Application of Nonaqueous Capillary Electrophoresis to the Separation of Long-Chain Surfactants

Abstract

The potential of nonaqueous capillary electrophoresis (CE) for the separation of hydrophobic solutes has been examined for a series of alkanesulfonates (C 2 -C 16 ), alkyl sulfates (C 8 -C 18 ), and linear alkyl benzenesulfonates. Sample loss and band broadening observed in aqueous CE separations was not observed in nonaqueous systems. Changes in separation selectivity induced by solvation and ion pair effects were examined. Separation selectivity was affected by changes in solvation and by a change from protic (methanol) to aprotic conditions (addition of acetonitrile). The addition of alkali metal ion caused changes in migration time via ion pairing but had only small effects on separation selectivity. However, the adjustment of the hydrophobicity of the electrolyte counterion was effective for separation optimization. The analytical features of these nonaqueous systems and applications to samples of shampoo, liquid detergent, and laundry detergents were also briefly examined. Alkanesulfonates and alkyl sulfates were separated in 0.01 mol/L sodium p-toluenesulfonate and 0.005 mol/L ptoluenesulfonic acid in methanol and in methanol/acetonitrile mixtures with indirect UV detection at 214 nm. Linear alkyl benzenesulfonates were separated in methanol and methanol/acetonitrile mixtures with tetramethylammonium as a counterion and direct detection at 214 nm.

Design and synthesis of a hydrophilic fluorescent derivatization reagent for carboxylic acids, 4‐N‐(4‐N‐aminoethyl)piperazino‐7‐nitro‐2,1,3‐benzoxadiazole (NBD‐PZ‐NH2), and its application to capillary electrophoresis with laser‐induced fluorescence detection

“…There have been several reports for the separation and detection of fatty acids by CE (Collet and Gareil, 1997;Koval et al, 1985;RoldanAssad and Gareil, 1995;Salimi-Moosavi and Cassidy, 1996;Schmitz and Gab, 1997;Drange and Lundanes, 1997;Erim et al, 1995;Wang et al, 1998;Wan et al, 1999). Most of the methods utilize the indirect UV absorbance detection system by adding p-methoxybenzoate (Collet and Gareil, 1997;Roldan-Assad and Gareil, 1995), p-toluenesulfonate (Salmi-Moosavi and Cassidy, 1996), anthraquinone-2-sulfonic acid (Drange and Lundanes, 1997), or dodecyl benzenesulfonate (Erim et al, 1995) as a chromophore, or utilize indirect fluorescence detection system by adding fluorescein (Wang et al, 1998) in the migration medium.…”

Determination of N-Acyl-l-glutamates Surfactants by Capillary Electrophoresis Using Organic Modifier

“…14,15 Some researchers reported that the addition of organic solvents to the buffer solutions was effective for separation optimization of alkyl sulfates and alkane sulfonates. 9,14 We also studied the effect of addition of organic solvents on the separation of N-acyl-L-glutamates.…”

“…14,15 Some researchers reported that the addition of organic solvents to the buffer solutions was effective for separation optimization of alkyl sulfates and alkane sulfonates. 9,14 We also studied the effect of addition of organic solvents on the separation of N-acyl-L-glutamates. In this study, methanol, as a protic solvent, and acetonitrile, as an aprotic one, were chosen as organic modifiers, because both of them possess water-miscibility in any ratios, good transmittance at low wavelength in UV region, and increase the solubility of hydrophobic analytes.…”

Électrophorèse capillaire en milieu non aqueux

“…C'est d'ailleurs une des raisons pour lesquelles le méthanol et l'acétonitrile sont les solvants les plus utilisés en milieu non aqueux. Il est cependant à signaler que d'autres modes de détection peuvent être envisagés, la détection UV indirecte [13,14], la détection fluorimétrique indirecte induite par LASER [15,16], la détection électrochimique qui est bien adaptée aux solvants dipolaires aprotiques comme le dimethylformamide, le dimethylsulfoxyde et l'acétonitrile [17][18][19] ou encore le couplage CE/MS qui nécessite des solvants volatils tels que le méthanol ou l'acétonitrile [4,[20][21][22]. Ainsi dans l'étude du métabolisme du tamoxifène en électrophorèse capillaire couplée à la spectrométrie de masse (ESI), il a été constaté une meilleure résolution et une sensibilité plus grande en milieu organique par rapport au milieu aqueux [22].…”