was functionalized with (3-aminopropyl)-triethoxysilane (APTES) and N-3-trimethoxypropylaniline. The adsorption behaviour of the synthesized sorbents was tested on three representative sugars: glucose, sucrose and fructose. The effect of initial sugar concentration (5000-350000 mg/L), of the pH (2.1-8.5) and of the solvent in which sugars are extracted (water and acetonitrile) on adsorption recovery is shown for each of the sugar molecule. The performances of the synthesized sorbents are compared with those of the commercial PSA. To quantify sugar adsorption, ion chromatography with amperometric detection was used. For both the extraction solvent tested, the best performances were obtained at pH 2.1, with a contact time of one minute: these conditions are compatible with those of the QuEChERS technique. The adsorption of sugars obtained for both the materials is 10% -30% higher than the adsorption obtained with PSA, thus suggesting a possible replacement of commercial PSA in the QuEChERS technique with the substrates proposed. To verify the performances of the substrates in food matrices analysis, we applied QuEChERS extractions on strawberries intentionally contaminated with PAHs and PCBs. After extraction, PAHs and PCBs were analysed by GC-MS. Signal-to-noise ratio and method detection limits were calculated and compared for samples treated with PSA and for samples treated with new materials synthesized. The suitability of the sorbents on the reduction of the organic load of industrial wastewaters was finally tested, simulating the typical composition of wastewater of a soft drink production process. The two proposed materials show better performance than PSA: glucose, sucrose and fructose removal was about 90% for SBA-15 functionalized with N-3-trimethoxypropylaniline, 70% for SBA-15 functionalized with APTES and 60% for PSA.