Timed Relay Contact Closure Controlled System for Parallel Second Dimensions in Multi-Dimensional Liquid Chromatography

Authors: Byrdwell, W Craig

Submitted to: BMC Research Notes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2019
Publication Date: 8/1/2019
Citation: Byrdwell, W.C. 2019. Timed relay contact closure controlled system for parallel second dimensions in multi-dimensional liquid chromatography. BMC Research Notes.12:477-482. https://doi.org/10.1186/s13104-019-4506-7.
DOI: https://doi.org/10.1186/s13104-019-4506-7

Interpretive Summary: Milk is such a complex sample that it requires unusually rigorous methods for separation and analysis of the components. Fats (triacylglycerols, TAGs) in milk include a much wider range range of fatty acids than the fats in edible oils, and those fatty acids present unique challenges for analysis, because there is so much overlap between closely related TAGs. Because of this complexity, previous methods for separation and analysis using comprehensive two-dimensional separation techniques are inadequate for separation of the complete set of milk TAGs. Therefore, a second parallel second-dimension separation is required. However, to accomplish this, a set of contact-closure controlled valves was installed, and an electronic timing circuit was connected to automatically repeatedly switch the valves. After passing through two partial separations, these valves sent components to be analyzed to a third and final separation to accomplish separation of short TAGs that could not be separated using the other two separations.

Technical Abstract: Two contact closure (CC) activated 4-port, 2-position valves (4P2PVs) for ultra-high performance liquid chromatography (UHPLC) were joined together and used for one of two second dimensions in comprehensive two-dimensional liquid chromatography (2D-LC) coupled to four mass spectrometers simultaneously in parallel in an LC1MS2 x (LC1MS1 + LC1MS1) = LC3MS4 configuration. A wireless communication contact closure system (WCCCS) was used to control all instruments, as well as a timed contact closure circuit (TCCC) which controlled the two UHPLC valves. The TCCC was wired through one of the relays in the WCCCS to activate the TCCC, which provided repetitive CCs for the 4P2PVs based on either 1) the time set on dip switches on the TCCC, or 2) based on relay controls in the chromatographic method. The TCCC-controlled 4P2PVs were used to direct a portion of the 1D eluent to one of the two 2D’s for separation by a quaternary UHPLC system that was not allowed by the commercial 2D-LC system. The 1D separation was a conventional non-aqueous reversed-phase HPLC instrument used for separation of TAGs; the commercial 2D-LC 2D binary UHPLC was used for silver-ion chromatography; and the CC-controlled second 2D was used for separation of short-chain (SC) triacylglycerols (TAGs) on a SC C8 column. This was necessitated because the saturated SC-TAGs were not resolved using silver-ion chromatography (which retention mechanism was coordination to double bonds) and required a different separation mechanism.