Capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C⁴D) has the advantages of high throughput (simultaneous detection of multiple ions), high separation efficiency (higher than 10⁵ theoretical plates) and rapid analysis capability (less than 5 min for common inorganic ions). A compact CE-C⁴D system is ideal for water quality control and on-site analysis. It is suitable not only for common cations (e.g. Na⁺, K⁺, Li⁺, NH₄⁺, Ca²⁺, etc.) and anions (e.g. Cl⁻, SO₄²⁻, BrO₃⁻, etc.) but also for some ions (e.g. lanthanide ions, Pb²⁺, Cd²⁺, etc.) that require complex derivatization procedures to be detected by ion chromatography (IC). However, an obvious limitation of the CE-C⁴D method is that its sensitivity (e.g. 0.3–1 μM for common inorganic ions) is often insufficient for trace analysis (e.g. 1 ppb or 20 nM level for common inorganic ions) without preconcentration. For this technology to become a powerful and routine analytical technique, the system should be made compact while maintaining trace analysis sensitivity. In this study, we developed an all-in-one version of the CE-C⁴D instrument with custom-made modular components to make it a convenient, compact and high-performance system. The system was designed using direct digital synthesis (DDS) technology to generate programmable sinusoidal waveforms with any frequency for excitation, a kilovolt high-voltage power supply for capillary electrophoresis separation, and an “effective” differential C⁴D cell with a low-noise circuitry for high-sensitivity detection. We characterized the system with different concentrations of Cs⁺, and even a low concentration of 20 nM was detectable without preconcentration. Moreover, the optimized CE-C⁴D setup was applied to analyse mixed ions at a trace concentration of 200 nM with excellent signal-to-noise ratios. In typical applications, the limits of detection based on the 3σ criterion (without baseline filtering) were 9, 10, 24, 5, and 12 nM for K⁺, Cs⁺, Li⁺, Ca²⁺, and Mg²⁺, respectively, and about 7, 6, 6 and 6 nM for Br⁻, ClO₄⁻, BrO₃⁻ and SO₄²⁻, respectively. Finally, the setup was also applied for the analysis of all 14 lanthanide ions and rare-earth minerals, and it showed an improvement in sensitivity by more than 25 times.

中文翻译：

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具有电容耦合非接触式电导检测功能的紧凑型高性能毛细管电泳装置 (CE-C4D)

电容耦合非接触电导检测毛细管电泳（CE-C ⁴ D）具有高通量（同时检测多个离子）、高分离效率（高于10 ⁵理论板）和快速分析能力（小于5 min）等优点。常见的无机离子）。紧凑型 CE-C ⁴ D 系统非常适合水质控制和现场分析。它不仅适用于常见的阳离子（如Na + ^、 K ⁺、Li ⁺、NH ₄ ⁺、Ca ²⁺等）和阴离子（如Cl - ^、 SO ₄ ²⁻、BrO ₃ ^-等）也适用于一些需要复杂的衍生化程序才能通过离子色谱（IC）检测的离子（例如镧系离子、Pb ²⁺、Cd ²⁺等）。然而，CE-C ⁴ D 方法的一个明显局限性是其灵敏度（例如，常见无机离子为 0.3–1 μM）在没有预浓缩的情况下通常不足以进行痕量分析（例如，常见无机离子为 1 ppb 或 20 nM 水平）。为了使这项技术成为一种强大的常规分析技术，系统应该变得紧凑，同时保持痕量分析灵敏度。在这项研究中，我们开发了一款一体化版本的 CE-C ⁴ D 仪器，具有定制的模块化组件，使其成为一个方便、紧凑和高性能的系统。该系统采用直接数字合成 (DDS) 技术设计，可生成任意频率的可编程正弦波形用于激励、用于毛细管电泳分离的千伏高压电源以及具有低噪声的“有效”差分 C ⁴ D 池。高灵敏度检测电路。我们用不同浓度的 Cs ⁺表征了系统，甚至无需预浓缩即可检测到 20 nM 的低浓度。此外，优化的 CE-C ⁴ D 设置用于分析痕量浓度为 200 nM 的混合离子，具有出色的信噪比。在典型应用中，基于 3 σ标准（无基线过滤）的 K ⁺、Cs ⁺、Li ⁺、Ca ²⁺和 Mg ²⁺的检测限为 9、10、24、5 和 12 nM ， Br ^-、ClO分别约为 7、6、6 和 6 nM_分别为4 ^-、BrO ₃ ^-和SO ₄ ^2-。最后，该装置还应用于所有 14 种稀土离子和稀土矿物的分析，灵敏度提高了 25 倍以上。