Thesis (M.Sc.)--Chulalongkorn University, 2010

N-Nitrosamines are carcinogen in testing animals and are prohibited to use in cosmetics as specified in Notification of Ministry of Public Health. This research has developed the method for determination of N-nitrosodimethylamine (NDMA) by gas chromatography-mass spectrometry (GCMS) using DB-WAX column (30 m long, 0.25 mm I.D., 0.25 μm film) with a temperature program from 60 to 200 °C. Headspace solid-phase microextraction (HS-SPME) was used for extraction and preconcentration of volatile NDMA in aqueous solutions. Factors affecting the extraction efficiency with HS-SPME were studied including type of fiber, concentration of NaCl in solution, pH of solution, extraction temperature and time. The carboxen/polydimethylsiloxane (CAR/PDMS) fiber was found to be suitable for the extraction of NDMA. For 40-mL vial, sample volume of 5–10 mL was used. NaCl concentration of 357 mg/mL was added, while pH of solution showed insignificant effect to extraction efficiency. Extraction temperature of 65 ℃ and extraction time of 10 min were selected. The validation results of the method showed good linearity in 0.1-200 ng/mL range; limit of detection (LOD) of 10 ng/g; limit of quantitation (LOQ) of 50 ng/g; recovery of 84–99 %; and repeatability of 3 % RSD. The developed method could be used to determine NDMA in shampoo.