Our regulations at §§？101.100（a）（4） and 130.9（a） specify the analytical method that FDA uses for determining sulfite concentrations in food. Both of these regulations establish the method of analysis in two steps. The first step incorporates by reference §§？20.123-20.125, “Total Sulfurous Acid,” in “Official Methods of Analysis of the Association of Official Analytical Chemists,” 14th Ed. （1984）； this method is known as the Monier-Williams method. The second step refines the Start Printed Page 48812Monier-Williams method to improve accuracy and reproducibility and make the method suitable for detecting sulfite concentrations as low as 10 ppm; the modifications are included in Appendix A to Part 101. Collectively, the Monier-Williams method with the Appendix A to Part 101 modifications is referred to as the “optimized Monier-Williams method.” After we incorporated by reference the Monier-Williams method and implemented the modifications to that method in Appendix A to Part 101, the AOAC amended the Official Methods of Analysis to include “Official Method 990.28, Optimized Monier-Williams Method,” which is the same as the two-step process in FDA's regulations; i.e, the Monier-Williams method and the refinements to the Monier-Williams method in Appendix A to Part 101. As such, this portion of the proposed rule would modernize our regulations to reflect the citation to the current AOAC method for determining sulfite concentrations in food, but would not result in a change in FDA methodology. We are, therefore, proposing to amend §§？101.100（a）（4） and 130.9（a） to replac the existing incorporation by reference with “AOAC Official Method 990.28, Sulfites in Foods, Optimized Monier-Williams Method,” （Final Action 1994）， Section 47.3.43, Official Methods of Analysis of AOAC INTERNATIONAL, 21st Edition （2019）， and to remove Appendix A to Part 101.