title: On-line solid-phase extraction using a C₁₈ minicolumn coupled to a flow injection system for determination of caffeine in green and roasted coffee beans.
abstract: A novel and fast method based on the solid phase extraction (SPE) coupled to a flow injection system for the determination of caffeine in coffee beans was developed. The caffeine extraction of coffee beans was carried out with hot water. A C18 reverse-phase mini-column was coupled to a continuous flow manifold to carry out the on-line SPE and the quantification of caffeine from aqueous extracts. Column length, retention time, elution volume, extracting solution and injection volume were evaluated. The retention time was of 90s and the elution was carried out with 400 μL of a methanol:water mixture (25:75). The proposed on-line SPE was compared against a chloroform extraction from aqueous extracts. With the proposed method the sample preparation was minimised and the sample throughput was increased (10 determination/h) because no dilution was required. Green coffee beans and beans with different roasting degree were analyzed.
authors.affiliation: Facultad de Química, Departamento de Química Analítica, Universidad Nacional Autónoma de México, México D.F. 04510, Mexico.
authors.forename: María E
authors.initials: ME
authors.lastname: Salinas-Vargas
authors.forename: María P
authors.initials: MP
authors.lastname: Cañizares-Macías
mesh_terms: D001331:Automation; D002110:Caffeine / Q000032:analysis* / Q000302:isolation & purification*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D040503:Coffea / Q000737:chemistry*; D003296:Cooking; D017022:Flow Injection Analysis / Q000295:instrumentation / Q000379:methods*; D012639:Seeds / Q000737:chemistry*; D052616:Solid Phase Extraction / Q000379:methods*
chemical_list: D002110:Caffeine
keywords: Caffeine; Flow injection; On-line solid phase extraction; Roasted coffee beans