Elemental Analysis of Propolis Tinctures by Microwave Plasma – Atomic Emission Spectrometry (MP-AES)

Abstract

Propolis tinctures are popular alternative medicines, but mandatory labeling requirements relating to the inorganic content or percentage of ethanol are absent. Knowing the elemental content is useful for quality assurance/quality control of the tinctures between batches, as well as the safety of the products for consumers. Microwave plasma – atomic emission spectrometry (MP-AES) is a relatively low-cost, robust, multielemental technique that can analyze ethanolic extracts of propolis following minimum sample preparation. However, there are no published papers using MP-AES for this application. The technique was evaluated for the determination of sixteen elements in lab-made preparations and in 23 products from markets in Mexico. The matrix effects of the ethanol content of the samples were also evaluated and were found to affect the detection limit of some elements. There was high variability in the elemental composition of the major (K, Fe, Mg, and Na) and minor (Al, Cd, Co, Cr, Cu, Mn, Ni, and Zn) elements among the samples. The median concentrations of cadmium, and lead in the propolis tinctures were below 0.28 µg·L⁻¹ and 2.8 µg·L⁻¹, respectively.

Keywords:

• Elemental profile
• ethanolic extracts
• microwave plasma – atomic emission spectrometry
• MP-AES
• propolis
• tinctures

Acknowledgments

The authors would like to thank National Council of Science and Technology (CONACyT) for supporting Patricia Vázquez-Quintal in her master studies at the Autonomous University of Yucatan (UADY). We also thank Mariela Lope Navarrete for his valuable assistance during the experimental part of this work.

Conflicts of interest

The authors have no competing interests relevant to the content of this article.

Authors’ contributions

Conceptualization: David Muñoz-Rodríguez; Methodology: David Muñoz-Rodríguez, Jesús Barrón-Zambrano, Yolanda Moguel-Ordóñez,; Formal analysis and investigation: Patricia Vazquez-Quintal, Salvador Medina-Peralta; Writing - original draft preparation, visualization, and validation: Patricia Vazquez-Quintal; Writing - review and editing: David Muñoz-Rodríguez, Jenny Nelson; Resources: David Muñoz-Rodríguez, Jesús Barrón-Zambrano, Yolanda Moguel-Ordóñez; Supervision: David Muñoz-Rodríguez, Jesús Barrón-Zambrano

Additional information

Funding

No funding was received for conducting this study.