Institute of Bioanalytical Chemistry, Saarland University, Campus B2.2, 66123, Saarbrücken, Germany.
Anal Bioanal Chem. 2012 Aug;404(2):433-45. doi: 10.1007/s00216-012-6138-9. Epub 2012 Jun 6.
Determination of trace constituents in biological and environmental samples usually requires a pre-concentration step. While solid-phase extraction (SPE) has been widely used, it is slow, labor intensive and adversely affected by analytical errors from handling. On-line SPE eliminates some of the flaws but often suffers from solvent compatibility problems with the subsequent chromatography separation. In this study, we are presenting a technical solution for overcoming some of these compatibility issues, by utilizing a fully automated, focused SPE sample transfer technique utilizing narrow-band solvent plugs, for seamless hyphenation with high-performance liquid chromatography (HPLC) or flow injection mass spectrometry (MS). A wide range of pharmaceutical compounds was studied in different sample matrices. Short plugs of high elution strength solvent were generated by means of an electrically actuated sample loop and enrichment and transfer steps monitored using on-line SPE-MS. The impact of the solvent plugs on chromatographic separation was studied using hyphenated SPE-LC-MS. By carefully examining elution profiles of solvent plugs of different compositions, optimum conditions for quantitative elution within well-defined volumes were found for all substances. In addition, the highly focused elution bands resulted in excellent retention time and peak area reproducibilities when injected on-line onto HPLC columns. Finally, to demonstrate proof-of-principle, the fully integrated on-line SPE-LC-MS system was applied to the analysis of spiked urine and river water samples.
通常，生物和环境样品中的痕量成分的测定需要进行预浓缩步骤。虽然固相萃取（SPE）已被广泛应用，但它速度较慢，劳动强度大，并且容易受到处理过程中分析误差的影响。在线 SPE 虽然消除了一些缺陷，但常常受到与后续色谱分离溶剂兼容性问题的困扰。在本研究中，我们提出了一种技术解决方案，通过利用全自动、聚焦 SPE 样品转移技术，利用窄带溶剂塞，实现与高效液相色谱（HPLC）或流动注射质谱（MS）的无缝连接，来克服这些兼容性问题。在不同的样品基质中研究了广泛的药物化合物。通过电动驱动的样品环产生具有高洗脱强度的短溶剂塞，并通过在线 SPE-MS 监测富集和转移步骤。通过联用 SPE-LC-MS 研究了溶剂塞对色谱分离的影响。通过仔细检查不同组成的溶剂塞的洗脱曲线，为所有物质找到了在定义良好的体积内定量洗脱的最佳条件。此外，当在线注入 HPLC 柱时，高度聚焦的洗脱带导致出色的保留时间和峰面积重现性。最后，为了证明原理验证，将完全集成的在线 SPE-LC-MS 系统应用于加标尿液和河水样品的分析。
