Column operation eluent composition

PL aquagel-OH consists of macroporous, hydrophilic particles that exhibit a polyhydroxyl functionality. The columns exhibit extremely good stability during operation they will tolerate an operating pressure up to 140 bar and an eluent composition containing organic modifier up to 50% by volume and eluent pH in the range of 2-10. 

The separation was developed on an analytical SFC system (Series SF3 Gilson System) with a 4.6 x 250mm analytical column packed with the CSP Chiralcel OD. The impact of the organic modifier, operating temperature, and pressure was studied on analytical equipment. The retention time and selectivity change with the eluent composition (percentage of IPA), and these variations are presented in Figure 12.19. The back pressure of the column was set at 80 bar and the temperature at 20 °C. 

The critical diagram M vs retention time for a short RP-18 column of 60 mm length is shown in Fig. 7A. At acetonitrile concentrations > 47 vol.% in the solvent mixture, the retention time decreases as the molar mass of the PEO calibration sample increases retention corresponds to a size-exclusion mode. The reverse behaviour, i.e. the adsorption mode, is obtained at acetonitrile concentrations < 45 vol.%. The critical point of adsorption is operating at an eluent composition of acetonitrile-water 46 54 v/v, where separation is accomplished exclusively with respect to the functional endgroups- (see Fig. 7B). For the alkoxy-terminated PEOs, two distinctively different fractions are obtained, due to the formation of polyethylene glycol as an unwanted by-product. In the case... 

LC-APCI-MS is a derivative of discharge-assisted thermospray, where the eluent is ionised at atmospheric pressure. In an atmospheric pressure chemical ionisation (APCI) interface, the column effluent is nebulised, e.g. by pneumatic or thermospray nebulisation, into a heated tube, which vaporises nearly all of the solvent. The solvent vapour acts as a reagent gas and enters the APCI source, where ions are generated with the help of electrons from a corona discharge source. The analytes are ionised by common gas-phase ion-molecule reactions, such as proton transfer. This is the second-most common LC-MS interface in use today (despite its recent introduction) and most manufacturers offer a combined ESI/APCI source. LC-APCI-MS interfaces are easy to operate, robust and do not require extensive optimisation of experimental parameters. They can be used with a wide variety of solvent compositions, including pure aqueous solvents, and with liquid flow-rates up to 2mLmin-1. 

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