Ultrafast separations via pulse flow valve modulation to enable high peak capacity multidimensional gas chromatography

Abstract Ultrafast modulation with a modulation period P M ≥ 50 ms via a pulse flow valve is demonstrated for comprehensive two-dimensional gas chromatography (GC × GC) and comprehensive three-dimensional (3D) gas chromatography (GC 3 ). Significant increases in peak capacity and peak capacity production are achieved for GC × GC and GC 3 relative to previous studies due to using pulse flow valve modulation. Due to the nature of the “partial” modulation process, the separation dimension following pulse flow valve modulation is not a traditional chromatogram, rather requires data processing to convert the data to expose the encoded chromatographic information, producing “apparent” chromatographic peaks. In the GC × GC mode, a 115-component test mixture was evaluated using a P M of 500 ms, creating an apparent 2 D peak width-at-base 2 W with an average of 25 ms, producing a 2 n c of 20. Based on the average 1 W of 1.0 s for the 6 min first dimension 1 D separation, an ideal peak capacity n c,2D of 7200 is achieved (1,200/min peak production). For a high-speed GC × GC separation (30 s run), a P M of 75 ms produced apparent 2 W of 8 ms, ideal for the third dimension of a GC 3 instrument. Using the knowledge gained from this high-speed GC × GC experiment, the pulse flow valve was implemented as the second modulator in GC 3 . Three samples were evaluated in the GC 3 mode: a simple mixture containing 18 compounds (to illustrate basic concepts), the 115-component test mixture (to determine peak capacity figures-of-merit), and a diesel spiked with 8 polar compounds (to illustrate chemical selectivity benefits of GC 3 ). For the 115-component test mixture with a 1 P M of 1.2 s and a 2 P M of 60 ms, average 1 W of 3.2 s, 2 W of 130 ms, and apparent 3 W of 13 ms were produced, resulting in a 1 n c of 210, 2 n c of 9.2, and 3 n c of 5, respectively. Hence, an ideal peak capacity, n c,3D of ∼10,000 for GC 3 was achieved for the 11 min 1 D separation window of the 115-component test mixture.