A quantitative model of ultraviolet matrix-assisted laser desorption/ionization including analyte ion generation.
A quantitative model of ionization in ultraviolet matrix-assisted laser desorption/ionization (Knochenmuss, R. J. Mass Spectrom. 2002, 37, 867) is extended to include secondary ion-molecule reactions. Matrix-to-analyte charge-transfer reaction kinetics are described by a hard-sphere Arrhenius expression. The activation energy is derived from the reaction exoergicity using a nonlinear free energy relationship. The approach is applied to the specific case of proton-transfer reactions. With no adjustable parameters, the model correctly predicts the existence and characteristics of the matrix and analyte suppression effects, the shapes of the two-pulse time-delayed yield curves, and the dependence of analyte yields on laser fluence, molecular weight, relative concentrations, and reaction exoergicity.
Knochenmuss
Richard
R
Novartis Institutes for Biological Research, 4002 Basel, Switzerland. richard.knochenmuss@pharma.novartis.com
D006096:Gramicidin / Q000032:analysis / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D008956:Models, Chemical; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013373:Substance P / Q000032:analysis / Q000737:chemistry; D013816:Thermodynamics; D014466:Ultraviolet Rays
D007477:Ions; D006096:Gramicidin; D013373:Substance P