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

Ultrafast modulation with a modulation period P-M >= 50 ms via a pulse flow valve is demonstrated for comprehensive two-dimensional gas chromatography (GC x GC) and comprehensive three-dimensional (3D) gas chromatography (GC(3)). Significant increases in peak capacity and peak capacity production are achieved for GC x 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 x GC mode, a 115-component test mixture was evaluated using a PM of 500 ms, creating an apparent D-2 peak width-at-base W-2 with an average of 25 ms, producing a (2)n(c) of 20. Based on the average W-1 of 1.0 s for the 6 min first dimension D-1 separation, an ideal peak capacity n(c,2D) of 7200 is achieved (1,200/min peak production). For a high-speed GC x GC separation (30 s run), a P-M of 75 ms produced apparent W-2 of 8 ms, ideal for the third dimension of a GC(3) instrument. Using the knowledge gained from this high-(s)peed GC x 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 P-1(M) of 1.2 s and a P-2(M) of 60 ms, average W-1 of 3.2 s, W-2 of 130 ms, and apparent W-3 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 similar to 10,000 for GC(3) was achieved for the 11 min D-1 separation window of the 115-component test mixture. (C) 2018 Elsevier B.V. All rights reserved.