AOAC SPIFAN Nutrients ERP Method Reviews (September 7, 2019)

FOR EXPERT REVIEW PANEL USE ONLY NOT FOR DISTRIBUTION

Expert Review Panel for Infant Formula and Adult Nutrition Evaluation of Method Fluor-03

Title: Determination of Fluoride in Infant and Adult/Pediatric Nutritional Formula by Ion Chromatography with sequentially suppressed conductivity detection Authors: Theresa Steurer, Dr Elke Suess, Dr Christian Emmenegger, Dr Michael Klein, Dr Hari Narayanan Reviewer Name: Reviewer 1 Summary of Method: This method determines the quantity of fluoride by ion chromatography with sequential suppression conductivity detection. Fluoride is extracted from the sample into water. Inline dialysis is used to extend column lifetime and sequential suppression with a dose-in gradient is used to increase sensitivity by removing matrix interferences. The chromatographic peak height for fluoride in the sample is compared to a calibration curve prepared in water to determine the concentration. Method Scope/Applicability: Quantitation of dissolved fluoride in infant, pediatric, and adult nutritional formulas. Demonstrated performance in powders and ready-to-feed liquids. General comments about the method: This method was reviewed in a general sense by the Nutrients ERP in March 2019. Several recommendations were made to the method authors, and additional information and experimental results were included in the write up. Method Clarity: Overall the method is written clearly and easy to follow. Pros/Strengths: • Sample preparation approach is simple, involving extraction into water with vortexing. • Option provided for use of dialysis to extend column lifetime. Cons/Weaknesses • The peak resolution and shape in the samples is significantly different than in the calibrants, and the authors recommend using a horizontal baseline with peak height approach for integration. This approach could become problematic during MLT with inexperienced users. However, we have observed similar types of chromatographic challenges when analyzing infant formula for fluoride by a similar approach. • The instrument set up seems complex and finding laboratories to participate in an MLT using this or similar equipment may pose a challenge. Supporting Data • General Comment: The method authors made an attempt to utilize all SPIFAN matrices, including 12 that contained measurable levels of fluoride and 7 that did not. All samples were used for spike recovery studies to demonstrate performance in the broad range of matrices.

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