doi:10.1016/j.chroma.2007.07.076 
Copyright © 2007 Elsevier B.V. All rights reserved.
Surfactant coated fullerenes C60 as pseudostationary phase in electrokinetic chromatography
Y. Moliner-Martíneza, S. Cárdenasa and M. Valcárcel
, a, 
aDepartment of Analytical Chemistry, Marie Curie Building (Annex), Campus de Rabanales, University of Córdoba, E-14071 Córdoba, Spain
Received 25 April 2007;
revised 24 July 2007;
accepted 31 July 2007.
Available online 3 August 2007.
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Abstract
In the present paper, surfactant coated fullerenes C60 (SC-C60) have been proposed as a novedous pseudostationary phase to improve separation of different aromatic compounds. The target analytes were β-lactams antibiotics, non-steroidal anti-inflammatory drugs and amphenicols. In all cases, the analytes interacted with the pseudostationary phase producing an important enhancement on resolution. The results were compared with those obtained with surfactant coated carbon nanotubes (single-walled and multi-walled nanotubes), showing that in the proposed conditions, fullerenes C60 were advantageous as interactions between the analytes and the pseudostationary phase were more effective. Finally, the procedure was applied to pharmaceuticals and urine samples, with satisfactory results.
Keywords: Electrokinetic chromatography; Pseudostationary phase; Surfactant coated fullerenes
Fig. 1. Influence of the CE modality employed on the separation of a mixture of β-lactams antibiotics (10 mg l−1 each): (A) CZE mode BGE (26 mM boric acid at pH 8.5), (B) EKC with SC-C60 as pseudostationary phase (26 mM boric acid, 1.25 mg l−1 SC-C60 at pH 8.5), (C) MEKC (26 mM boric acid, 50 mM SDS at pH 8.5) and (D) MiNDEKC (26 mM boric acid, 50 mM SDS and 1.25 mg l−1 SC-C60 at pH 8.5, and partial filling (10 mg l−1 SC-C60, 10 s at 0.5 psi).
Fig. 2. Influence of SDS concentration when SC-C60 as pseudostationary phase for the electrophoretic separation of non-steroidal anti-antiflammatory drugs (10 mg l−1 each, except ketoprofen 5 mg l−1): (A) 20 mM SDS, (B) 40 mM SDS and (C) 100 mM SDS. The BGE was 50 mM boric acid, SC-C60 (1.25 mg l−1) at pH 8.5 Partial filling conditions: 10 mg l−1 SC-C60 prepared in the corresponding BGE, 10 s at 0.5 psi.
Fig. 3. Separation of a mixture of amphenicols (10 mg l−1) with the proposed procedure. The experimental conditions were 26 mM of boric acid, 25 mM of SDS, 1.25 mg l−1 SC-C60 at pH 8.5 and partial filling (10 mg l−1 SC-C60, 10 s at 0.5 psi).
Fig. 4. Electropherogram obtained for a mixture of β-lactams antibiotics, non-steroidal anti-antiflammatory drugs and amphenicols (5 mg l−1 each, except ketoprofen 2.5 mg l−1) using MiNDEKC. The experimental conditions were 50 mM boric acid, 40 mM SDS and 1.25 mg l−1 SC-C60 at pH 8.5 and partial filling (10 mg l−1 SC-C60, 10 s at 0.5 psi).
Fig. 5. Electropherograms of obtained with MiNDEKC with SC-MWNTs in the BGE (3.2 mg l−1) and partial filling (6.4 mg l−1, 10 s at 0.5 psi) for (A) β-lactams antibiotics (10 mg l−1 each); BGE: 26 mM boric acid and 50 mM SDS at pH 8.5, (B) non-steroidal anti-antiflammatory drugs (10 mg l−1, except ketoprofen 5 mg l−1); BGE: 50 mM boric acid and SDS 40 mM at pH 8.5 and (C) amphenicols (10 mg l−1 each); BGE: 26 mM of boric acid and 25 mM of SDS at pH 8.5.
Fig. 6. Urine sample analysis with the proposed methodology. (A) Directly injected urine sample spiked with ibuprofen (10 mg l−1) and amoxicillin (20 mg l−1), (B) urine sample spiked with ibuprofen (10 mg l−1) and amoxicillin (20 mg l−1), treated with the SPE clean-up procedure and (C) blank of urine sample treated with the SPE procedure. The experimental conditions were 50 mM boric acid, SDS 40 mM and SC-C60 (1.25 mg l−1) at pH 8.5 and partial filling (10 mg l−1 of SC-C60, 10 s at 0.5 psi).
Table 1.
Comparison of experimental conditions for dispersion of carbon nanotubes [9] and [12] and fullerenes C60 [19]
Table 2.
Analytical parameters for the proposed procedures
a y = absorbance;
x = concentration (mg l
−1).
b Concentration.
Table 3.
Found concentrations (mg l−1), recovery values (%R) and precision values (%RSD) for pharmaceutical and urine samples
a Added concentration to urine samples spiked or found concentration in urine samples (mg l
−1).
b Relative error (%) calculated for pharmaceutical samples.
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