title: Direct determination of melamine in dairy products by gas chromatography/mass spectrometry with coupled column separation.
abstract: A coupled capillary column system was developed for the qualitative and quantitative determination of melamine with isotope internal standard in dairy products by gas chromatography/mass spectrometry (GC/MS) without derivatization. A 30 m of DB-5 ms ((5%-phenyl)-methylpolysiloxane, 0.25 mm i.d., 0.25 microm df) coupled with a 1.5 m of Innowax (polyethylene glycol, 0.32 mm i.d., 0.25 microm df) by a quartz capillary column connector was introduced as separation column. Three advantages were discussed for the coupled system. The sample was fortified with a ring-labeled (13)C(3)(15)N(3)-melamine as an isotope internal standard and extracted by 1% of trichloroacetic acid aqueous solution. 2.2% of lead acetate solution was then added to deposit protein in the sample matrix. After purification by cation exchange cartridge, the sample solution was directly injected and detected by GC/MS. A six-point calibration curve ranging from 0.05 to 2 mg kg(-1) of melamine in sample was used to establish instrument response. The recovery was 93.9-102% with relative standard deviation from 3.1 to 8.7% when isotope internal standard used. The calculated method detection limit was 0.01 mg kg(-1).
authors.affiliation: Department of Chemistry, Xixi Campus, Zhejiang University, Hangzhou, 310028, China.
authors.forename: Xiao-min
authors.initials: XM
authors.lastname: Xu
authors.forename: Yi-ping
authors.initials: YP
authors.lastname: Ren
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhu
authors.forename: Zeng-xuan
authors.initials: ZX
authors.lastname: Cai
authors.forename: Jian-long
authors.initials: JL
authors.lastname: Han
authors.forename: Bai-fen
authors.initials: BF
authors.lastname: Huang
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhu
mesh_terms: D000818:Animals; D002417:Cattle; D003611:Dairy Products / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D007553:Isotope Labeling; D008892:Milk / Q000737:chemistry; D014227:Triazines / Q000032:analysis* / Q000302:isolation & purification; D014238:Trichloroacetic Acid / Q000737:chemistry
chemical_list: D014227:Triazines; D014238:Trichloroacetic Acid; C011907:melamine