Solvent and temperature gradients in separation of synthetic oxyethylene‐oxypropylene block (co)polymers using high‐temperature liquid chromatography

Abstract

Chromatographic behavior of synthetic block (co)oligomer samples (EO)n(PO)m(EO)n and (PO)n(EO)m(PO)n with different distribution of propylene oxide (PO) and ethylene oxide (EO) monomer units was investigated on three types of stationary phases on zirconium dioxide support: Zr-PS (polystyrene), Zr-carbon, and Zr-carbon C18. The effects of the distribution and sequence of the oxyethylene and oxypropylene monomer units on the chromatographic retention depend on the type of the stationary phase, but are strongly affected by the organic modifier (methanol or ACN) in aqueous-organic mobile phase. Special attention was focused on the influence of the mobile-phase composition on the separation according to the EO and PO distribution. Zirconia-based columns are stable at elevated temperatures and can be used in high-temperature LC (HTLC); hence, we investigated the temperature effects on the chromatographic behavior up to 90 degrees C. The applications of solvent and temperature gradients were compared on the zirconia stationary phases in the RP mode.

Controlling the retention in capillary LC with solvents, temperature, and electric fields

“…Figure 2 illustrates the extent of gradient pre-elution in a commercial instrument with V D = 18 lL, more than twice the hold-up volume, V m = 8 lL, of a 15060.3 mm ID C8 column at 3 lL/min. As the gradient delay time is 6 min, the separation of benzene to butylbenzene in a 10 min gradient run from 80 to 100% methanol (Figure 2.B) is the same as the isocratic separation in 80% methanol ( Figure 2.A); the retention times of amylbenzene and hexylbenzene are only slightly shorter under gradient than under isocratic conditions [53].…”

Retention and Separation Selectivity of Natural Phenolic Antioxidants on Zirconia Based Stationary Phases

“…The investigation of the chromatographic behaviour of synthetic oxyethyleneoxypropylene block (co)polymers on zirconia based stationary phases [37] showed that the retention and the selectivity of separation depend not only on the type of the stationary phase, but are strongly affected by the composition of the mobile phase. Based on our earlier study, [17] using a ZirconiaCarbon column in the second dimension of a comprehensive 2-D LCxLC system for the separation of phenolic antioxidants, we compared the retention behaviour of natural antioxidants on three types of Zirconia based stationary phases (Zirconia-Carbon, Zirconia-Carbon C 18 , Zirconiapolystyrene).…”

“…[17] However, chromatographic behaviour of these compounds on various types of zirconia phases has not been systematically compared so far, except for the separation of oxyethylene glycol and oxypropylene glycol surfactants. [37] EXPERIMENTAL…”

Temperature effects on nano‐LC column packing technology

“…In addition, it is also possible to use a temperature gradient alone or in combination with a solvent gradient to increase the resolution []. Up to a few years ago, the use of HTLC was limited by the scarce stability of the stationary phases available.…”