Key Laboratory of Pesticides & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, China.
Key Laboratory of Pesticides & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, China; School of Mathematics and Statistics, Wuhan University, Wuhan 430072, China.
Talanta. 2019 Jun 1;198:404-411. doi: 10.1016/j.talanta.2019.01.076. Epub 2019 Jan 25.
Microfluidic chips coupled with electrospray ionization (ESI) mass spectrometry (MS) is an analytical platform with high detection throughputs and low sample consumptions. However, its applications in probing real samples are limited by the absence of reliable on-chip sample pretreatments, which are indispensable due to both the low contents of analytes and the poor salt tolerance of ESI MS. Herein, we propose an automated extraction and ESI chip (AEEC), consisting of a solid phase extraction (SPE) zone, seven on-chip pneumatic micro-valves, a monolithic ESI nozzle, and other components, to implement on-chip SPE prior to on-line ESI for analytes. In the SPE zone, magnetic silica beads were immobilized by magnets, and used as the SPE sorbent. Additionally, open and closed statuses of all micro-valves were simultaneously controlled by turning off and on applied pneumatic pressures, thus regulating the direction of various flows in AEEC. Further, the SPE in AEEC, consisting of sample introduction and extraction, elution introduction, and analytes elution, was automatically implemented by regulating the direction of both sample and elution flows in AEEC. After these steps, the analytes elution was on-line introduced to the monolithic ESI nozzle, at which the ESI for analytes was achieved. After optimizations, the AEEC-MS method was used to investigate two standard chemicals and ten pesticides, achieving a limit of detection and an enrichment ratio between 0.10 and 0.75 ng μL and 2.1-6.2, respectively. In addition, linear calibration curves with and without the SPE beads were compared, demonstrating the effect of the automated SPE in improving reliability and sensitivity of the AEEC method. Finally, we applied AEEC to quantify a new herbicide, quinotrione, in sorghum plant as 0.176 mg kg (RSD=5.70%), presenting an improved error compared with related reports. With the AEEC method, a SPE and ESI MS investigation for analytes could be automatically implemented within 300 s, effectively reducing random error and analytical time compared with manual strategies.
微流控芯片与电喷雾电离（ESI）质谱（MS）联用是一种具有高通量检测和低样品消耗的分析平台。然而，由于分析物含量低和 ESI MS 的耐盐性差，其在探测实际样品中的应用受到限制，这就需要可靠的芯片上样品预处理。在此，我们提出了一种自动化提取和 ESI 芯片（AEEC），由固相萃取（SPE）区、七个芯片上气动微阀、整体式 ESI 喷嘴和其他组件组成，用于在在线 ESI 之前实现芯片上的 SPE 对分析物进行萃取。在 SPE 区，通过磁铁将磁性硅胶珠固定在磁场中，作为 SPE 吸附剂。此外，通过关闭和打开施加的气动压力来同时控制所有微阀的开/关状态，从而调节 AEEC 中各种流的方向。进一步地，通过调节 AEEC 中样品和洗脱液的流动方向，实现了 AEEC 中的 SPE 萃取，包括样品引入和萃取、洗脱液引入和分析物洗脱。这些步骤完成后，洗脱液在线引入到整体式 ESI 喷嘴，在那里实现了对分析物的 ESI。经过优化，AEEC-MS 方法被用于研究两种标准化学品和十种农药，实现了检测限和富集比分别为 0.10-0.75ngμL 和 2.1-6.2。此外，还比较了有无 SPE 珠的自动 SPE 对 AEEC 方法可靠性和灵敏度的影响。最后，我们将 AEEC 应用于高粱植株中一种新型除草剂喹恶酮的定量分析，结果为 0.176mgkg（RSD=5.70%），与相关报道相比，误差有所改善。使用 AEEC 方法，可在 300s 内自动完成 SPE 和 ESI MS 对分析物的分析，与手动策略相比，可有效减少随机误差和分析时间。
