AOAC SPIFAN Nutrients ERP (December 7, 2022)

Fluor-06 (SLV) 10-2022 FOR ERP USE ONLY DO NOT DISTRIBUTE

Figure 4. Overlay plot of chromatograms of infant formula sample SRM1869 containing fluoride at a level of 1.0 mg/kg (blue) and an analytical standard of 1.0 µg fluoride/vial (red).

In most samples analysed routinely the TMFS peak elutes as a single peak without any co-eluting compounds. On rare occasions some samples show extra peaks. These peaks are usually nearly baseline separated (Figure 5) and in those cases a vertical marker is used to determine the peak area. To ensure that these are not fluoride related and better understand the composition of the sample, some GC-mass spectrometry experiments where performed (GC-MS) to identify these compounds (Figure 6). The largest peaks in the overall chromatogram are byproduct of the derivatizing agent. The inset shows the enlarged range where TMFS elutes. Some of the compounds eluting in the same area were dichloromethane, acetone, furan, propanal and pentane.

Figure 5. GC-FID chromatogram showing the peaks in occasional samples that elute close to the TMFS peak.

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