Determination of N-Nitrosodiethanolamine in Cocoamide Surfactants by High Performance Liquid Chromatography

A method of high performance liquid chromatography-ultraviolet detector was applied to determination of N-nitrosodiethanolamine in coconut oil monoethanolamide and coconut oil diethanolamide. The sample (0.100 0 g) was dissolved in methanol (8+2) solution, and the solution was made up to 10.0 mL with methanol (8+2) solution. After ultrasonically extracting for 10 min, and filtering with 0.45 μm micro filter membrane, the filtrate was analyzed by high performance liquid chromatography. Diamonsil C₁₈ silica gel bonded phase column (4.6 mm×250 mm, 5 μm) was used as stationary phase, with a mixture of methanol and water with different ratios as mobile phase for gradient elution. UV detection was carried out at the wavelength of 233 nm. Linear relationship was found between chromatogaphic peak area and mass concentration of N-nitrosodiethanolamine in the range of 0.05-25.00 mg·L^-1, with detection limit (3S/N) and the lower limit of determination (10S/N) of 15, 48 μg·L^-1, respectively. Values of recovery obtained by standard addition method were in the range of 94.5%-98.5%, and relative standard deviations (n=5) were in the range of 3.8%-5.9%.