BRIEFING

 Guanidine Hydrochloride. This proposal is based on the version of the monograph official as of August 1, 2023. On the basis of comments and lab work received, it is proposed to make the following changes:

1. In the Definition and Assay, revise the Acceptance criteria from NLT 99.5% and NMT 101.0% to NLT 98.0% and NMT 102.0% to account for the performance of the proposed HPLC procedure used in the Assay.

2. Revise Identification B by replacing the UV-based spectroscopic identification test with a test for Chromatographic Identity.

3. Replace the titrimetric method in the Assay with an HPLC method. The proposed HPLC method is based on analyses performed with the Agilent Zorbax SCX 300 Å brand of column with L9 packing. The proposed method separates and detects three potential Guanidine Hydrochloride related substances. The typical retention time for guanidine is about 7.3 min.

4. Add a test for Organic Impurities based on the HPLC method in the Assay. The typical retention times for ammeline, melamine, and biguanide are about 5.5, 11.1, and 13.0 min, respectively.

5. Delete the Melting Range or Temperature test from Specific Tests. Move the information for melting range listed as acceptance criteria in the corresponding tests to the Description and Relative Solubility table appearing elsewhere in this issue of PF.

6. Add USP Melamine RS to the USP Reference Standards section.

 Additionally, minor editorial changes have been made to update the monograph to current USP style.

 (SE: S. Saladi)

 Correspondence Number—C241639