Abstract:

In order to manage and limit the types and amounts of preservatives in toothpaste and to improve the quality of toothpaste, a method for determining the content of preservatives in toothpaste by high performance liquid chromatography was studied. The mixed standard solution of preservatives was prepared with five reagents including methylparaben, ethylparaben and benzoic acid, and the toothpaste samples were treated with solutions such as acetonitrile. Sodium dihydrogen phosphate solution, methanol and acetonitrile mixed solution were used as mobile phases. The mixed standard solution and toothpaste samples were measured under the conditions that the column temperature, injection volume and flow rate were room temperature, 5 μL and 1.5 mL/min, respectively. A standard curve was drawn according to retention time and area of chromatographic peak of mixed standard solution. The results show that: under the condition that the ratio of sodium dihydrogen phosphate solution, methanol and acetonitrile in the mobile phase is 55∶25∶20, the separation degree of the mixed standard solution is the highest. The recovery rate of various preservatives fluctuates between 88.68% and 99.61%, and the relative standard deviation fluctuates between 0.39% and 2.44%. The repeatability test results meet the needs of practical applications.

Key words: high performance liquid chromatography, toothpaste, preservative