Abstract
Sodium chloride is a thickener used to adjust the viscosity of shampoos. This study evaluated three physicochemical parameters (i.e., pH, viscosity, and conductivity) in six shampoo formulations with increasing concentrations of sodium chloride. The formulations were made with different concentrations of sodium chloride (i.e., 0 %, 1 %, 3 %, 5 %, 10 %, and 20 %). The pH and conductivity were determined using a digital pH meter and conductivity meter, respectively, and the tests were performed in triplicate. The viscosity was measured in a single assay using a Brookfield rotational viscometer. The formulations showed a constant pH value, with a mean of 4.8, appropriate pH range for shampoos. Regarding conductivity, the higher the concentration of sodium chloride, higher the conductivity. There was a steady increase in viscosity between the concentrations 0 %, 1 %, and 3%, whereas beginning at a concentration of 5 % there was a proportional decrease in viscosity (i.e., at concentrations of 5 %, 10 %, and 20 %). Thus, it is arguable that the pH of all samples of shampoos were appropriate. The conductivity increases proportionally to the concentration of sodium chloride and the viscosity increase until the breaking of formulation. The formulations with sodium chloride concentrations of between 1 % and 5 % presented ideal physicochemical characteristics for shampoos.
