title: Desorption electrospray ionization mass spectrometry for the analysis of pharmaceuticals and metabolites.
abstract: The performance of desorption electrospray ionization (DESI) in the analysis of a group of pharmaceuticals and their glucuronic acid conjugates is reported. The suitability of different sprayer solvents and different surfaces was examined. In the positive ion mode, water/methanol/trifluoroacetic acid performed best, whereas, in the negative ion mode, water/methanol/ammonium hydroxide was found to be the most suitable spray solvent. Of the surfaces investigated, polymethylmethacrylate (PMMA) was found to give the best performance in terms of sensitivity. Spray solution flow rate and the distance of the sprayer tip from the surface were also found to have significant effects on the signal intensity. Analytes with basic groups efficiently formed the corresponding protonated molecules in the positive ion mode, whereas acidic analytes, such as the glucuronic acid conjugates, formed intense signals due to the deprotonated molecules in the negative ion mode. Ionization of neutral compounds was less efficient and in many cases it was achieved through adduct formation with simple anions or cations.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084, USA.
authors.forename: Tiina J
authors.initials: TJ
authors.lastname: Kauppila
authors.forename: Justin M
authors.initials: JM
authors.lastname: Wiseman
authors.forename: Raimo A
authors.initials: RA
authors.lastname: Ketola
authors.forename: Tapio
authors.initials: T
authors.lastname: Kotiaho
authors.forename: R Graham
authors.initials: RG
authors.lastname: Cooks
authors.forename: Risto
authors.initials: R
authors.lastname: Kostiainen
mesh_terms: D015394:Molecular Structure; D004364:Pharmaceutical Preparations / Q000737:chemistry / Q000378:metabolism* / Q000652:urine*; D012680:Sensitivity and Specificity; D012997:Solvents; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013329:Structure-Activity Relationship; D014556:Urine / Q000737:chemistry
chemical_list: D004364:Pharmaceutical Preparations; D012997:Solvents