Tracing the origin of the anomalous matrix suppression in matrix-assisted laser desorption ionization and extending the linear dynamic range during analyte quantification

Abstract

In the matrix-assisted laser desorption ionization-based quantification method developed in this laboratory, a linear calibration curve is constructed by plotting the analyte-to-matrix ion abundance ratio as a function of the analyte concentration. As the analyte concentration increases, however, the curve deviates from linearity. Previously, we observed that the occurrence of this deviation correlated with the decrease in the matrix ion signal, or matrix suppression. In this work, we found that saturation of the detector was one of the factors responsible for the above phenomena. As we decreased the detector gain, the upper limit of the linear dynamic range increased by as much as one order of magnitude. Even after a substantial decrease in the detector gain, however, the nonlinearity remained at a high analyte concentration, which we cannot account for at present. The method developed in this work can be useful for the quantitative imaging of analytes in heavily contaminated samples.