Macedo Leonel Bortolotto, Bonatto Cristian, Kist Tarso B Ledur
Faculty of Pharmacy, Federal University of Rio Grande Do Sul, Porto Alegre, Brazil.
Institute of Physics, Federal University of Rio Grande Do Sul, Porto Alegre, Brazil.
J Sep Sci. 2025 Aug;48(8):e70240. doi: 10.1002/jssc.70240.
Current commercially available capillary electrophoresis instruments lack centrosymmetric and efficient temperature control along the whole extend of the capillary. Here we studied the characteristics and thermal performance of a cooling system that consists of cooling capillaries (fused silica microtubes) which are tied around the complete extent of the analytical capillaries. Six cooling capillaries with only 75 µm inner diameter (320 µm outer diameter-without polyimide) were tied around the outer surface of 320 µm outer diameter analytical capillaries (also without polyimide). The tying process is detailed in a previous publication (J Sep Sci. 2025; 48: e70081. https://doi.org/10.1002/jssc.70081). The application of a pressure gradient of 0.25 bar/cm in the cooling liquid was enough to efficiently remove heat and control temperature. Very strong electric fields could be applied, producing very high and stable electric currents. Fields beyond 3500 Volts/cm were applied in a 50 µm inner diameter capillary filled with 20 mM sodium phosphate buffer solution at pH 7.20 and the coolant set at 25°C. This cooling system outperformed the two most used systems: forced air and recirculating liquid coolant in a tube with a capillary inside. The spatial steady-state temperature profiles of the systems were simulated by numerically solving the heat equation using a finite element method. The centrosymmetric temperature profile and efficiency of this cooling system was corroborated by these numerical results. An objective parameter indicating cooling asymmetry was introduced and used to quantify the superior performance of this new cooling system.
目前市面上的毛细管电泳仪器在毛细管的整个长度范围内缺乏中心对称且高效的温度控制。在此，我们研究了一种冷却系统的特性和热性能，该系统由围绕分析毛细管整个长度捆绑的冷却毛细管（熔融石英微管）组成。六根内径仅为75 µm（外径320 µm - 无聚酰亚胺）的冷却毛细管被捆绑在320 µm外径的分析毛细管（同样无聚酰亚胺）的外表面。捆绑过程在之前的一篇出版物中有详细描述（《分离科学杂志》。2025年；48：e70081。https://doi.org/10.1002/jssc.70081）。在冷却液中施加0.25 bar/cm的压力梯度足以有效散热并控制温度。可以施加非常强的电场，产生非常高且稳定的电流。在一根内径为50 µm、填充有pH 7.20的20 mM磷酸钠缓冲溶液且冷却液设定为25°C的毛细管中施加了超过3500伏/厘米的电场。该冷却系统优于两种最常用的系统：强制风冷和内部有毛细管的管内循环液体冷却剂系统。通过使用有限元方法对热方程进行数值求解，模拟了这些系统的空间稳态温度分布。这些数值结果证实了该冷却系统的中心对称温度分布和效率。引入了一个指示冷却不对称性的客观参数，并用于量化这种新型冷却系统的卓越性能。
