Department of Chemistry, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan.
Department of Applied Chemistry, National Yang Ming Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan.
J Am Soc Mass Spectrom. 2021 Dec 1;32(12):2803-2811. doi: 10.1021/jasms.1c00243. Epub 2021 Nov 5.
Sweat analysis provides an alternative and noninvasive way of clinical diagnostics. However, sampling and transferring sweat-derived samples to analytical instruments is challenging. In this report, we demonstrate a method utilizing a flat disc-shaped sampling probe, and a compatible re-extraction apparatus coupled online with extractive electrospray ionization (EESI) mass spectrometry (MS). The probe enables sampling of metabolites from a skin area of ∼2.2 cm. The subsequent online re-extraction and analysis by EESI-MS further mitigates matrix effects caused by sweat components, thus eliminating sample preparation steps. The total analysis time is only 6 min. We have optimized the key parameters of the system, including flow rate of the nebulizing gas in ESI, pressure of the nebulizing gas in pneumatic sample nebulizer, flow rate of the solvent in ESI, and composition of extractant. The standard solutions (0.1 mL) were supplemented with 0.04 M sodium chloride to mimic the matrix effect normally observed in sweat samples. The method has been characterized with four chemical standards (positive-ion mode of histidine, leucine, urocanic acid; negative-ion mode of lactic acid). The limits of detection range from 1.09 to 95.9 nmol. We have further demonstrated the suitability of the method for analysis of sweat. An attempt was made to identify some of the recorded signals by product-ion scan and accurate/exact mass matching.
汗液分析提供了一种替代的、非侵入性的临床诊断方法。然而，从汗液中采样并将样本转移到分析仪器中具有挑战性。在本报告中，我们展示了一种利用扁平圆盘状采样探针和兼容的再提取装置与提取电喷雾电离（EESI）质谱（MS）在线耦合的方法。探针能够从约 2.2cm2 的皮肤区域采集代谢物。随后通过 EESI-MS 进行在线再提取和分析，进一步减轻了由汗液成分引起的基质效应，从而省去了样品制备步骤。总分析时间仅为 6 分钟。我们已经优化了系统的关键参数，包括 ESI 中雾化气体的流速、气动样品雾化器中雾化气体的压力、ESI 中溶剂的流速以及萃取剂的组成。将标准溶液（0.1mL）中补充了 0.04M 氯化钠，以模拟通常在汗液样本中观察到的基质效应。该方法用四种化学标准品进行了表征（组氨酸、亮氨酸、尿刊酸的正离子模式；乳酸的负离子模式）。检测限范围从 1.09 到 95.9nmol。我们还进一步证明了该方法适用于汗液分析。通过产物离子扫描和精确/准确质量匹配尝试对记录的部分信号进行鉴定。
