建立了一种中性红（NR）褪色光度法测定过氧化氢酶（CAT）活性的方法。称取20 g本地大白菜样品，研碎，用磷酸盐缓冲溶液（pH 7.0）定容至1 000.0 mL，取稀释液1.00 mL于50 mL容量瓶中，再加入1 mmol·L^-1 H₂O₂基质溶液5.00 mL，在25℃下进行酶催化反应15 min后，立即加入0.01 mol·L^-1酸性Fe³⁺溶液（内含0.02 mol·L^-1 H₂SO₄溶液）1.00 mL用于终止酶促反应（H₂SO₄）和催化褪色反应（Fe³⁺），再加入5×10^-4mol·L^-1 NR溶液3.00 mL，摇匀，在80℃水浴中进行褪色反应，25 min后加水定容。取适量样品溶液于1 cm比色皿中，以水为参比，于波长528 nm处测量其吸光度A。同时完成空白试验吸光度A₀测定，根据吸光度的变化ΔA（ΔA=A₀-A）确定CAT的活性（E）。结果表明：在10 min内，酶促反应符合一级动力学反应的特征，CAT活性E在0.3 U·mL^-1内与ΔA呈线性关系，检出限（3S/N）为0.006 8 U·mL^-1。对大白菜的叶、茎、根进行加标回收试验，CAT的含量依次为6.25，9.00，8.00 U·g^-1，回收率均为104%，测定值的相对标准偏差（n=6）为1.7%~3.4%。将大白菜茎部自然放置4 d后，CAT活性降至最初的30%。

A new neutral red discoloration spectrophotometry was developed for the determination of catalase activity. 20 g of local Chinese cabbage sample was taken and grinded. The mixture was made up to 1 000.0 mL with phosphate buffer solution (pH 7.0). 1.00 mL of diluent was taken and placed into a 50 mL volumetric flask in which 5.00 mL of 1 mmol·L^-1 H₂O₂ substrate solution was added, and the mixed solution enzymatically catalyzed at 25℃ for 15 min. After completing the reaction, 1.00 mL of acidic Fe³⁺ solution containing 0.02 mol·L^-1 H₂SO₄ was added to terminate the enzymatic reaction (H₂SO₄) and catalyze the fading reaction (Fe³⁺). 3.00 mL of 5×10^-4mol·L^-1 NR solution was mixed with the sample solution by shaking. The fading reaction of the mixed solution was performed in a water bath at 80℃ for 25 min. After reaction, water was used to make its volume to 50.0 mL. An appropriate amount of sample solution was taken into a 1 cm cuvette with water as the reference, and its absorbance was measured at 528 nm. The determination of the absorbance A₀ of the blank tested solution was measured by the above method, and ΔA(A₀-A) was calculated to obtain the activity E of CAT. As shown by the results, the enzymatic reaction was consistent with the characteristics of the first order reaction within 10 minutes. Catalase activity within the range of 0.3 U·mL^-1 was linearly correlated to the absorbance change ΔA, with the detection limits (3S/N) of 0.006 8 U·mL^-1. The spiked recovery test was made on the leaves, stems, and roots of the Chinese cabbage, giving determined values of 6.25, 9.00, 8.00 U·g^-1, and the recovery was found to be 104%, with RSDs (n=6) of the determined values in the range of 1.7%-3.4%. After leaving the stems of Chinese cabbage naturally for four days, the CAT activity dropped to 30% of the original content.