Optimization of the suspension procedure by Box-Behnken design for the determination of manganese, iron, and zinc in zeolite clinoptilolite with the TXRF system and insight into its antioxidant properties.

Zeolites are a large family of minerals and the most studied is the naturally occurring clinoptilolite. They possess anti-inflammatory, antioxidant, and detoxifying properties which makes them valuable for medicinal use. Element analysis of zeolite's composition is necessary for its precise chemical characterization, and within this work development of a suspension method for the determination of manga nese, iron, and zinc by total reflection X-ray fluorescence spec-trometry (TXRF) was presented. The Box-Behnken design based on the response surface methodology was applied to determine the optimal sample preparation conditions. The significant variables such as sample amount, volume deposition, and dispersant were selected as critical variables. Based on the results obtained, sample suspensions were prepared by weighing 10 mg of the sample and adding 1 mL of 5 % Triton X-100 with 10 mL Ga as internal standard and deposition volume was set at 10 mL. The results obtained with TXRF were comparable with those obtained with the FAAS method, indicating that this technique can be used instead of the conventional methods. Using the best analytical conditions, the limits of detection for trace elements were in the range of 0.2-0.6 mg kg^-1. Trueness and precision of the results, evaluated by CRM sample analysis, were in most cases acceptable with recoveries values in the range of 104.9-111.4 % and relative standard deviations of 2-10 % (. = 6). Zeolites showed no ability to quench free radicals nor the ability to influence dietary antioxidants.