目的 建立并验证培尿酸酶生产工艺中聚乙二醇（polyethylene glycol，PEG）修饰率的测定方法。方法 通过半胱氨酸（Cys）浓度计算修饰率。探索吸光度和Cys浓度之间的关系，建立标准曲线和检测范围，优化显色剂的使用量和反应时间。验证方法的专属性、准确度、精密度和耐用性，并应用该方法进行样品检测。结果 Cys浓度在5～200 μmol/L范围内与吸光度呈现良好的线性关系，决定系数≥0.99。显色剂使用量10 μL，即终浓度约为0.2 mg/mL时，测得Cys浓度与理论浓度差别较小，回收率符合可接受标准。温度对检测结果影响不大，故采用室温。方法的准确度和精密度良好，准确度回收率在90%～110%之间，相对标准偏差（relative standard deviation，RSD）均＜10.0%。空白溶剂和残留PEG对检测体系无影响，专属性良好。加入显色剂后10～22 min内读板，测得Cys浓度的批间RSD为5.1%，符合可接受标准，方法耐用性良好。3个不同批次培尿酸酶样品的PEG修饰率分别为98.8%、98.4%、98.8%，批间RSD为0.2%，修饰率高且批间差异小，结果符合质量要求。结论 成功建立了培尿酸酶生产工艺中PEG修饰率的分光光度法检测方法，该方法具有良好的线性、专属性、精密度、准确度和耐用性。

Objective To establish and verify a determination method for the modification rate of polyethylene glycol (PEG) in the production process of PEG-uricase. Methods PEG modification rate was calculated by cysteine (Cys) concentration.The relationship between absorbance and Cys concentration was explored. The standard curve and measurement range were established. The amount of chromogenic agent and reaction time were optimized. The specificity， precision， accuracy， and durability of the method were verified. The method was applied for sample detection. Results Cys concentration and absorbance showed a good linear relationship in the range of 5-200 μmol/L,with coefficent of determination ≥0.99. When the dosage of the chromogenic agent was 10 μL (resulting in a final concentration of approximately 0.2 mg/mL), the Cys concentration was close to the theoretical concentration, and the recovery rate met the acceptable criteria. Temperature had little effect on the results, so room temperature was recommended. The method showed good precision and accuracy. The recovery rate for accuracy was between 90% and 110%, and all relative standard deviations (RSDs) values were less than 10.0%. Blank solvent and residual PEG had no effect on the detection system, indicating good specificity. When plate was read within 10-22 min after adding the chromogenic agent, the inter-batch RSD of Cys concentration was 5.1%, which met the acceptable criteria, indicating good durability of the method. The PEG modification rates of uricase samples from 3 different batches were 98.8%, 98.4% and 98.8%, respectively, and the RSD among batches was 0.2%. The difference among batches was small and the results met the quality requirements.Conclusions A spectrophotometric method for the determination of PEG modification rate of uricase in PEG-uricase production process is established. This method possesses good linearity, specificity, precision, accuracy, and durability.