Akbal Laura, Hopfgartner Gérard
Life Sciences Mass Spectrometry, Department of Inorganic and Analytical Chemistry, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland.
Life Sciences Mass Spectrometry, Department of Inorganic and Analytical Chemistry, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland.
J Chromatogr A. 2017 Sep 29;1517:176-184. doi: 10.1016/j.chroma.2017.08.044. Epub 2017 Aug 19.
In supercritical fluid chromatography coupled to atmospheric pressure ionization mass spectrometry (SFC-MS), the use of a make-up post-column is almost mandatory to avoid analyte precipitation, especially when using low percentage of modifier (<5%) in the mobile phase. Due to the specific nature of gaseous CO, the tuning of the make-up conditions in electrospray becomes an important factor and can be used to tune analyte sensitivity. Neither a dilution effect (loss of signal) nor a relevant degradation of chromatographic performances is observed with the addition of a make-up at various flow-rates, up to 0.7mL/min. From supercritical conditions (1mL/min 40°C, 150bar) to gaseous state (room temperature, atmospheric pressure), the CO expands around 430 times, contributing to almost 5% of the nebulizing process. In positive mode, the presence of ammonium ions either in the mobile phase or in the make-up did significantly increase the MS signal, even at basic apparent pH. The ionization performance of electrospray is influenced by the acidic buffer power of the carbon dioxide, and was found to be restricted in the apparent pH range of 3.8-7.2 in the various conditions investigated. This may challenge sensitive detection in negative mode, as illustrated for bosentan. The use of DMSO as make-up additive (up to 30%) showed a simplification of the full scan spectrum regarding the adducts. Finally, the optimization of make-up composition leads to an enhancement up to a factor of 69 on the electrospray MS response signal, for the SFC-SRM/MS analysis of HIV protease inhibitors in plasma extracted from Dried Plasma Spots.
在超临界流体色谱与大气压电离质谱联用（SFC-MS）中，几乎必须使用柱后补充装置以避免分析物沉淀，尤其是在流动相中使用低比例改性剂（<5%）时。由于气态CO的特殊性质，电喷雾中柱后补充条件的调节成为一个重要因素，可用于调节分析物的灵敏度。在添加高达0.7mL/min的不同流速的柱后补充液时，未观察到稀释效应（信号损失）或色谱性能的显著下降。从超临界条件（1mL/min，40°C，150bar）到气态（室温，大气压），CO膨胀约430倍，几乎占雾化过程的5%。在正模式下，流动相或柱后补充液中铵离子的存在即使在表观pH为碱性时也会显著增加质谱信号。电喷雾的电离性能受二氧化碳酸性缓冲能力的影响，在所研究的各种条件下，发现在表观pH范围为3.8 - 7.2时受到限制。这可能对负模式下的灵敏检测构成挑战，如波生坦所示。使用DMSO作为柱后补充添加剂（高达30%）显示出关于加合物的全扫描谱图得到简化。最后，对于从干血斑中提取的血浆中HIV蛋白酶抑制剂的SFC-SRM/MS分析，柱后补充液组成的优化使电喷雾质谱响应信号增强高达69倍。
