Characterization of Carnauba Wax Inorganic Content

In this work the analysis of inorganic elements (Al, Ca, Cu, Fe, K, Mg, Mn, Na and Zn) in different types of carnauba waxes (types 1, 3 and 4) was implemented. The Box‐Behnken experimental design was used to optimize the digestion of the carnauba wax sample using a microwave‐assisted approach. The following parameters were evaluated: microwave power applied (600–1,000 W), time of microwave power application (5–20 min) and nitric acid volume (1–4 mL). The residual carbon content (%RCC) was measured by ICP OES (inductively coupled plasma optical emission spectrometry) to evaluate the efficiency of the digestion. The %RCC values in all of the experiments were below 16 %. The best conditions for carnauba wax digestion were found: 800 W applied power for 15 min using 2.5 mL of HNO₃. In these conditions the %RCC was lower than 4 %. The amounts of Al, Ca, Cu, Fe, K, Mg, Mn, Na and Zn in these samples were determined by ICP OES. The average contents of Al, Ca, Fe and K found in the carnauba wax type 1 were 28.6 ± 1.5, 33.8 ± 2.8, 18.5 ± 1.1 and 37.2 ± 2.5 mg kg^?1, respectively. For carnauba wax types 3 and 4 larger amounts were found. The principal components analysis (PCA) showed three groups of carnauba wax with the first two principal components.