Department of Analytical Chemistry, University of Barcelona, Diagonal 645, 08028 Barcelona, Spain; Biomolecular Analysis, Utrecht University, P.O. Box 80082, 3508 TB Utrecht, The Netherlands.
Biomolecular Analysis, Utrecht University, P.O. Box 80082, 3508 TB Utrecht, The Netherlands.
J Chromatogr A. 2014 Feb 7;1328:1-6. doi: 10.1016/j.chroma.2013.12.080. Epub 2013 Dec 31.
A novel fritless solid-phase extraction (SPE) microcartridge was designed for combination with sheathless capillary electrophoresis-mass spectrometry (sheathless CE-MS) employing a prototype porous-tip capillary for nanoelectrospray ionization (nanoESI). The inlet of the separation capillary (30μm inner diameter (id), 150μm outer diameter (od)) was inserted in a 4mm long SPE microcartridge (150μm id, 365μm od) packed with a C18 sorbent of 55-105μm particle size. Performance of the SPE-CE-MS system was evaluated using diluted solutions of the three opioid peptides dynorphin A (1-7) (DynA), endomorphin 1 (End1) and met-enkephalin (Met). Sample volumes of 1.5μL were loaded on the SPE microcartridge and the retained peptides were eluted with 22nL of an acidic methanol/water (60:40, v/v) solution. Using a pressure of 50mbar during separation to speed up the analysis, good peptide resolution was obtained with acceptable plate numbers (between 53,000 and 92,000). Intraday relative standard deviations (% RSD) for peptide migration times and peak areas were below 4% and 9%, respectively. The SPE-CE-MS method showed good linearity in the 0.05-5ngmL(-1) range and limits of detection (LODs) were 10pgmL(-1). However, loading a larger volume of sample (8μL), LODs could be decreased down to 2pgmL(-1) (2.2-3.5pM). This represents an improvement of up to 5000-fold with respect to the LODs achieved by sheathless CE-MS without on-line preconcentration demonstrating the potential of on-line SPE for further enhancing sensitivity.
一种新型无滤片固相萃取（SPE）微柱被设计用于与无鞘毛细管电泳-质谱联用（鞘流 CE-MS）结合，采用一种用于纳喷雾电离（nanoESI）的原型多孔尖端毛细管。分离毛细管的入口（内径 30μm，外径 150μm）插入一个长 4mm 的 SPE 微柱（内径 150μm，外径 365μm）中，该微柱中填充了粒径为 55-105μm 的 C18 吸附剂。使用三种阿片肽 dynorphin A (1-7) (DynA)、endomorphin 1 (End1) 和 met-enkephalin (Met) 的稀释溶液评估 SPE-CE-MS 系统的性能。将 1.5μL 的样品体积加载到 SPE 微柱上，并用 22nL 的酸性甲醇/水（60:40，v/v）溶液洗脱保留的肽。在分离过程中施加 50mbar 的压力以加速分析，获得了良好的肽分辨率，可接受的板数（在 53000 和 92000 之间）。肽迁移时间和峰面积的日内相对标准偏差（%RSD）分别低于 4%和 9%。SPE-CE-MS 方法在 0.05-5ngmL(-1) 范围内具有良好的线性，检测限（LOD）为 10pgmL(-1)。然而，当加载更大体积的样品（8μL）时，LOD 可降低至 2pgmL(-1)（2.2-3.5pM）。与无鞘 CE-MS 无在线预浓缩相比，这代表灵敏度提高了高达 5000 倍，证明了在线 SPE 用于进一步提高灵敏度的潜力。
