ELECTROSPRAY SAMPLE PREPARATION FOR IMPROVED QUANTITATION IN MATRIX-ASSISTED-LASER-DESORPTION IONIZATION TIME-OF-FLIGHT MASS-SPECTROMETRY/

The goal of this,work is the development of a rapid and objective matr ix-assisted laser desorption/ionization time-of-flight mass spectromet ry (MALDI-TOFMS) method for the quantitation of peptides and proteins in human plasma suitable for use in the Good Laboratory Practices (GLP ) environment, where the analytical method, validation and pharmacokin etic parameters derived from concentration data will be scrutinized by global regulatory agencies, Electrospray deposition has traditionally been used to prepare thin, uniform samples for a number of techniques , including Cf-252 plasma desorption and secondary ion mass spectromet ry, Here the electrospray process of sample application is used to red uce the segregation of analyte from matrix during the sample drying st ep, The small droplets formed during the electrospray process are foun d to significantly improve the homogeneity of the sample surface prepa red, Experiments comparing the traditional air dried and electrospraye d methods of sample preparation show that the increase in sample homog eneity from electrosprayed samples deccreases both the within-sample s pot and between-sample spot variability, resulting in a decrease in pe rcent coefficient of variation (%CV) for the recorded MALDI mass spect ra, The increase in sample homogeneity permits a more objective use of MALDI-TOFMS as a quantitative analytical method and has led to the de velopment of an assay for the determination of desamino-[8-D-arginine] vasopressin (DDAVP) using arginine vasopressin (AVP) as internal stan dard in human plasma, The range of quantitation observed (2.0-10 mu g/ mL) is of limited value for bioanalytical application; however, the an alysis of neat standards shows lower quantitation limits are easily ac hieved, (C) 1997 John Whey & Sons, Ltd.