Development of a Rapid Chemical Identification System (RCIS) for the Detection of Fraudulently Labelled 5-nitroimidazole Products
Purpose: A simple, reliable and rapid chemical identification system (RCIS) consisting of three colour reactions based on the functional groups in the molecule and two TLC methods was developed for preliminary detection of the 5–nitroimidazole drugs.
Methods: Three members of this group of drugs (tablet form) available in the Nigerian market and labelled MA and MB for metronidazole, T A and TB for tinidazole and S for secnidazole, were used. The extraction of the active ingredient from the solid dosage form was performed using acetone. The reaction of the extracted drug with zinc and 1M hydrochloric acid at 100 oC converted the nitroimidazole group to a characteristic primary aromatic amine. TLC methods A and B were carried out on GF254 plates (5cm x 10cm) to further identify the individual members of the group. TLC method A with mobile phase consisting of acetone, ethyl acetate and ammonia (100:5:1) and method B with mobile phase consisting of acetone, chloroform and ammonia (100:15:1) were developed for the identification.
Results: The aromatic character of 5-nitroimidazole was highlighted in nitric acid when combined with sulphuric acid resulting in an orange colour. 40% sodium hydroxide gave the alkali-induced characteristic orange colour of aromatic amino compounds. All the samples of the various brands gave characteristic colours that distinguished the compounds of the 5-nitroimidazole group as primary or secondary nitroimidazole compounds.
Conclusion: Using the developed method, fraudulently labelled product 5-nitroimidazole antiprotozoal and antibacterial agents can now be detected in approx. 40 min with limited reagents and a simple TLC
technique. The method is rugged, simple, and should be particularly handy for use in detecting substandard products of the drug in the drug distribution chain where sophisticated equipment are often not available.
Keywords: 5–nitroimidazole; Fraudulently labeled; Chemical identification system; Antiprotozoal; Antibacterial.
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