A new experimental technique has been developed for the investigation of secondary particle emission from liquid targets resulting from collision interactions with fast charged particles. Secondary ion mass spectra are presented for the first time for liquid water and 0.1 M, 1 M and 5 M NaCl aqueous solutions bombarded by 2.0 MeV He(+) ions. The mass spectra exhibit a series of negative cluster ions of the form of X(m)Y(n)R(-), where X and Y stand for neutral molecules such as H(2)O, NaCl and NaOH and R(-) stands for a negative charged ion such as O(-), OH(-) and Cl(-). Intensities of negative ions are found to change significantly as a function of the concentration. The results imply evidently that the cluster structure in liquid targets changes drastically depending on the abundance of NaCl in solutions. (C) 2009 Elsevier B.V. All rights reserved.