Malan D, van der Walt S J, Rohwer E R
Department of Chemistry, University of Pretoria, Pretoria 0002, South Africa.
Rev Sci Instrum. 2020 Mar 1;91(3):034101. doi: 10.1063/1.5125060.
We present a fast gas chromatographic system that can be used as a second dimension in comprehensive two-dimensional (supercritical fluid × gas) chromatography (SFC × GC). The temperature of the short (1 m long) capillary column is controlled by a resistively heated coaxial stainless-steel tube. The electrical resistance and, therefore, temperature of the stainless-steel tube are measured by continuous monitoring of the current/voltage ratio. Highly repeatable heating rates of up to 2100 °C min (35 °C s) are obtained, which should be high enough for the most demanding fast chromatograms. To reduce the cooling time between temperature programs, the column is cooled by injecting evaporating carbon dioxide into the space between the coaxial heater and the column. This gives cooling rates of 5100 °C min (85 °C s), which allows quick succession of temperature programs. More repeatable heating profiles with stable GC retention times together with faster cooling are significant improvements on previous SFC × GC systems. Cycle times of four gas chromatograms per minute could readily be achieved, which allows efficient coupling to high-resolution stop-flow SFC in the first dimension. We demonstrate the fast chromatograph by separating fatty acid methyl esters, yielding information that would be useful in the food and biodiesel industries.
我们展示了一种快速气相色谱系统，该系统可用作全二维（超临界流体×气相）色谱（SFC×GC）中的第二维。短（1米长）毛细管柱的温度由电阻加热的同轴不锈钢管控制。通过连续监测电流/电压比来测量不锈钢管的电阻，进而测量其温度。可获得高达2100℃/分钟（35℃/秒）的高度可重复升温速率，这对于要求最苛刻的快速色谱图来说应该足够高了。为了减少温度程序之间的冷却时间，通过将蒸发的二氧化碳注入同轴加热器和色谱柱之间的空间来冷却色谱柱。这样可实现5100℃/分钟（85℃/秒）的冷却速率，从而能够快速连续进行温度程序。与更稳定的气相色谱保留时间一起，更可重复的升温曲线以及更快的冷却速度是对先前SFC×GC系统的重大改进。每分钟可轻松实现四个气相色谱图的循环时间，这使得能够与一维中的高分辨率停流SFC进行有效联用。我们通过分离脂肪酸甲酯来展示这种快速色谱仪，得到的信息在食品和生物柴油行业中会很有用。
