Butterworth Laboratories has been undertaking Ninhydrin-Positive Substances (NPSs) analysis to the Ph.Eur general monograph 2.2.56. Method 1 since it was first published, having previously performed testing using TLC that was originally detailed within the individual monographs. In addition to the analysis of NPSs, the method also covers the limit test for ammonium.
We originally used an HPLC system with post-column derivatisation but have since moved to a dedicated amino acid analyser (a Hitachi LA8080). To date, using our Amino Acid Analyser, we have verified our capability to perform the monograph testing on the following amino acids (which include their base and anhydrous forms and optical isomers):
- Alanine
- Arginine
- Arginine hydrochloride
- Aspartic Acid
- Glycine
- Histidine
- Histidine hydrochloride monohydrate
- Isoleucine
- Leucine
- Lysine hydrochloride
- Phenylalanine
- Proline
- Tryptophan
We have plans to verify Threonine, Cystine and Cysteine Hydrochloride and hope to complete these in Q1 2024. We are also aware that the same technique can be applied to the Related Substances of Amino Acids in the JP, where we have successfully qualified Alanine and performed similar related substances tests in other amino acids, such as Glutamic acid.
If you have any questions on this Ninhydrin-Positive Testing or would like to discuss the testing of materials not listed etc., please click here
