Acidic virus inactivation is commonly used during production of biotherapeutic products to provide virus safety in case of undetected virus contamination. Accurate pH measurement is required to ensure the product pH reaches a virus‐inactivating level (typically 3.5–3.7), and a level post‐inactivation that is appropriate for later purification steps (typically 5.5–7.5). During batch low‐pH inactivation in discrete tanks, potentiometric glass probes are appropriate for measuring pH. During continuous inactivation for 2–3 weeks in an enclosed product stream, probe calibration drift and lag may lead to poor accuracy, and operational difficulties when compensating for drift. Monitoring the spectral response of compounds (indicators) in the product stream whose spectra are pH‐sensitive offers a possible alternative way to measure pH without these drawbacks. Such indicators can already exist in the stream (intrinsic) or can be added (extrinsic). Herein are reported studies evaluating the feasibility of both.Promising ultraviolet screening results with the two extrinsics studied, thiamine and ascorbic acid, led to the addition of both to product stream samples titrated to different potentiometric pH values in the 3.3–4.5 range (a representative range encountered during continuous inactivation), and attempts to model pH using sample ultraviolet spectra. One model, based on variability in six spectral attributes, was able to predict pH of an independent sample set within ±0.07 units at the 95% confidence level. Since a typical inactivating pH tolerance is ±0.1 units, the results show that extrinsic indicators potentially can measure inactivation pH with sufficient accuracy. Suggested future steps and an alternative approach are presented.

中文翻译：

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在连续治疗性抗体生产的低 pH 病毒灭活步骤期间光谱 pH 测量的可行性。

酸性病毒灭活通常用于生物治疗产品的生产过程中，以在未检测到病毒污染的情况下提供病毒安全。需要准确测量 pH 值以确保产品 pH 值达到病毒灭活水平（通常为 3.5-3.7），以及适合后续纯化步骤的灭活后水平（通常为 5.5-7.5）。在离散罐中的批量低 pH 灭活期间，电位计玻璃探头适用于测量 pH。在连续在封闭的产品流中失活 2-3 周，探头校准漂移和滞后可能会导致精度差，以及补偿漂移时的操作困难。监测光谱对 pH 敏感的产物流中化合物（指示物）的光谱响应提供了一种可能的替代方法来测量 pH 值而没有这些缺点。此类指标可以已经存在于流中（内部）或可以添加（外部）。这里报告了评估两者可行性的研究。 研究的两种外在物质硫胺素和抗坏血酸的有希望的紫外线筛选结果导致将这两种物质添加到滴定到 3.3-4.5 范围内不同电位 pH 值的产品流样品中（代表性的连续失活期间遇到的范围），并尝试使用样品紫外光谱模拟 pH 值。一种基于六种光谱属性可变性的模型能够在 95% 的置信水平下预测 ±0.07 个单位内的独立样本集的 pH 值。由于典型的失活 pH 耐受性为 ±0.1 单位，结果表明外在指示剂有可能以足够的准确度测量失活 pH。提出了建议的未来步骤和替代方法。