Analytical Sciences

Flow-Injection and Sequential-Injection Determinations of Paracetamol in Pharmaceutical Preparations Using Nitrosation Reaction

Rodjana BURAKHAM,* Supunnee DUANGTHONG,* Lop PATIMAPORNLERT,* Narong LENGHOR,* Suphaphorn KASIWAD,* Lalida SRIVICHAI,* Somchai LAPANANTNOPPAKHUN,*^,** Jaroon JAKMUNEE,*^,** and Kate GRUDPAN*^,**

*Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
**Institute for Science and Technology Research and Development, Chiang Mai University, Chiang Mai 50200, Thailand

A simple FI and two different SI systems have been investigated for the determination of paracetamol by employing a simple reagent for a nitrosation reaction. It is based on the on-line nitrosation of paracetamol with sodium nitrite in an acidic medium. The formed nitroso derivative species reacts further with sodium hydroxide to convert it to a more stable compound. The yellow product is continuously monitored at 430 nm. The FI system is very simple and cost effective for fast manual operation (60 injections/h; y = 0.268x + 44.314, r² = 0.9910 for 400 - 1000 mg/l and y = 0.1687x + 145.72, r² = 0.9970 for 1000 - 2500 mg/l). The two SI systems with different components and configurations are automated and optimized for the conditions for which no extra dilution is to be required for sample handling: one with a syringe pump and two selection valves (60 samples/h; y = 0.1488x - 4.7297, r² = 0.9946 for 400 - 1000 mg/l and y = 0.0858x + 63.933, r² = 0.9849 for 1000 - 2500 mg/l); the other is simpler and more cost-effective, with an autoburette and only one selection valve (15 samples/h; y = 0.0072x + 1.1467, r² = 0.9977 for 200 - 1000 mg/l and y = 0.0028x + 5.4699, r² = 0.9879 for 1000 - 2500 mg/l). They have all been applied to assay paracetamol in pharmaceutical preparations. The obtained results agree with those by the US Pharmacopeia method.

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