A comprehensive two-dimensional gas chromatography valve modulation method using hold-release primary column flow for...

A valve modulator with a hold-release primary column flow method has been proposed. This method uses a valve plumbed so that the head and tail of the primary column are connected during the secondary separation, to reverse, slow down, and finally stop the primary column flow. This keeps the sample in the primary column longer, gaining more time for secondary separation. Applying this method, a 60-second secondary retention time with 100% transfer, 133 ms secondary peak width at base, and no primary peak profile loss has been achieved. A standard sample with 19 compounds in 3 groups has been tested. The relative standard deviations for the retention time of this standard mixture are <0.26% for primary dimension and <0.94% for secondary dimension. A gasoline sample analysis with 5, 15, and 30-meter-long secondary columns has been demonstrated. With the secondary column length increase, the secondary separation has greatly improved even though the total run time increases to 45, 110, and 120 min and the toluene primary peak width at base increases to 0.51, 1.81, and 1.85 min respectively. A diesel samplerun by this method has also been demonstrated.