用液质联用仪通过柱后添加二价金属盐的方法对环孢素 A 与异环孢素 A 进行区分。
Differentiation of cyclosporin A from isocyclosporin A by liquid chromatography/electrospray ionization mass spectrometry with post-column addition of divalent metal salt.
机构信息
Departamento de Química Orgánica, UMyMFOR-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 3° piso, C1428EHA, Buenos Aires, Argentina.
出版信息
Rapid Commun Mass Spectrom. 2014 Mar 15;28(5):465-70. doi: 10.1002/rcm.6805.
RATIONALE
Cyclosporin A (CsA) rearranges to its isomer isocyclosporin A (isoCsA) upon acid hydrolysis and also during ionization in the ion source of the mass spectrometer. It has been reported that both compounds could not be differentiated by tandem mass spectrometry (MS/MS) using atmospheric pressure ionization (API) sources and ambiguously differentiated by using other sources. In order to analyze these compounds which are common fungal metabolites, it is relevant to develop a simple method for their differentiation.
METHODS
CsA and isoCsA were analyzed by liquid chromatography/mass spectrometry (LC/MS) with post-column addition of metal ion solutions in a quadrupole time-of-flight instrument equipped with an electrospray ionization (ESI) source.
RESULTS
Mass spectra of CsA obtained upon post-column addition of solutions of Ca(II), Cu(II) and Zn(II) showed complexes between cyclosporin and the metal, including 2CsA + Me and CsA-H + Me. These complexes were not observed in the spectra of isoCsA. The same results were observed at different metal concentrations.
CONCLUSIONS
Differentiation via metal complexation in positive ion mode LC/ESI-MS was performed to simultaneously distinguish CsA and its isomer isoCsA.
原理
环孢素 A（CsA）在酸水解时会发生异构化，转化为异环孢素 A（isoCsA），同时在质谱仪的离子源中也会发生离子化。据报道，这两种化合物都不能通过大气压电离（API）源的串联质谱（MS/MS）进行区分，而通过其他源则可以模糊地区分。为了分析这些常见的真菌代谢产物，开发一种简单的方法来区分它们是很重要的。
方法
使用配备电喷雾电离（ESI）源的四极杆飞行时间仪器，通过柱后添加金属离子溶液的方法，对 CsA 和 isoCsA 进行液相色谱/质谱（LC/MS）分析。
结果
在柱后添加 Ca(II)、Cu(II)和 Zn(II)溶液后，CsA 的质谱显示出环孢素与金属之间的复合物，包括2CsA + Me和CsA-H + Me。这些复合物在 isoCsA 的光谱中没有观察到。在不同的金属浓度下也观察到了相同的结果。
结论
通过正离子模式 LC/ESI-MS 中的金属络合作用进行区分，可以同时区分 CsA 和其异构体 isoCsA。
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