Quasi-Stop-Flow Modulation Strategy for Comprehensive Two-Dimensional Gas Chromatography

Abstract

An easy-to-implement strategy of differential flow modulation for comprehensive two-dimensional gas chromatography was innovated. With this approach, an independent auxiliary pneumatic control device for flow modulation was not a prerequisite. The strategy involved splitting the carrier gas stream into two separate streams before reaching the inlet embodiment. One stream was employed as a mobile phase for chromatographic separation. The other stream, for flow modulation, was routed to one of the ports of a three-way solenoid valve. The modulation stream flowed onward to a fluidic path and a T-junction that joined the primary and secondary dimension columns. With this arrangement and depending on the configuration of the three-port valve, the analytical platform can be operated in three different modes: bypass stop-flow, vent stop-flow, and quasi-stop flow. Quasi-stop-flow mode was demonstrated to have a significantly better chromatographic performance, as demonstrated in various types of real-life petroleum samples such as gasoline and light cycle oil. In the light cycle oil sample, a respectable separation between compound classes was achieved with peak width at half height of 34 ms or less for alkanes on a second dimension with polyethylene glycol stationary phase. Excellent repeatability was shown with normal alkanes standards of nC8-nC25. Relative standard deviations for retention times are almost zero in 1D, less than 0.2% in 2D, and less than 3.5% for peak areas (n = 9).

Comprehensive two‐dimensional gas chromatography— A discussion on recent innovations

“…Guan et al. [59] describe a simple modulator that employs a solenoid valve (outside the column oven) that connects the carrier‐gas supply line with a T‐piece positioned between the 1 D and 2 D columns (inside the oven). This modulator allowed three different modes of operation: bypass stop‐flow (closing one port of the solenoid valve), vent stop‐flow (opening one port of the solenoid valve to atmosphere), and quasi‐stop flow.…”

30th Anniversary of comprehensive two‐dimensional gas chromatography: Latest advances

“…Another recent design has been introduced, similar to and simpler than the original differential flow modulation from Seeley and Amirav, in which the auxiliary pressure controller is eliminated, and the same inlet pressure controller provides the gas flows to the first and second dimension and ensure the filling and flushing of the accumulation loop (Figure 2B). 19 The last year has seen a few reports on the use and further development of three dimensional comprehensive GC, exploiting a thermalflow modulation-hybrid GC×GC×GC-MS system. 20,21 As shown, the interest of developing novel forms of modulation that are simpler in hardware and hold limited running costs is confirmed also by the refinement or improvement of the separation capacity of existing forms of flow modulation.…”

“… A and B, Schematic diagram of the two novel GC×GC flow modulation approaches: A, dynamic pressure gradient modulation, repoduced with permission from 17 ; B, quasi‐stop‐flow modulation, permission from 19 …”

Determination of the Signal-To-Noise Ratio Enhancement in Comprehensive Three-Dimensional Gas Chromatography

“…Comprehensive two-dimensional gas chromatography (GC×GC) is becoming a mature technique for the analysis of volatile and semivolatile compounds. 1−4 While new instrumental developments are being reported, 5 the bulk of recent research has shifted to developing data analysis tools 2,6 and exploring new applications, often with a focus on sample preparation. 7 Three key benefits motivate the usage of GC×GC over one-dimensional-GC (1D-GC): ∼10-fold higher peak capacity, 8 chemical class structured separations, and increased detectability from modulation.…”

“…Comprehensive two-dimensional gas chromatography (GC×GC) is becoming a mature technique for the analysis of volatile and semivolatile compounds. − While new instrumental developments are being reported, the bulk of recent research has shifted to developing data analysis tools , and exploring new applications, often with a focus on sample preparation . Three key benefits motivate the usage of GC×GC over one-dimensional-GC (1D-GC): ∼10-fold higher peak capacity, chemical class structured separations, and increased detectability from modulation. − Despite the excellent separation performance provided by GC×GC, many samples are of such complexity that the peak capacity is often insufficient. , One intriguing solution is the addition of a third dimension ( 3 D) to a GC×GC system, that is, comprehensive three-dimensional (3D) gas chromatography (GC 3 ), − configured by sampling the 2 D peaks by a second modulator interfaced to a 3 D column of unique selectivity.…”