HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY AND DETECTION OF POLYETHERS AND THEIR MONO(CARBOXY)ALKYL-SUBSTITUTED AND ARYLALKYL-SUBSTITUTED SUBSTITUTED DERIVATIVES

This review deals with high-performance liquid chromatographic (HPLC) separation techniques and detection methods for a wide variety of poly ether derivatives, including alkyl-, arylalkyl-, carboxyalkyl-substitu ted polyethylene glycols mainly applied as non-ionic surfactants (NIS) , and native (underivatized) polyethylene glycols (PEGs), polypropylen e glycols (PPGs) and polybutylene glycols (PBGs) widely used in either industrial or pharmaceutical applications. Normal-phase (NP) and reve rsed-phase (RP) systems have been considered for NIS, the NP technique being the most suitable for separation according to the number of eth oxylate units, whereas separation according to the hydrophobic alkyl c hain is favored on RP stationary phases. At variance with NIS mainly R P-HPLC is applied for native (underivatized) polyethers of the PEG, PP G and PEG type. Ion-exchange chromatography (IEC) is still a minor tec hnique for the separation of PEG derivatives, which exploits the capab ility of the 1,2-dioxoethylene moiety to form complexes with potassium ions. Liquid chromatography under critical conditions (LCCC) is the m ethod of choice for separation of polyethers according to their chemic al composition and is preferably applicable to copolymers built up fro m different components. A multitude of detection principles substantia lly differing in either selectivity or sensitivity has been successful ly used for signal monitoring, with detection by measurement of refrac tive indexes (RI), UV absorption, fluorescence acid responses from eva porative light scattering of ''solid'' droplets being the most promine nt. Nevertheless, UV detection still dominates because of the existenc e of the phenyl chromophor in many NIS and the ease of derivatization of polyethers lacking an inherent aromatic moiety with a large variety of chromophoric agents. Additionally, well-established methods are av ailable for low wavelength UV detection below 200 nm even for the nati ve polyethers.