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
- Cystine
- Glycine
- Histidine*
- Histidine hydrochloride monohydrate
- Isoleucine
- Leucine
- Lysine hydrochloride
- Phenylalanine
- Proline
- Threonine
- Tryptophan
*Note that verification has been performed on the salt/hydrated forms but is inferred on the base/anhydrous forms due to dissociation in solution
We are currently working on verifying Cysteine Hydrochloride and hope to complete this soon, so please enquire. We would also value enquiries about Lycine acetate, Magnesium aspartate dihydrate, Serine Tyrosine and Valine, as we intend to verify these in the near future. We also know 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.
