Determinación de metales en propóleo y sus extractos etanólicos por espectrometría de emisión atómica con plasma de microondas

Abstract

Propolis is a bee product made by worker bees from various parts of the plants. Bees use it to seal their honeycomb, avoid microbial contamination, etc. Its complex chemical composition gives it beneficial properties and is used for medicinal, therapeutic and nutritional purposes. Propolis is used in crude form and as ethanolic extracts (tinctures). It is necessary to develop adequate methods to know the amount of essential and contaminants elements in propolis and tinctures. The existing methods are based on expensive, risky and/or restricted techniques to the use of specialized equipment. In addition, it is important to have studies of Mexican propolis, since it represents an area of diversification for national beekeepers. An innovative, simple, safe and fast alternative for the routine analysis of crude propolis and tinctures is Microwave Plasma Atomic Emission Spectrometry (MP-AES). In this work was developed and validated a methodology, based on MP-AES, to determine concentration of Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Se, Sr and Zn in raw propolis, tincture and solid residue. The method was selective, sensitive, precise and accurate for most of the elements, and was applied in analysis of 23 commercial propolis tinctures. It was observed that transfer of propolis elements to the tincture was poor. Content of the commercial tinctures was similar to the control tincture. Effect of ethanol content on slope and intercept of calibration curves was evaluated, and a method for determining the ethanol content was developed and validated. The method was applied to the 23 commercial tinctures. Ethanol (up to 80% v/v) increased sensitivity and decreased limits of detection and quantification. The calibration curves with 70, 80 and 90% ethanol did not differ significantly. Average ethanol content in the commercial tinctures was 80% v/v