title: Capillary electrophoresis with capacitively coupled contactless conductivity detection for the determination of cis/trans isomers of octadec-9-enoic acid and other long chain fatty acids.
abstract: A capillary electrophoresis (CE)-capacitively coupled contactless conductivity detection (C(4)D) method for the simultaneous separation of eleven underivatized fatty acids (FAs), namely, lauric, myristic, tridecanoic (internal standard), pentadecanoic, palmitic, stearic, oleic, elaidic, linoleic, linolenic and arachidic acids is described. The separation was carried out in normal polarity mode at 20 °C, 30 kV and using hydrodynamic injection (50 mbar for 1 s). The separation was achieved in a bare fused-silica capillary (70 cm × 75 μm i.d.) using a background electrolyte of methyl-β-cyclodextrin (~6 mM) and heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (~8 mM) dissolved in a mixture of Na2HPO4/KH2PO4 (5 mM, pH 7.4):ACN:MeOH:n-octanol (3:4:2.5:0.5, v/v/v/v). C(4)D parameters were set at fixed amplitude of 100 V and frequency of 1000 kHz. The developed method was validated. Calibration curves of the ten FAs were well correlated (r(2)>0.99) within the range of 5-250 μg mL(-1) for lauric acid, and 3-250 μg mL(-1) for the other FAs. The method was simple and sensitive with detection limits (S/N=3) of 0.9-1.9 μg mL(-1) and good relative standard deviations of intra- and inter-day for migration times and peak areas (≤9.7%) were achieved. The method was applied to the determination of FAs in margarine samples. The proposed method offers distinct advantages over the GC and HPLC methods, especially in terms of simplicity (without derivatization) and sensitivity.
authors.affiliation: School of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia.
authors.forename: Yong Foo
authors.initials: YF
authors.lastname: Wong
authors.forename: Bahruddin
authors.initials: B
authors.lastname: Saad
authors.forename: Ahmad
authors.initials: A
authors.lastname: Makahleh
mesh_terms: D020003:1-Octanol / Q000737:chemistry; D000097:Acetonitriles / Q000737:chemistry; D003505:Cyclodextrins / Q000737:chemistry; D004553:Electric Conductivity; D019075:Electrophoresis, Capillary / Q000379:methods*; D005227:Fatty Acids / Q000032:analysis* / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D057230:Limit of Detection; D016014:Linear Models; D008383:Margarine / Q000032:analysis; D000432:Methanol / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry; D015203:Reproducibility of Results; D013229:Stearic Acids / Q000032:analysis* / Q000737:chemistry*
chemical_list: C114874:5-octadecenoic acid; D000097:Acetonitriles; D003505:Cyclodextrins; D005227:Fatty Acids; D010710:Phosphates; D013229:Stearic Acids; D008383:Margarine; D020003:1-Octanol; D000432:Methanol; C032159:acetonitrile