Mills Quinn, Kibbe Russell R, Sohn Alexandria L, Percy Andrew J, Backiel Krista, Muddiman David C
Biological Imaging Laboratory for Disease and Exposure Research (BILDER), Department of Chemistry, North Carolina State University, Raleigh, North Carolina, USA.
Cambridge Isotope Laboratories Inc., Tewksbury, Massachusetts, USA.
Rapid Commun Mass Spectrom. 2025 Apr 30;39(8):e9993. doi: 10.1002/rcm.9993.
While quality control (QC) and system suitability testing (SST) methods are commonly employed in mass spectrometry, the field of mass spectrometry imaging (MSI) currently lacks any universally accepted QC/SST protocols. These methods can prevent the loss of precious samples due to suboptimal instrument conditions and/or data quality, but they are more challenging to implement on MSI platforms. Herein, a panel of analytes is conveniently analyzed in a setup that reflects a typical MSI imaging experiment, and guidance is provided for downstream QC/SST evaluation.
The analyte panel will be commercially available and consists of three pairs of unlabeled (NAT) analytes and their stable isotope-labeled (SIL) analogues; a deviation from the standard procedure is also included, which incorporates a polymer to expand m/z coverage. The NAT three-plex (or four-plex with the added polymer) is analyzed as a droplet on a slide, and the SIL three-plex is doped into the electrospray solvent, isolating the NAT and SIL compounds to different source components. Datasets are collected on clean and compromised instruments to inform QC/SST software and later evaluate instrument conditions or isolated metrics of data quality.
A procedure was created for QC/SST analysis on MSI platforms, which can be optionally paired with the freely available software Supervised Learning for Instrument Classification and Evaluation for Mass Spectrometry Imaging (SLICE-MSI) to classify the condition of the instrument. The SIL data may be monitored separately during imaging experiments for continuous evaluation of electrospray stability. The protocol highlights areas that may be adapted for other ionization sources for widespread use.
The protocol described herein uses a panel of NAT and SIL compounds to offer an objective and accurate determination of QC/SST on MSI platforms.
虽然质量控制（QC）和系统适用性测试（SST）方法在质谱分析中普遍使用，但质谱成像（MSI）领域目前缺乏任何普遍接受的QC/SST方案。这些方法可以防止由于仪器条件欠佳和/或数据质量问题导致珍贵样品的损失，但在MSI平台上实施起来更具挑战性。在此，在一个反映典型MSI成像实验的设置中方便地分析了一组分析物，并为下游的QC/SST评估提供了指导。
该分析物组将是市售的，由三对未标记（NAT）分析物及其稳定同位素标记（SIL）类似物组成；还包括一个与标准程序的偏差，其中加入了一种聚合物以扩大m/z覆盖范围。NAT三联体（或加入聚合物后的四联体）作为载玻片上的液滴进行分析，SIL三联体掺入电喷雾溶剂中，将NAT和SIL化合物分离到不同的源组件中。在清洁和受损的仪器上收集数据集，以为QC/SST软件提供信息，并随后评估仪器条件或孤立的数据质量指标。
创建了一种用于MSI平台上QC/SST分析的程序，该程序可以选择与免费提供的软件“用于质谱成像的仪器分类和评估的监督学习”（SLICE-MSI）配对，以对仪器状况进行分类。在成像实验期间，可以单独监测SIL数据，以持续评估电喷雾稳定性。该方案突出了可适用于其他电离源以广泛使用的领域。
本文所述的方案使用一组NAT和SIL化合物，以客观、准确地确定MSI平台上的QC/SST。
