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Anal Chem. 2020 Dec 15;92(24):15818-15826. doi: 10.1021/acs.analchem.0c02999. Epub 2020 Oct 16.
Acoustic ejection mass spectrometry is a recently developed concept in which low nanoliter-volume sample droplets are acoustically dispensed from microtiter plate wells into a continuous fluid transfer open-port interface for subsequent ionization at atmospheric pressure. This manuscript focuses on the acoustic droplet dispensing component of a prototype system, in particular the well-to-well sampling speed, droplet volume calibration, precision, reproducibility, and various modes of operation this device enables. A new method to measure the volume of individually dispensed droplets is presented to both aid method validation and potentially assist in the tuning of acoustic dispense parameters for samples having a wide range of viscosities and surface tensions. Acoustic dispensing modes of operation discussed are high-speed, well-to-well dispensing of individual nanoliter-scale droplets from microtiter plates, including the first demonstration of 1536-well compatibility using this approach. Multiple nanoliter-volume droplets per sampling event to increase detection dynamic range is described, and a "continuous infusion" mode to provide a low sample consumption sustained steady-state signal for analyte detection optimization, improved ion statistics and signal-to-noise ratio (S/N), or time for in-depth tandem mass spectrometry of the components in a sample is presented. The concept of "bar coding" using combinations of dispensed droplet patterns to register well-plate position to specific mass spectral signals is introduced, as well as judicious well-plate sample layout to enable assay "multiplexing" as a means to maximize well-to-well sample analysis throughput, is also demonstrated.
声喷射质谱是一种新发展的概念，它通过将微滴定板孔中的低纳升级样品液滴通过声波分配到连续流体传输的开口接口中，在大气压下进行后续离子化。本文主要关注原型系统中的声液滴分配组件，特别是孔间采样速度、液滴体积校准、精度、重现性以及该设备支持的各种操作模式。本文提出了一种测量单独分配液滴体积的新方法，不仅有助于方法验证，还可能有助于调整具有广泛粘度和表面张力的样品的声分配参数。本文讨论了多种声分配操作模式，包括从微滴定板高速、逐孔分配单个纳升级液滴，包括首次使用该方法演示 1536 孔兼容性。还描述了每次采样事件中多个纳升级液滴的分配，以增加检测动态范围，以及“连续输注”模式，用于优化分析物检测的低样品消耗持续稳态信号，改善离子统计和信号噪声比（S/N），或用于对样品中成分进行深入串联质谱分析的时间。本文还介绍了使用分配液滴图案组合进行“条形码”注册的概念，以及明智的微孔板样品布局，以实现作为最大限度提高孔间样品分析吞吐量的手段的分析物“多重化”。
