The efficacy of microwave digestion followed by ICP-MS/AAS for heavy metal quantification in imported food commodities: A systematic review of methodological approaches and U.S. regulatory compliance

Toxic heavy metals in the environment can accumulate in food and cause a serious health risk when consumed. Microwave-assisted acid digestion (MAD) is commonly used for preparing food samples for analysis by inductively coupled plasma–mass spectrometry (ICP-MS) or atomic absorption spectroscopy (AAS). These methods enable accurate detection of elements such as arsenic, cadmium, lead, and mercury, ensuring compliance with food safety regulations and protecting public health. This review examines the effectiveness of microwave digestion across various food matrices commonly imported. It also discusses the advantages and disadvantages of ICP-MS, AAS techniques, quality control, and validation procedures. It outlines how current U.S. regulatory frameworks and guidance incorporate these methods for import compliance. Microwave-assisted digestion coupled with ICP-MS gives a detailed elemental coverage and the lowest detection limits for regulatory screening. AAS (flame or graphite furnace) is a practical alternative for laboratories with limited expenses when ICP-MS is not available. Both methods require strict quality control, which includes matrix-matched certified reference materials, spikes, and blanks. The methods also require complete digestion verification and careful handling of spectral interferences to comply with US monitoring standards. The review highlighted that MAD showed excellent completeness of digestion, reduced sample preparation time, and minimized contamination risk compared to conventional open-vessel methods.  ICP-MS remains the analytical benchmark due to its multi-element capability and its sub-ppb level sensitivity, while AAS (particularly GFAAS) continues to be a suitable low-cost alternative in laboratories with limited resources.