Thesis (M.Sc.)--Chulalongkorn University, 2004

Involves the method for determination of molecular weight distribution and quantitative analysis of polysorbate emulsifier, using matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). The following MALDI-MS conditions were found to provide the good MS spectrum: sample preparation using dried droplet method, alpha-cyano-4-hydroxycinamic acid in THF as an ideal matrix. The ratio of surfactant: matrix was 1:75 by volume and the laser power was 310 [micro]J. MALDI spectrum indicated that the presence of residue ethylene oxide polymer, free esterified sorbitan-based, sorbide-based and disorbitan-based species. Linear calibration curves were obtained in the range 5-50 mg/ml. The limit of detection was determined to be 1.03 femtomole. Two commercial pharmaceutical suspension and two commercial lotion were analyzed. The results indicated that all of the samples showed their molecular weight distributions in the range of 1000-2000 Da. Then,the amount of polysorbate in commercial drug A and B were found to be 0.091 +- 0.004 and 0.090 +- 0.006 precent by weight, and commercial lotion A and B were found to be 0.83 +- 0.060 and 1.32 +- 0.150 precent by weight, respectively. Thus, the MALDI-MS technique was an excellent method for determination of the molecular weight distribution and quantitative analysis of polysorbate emulsifier in drugs and cosmetic products