A 0.1 M sodium carbonate buffer was prepared and the pH was adjusted to 10.2. Stock luminol solution was prepared as described by Perez and Rubio (2006) by dissolving 11.5 mg luminol in 10 ml sodium carbonate buffer. Stock cobalt chloride was prepared by dissolving 7.14 mg in 10 ml sodium carbonate buffer. 5% TCA was prepared in water. A 50 U catalase solution was prepared in water. A stock mixed reagent was prepared by diluting 10 ml of the stock luminal and 2 ml of the cobalt chloride in 100 ml sodium carbonate buffer. This solution was stored at 4 8C in the dark for at least 1 h,
diluted 10 times with buffer and stored at 4 8C in the dark for approximately 18 h before use. A stock solution of H2O2 standard was prepared by diluting 10 ml of the H2O2 (30%, w/w) in 1.0 ml 5% TCA. A series of standards were prepared from the stock ranging from 0.00677–0.10170 nmol H2O2 in 5% TCA. A full set of standards was run with each set of samples.