Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, CZ-166 10 Prague 6, Czech Republic.
Department of Analytical Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, CZ-128 43 Prague 2, Czech Republic.
Anal Chem. 2023 Feb 28;95(8):4196-4203. doi: 10.1021/acs.analchem.2c05349. Epub 2023 Feb 17.
Electrospray may exhibit inadequate ionization efficiency in some applications. In such cases, atmospheric-pressure chemical ionization (APCI) and photoionization (APPI) can be used. Despite a wide application potential, no APCI and APPI sources dedicated to very low sample flow rates exist on the market. Since the ion source performance depends on the transfer of analytes from the liquid to the gas phase, a nebulizer is a critical component of an ion source. Here, we report on the nebulizer with a gas dynamic virtual nozzle (GDVN) and its applicability in APCI at microliter-per-minute flow rates. Nebulizers differing by geometrical parameters were fabricated and characterized regarding the jet breakup regime, droplet size, droplet velocity, and spray angle for liquid flow rates of 0.75-15.0 μL/min. A micro-APCI source with the GDVN nebulizer behaved as a mass-flow-sensitive detector and provided stable and intense analyte signals. Compared to a classical APCI source, an order of magnitude lower detection limit for verapamil was achieved. Mass spectra recorded with the nebulizer in dripping and jetting modes were almost identical and did not differ from normal APCI spectra. Clogging never occurred during the experiments, indicating the high robustness of the nebulizer. Low-flow-rate APCI and APPI sources with a GDVN sprayer promise new applications for low- and medium-polar analytes.
电喷雾在某些应用中可能表现出不足的离子化效率。在这种情况下，可以使用大气压化学电离（APCI）和光电离（APPI）。尽管具有广泛的应用潜力，但市场上没有专门用于非常低样品流速的 APCI 和 APPI 源。由于离子源的性能取决于分析物从液相到气相的转移，因此雾化器是离子源的关键组成部分。在这里，我们报告了带有气动虚拟喷嘴（GDVN）的雾化器及其在微升/分钟流速下的 APCI 中的适用性。制造了具有不同几何参数的雾化器，并针对 0.75-15.0 μL/min 的液体流速，研究了射流破裂模式、液滴尺寸、液滴速度和喷雾角度。带有 GDVN 雾化器的微 APCI 源作为质量流量敏感的检测器，提供了稳定且强烈的分析物信号。与传统的 APCI 源相比，维拉帕米的检测限低了一个数量级。在滴状和射流模式下用雾化器记录的质谱几乎相同，与正常的 APCI 谱没有区别。在实验过程中从未发生堵塞，表明雾化器具有很高的稳健性。带有 GDVN 喷雾器的低流速 APCI 和 APPI 源有望为低极性和中等极性分析物提供新的应用。
