GRAS Screen 4 samples twenty four salts, encompassing pH 4-9 versus four medium molecular weight Polyethylene glycols (1,000, MME 2,000, 3,350 & 4,000). GRAS Screen 4 is supplied in a 96 Deep Well block format and is compatible with robotic and multi-channel pipet liquid handling systems. GRAS Screen 4 is compatible with vapor diffusion, free interface diffusion, and microbatch crystallization methods. For research use only.