Polyoxyethylene-Delta(9,11)-didehydrostearate and glycerol-polyoxyethylene-Delta(9,11)-didehydrostearate: two new components of the non-ionic emulsifier Cremophor EL

The polyethoxylated heterogeneous components of the so far poorly characterised non-ionic emulsifier Cremophor EL (polyoxyl 35 castor oil) (CrEL) were fractionated by cyclodextrin modified micellar electrokinetic capillary chromatography (CD-MEKC) combined with indirect UV detection. The resulting peaks were assigned to the corresponding components by delayed extraction matrix-assisted laser desorption/ionization time of flight mass spectrometry (DE-MALDI-TOF-MS) as detection device. In order to combine CE and MS the fractionating robot Probot was employed which enables both the online fractionation of the CE eluate on a MALDI target during the electrophoretic separation and the simultaneous dosage of the MALDI matrix. The obtained mass spectra were evaluated by comparing the residue masses of the homologue peak series of the polyethoxylates with the calculated residue masses of potential CrEL-components. The overlapping of homologue peak series with isobaric residue masses was detected by using the residue mass plot, the newly developed evaluation method. Combining theses techniques, both the first detailed structure elucidation and a semiquantitative analysis of the polyethoxylated CrEL-components was achieved. Together with the polyethoxylate series of yet elucidated structures two additional series were observed the corresponding components of which could not be identified at the beginning. Systematic investigations showed that the elimination of water from ricinoleic acid during the synthesis of the emulsifier leads to the polyethoxylates glycerol POE-Delta(9,11)-didehydrostearate and POE-Delta(9,11)-didehydrostearate so far unknown in CrEL.