THE POSSIBILITY OF THE DIRECT MEASUREMENT OF MICELLE WEIGHT BY ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY

Measurement of the molecular weight of micelles, which are characteris tic aggregates of molecules, was conducted using electrospray ionizati on mass spectrometry (ESI-MS). Micelle solutions were prepared by diss olving octyltrimethylammonium bromide [OTAB: C8H17N(CH3)(3)Br] in wate r alone, without other additives. From the measurement of the m/z of t he doubly or triply charged ions, it was revealed that the micelle of OTAB exhibited an almost symmetrical and polydisperse distribution abo ut the mean molecular weight of 5000-5500. This molecular weight infor mation is in good accordance with other estimated values. This result demonstrated the possibility of a direct measurement of micelle weight by mass spectrometry. (C) 1998 John Wiley & Sons, Ltd.