Li Yan, Cole Richard B
Department of Chemistry, University of New Orleans, 2000 Lakeshore Drive, New Orleans, Louisiana 70148, USA.
Anal Chem. 2003 Nov 1;75(21):5739-46. doi: 10.1021/ac0301402.
The influence of the diameter of the spray tip employed for nano-electrospray mass spectrometry (nano-ES-MS) upon mass spectral charge state distributions was investigated using angiotensin I (M(r) = 1296), insulin (M(r) = 5774), and ubiquitin (M(r) = 8560) as test analytes. Under a variety of experimental conditions, the charge state distributions of the test peptides and protein consistently shifted toward higher values as the tip orifice diameter decreased. This finding indicates that the use of narrow diameter capillaries can promote the formation of higher charge state ions that are more reactive precursors in tandem mass spectrometry experiments. A detailed comparison of charge state distributions obtained for nanospray capillaries of varying diameters was undertaken while systematically varying experimental parameters such as sample flow rate, analyte concentration, solvent composition, and electrospray current. The general tendency to obtain higher charge states from narrow diameter capillaries was conserved throughout, but tips with smaller orifices were more sensitive to sample flow rate (the average charge state was lowered significantly as flow was raised), whereas tips with bigger orifices were more sensitive to analyte concentration and pH of the solution (as each was lowered, the average charge state increased).
使用血管紧张素I（M(r)=1296）、胰岛素（M(r)=5774）和泛素（M(r)=8560）作为测试分析物，研究了用于纳米电喷雾质谱（nano-ES-MS）的喷雾尖端直径对质谱电荷态分布的影响。在各种实验条件下，随着尖端孔直径减小，测试肽和蛋白质的电荷态分布一致地向更高值移动。这一发现表明，使用窄直径毛细管可以促进更高电荷态离子的形成，这些离子在串联质谱实验中是更具反应性的前体。在系统地改变诸如样品流速、分析物浓度、溶剂组成和电喷雾电流等实验参数的同时，对不同直径的纳米喷雾毛细管获得的电荷态分布进行了详细比较。从窄直径毛细管获得更高电荷态的一般趋势始终存在，但孔较小的尖端对样品流速更敏感（随着流速增加，平均电荷态显著降低），而孔较大的尖端对分析物浓度和溶液pH更敏感（随着每一项降低，平均电荷态增加）。
