Flow injection determination of thyroxine in pharmaceutical preparations using tris(2,2′-bipyridyl)ruthenium(III)–NADH chemiluminescence detection

A flow injection (FI) method is reported for the determination of thyroxine based on its enhancement of chemiluminescence (CL) from the Ru(bpy)33+–NADH system. The calibration graph was linear over the range 2.0–10 × 10−8 mol L−1 (r2 = 0.9989) with relative standard deviations (R.S.D.) in the range 2.0–4.5% (n = 4). The limit of detection (3σ blank) was 1.0 × 10−9 mol L−1 with sample throughput of 120 h−1. The effect of some organic compounds, anions and cations were studied for l-thyroxine determination. The method was applied to pharmaceutical preparations and the results obtained were in reasonable agreement with the amount labeled. The method was statistically compared with the results obtained by RIA; no significant disagreement at 95% confidence limit was observed. A calibration graph of NADH over the range 1.3 × 10−8–1.3 × 10−6 mol L−1 was also established (r2 = 0.9992) with R.S.D. in the range1.0–3.5% (n = 4). The limit of detection (3σ) was 1.0 × 10−10 mol L−1 NADH.