电喷雾/飞行时间质谱法测定红霉素类抗生素的准 确质量

研究了聚乙二醇(PEG)为内标物的电喷雾(ESI)/飞行时间质谱(TOF-MS)准确质量测定方法，并应用于5个红霉类类抗生素质子化分子离子(MH^+)的质量测定。与理论值相比，相对误差均在5×10^-^6以内。PEG可与K^+，Na^+，H^+等形成三种加合离子形式，通过选择适当的实验条件，控制PEG仅以其中的一种加合离子形式出现，这一特点扩大了其应用范围，使之可作为一种普适性的内标物。另外讨论了扫描质量范围、扫描速度等因素对测定结果的影响，并且比较了采用多峰校正法和两峰校正法的结果。结果表明，以PEG为内标的ESI/TOF质谱法可对不稳定碱性化合物的化分子离子(MH^+)进行准确质量测定，而且简便、快速。

Determination of the accurate mass of erythromycin analogue antibiotic by electrospray ionization/time-of-flight mass spectrometry

Using polyethylene glycol (PEG) as internal reference, electrospray ionization (ESI)/time-of-flight mass spectrometry (TOF-MS) was developed to determine the accurate mass of the protonated molecular ions of five erythromycin analogue antibiotics. Compared with the theoretical values, all relative errors were less than 5×10^-^6. PEG can form three adduct ions with K^+, Na^+, H^+, respectively, and may appear with single kind of adduct ions in suitable experiment conditions. PEG was recommended as a general internal reference compound. Besides, two-peak calibration is preferred to the multi- peak calibration. Scan mass width and scan speed were also studied, 104～144amu 5 seconds was recommedned. Using polyethylene glycol(PEG) as internal reference, ESI/TOF mass spectrometry can determine the accurate mass of the protonated molecular ions of the unsteady basic compounds. This method is simple and expeditious.