Inhibition kinetic determination of trace amount of iodide by the spectrophotometric method with rhodamine B

Trace iodide was determined by inhibition kinetic method, which based on its inhibition effects on the reaction between rhodamine B (RhB) and KBrO3 in H2SO4 medium in 45 ± 0.5 °C for 15 min. The signal difference (ΔA, ΔF) between inhibited reaction and non-inhibited reaction is linear with the concentration of iodide. The linear range were 2.0–6.0 and 1.0–6.0 ng mL−1 and the detection limit were 0.06 and 0.07 ng mL−1, respectively. The method has been applied satisfactorily to the determination of iodide in kelp.