Iodine determination in animal feed by inductively coupled plasma mass spectrometry – results of a collaborative study

ABSTRACT

A collaborative study was conducted in order to fully validate the performance characteristics and to evaluate the suitability of a method for determination of iodine in animal feed. The method consists of an alkaline extraction in tetramethylammonium hydroxide (TMAH) solution followed by the determination of iodine by inductively coupled plasma-mass spectrometry (ICP-MS). The method was validated for different types of feed and feed materials with a broad concentration range of 0.65–622 mg I/kg. Good agreement was found between the overall mean mass fraction values from the collaborative trial (13.8 ± 1.3 mg I/kg and 0.657 ± 0.228 mg I/kg) and the values previously determined in proficiency tests for two of the test materials (12.65 ± 2.47 mg I/kg and 0.72 ± 0.22 mg I/kg) indicating satisfactory accuracy of the method. Reproducibility standard deviations were between 7.85% and 34.65% and the HorRat values were under the acceptable limit of 2 so the between-laboratory precision was considered acceptable. Based on the statistical evaluation of the results it was concluded that the method is suitable for its intended purpose; it has been accepted as European Standard EN17050:2017 by the European Committee for Standardisation (CEN).

KEYWORDS:

• Animal feed
• iodine
• ICP-MS
• collaborative study
• performance characteristics

Acknowledgments

The authors thank Ms Marianne Hansen, Mrs Annette Landin, and Mrs Birgitte Koch Herbst (DTU Food) for their skilfully conducted practical work with the characterisation of test materials as well as preparation and shipping of test materials to the participants. All the participating laboratories are thanked for their voluntary participation in the collaborative study, for their production of important results, and for their useful comments on the method description. The members of the CEN TC327/WG4 expert group are thanked for their constructive comments and encouragement during the project.

Disclosure statement

No potential competing interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by the European Committee for Standardisation (CEN).