ABSTRACT
Objective: To establish an ion chromatography (IC) method to determine the content of chloride ion and sulfate ion in ethylparaben, and evaluate the quality status of chloride ion and sulfate ion in ethylparaben at different levels.Methods: Ion chromatograph was used.The column was Dionex IonPac AS 18 (250 mm ×4 mm,5 μm) using potassium hydroxide as the mobile phase with gradient elution, the flow rate was 1.0 ml·min-1 , the injection volume was 25 μl, and the quantitative method was standard curve.Results: The method showed good linear relationship within the range of 0.02-4.00 μg·ml-1 for chloride ion (r=0.999 9) and 0.10-10.00μg·ml-1 for sulfate ion (r=0.999 5).The average recovery was 90.12% (RSD=3.4%) and 85.54% (RSD=6.2%) for chloride ion and sulfate ion, respectively (n =9).The content range of chloride ion and sulfate ion was 0.000 3%-0.015 7% and 0.000 9%-0.024 4% in 63 batches of samples, respectively.Conclusion: The established method is simple, fast and accurate, which can be used to determine the contents of chloride ion and sulfate ion in ethylparaben and is helpful to its quality control.
ABSTRACT
Objective:To determine the phase-transition temperature of white vaseline produced by different processes by differen-tial scanning calorimetry ( DSC) in order to analyze the relevance between the melting point and the phase-transition temperature and the relevance between different production processes and the phase-transition temperature. Methods: Hermertic aluminum pans were used to encapsulate the samples, and the testing conditions were optimized. The sample weight was about 10 mg, and the range of measuring temperature was -20-100℃. The heating rate was 5℃·min-1 and the flow rate of nitrogen was 30 ml·min-1 . Results:The phase-transition temperature and the melting point were significantly different. The phase-transition temperature of white vaseline samples produced by different processes was quite different. Conclusion:Melting point determination in the current standard method of white vaseline exists defects, and the composition of white vaseline produced by various processes is quite different.