Qualitative and quantitative determination of poloxamer surfactants by mass spectrometry

Poloxamers are polyethylene-polypropylene glycol linear co-polymers. A simp le matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) method has been developed for the determination of the average molecular w eight of poloxamers. The molecular mass of five standard poloxamers determi ned by MALDI closely corresponds to that specified by the manufacturers, an d no mass distribution effects were observed. Quantitation of distributions based on the molecular mass envelope using electrospray (ES) ionization wa s unsuccessful. To overcome this problem, quantitation was based on fragmen t ions (m/z 45 and 59) which gave reproducible signals using a very high or ifice voltage (similar to 200 eV). Poloxamer concentrations were determined accurately with a good linear response using the standard addition method. We believe that the use of very small fragment ions for quantitation of po lymers may become a widely applicable general technique. Copyright (C) 2001 John Wiley & Sons, Ltd.