Observation of the matrix effect due to the electron transfer in laser ablation plasma

We investigate the so-called “matrix effect” on the relative intensities of ions in mixed solutions of alkali salts by using femtosecond laser ablation time-of-flight mass spectrometry (fsLA-TOFMS). For the 1:1 mixed solution of sodium and potassium salts, the intensity ratio of cations (Na+/K+) decreases as the total concentration increases. From the measurement for the mixed solution of lithium, sodium, potassium, rubidium, and cesium solutions, we find out significant dependence of each ion intensity on the total concentration. The results suggest that the electron transfer from neutral atoms to cations coexistent in the ablation plasma affects the relative ion intensities observed with TOFMS when the total ion concentration is high.