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 M
A and M
B for metronidazole, T
A and T
B 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°C converted the nitroimidazole
group to a characteristic primary aromatic amine. TLC methods A and B were carried out on GF
254
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.
