The amount of AH + and A⁞Met + in the solid sample can be estimated using the corresponding equilibrium constants of equations (12-14). For AH + , in an exemplary case of A being diethyl ether, which is one of the weakest coordinating molecules, and M being CHCA, the concentration of AH + would be 2.4 × 10 -4 M assuming that the pKa of 3.5 in water for the conjugate acid of diethyl ether and 1.17 in water for CHCA can be used here, and the sample consists 10 pmol analyte in 25 nmol matrix. For A⁞Met + , in an exemplary case of A being 15-crown-5, Met + being Na + , and M being CHCA, the concentration of A⁞Met + would be 2.2 × 10 -5 M, which corresponds to a ratio of 7.3 × 10 -3 for A⁞Met + over A, assuming that the equilibrium constant 2.8 in water can be used for equation (14), 1 µL typical LC-MS grade water with 0.2 ppm Na + is used to prepare the sample, and the sample consists 10 pmol analyte in 25 nmol CHCA (molar volume 133 mL/mol). Again, it is noted that the pKa values and equilibrium constant from the literature may be significantly different from the actual values in solid MALDI MS samples and estimations may be far away from being accurate.