Dolan, Willey, 2010, 3rd ed.).įor different solvents look in the Mixtures of Water and Organic Compounds file in Landolt-Börnstein Database. These data are based on the table presented in Introduction to Modern Liquid Chromatography (L.R. Solution for At 68F water has a dynamic viscosity of about 2.11 E-5 lb-s/ft. The viscosity of water has been studied thoroughly because of the precision with which water flow must be controlled in many industrial applications. The low viscosity of water is important in its role as the solvent for life's chemical reactions and for blood circulation. The absolute salinity is taken as 35.16504 / 35 times the practical salinity. The viscosity of water measures its resistance to flow and is critical to its many functions. Practical salinity parts per thousand of dissolved solids (mainly salt). Further, as you can see from the following figures, the viscosity decrease with higher temperature, which forces further research in the field of high temperature liquid chromatography. The fresh water viscosity is calculated from temperature and density using the IAPWS R12-08 industrial equations. Generaly, the viscosity decreases with increase in concentration of the organic modifier, acetonitrile or methanol, respectively. Thus, higher flow rates of the mobile phase can be used and lead to the shorter analysis time.įollowing tables and plots show dependence of the viscosity for a acetonitrile-water and a methanol-water mixtures at different composition of the binary solvent and temperature. Clearly, the mobile phase with lower viscosity shows lower instrumental pressure. In liquid chromatography, the viscosity of the mobile phase plays crucial role. The SI unit for the viscosity is Pascal-second (Pa.s).ġ cP = 0.001 Pa.s Viscosity of the mobile phase Its a term used to describe the friction that occurs within a moving fluid. The unit of viscosity is called the poise (P). A fluids viscosity is a measure of its resistance to movement or evaporation. More technically speaking, viscosity is classically defined as the tangential force per unit area necessary to maintain unit relative velocity between two parallel plates in a liquid unit distance apart. For example, water is “thin” with low viscosity, while honey is “thick” having a higher viscosity (see example on right).
In case of liquids, the viscosity can be simply expressed as “thickness”. This resistance is called viscosity and can be expressed as a resistance to flow. UPDATED – One of the general property of the liquids is their resistance to change a form. Example of liquids with different viscosity