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The chemical degradation of phenylmercuric nitrate by disodium edetate during heat sterilization at pH values commonly encountered in ophthalmic products
Author(s) -
Parkin J. E.,
Duffy M. B.,
Loo C. N.
Publication year - 1992
Publication title -
journal of clinical pharmacy and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.622
H-Index - 73
eISSN - 1365-2710
pISSN - 0269-4727
DOI - 10.1111/j.1365-2710.1992.tb01309.x
Subject(s) - chemistry , high performance liquid chromatography , sterilization (economics) , nuclear chemistry , diluent , atomic absorption spectroscopy , benzene , chemical stability , nitrate , chromatography , diethylamine , organic chemistry , physics , quantum mechanics , monetary economics , economics , foreign exchange market , foreign exchange
SUMMARY The stability following heat sterilization (121°C for 15 min) of phenylmercuric (PM) nitrate in the presence of disodium edetate at pH values 5–8 has been investigated by both high‐performance liquid chromatography (HPLC) and atomic absorption spectroscopy (AAS). A stability‐indicating HPLC method involving formation of the diethylamine‐dithiocarbamate complexes of phenylmercuric and mercuric ions was found to suffer a pH‐dependent interference from disodium edetate. A second method was therefore also employed involving selective extraction into diethylether of the phenylmercuric ion followed by HPLC of the piperidinedithiocarbamate complex with concomitant analysis of the unextracted mercuric ion by AAS using the cold‐vapour technique. An HPLC method was also developed for benzene in the degraded mixtures. The application of these methods to autoclaved solutions containing PM nitrate and disodium edetate demonstrates that under the conditions of heat sterilization the phenylmercuric ion is degraded to mercuric ion and benzene to the extent of 15% at pH 8, 80% at pH 7 and completely degraded at pH 5 and 6.