Cp2245

The chemicals were of analytical grade and utilized without further purification. H₂SO₄ (95–97%, Riedel deHaen), H₂O₂ (36%, Pharaohs Trading and Import), HCl (30%, El Salam for Chemical Industries), KMnO₄ (99%, Long live), and graphite (200 mesh, 99.99%, Alpha Aesar). Iron chloride (FeCl₃) (Sigma-Aldrich), MnSO₄·H₂O (99%, Sigma-Aldrich), NiSO₄·6H₂O (99%, Sigma-Aldrich), tri-sodium citrate (Sigma-Aldrich), tetraethylorthosilicate (TEOS) (99%, Across), ethanol absolute (Sigma-Aldrich).
Analytical balance (CP 2245, Sartorius, USA.), Hot plate stirrer (IKA, C-MAG HS7, IKA®-Werke GmbH & Co. KG, Germany), pH meter (3510, Genway), Hot plate stirrer (SB 162, Stuart, UK.), and Centrifuge, (Mikro 220R, Hettich, UK.) were used.

All samples were weighed on an analytical balance (Sartorius CP2245, Gaithersburg, USA) directly into the 25 mL Teflon flask. Then, the samples were mineralized by microwave-assisted digestion (Mars6; CEM, Matthews, USA). Initially, 4 mL of concentrated ultrapure nitric acid (HNO₃; Merck, Darmstadt, Germany) were carefully added to 200 mg of mass of each sample. After 10 minutes at room temperature, 1 mL 30% v.v⁻¹ of hydrogen peroxide (H₂O₂; Synth, São Paulo, Brazil) was added before subsequent digestion in the microwave oven. The digestion program chosen was the built-in method: power 1030–1800 W; total duration time including cooling 40 minutes; and maximum temperature 200°C. The propolis samples were placed in this category because of its texture characteristics. Afterwards, the mineralized samples were transferred into graduated centrifuge tubes and volume adjusted to 10 mL with ultrapure water (Milli Q, Millipore, Bedford, USA).

The formulated patches were characterized through weight variation, moisture content and moisture uptake by the patch. The weight of (n = 6) patches of each formulation was determined through analytical balance (Sartorius CP-2245, Gottingen, Germany).
Moisture content and moisture uptake were assessed according to the method reported by (Arora and Mukherjee 2002 (link)). The individually weighed patches were stored in activated silica containing desiccator for 24 h at room temperature. The patches were individually weighed again until constant weight was obtained. The moisture content was computed by comparing the difference between initial and final weights with final weight.
The weighed patches placed in a desiccator for 24 h at room temperature were exposed to relative humidity of 84% (a saturated solution of potassium chloride). The weight obtained by patches was determined and the moisture uptake was estimated by comparing the difference of final and initial weight with initial weight.