Multielement Analysis and Selenium Speciation in Cattle and Fish Feed using LC-ICP-QQQ

Importance of the Topic

Animal feed safety is critical under FDA and EFSA regulations to ensure trace elements like selenium are within safe limits and present in non-toxic forms. Selenium speciation is essential because its toxicity varies with chemical form.

Objectives and Overview

This study aimed to develop and validate methods for determining total selenium and its individual species in commercial cattle and fish feeds. It combines triple quadrupole ICP-MS (ICP-QQQ) for total element analysis with reversed-phase ion pairing LC-ICP-QQQ for selenium speciation.

Methods and Instrumentation

Microwave-assisted acid digestion with nitric acid and hydrogen peroxide was used for total element extraction. Enzymatic extraction with protease and lipase followed by sonication was applied for selenium species. Instrumentation included an Agilent 8800 ICP-QQQ with MassHunter software and an Agilent 1100 HPLC equipped with a C18 reverse-phase column. Calibration involved mixed standards of six selenium species.

Key Results and Discussion

Multielement analysis showed selenium concentrations above the regulatory limit of 0.3 mg/kg in all samples, ranging from 0.55 to 1.07 mg/kg. Certified reference materials yielded recoveries between 91 and 107 percent, confirming method accuracy and interference removal. Speciation revealed selenomethionine as the dominant form in both cattle and fish feeds, with inorganic selenium species present at lower levels. Extraction efficiencies ranged from 45 to 68 percent.

Benefits and Practical Uses

• The method achieves low detection limits and effective interference control, ensuring accurate quantification of total selenium and its species.
• Regulatory compliance is supported through detailed speciation, aiding feed producers and quality control laboratories.
• Optimization of selenium supplementation strategies in animal nutrition can be informed by species distribution data.

Future Trends and Applications

Advancements may include high-throughput automation, novel chromatographic separations, coupling with high-resolution mass spectrometry, and integration of data analytics to enhance speciation in diverse matrices. Expansion to other trace element speciation studies and real-time monitoring in production environments is anticipated.

Conclusion

The combined ICP-QQQ and LC-ICP-QQQ approach provides a robust, sensitive, and accurate platform for multielement analysis and selenium speciation in animal feeds, ensuring safety and informed nutritional supplementation.

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