Determination of l-thyroxine in pharmaceutical preparations by flow injection analysis with chemiluminescence detection based on the enhancement of the luminol–KMnO4 reaction in a micellar medium

• Flow injection technique coupled with a novel CL system was developed.
• The CL system was luminol–KMnO4 in CTMAB surfactant micelles.
• l-Thyroxine has great signal enhancement on the CL system sensitized by CTMAB.
• The method was applied for the detection of l-thyroxine in commercial tablets.

A novel flow injection chemiluminescence (CL) method for the determination of l-thyroxine in the presence of cethyltrimethylammonium bromide (CTMAB) surfactant micelles is developed. The method is based on the significant signal enhancement of l-thyroxine on the luminol–KMnO4 system in alkaline solution sensitized by CTMAB. Parameters affecting the reproducibility and CL detection were optimized systematically. Under the optimum conditions, the net CL intensity versus l-thyroxine concentration was linear in the range of 5.0 × 10−8–3.0 × 10−6 mol/L with the detection limit of 8.9 × 10−9 mol/L. The sample throughput is calculated to be 140 samples/h and the relative standard deviations (RSDs) for 13 replicate determination of 1.0 × 10−6l-thyroxine is 1.1%. The proposed method was successfully applied for the determination of l-thyroxine in pharmaceutical preparations with satisfactory recoveries in the range of 93.9–105.2%. This rapid, sensitive, and high throughput method would provide a new tool for l-thyroxine analysis.

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