Pressure variation in-syringe dispersive liquid-liquid microextraction associated with digital image colorimetry: Determination of cobalt in food samples

• Published in: Microchemical journal Vol. 157; p. 105064
• Main Authors: Barreto, Jeferson Alves, dos Santos de Assis, Rosivan, Santos, Luana Bastos, Cassella, Ricardo Jorgensen, Lemos, Valfredo Azevedo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-09-2020
• Subjects: Cobalt; Digital image; Food; In-syringe microextraction; Pressure variation; In-syringe microextraction; Digital image; Cobalt; Pressure variation; Food
• ISSN: 0026-265X; 1095-9149
• DOI: 10.1016/j.microc.2020.105064

•PV-IS-DLLME was combined with digital image colorimetry a for the first time.•The digital image is obtained directly from the enriched phase.•Optimization performed by full factorial design followed by Doehlert matrix.•Determination of cobalt in food samples at μg L−1 level.
In the present work, preconcentration by pressure variation in-syringe dispersive liquid-liquid microextraction (PV-IS-DLLME) was used for the determination of cobalt by digital image colorimetry. The detection system, built in the laboratory, involved a portable multifunction microscope used for image acquisition. The extraction solvent was trichloroethylene, while 2,2′-(thiazolylazo)-p-cresol (TAC) was used as a complexing agent. The pH, volume of extraction solvent, sample volume, and time of extraction were evaluated using a fractional factorial design 24-1. All factors were significant, and their optimum values were established with a central composite design. The limits of detection and quantification presented by the method were 0.08 and 0.23 mg kg−1, respectively, and the enrichment factor was 65. The procedure was applied to the analysis of real food samples (green banana flour, eggplant, Bahian seasoning, and Tribulus terrestris) and a certified reference material (NIST 1573a, tomato leaves). The PV-IS-DLLME technique presented itself as an efficient, simple, fast, and low-cost alternative for the preconcentration of substances at trace levels.