Top–down lipidomic analysis of human lipoproteins by chip-type asymmetrical flow field-flow fractionation–electrospray ionization-tandem mass spectrometry

Study on aggregation behavior of low density lipoprotein in hen egg yolk plasma by asymmetrical flow field-flow fractionation coupled with multiple detectors

“…Asymmetrical flow field-flow fractionation (AF4) has attracted increasing interest in recent years owing to its broad dynamic separation range (approximately from 1 nm to well above 1 lm) and the utilization of an ''open channel'' void of stationary phase or packing materials (Giddings, 1993;Wahlund & Giddings, 1987). The absence of a stationary phase makes AF4 a gentle fractionation technique with limited shear and mechanical stress applied on sample components, particularly suited for the analysis of delicate analytes (such as, proteins and DNA) with full preservation of their native properties (Kim, Lee, Lim, & Moon, 2013;Williams, Runyon, & Ashames, 2010). Another main advantage of AF4 is the wide choice of carrier liquid which allows for the analysis of a sample in the formulation buffer.…”

Top-down and bottom-up lipidomic analysis of rabbit lipoproteins under different metabolic conditions using flow field-flow fractionation, nanoflow liquid chromatography and mass spectrometry

“…Lipid analysis can also be made using a top-down approach in which plasma or serum lipoproteins can be injected directly into electrospray ionization-tandem MS (ESI-MS n ) during the separation of lipoproteins. Development of a chip-type asymmetrical FlFFF (or AF4) channel offered an on-line hyphenation with MS (cAF4-ESI-MS/MS) to carry out a direct analysis of the lipids in different lipoproteins [21,22]. Use of miniaturized FlFFF channel prior to ESI-MS offers great advantages such as the on-line desalting of plasma samples, which can enhance the ionization of lipid species, and a high-speed lipid screening capability (∼200 min per sample) with the bypass of the time consuming analytical steps (∼36 h): isolation of the HDL/LDL fraction and extraction of the lipids from each lipoprotein fraction prior to LC-MS/MS analysis.…”

Flow Field-Flow Fractionation with Mass Spectrometry for Top-Down and Bottom-Up Lipidomics

“…Unlike the MxHF5, in which the channel is cylindrical, the rectangular channel design of mAF4 forces the field to travel in one direction (from the top of the channel to its bottom) through a permeable wall (a regenerated cellulose membrane sheet layered above the frit). With the use of FlFFF prior to ESI-MS, online desalting effect is achieved as salts and other types of metabolites with small molecular weights permeate through the membrane and frit during the focusing/relaxation step along with the crossflow, enhancing the ESI of lipids [31]. Figure 6 shows a schematic of mAF-ESI-MS/ MS with suction pump, which is employed to adjust the rate of the outflow.…”

“…Figure 6 shows a schematic of mAF-ESI-MS/ MS with suction pump, which is employed to adjust the rate of the outflow. Without the pump, the outflow rate would be too high, impeding ionization; however, decreasing the outflow would lengthen analysis time, necessitating the use of a pump [31]. As the carrier liquid of mAF4 was aqueous NH 4 HCO 3 solution, ionization modifier (1% formic acid in CH 3 CN for positive ion mode and 0.5% NH 4 OH for negative ion mode) was mixed at a constant rate through the micro-tee prior to ESI-MS analysis.…”

“…This can be achieved by implementing a miniaturized asymmetrical FlFFF (mAF4) channel to ESI-MS (a standard FlFFF channel typically outputs a few tenths of a mL/min and is, therefore, insufficient for the task). The mAF4 channel is assembled by stacking frit-inserted, 1.5-mm-thick stainless steel plates to form a 13-cm-long and 6-mm-wide channel [29][30][31][32]. Unlike the MxHF5, in which the channel is cylindrical, the rectangular channel design of mAF4 forces the field to travel in one direction (from the top of the channel to its bottom) through a permeable wall (a regenerated cellulose membrane sheet layered above the frit).…”