title: Cloud point sample clean-up and capillary zone electrophoresis with field enhanced sample injection and micelle to solvent stacking for the analysis of herbicides in milk.
abstract: Sample clean-up by cloud point phase separation and analysis by capillary electrophoresis with stacking was developed for quaternary ammonium herbicides (i.e., paraquat and diquat) in milk. For sample clean-up, a mixture of 845μL of milk sample, 5μL of 100mM phosphoric acid, and 150μL of Triton X-114 was heated (60°C for 2min) and centrifugated (3000rpm for 2min) in 2-mL Eppendorf tube. The upper phase was directly analysed by capillary electrophoresis via electrokinetic injection at 10kV for 150s. The separation electrolyte was 100mM phosphate buffer with 20% acetonitrile at pH 2.5. Before sample injection, a micellar solution (10mM SDS in 80mM phosphate buffer at pH 2.5) and an organic solvent rich solution (30% ACN) was hydrodynamically introduced into the capillary. These solutions provided the necessary conditions for stacking the cationic herbicides via the combination of field enhanced sample injection and micelle to solvent stacking. The LODs (S/N=3) obtained from the entire strategy for paraquat and diquat in milk was 0.004 and 0.018μg/mL, respectively. This is 1.5 to >2 orders of magnitude better than the corresponding LODs obtained from the electrophoretic analysis of herbicide standards prepared in the separation electrolyte. The strategy was also successfully applied to 5 milk samples available in the market.
authors.affiliation: Australian Centre for Research on Separation Science (ACROSS), School of Physical Sciences-Chemistry, University of Tasmania, Hobart 7001, TAS, Australia; Materials Chemistry Research Unit, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand.
authors.forename: Chunyapuk
authors.initials: C
authors.lastname: Kukusamude
authors.affiliation: Materials Chemistry Research Unit, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand.
authors.forename: Supalax
authors.initials: S
authors.lastname: Srijaranai
authors.affiliation: Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Kato
authors.affiliation: Australian Centre for Research on Separation Science (ACROSS), School of Physical Sciences-Chemistry, University of Tasmania, Hobart 7001, TAS, Australia; Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan. Electronic address: jquirino@utas.edu.au.
authors.forename: Joselito P
authors.initials: JP
authors.lastname: Quirino
mesh_terms: D000818:Animals; D004178:Diquat / Q000032:analysis; D019075:Electrophoresis, Capillary; D005524:Food Technology / Q000295:instrumentation* / Q000379:methods*; D006540:Herbicides / Q000032:analysis*; D008823:Micelles; D008892:Milk / Q000737:chemistry*; D017830:Octoxynol; D010269:Paraquat / Q000032:analysis; D011092:Polyethylene Glycols / Q000032:analysis; D015203:Reproducibility of Results
chemical_list: D006540:Herbicides; D008823:Micelles; D011092:Polyethylene Glycols; D017830:Octoxynol; C010615:Nonidet P-40; D004178:Diquat; D010269:Paraquat
keywords: Capillary electrophoresis; Cloud point; Herbicides; Milk; Stacking