The effect of laser exposure (the number of laser shots) on the stability of production of matrix (gentisic acid, sinapinic acid, nicotinic acid and benzoic acid) and biomolecule (insulin and cytochrome-c) ions is presented. Two methods of sample preparation, dried-droplet and pressure, were examined. In the case of pressure preparation, the dry powder sample was pressed mechanically with a pressure of 30 MPa. The best results were obtained for the pressure method and gentisic acid as matrix.