Erngren Ida, Nestor Marika, Pettersson Curt, Hedeland Mikael
Analytical Pharmaceutical Chemistry, Department of Medicinal Chemistry, Uppsala University, 75123 Uppsala, Sweden.
Department of Immunology, Genetics and Pathology, Uppsala University, 75123 Uppsala, Sweden.
Metabolites. 2021 Mar 15;11(3):170. doi: 10.3390/metabo11030170.
Inorganic ions, such as sodium and potassium, are present in all biological matrices and are sometimes also added during sample preparation. However, these inorganic ions are known to hamper electrospray ionization -mass spectrometry (ESI-MS) applications, especially in hydrophilic interaction liquid chromatography (HILIC) where they are retained and can be detected as adducts and clusters with mobile phase components or analytes. The retention of inorganic ions leads to co-elution with analytes and as a result ion-suppression, extensive adduct formation and problems with reproducibility. In the presented work, a sample preparation method using cation exchange solid phase extraction (SPE) was developed to trap Na and K ions from human blood plasma and head and neck cancer cells for the analysis of small cationic, anionic as well as neutral organic analytes. The investigated analytes were small, hydrophilic compounds typically in focus in metabolomics studies. The samples were analyzed using full-scan HILIC-ESI-quadrupole time of flight (QTOF)-MS with an untargeted, screening approach. Method performance was evaluated using multivariate data analysis as well as relative quantifications, spiking of standards to evaluate linearity of response and post-column infusion to study ion-suppression. In blood plasma, the reduction of sodium and potassium ion concentration resulted in improved sensitivity increased signal intensity for 19 out of 28 investigated analytes, improved linearity of response, reduced ion-suppression and reduced cluster formation as well as adduct formation. Thus, the presented method has significant potential to improve data quality in metabolomics studies.
无机离子，如钠和钾，存在于所有生物基质中，有时在样品制备过程中也会添加。然而，众所周知，这些无机离子会妨碍电喷雾电离质谱（ESI-MS）的应用，尤其是在亲水相互作用液相色谱（HILIC）中，它们会被保留下来，并可作为与流动相成分或分析物的加合物和簇被检测到。无机离子的保留会导致与分析物共洗脱，从而导致离子抑制、大量加合物形成以及重现性问题。在本研究中，开发了一种使用阳离子交换固相萃取（SPE）的样品制备方法，用于从人血浆和头颈部癌细胞中捕获钠和钾离子，以分析小阳离子、阴离子以及中性有机分析物。所研究的分析物是代谢组学研究中通常关注的小的亲水性化合物。使用全扫描HILIC-ESI-四极杆飞行时间（QTOF）-MS，采用非靶向筛选方法对样品进行分析。使用多变量数据分析以及相对定量、添加标准品以评估响应线性和柱后注入以研究离子抑制来评估方法性能。在血浆中，钠和钾离子浓度的降低导致28种被研究分析物中的19种灵敏度提高、信号强度增加、响应线性改善、离子抑制降低以及簇形成和加合物形成减少。因此，所提出的方法在提高代谢组学研究数据质量方面具有巨大潜力。
