Mol Roelof, de Jong Gerhardus J, Somsen Govert W
Department of Biomedical Analysis, Utrecht University, P.O. Box 80082, 3508 TB Utrecht, The Netherlands.
Anal Chem. 2005 Aug 15;77(16):5277-82. doi: 10.1021/ac0502697.
Atmospheric pressure photoionization (APPI) is presented as a novel means for the combination of micellar electrokinetic chromatography (MEKC) and mass spectrometry (MS). The on-line coupling is achieved using an adapted sheath flow interface installed on an orthogonal APPI source. Acetone or toluene is added as dopant to the sheath liquid to enhance analyte photoionization. It is demonstrated that with APPI signal suppression and interferences by the surfactant sodium dodecyl sulfate (SDS) and nonvolatile buffers can be circumvented. This implies that MEKC conditions can be selected independently from MS detection. Moreover, it is shown that both polar and apolar compounds can be photoionized, thereby also facilitating the analysis of compounds that are not amenable to electrospray ionization. Consequently, the MEKC-APPI-MS system can provide effective separation and detection of compounds of diverse character in one run using background electrolytes containing up to 50 mM SDS. Concentration limits of detection derived from extracted-ion traces (full scan mode) of test compounds were approximately 1 microg/mL, and the detection sensitivity remained unaffected during 1 day of continuous use. Overall, the system features are very favorable for applications such as drug impurity profiling as is illustrated by the analysis of mebeverine and related compounds (both charged and neutral) at the 0.25% (w/w) level.
大气压光电离（APPI）被提出作为一种将胶束电动色谱（MEKC）与质谱（MS）联用的新方法。通过安装在正交APPI源上的适配鞘流接口实现在线联用。向鞘液中添加丙酮或甲苯作为掺杂剂以增强分析物的光电离。结果表明，利用APPI可避免表面活性剂十二烷基硫酸钠（SDS）和非挥发性缓冲剂对信号的抑制和干扰。这意味着MEKC条件可独立于MS检测进行选择。此外，研究表明极性和非极性化合物均可被光电离，从而也便于分析不适用于电喷雾电离的化合物。因此，MEKC - APPI - MS系统使用含高达50 mM SDS的背景电解质，可在一次运行中对不同性质的化合物进行有效分离和检测。由测试化合物的提取离子痕量（全扫描模式）得出的检测浓度限约为1μg/mL，且在连续使用1天期间检测灵敏度保持不变。总体而言，该系统特性非常有利于药物杂质分析等应用，如对美贝维林及相关化合物（包括带电和中性化合物）在0.25%（w/w）水平的分析所示。
