Electrokinetic capillary chromatography in a polar continuous-phase water-in-oil microemulsion constituted by water, sodium dodecyl sulfate, and n-pentanol.
A water-in-oil (w/o) microemulsion (ME) constituted by 15% Tris buffer, pH 8.4, in water and 85% sodium dodecyl sulfate (SDS)/n-pentanol 1:4 mixture, capable of dissolving up to 30% vegetable oils and lard, was used as background electrolyte in reverse microemulsion electrokinetic capillary chromatography (RMEEKC). Owing to the free SDS ions in the continuous phase and some degree of percolation, the ME showed a high conductivity (0.65 mS. cm(-1) at 25 degrees C) and sustained a very stable capillary current. Previous rinsing of the capillary with a quaternary ammonium salt for electroosmotic flow (EOF) reduction, a series of nonionic and anionic solutes dissolved either in the ME or in fat samples diluted with the ME (1:4 ratio), were injected. Using -20 kV, fair separations of the solutes in the migration time order singly charged anions < nonionic solutes < doubly charged anions approximately pyromellitate were obtained, salicylate (I) showing by far the shortest migration time, and phthalate (II) and pyromellitate the longest. Separation was attributed to partition between the aqueous droplets, where pyromellitate and II were assumed to be trapped, and the n-pentanol continuous phase, where the mobilitites could be also modified by association of the solutes with SDS ions. Adequate EOF markers were not found, thus the relative mobility of any solute with respect to the mobility of the droplets, mu(r), was expressed as a fraction of the mobility of I with respect to that of the droplets, being mu(r) = (t(II) - t(R)) t(I) / [(t(II) - t(I)) t(R)], where t(R), t(I), and t(II) are the migration times of the solutes I and II, respectively. The application of RMEEKC to the analysis of both hydrophilic and hydrophobic samples, including edible fats, was demonstrated.
Mendonça
Carla R B
CRB
Dept. de Química Analítica, Facultat de Química, Universitat de Valéncia, Burjassot, Spain.|Instituto de Química, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
Bica
Clara I D
CID
Instituto de Química, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
Piatnicki
Clarisse M S
CMS
Instituto de Química, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
Simó-Alfonso
Ernesto F
EF
Dept. de Química Analítica, Facultat de Química, Universitat de Valéncia, Burjassot, Spain.
Ramis-Ramos
Guillermo
G
Dept. de Química Analítica, Facultat de Química, Universitat de Valéncia, Burjassot, Spain.
D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D004041:Dietary Fats / Q000032:analysis; D019075:Electrophoresis, Capillary / Q000379:methods; D004655:Emulsions / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D000439:Pentanols / Q000737:chemistry; D010938:Plant Oils / Q000737:chemistry; D015203:Reproducibility of Results; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D014867:Water / Q000737:chemistry
D004041:Dietary Fats; D004655:Emulsions; D000439:Pentanols; D010938:Plant Oils; D014867:Water; D012967:Sodium Dodecyl Sulfate; C024999:n-pentanol; C029310:lard
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