title: Determination of phthalate esters in cow milk samples using dispersive liquid-liquid microextraction coupled with gas chromatography followed by flame ionization and mass spectrometric detection.
abstract: A simple and economic method for the analysis of phthalate esters, dimethyl phthalate, diethyl phthalate, di-iso-butyl phthalate, di-n-butyl phthalate, and di-2-ethylhexyl phthalate in cow milk samples by means of gas chromatography-flame ionization detection and gas chromatography-mass spectrometry has been developed. In this work, NaCl and ACN were added to 5 mL of the milk sample as the salting out agent and extraction solvent, respectively. After manual shaking, the mixture was centrifuged. In the presence of NaCl, a two-phase system was formed: upper phase - acetonitrile containing phthalate esters -and lower phase - aqueous phase containing soluble compounds and the precipitated proteins. After the extraction of phthalate esters from milk, a portion of supernatant phase (acetonitrile) was removed, mixed with 1,2-dibromoethane at microliter level and injected by syringe into NaCl solution. After the extraction of the selected phthalate esters into 1,2-dibromoethane, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. Under the optimum extraction conditions, low limits of detection and quantification between 1.5-3 and 2.5-11 ng/mL, respectively was observed. Enrichment factors were in the range of 397-499. The relative standard deviations for the extraction of 100 ng/mL of each phthalate ester were in the range of 3-4% (n = 6). Finally, some milk samples were successfully analyzed using the proposed method and two analytes, di-n-butyl phthalate and di-2-ethylhyxel phthalate, were determined in them in nanogram per milliliter level.
authors.affiliation: Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz, Iran. mafarajzadeh@yahoo.com
authors.forename: Mir Ali
authors.initials: MA
authors.lastname: Farajzadeh
authors.forename: Djavanshir
authors.initials: D
authors.lastname: Djozan
authors.forename: Mohammad Reza Afshar
authors.initials: MR
authors.lastname: Mogaddam
authors.forename: Jamal
authors.initials: J
authors.lastname: Norouzi
mesh_terms: D000818:Animals; D002417:Cattle; D002849:Chromatography, Gas / Q000379:methods*; D004952:Esters / Q000032:analysis* / Q000302:isolation & purification; D005410:Flame Ionization; D005506:Food Contamination / Q000032:analysis*; D059627:Liquid Phase Microextraction / Q000379:methods*; D013058:Mass Spectrometry; D008892:Milk / Q000737:chemistry*; D010795:Phthalic Acids / Q000032:analysis* / Q000302:isolation & purification
chemical_list: D004952:Esters; D010795:Phthalic Acids; C032279:phthalic acid