title: [Determination of N-nitrosodimethylamine in beer by frozen zone melting liquid-liquid extraction/gas chromatography].
abstract: A simple and effective sample enrichment method of frozen zone melting liquid-liquid extraction was optimized and validated for the analysis of trace N-nitrosodimethylamine (NDMA) in beer samples. The method was based on high pressure liquid-liquid extraction with a low temperature frozen step. The 90 mL beer was placed in a container with 10 mL dichloromethane. After agitation, the sample was kept in a freezer for 16 h at -19 degrees C. The organic extract was analyzed by gas chromatography with a flame ionization detector (GC-FID). The accuracy, precision, detection and quantification limits and linearity of the method were evaluated. The results showed that the calibration curve of NDMA was linear in the range of 5-200 mg/L with a good correlation coefficient (r2) of 0.999 6. The recoveries at the spiked levels of 5, 10 and 20 mg/L were 84.94%, 83.24%, 85.14% with the relative standard deviations (n = 7) of 3.06%, 3.19%, 2.63%, respectively. The ordinary extraction method of N-nitrosodimethylamine in beer includes the four steps of low-temperature distillation, liquid-liquid extraction, rotary evaporation and nitrogen blowing concentration. With the extremely low volume of solvent used, the proposed extraction method proved to be easy and simple, and adequate for high-throughput analysis at low cost.
authors: Qiaorong
authors: Q
authors: Peng
authors: Tao
authors: T
authors: Tang
authors: Shuxin
authors: S
authors: Yu
authors: Yuanshe
authors: Y
authors: Sun
authors: Wu
authors: W
authors: Lei
authors: Fengyun
authors: F
authors: Wang
authors: Weibing
authors: W
authors: Zhang
authors: Tong
authors: T
authors: Li
mesh_terms: D001515:Beer / Q000032:analysis*; D002849:Chromatography, Gas; D004128:Dimethylnitrosamine / Q000032:analysis*; D005410:Flame Ionization; D059625:Liquid-Liquid Extraction; D012997:Solvents
chemical_list: D012997:Solvents; D004128:Dimethylnitrosamine