Microwave-assisted microscale acid decomposition for determination of essential elements in processed meats by MIP OES

Abstract

In this work, a method of acid micro decomposition using a domestic microwave was proposed, which has low acquisition cost and easy operation. The objective was to determine Ca, Cu, Fe, K, Mg, Na and Zn in processed meat samples using the Microwave-Induced Plasma Optical Emission Spectrometry (MIP OES) technique. To increase the analytical frequency, a power mapping was carried out inside the microwave, allowing the decomposition of 6 samples simultaneously. The optimized method consisted of weighing 40 mg of the sample in PTFE tubes and adding 400 μL of concentrated HNO₃. The tubes were sealed and placed inside the domestic microwave in previously evaluated positions according to the power distribution inside and subjected to radiation for 3 min at power level 7 (equivalent to 440 W). Then, the resulting solution was diluted to 5 mL with deionized water. The method showed good linearity (R² > 0.99) for all analytes. The detection limit of the method was 0.27, 0.17, 0.33, 0.13, 0.59, 0.86 and 0.25 mg kg⁻¹ for Ca, Cu, Fe, K, Mg, Na and Zn, respectively. Accuracy was evaluated using certified reference materials, Meat Homogenate (NIST - 1546) for Ca, K, Mg and Na, obtaining agreement of 81–118%, and TORT-2 (NRC - CNRC) for Cu, Fe, and Zn, with agreement of 86–103% with certified values. The optimized method was applied to samples of sausage, pate, frozen hamburger, breaded steak, salami, mortadella, ham and turkey breast.