The principle of SPR is based on the reaction between the fatty components in the traces and the hydrophobic tails of each specific reagent. These tails are linked to the hydrophilic heads which react with metal salt to give a precipitate.(1) Choline chloride is one such water soluble organic compound with a hydrophilic cation with the chloride anion, and a hydrophobic tail. Thus, the presence of choline chloride in SPR II may help to enhance the effectiveness of this formula by giving more attachment sites between the metal salt and the hydrophilic head based upon its polar property.