Hommerson Paul, Khan Amjad M, de Jong Gerhardus J, Somsen Govert W
Department of Biomedical Analysis, Utrecht University, Utrecht, The Netherlands.
J Am Soc Mass Spectrom. 2009 Jul;20(7):1311-8. doi: 10.1016/j.jasms.2009.03.005. Epub 2009 Mar 13.
The feasibility of atmospheric pressure chemical ionization (APCI) as an alternative ionization technique for capillary electrophoresis-mass spectrometry (CE-MS) was investigated using a grounded sheath-flow CE-MS sprayer and an orthogonal APCI source. Infusion experiments indicated that highest analyte signals were achieved when the sprayer tip was in close vicinity of the vaporizer entrance. The APCI-MS set-up enabled detection of basic, neutral, and acidic compounds, whereas apolar and ionic compounds could not be detected. In the positive ion mode, analytes could be detected in the entire transfer voltage range (0-5 kV), whereas highest signal intensities were observed when the corona discharge current was between 1000 and 2000 nA. In the negative ion mode, the transfer voltage typically was 500 V and the optimum corona discharge current was 6000 nA. Analyte signals were raised with increasing nebulizing gas pressure, but the pressure was limited to 25 psi to avoid siphoning and current drops. Signal intensities appeared to be optimal and constant over a wide range of sheath liquid flow rate (5-25 microL/min) and vaporizer temperature (200-350 degrees C). APCI-MS signals were unaffected by the composition of the background electrolyte (BGE), even when it contained sodium phosphate and sodium dodecyl sulfate (SDS). Consequently, BGE composition, sheath-liquid flow rate, and vaporizer temperature can be optimized with respect to the CE separation without affecting the APCI-MS response. The analysis of a mixture of basic compounds and a steroid using volatile and nonvolatile BGEs further demonstrates the feasibility of CE-APCI-MS. Detection limits (S/N = 3) were 1.6-10 microM injected concentrations.
采用接地鞘流毛细管电泳-质谱联用（CE-MS）喷雾器和正交大气压化学电离（APCI）源，研究了大气压化学电离作为毛细管电泳-质谱联用替代电离技术的可行性。进样实验表明，当喷雾器尖端靠近蒸发器入口时，可获得最高的分析物信号。APCI-MS装置能够检测碱性、中性和酸性化合物，而极性和离子型化合物无法检测。在正离子模式下，在整个转移电压范围（0 - 5 kV）内均可检测到分析物，而当电晕放电电流在1000至2000 nA之间时，观察到最高信号强度。在负离子模式下，转移电压通常为500 V，最佳电晕放电电流为6000 nA。分析物信号随雾化气体压力的增加而增强，但压力限制在25 psi，以避免虹吸和电流下降。在较宽的鞘液流速范围（5 - 25 μL/min）和蒸发器温度范围（200 - 350℃）内，信号强度似乎最佳且恒定。APCI-MS信号不受背景电解质（BGE）组成的影响，即使其中含有磷酸钠和十二烷基硫酸钠（SDS）。因此，可在不影响APCI-MS响应的情况下，针对CE分离优化BGE组成、鞘液流速和蒸发器温度。使用挥发性和非挥发性BGE对碱性化合物混合物和类固醇进行分析，进一步证明了CE-APCI-MS的可行性。检测限（S/N = 3）为进样浓度1.6 - 10 μM。
