Electrospray ionization mass spectrometry (ESI-MS) is widely used in drug development, therapeutic drug monitoring, and other fields. However, unstable mass spectral signals, especially during the initial stages of instrument operation, plague analysts. Generally, in quantitative experiments, the stability of response can be achieved by running the analytical system for some time. However, the equilibration time required for the responses of different compounds to stabilize has been elusive. To investigate the response stability of the ESI-MS system, 72 compounds with different physicochemical properties were employed on three systems, and flow injection analysis was performed in positive ion mode. With the use of 5.00% (response stable factor, RSF) as the stability limit, about 80% of the compounds were stable within 60 min. Under a 2.00% criterion, the stabilization time was significantly longer. The stabilization time varies with different instruments and physicochemical properties of the compounds. When positive ion detection is performed in an acidic mobile phase, the octanol–water partition coefficient (Log P), molecular weight, and molar volume can all affect the time required to stabilize the response. In general, it is necessary to balance the ESI-MS system for an appropriate time before sample detection, especially for the analysis of compounds with strong hydrophilicity, small molecular weight, or small molar volume under the conditions above.

中文翻译：

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定量分析中电喷雾电离质谱法的平衡

电喷雾电离质谱（ESI-MS）广泛应用于药物开发、治疗药物监测等领域。然而，不稳定的质谱信号，特别是在仪器操作的初始阶段，困扰着分析人员。通常，在定量实验中，通过运行分析系统一段时间可以实现响应的稳定性。然而，不同化合物的响应稳定所需的平衡时间一直难以捉摸。为了研究 ESI-MS 系统的响应稳定性，在三个系统上使用了 72 种不同理化性质的化合物，并在正离子模式下进行流动注射分析。以 5.00%（响应稳定因子，RSF）为稳定限，约 80% 的化合物在 60 分钟内稳定。2下。00% 标准，稳定时间明显更长。稳定时间因仪器的不同和化合物的理化性质而异。当在酸性流动相中进行正离子检测时，辛醇-水分配系数（LogP )、分子量和摩尔体积都会影响稳定响应所需的时间。一般来说，样品检测前需要平衡ESI-MS系统适当的时间，尤其是在上述条件下分析亲水性强、分子量小或摩尔体积小的化合物。