VICI Valco Instruments Co. Inc., P.O. Box 55603, Houston, TX 77255, USA.
J Chromatogr A. 2010 Jul 2;1217(27):4629-38. doi: 10.1016/j.chroma.2010.04.050.
Nickel clad or nickel wired fused silica column bundles were constructed and evaluated. The nickel sheathing or wire functions not only as the heating element for direct resistive heat, but also as the temperature sensor, since nickel has a large resistive temperature coefficient. With this method the temperature controller is able to apply power and measure the temperature simultaneously on the same nickel element, which can effectively avoid the temperature overshoot caused by any delayed response of the sensor to the heating element. This approach also eliminates the cool spot where a separate sensor touches the column. There are some other advantages to the column bundle structure: (1) the column can be heated quickly because of the direct heating and the column's low mass, shortening analysis time. We demonstrate a maximum heating rate of 13 degrees C/s (800 degrees C/min). (2) Cooling time is also short, increasing sample throughput. The column drops from 360 degrees C to 40 degrees C is less than 1 min. (3) Power consumption is very low - 1.7 W/m (8.5 W total) for a 5 m column and 0.69 W/m (10.4 W total) for a 15 m column when they are kept at 200 degrees C isothermally. With temperature programming, the power consumption for a 5 m column is less then 70 W for an 800 degrees C/min ramp to 350 degrees C. (4) The column bundle is small, with a diameter of only about 2.25 in. All these advantages make the column bundle ideal for fast GC analysis or portable instruments. Column efficiencies and retention time repeatability have been evaluated and compared with the conventional oven heating method in this study. For isothermal conditions, the column efficiencies are measured by effective theoretical plate number. It was found that the plate number with resistive heat is always less than with oven heat, due to uneven heat in the column bundle. However, the loss is not significant - an average of about 1.5% for the nickel clad column and 4.5% for the nickel wired column. Separation numbers are used for the comparison with temperature programming, with results similar to those observed for isothermal conditions. Retention time repeatability for direct heat were 0.010% RSD for isotheral and 0.037% RSD for temperature programming, which is similar to those obtained by oven heat. Applications have been demonstrated, including diesel and PAH analysis.
镍包或镍丝熔凝硅柱束被构建并进行了评估。镍护套或线不仅作为直接电阻加热的加热元件，而且作为温度传感器，因为镍具有大的电阻温度系数。通过这种方法，温度控制器能够同时在同一镍元件上施加功率和测量温度，这可以有效地避免由于传感器对加热元件的任何延迟响应而导致的温度过冲。这种方法还消除了单独的传感器接触柱的冷点。柱束结构还有其他一些优点：（1）由于直接加热和柱的低质量，柱可以快速加热，缩短分析时间。我们展示了最大加热速率为 13°C/s（800°C/min）。（2）冷却时间也很短，增加了样品通量。柱从 360°C 降至 40°C 不到 1 分钟。（3）功耗非常低 - 5m 柱的 1.7 W/m（8.5W 总功率），15m 柱的 0.69 W/m（10.4W 总功率），当它们保持在 200°C 等温时。进行温度编程时，对于 5m 柱，从 800°C/min 斜坡升温到 350°C，功耗小于 70W。（4）柱束很小，直径只有约 2.25 英寸。所有这些优点使柱束成为快速 GC 分析或便携式仪器的理想选择。在这项研究中，已经评估并比较了柱束与传统的烘箱加热方法的柱效率和保留时间重复性。对于等温条件，通过有效理论板数测量柱效率。发现由于柱束中的不均匀加热，电阻加热的板数始终小于烘箱加热的板数。然而，损失并不显著 - 镍包柱的平均损失约为 1.5%，镍丝柱的平均损失约为 4.5%。对于温度编程，使用分离数进行比较，结果与等温条件下观察到的结果相似。直接加热的保留时间重复性为等温条件下的 0.010%RSD 和温度编程下的 0.037%RSD，与烘箱加热获得的结果相似。已经展示了应用，包括柴油和 PAH 分析。
