血清脂质组学研究中多重离子化液相色谱-质谱方法的比较

系统地比较了3种常用的离子化技术电喷雾电离(ESI)、大气压化学电离(APCI)、大气压光致电离(APPI)对脂类化合物的离子化效率、检测灵敏度和覆盖范围,以探讨多重离子化液相色谱-质谱(LC-MS)方法在血清脂质组学研究中的适用性.血清样本经甲基叔丁基醚萃取后,采用Ascentiss Express C8 色谱柱(150 mm×2.1 mm, 2.7 μm)和二元线性梯度洗脱分离,流动相(A)为乙腈-水(3∶2, V/V, 含0.1%甲酸, 10 mmol/L甲酸铵),B为异丙醇-乙腈(9∶1, V/V, 含0.1%甲酸,10 mmol/L甲酸铵),分别采用ESI、APCI和APPI离子源正、负离子模式进行质谱检测.结果表明,ESI离子源对脂肪酸类、甘油脂类、甘油磷脂类化合物、鞘磷脂类化合物的离子化效率最高,对异戊烯醇脂类化合物的离子化效率与APPI离子源相当,APPI离子源对胆固醇(酯)类化合物的检测灵敏度最高,APCI离子源对各类化合物的检测灵敏度均低于ESI或APPI离子源;采用ESI和APPI离子源相结合的LC-MS脂质组学分析方法可以提高分析方法的整体灵敏度和血清中脂类信息检测的完整性.

Comparison of Multiple Ionization Methods Coupled with Liquid Chromatography-Mass Spectrometry inLipidomics Study of Serum Samples

Three commonly used ionization techniques, including electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI) were compared systemically for their ionization ability, sensitivity and coverage for detecting lipids, aiming to explore their applicability in lipidomics study of serum samples.Serum samples were pretreated by liquid-liquid extraction with methyl tertiary butyl ether and then introduced into a LC-MS system equipped with electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI) source.Chromatographic separation was performed on an Ascentiss Express C8 column (150 mm×2.1 mm, 2.7 μm).A binary gradient system of acetonitrile-water (3∶2, V/V) and isoropyl alcohol-acetonitrile (9∶1, V/V), both containing 10 mmol/L ammonium formate and 0.1% formic acid, was used as eluent A and B, respectively.Data were acquired in both positive and negative ion modes for each ionization technique.The results showed that fatty acids (FFAs), phospholipids (PLs), sphingophosphalipids (SPs), glycerolipids (GLs), could be ionized most efficiently under ESI source, while APPI source gave the best sensitivity for cholesterol (CHOL), cholesterol esters (CEs) and Sphinganine (Sphingolipids, SPs).Prenol lipids could be ionized equally well under ESI and APPI source, and that the application of ESI and APPI integrated approach was expected to enhance the overall sensitivity of the method and provided more comprehensive lipids information for the global serum lipidomics study.