Comparison of off- and in-line solid-phase extraction for enhancing sensitivity in capillary electrophoresis using ochratoxin as a model compound

• Published in: Analytical and bioanalytical chemistry 2009-05, Vol.394 (2), p.609-615
• Main Authors: Almeda, S, Arce, L, Benavente, F, Sanz-Nebot, V, Barbosa, J, Valcárcel, M
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Biochemistry; Capillarity; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Chromatographic methods and physical methods associated with chromatography; Electrophoresis; Exact sciences and technology; Extraction; Food Science; Freshwater; Inlets; Laboratory Medicine; Mathematical analysis; Mathematical models; Monitoring/Environmental Analysis; Original Paper; Other chromatographic methods; Solid phases; Sorbents
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-009-2696-x

This paper proposes and compares two approaches based on off- and in-line solid-phase extraction (SPE), intended to enhance sensitivity in capillary electrophoresis with ultraviolet detection (CE-UV) using as a model the determination of ochratoxin A (OA) in river water samples. In the off-line SPE mode, the reversed-phase sorbent (octadecilsylane, C₁₈) selectively retains the target analyte (OA) and allows large volumes of the sample (70 mL) to be introduced and subsequently eluted in a small volume (0.1 mL) of an appropriate solution. In the in-line SPE mode, a custom-made microcartridge is inserted near the inlet of the capillary, which is filled with the same C₁₈ sorbent. This solid phase selectively retains OA present in a sample volume as low as approximately 640 μL for subsequent elution with ca. 135 nL of an appropriate eluent. The limit of detection (LOD) obtained with the in-line SPE method was 1 ng L⁻¹, which is 3 orders of magnitude lower than that obtained with CE-UV and roughly 1 order lower than that provided by the off-line SPE-CE-UV method.