Evaluation of Dietary Supplement Contamination by Xenobiotic and Essential Elements Using Microwave-Enhanced Sample Digestion and Inductively Coupled Plasma-Mass Spectrometry

ABSTRACT

Dietary supplements were analyzed by evaluating the elemental content in six widely consumed products manufactured by four well-known companies. The elements included the neurotoxic and carcinogenic elements cadmium, mercury, aluminum, lead, arsenic, and antimony, as well as the essential elements zinc, selenium, chromium, iron, and copper, which were often not listed as ingredients on the product labels. Contamination from either xenobiotic or essential elements was found in all samples analyzed. The samples were prepared using US Environmental Protection Agency (EPA) Method 3052, microwave-enhanced digestion. The resulting digests were analyzed by Inductively Coupled Plasma-Mass Spectrometry based on EPA Method 6020B. The analytical protocols were validated by analyzing a multivitamin standard reference material, the National Institute of Standards and Technology Standard Reference Material 3280. The application of EPA standard methods demonstrated their utility in making accurate and precise measurements in complex matrices with multiple ingredients and excipients. In the future, the use of these methods could provide a uniform quality assurance protocol that can be implemented along with other industry guidelines to improve the production of dietary supplements.

KEYWORDS. :

• dietary supplements
• elemental contamination
• EPA Method 3052
• EPA Method 6020B
• inductively coupled plasma-mass spectrometry
• microwave-enhanced digestion

ACKNOWLEDGMENTS

The authors would like to acknowledge Dr. Gerra Bosco for her assistance in the preparation of this manuscript. Dan Bodnar, Dave Hardesty, Lance Crosby, and Ben Lauterbach were responsible for instrument maintenance. Duquesne University and Applied Isotope Technologies (AIT) supplied the resources to perform the study. The authors thank Agilent Technologies and Milestone for instrumentation support.

ABOUT THE AUTHORS

Dr. Zinn received his Ph.D. in Analytical Chemistry from Duquesne University in 2014. His dissertation focused on the evaluation and assessment of autism spectrum disorders through the application of mass spectrometric measurement techniques. Dr. Rahman is a senior chemist at BASF. He previously worked as the R&D Manager at AIT where he developed and performed both elemental and speciation methods using ICP-MS. Dr. Faber is a developmental pediatrician who works at The Children.s Institute of Pittsburgh. He provides outpatient services for children with severe developmental and behavioral disorders along with conducting clinical research involving children with autism spectrum disorders. Dr. Wolle is a Research Fellow at the US Food and Drug Administration. He previously worked as Post-Doctoral Fellow at Duquesne University during which he worked to develop speciation methods using ICP-MS. Mr. Pamuku is the CEO of AIT, a company that provides elemental, speciation, and molecular measurement solutions using advanced measurement techniques. Dr. Kingston is a Professor of Analytical Chemistry at Duquesne University in the Department of Chemistry and Biochemistry. His research focuses on the development and application of mass spectrometric methods in environmental human health, most notably Speciated Isotope Dilution Mass Spectrometry.