Admittance Scanning for Whole Column Detection
Admittance Scanning for Whole Column Detection
复制标题
用于整列检测的导纳扫描
DOI：
10.1021/acs.analchem.7b01412
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发表时间：
2017
影响因子：
7.4
通讯作者：
Ohira Shin-Ichi
中科院分区：
文献类型：
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作者：
Stamos Brian N.;Dasgupta Purnendu K;Ohira Shin-Ichi
全柱检测（WCD）与色谱本身一样古老。WCD需要能够从外部询问列内容。除了通过透明柱进行光学检测的明显情况外，导纳（通常称为非接触电导）测量还可以从外部感测柱内容物（特别是离子含量）的变化，而无需与溶液进行电流接触。我们建议在这里机电扫描导纳成像，并将其应用于开管（OT）色谱。检测器扫描整个色谱柱;长度分辨率取决于扫描速度和数据采集频率，最终受物理步进分辨率（当前设置中为40 μm）的限制。在21 μm毛细管内定位两种不混溶液体之间的界面时，观察到与该阶跃分辨率相等的精度。机械上，最大扫描速度为100 mm/s，但在1 kHz采样率和25 ms的时间常数下，最高实际扫描速度（无峰值失真）为28 mm/s。在0、4和28 mm/s的扫描速度下，180 pL的S/N（在11 μm i.d.柱）分别为6450、3850和1500。为了促进与柱的恒定和可再现的接触，而不管外径的微小变化，开发了双四极电极系统。可以容易地扫描显著长度（>1 m）的柱。我们证明了它的适用性与OT和商业填充柱，并探讨沿沿着列保留的均匀性，增加S/N的停流重复扫描等独特的应用。
Whole column detection (WCD) is as old as chromatography itself. WCD requires an ability to interrogate column contents from the outside. Other than the obvious case of optical detection through a transparent column, admittance (often termed contactless conductance) measurements can also sense changes in the column contents (especially ionic content) from the outside without galvanic contact with the solution. We propose here electromechanically scanned admittance imaging and apply this to open tubular (OT) chromatography. The detector scans across the column; the length resolution depends on the scanning velocity and the data acquisition frequency, ultimately limited by the physical step resolution (40 μm in the present setup). Precision equal to this step resolution was observed for locating an interface between two immiscible liquids inside a 21 μm capillary. Mechanically, the maximum scanning speed was 100 mm/s, but at 1 kHz sampling rate and a time constant of 25 ms, the highest practical scan speed (no peak distortion) was 28 mm/s. At scanning speeds of 0, 4, and 28 mm/s, the S/N for 180 pL (zone length of 1.9 mm in a 11 μm i.d. column) of 500 μM KCl injected into water was 6450, 3850, and 1500, respectively. To facilitate constant and reproducible contact with the column regardless of minor variations in outer diameter, a double quadrupole electrode system was developed. Columns of significant length (>1 m) can be readily scanned. We demonstrate its applicability with both OT and commercial packed columns and explore uniformity of retention along a column, increasing S/N by stopped-flow repeat scans, etc. as unique applications.