A deep eutectic solvent based liquid phase microextraction for the determination of caffeine in Turkish coffee samples by HPLC-UV

ABSTRACT

A novel liquid-phase microextraction procedure for the determination and extraction of caffeine using a deep eutectic solvent based liquid-phase microextraction method (DES-LPME) was developed. A deep eutectic solvent consisting of choline chloride-phenol (1:3) and tetrahydrofuran as a dilution solvent were used for the extraction of caffeine from Turkish coffee samples. The quantitative recoveries were obtained when the DES volume was 400 µL, and the volume of tetrahydrofuran that was used as an emulsifier solvent was 800 µL. The limit of detection and the limit of quantification were found to be 0.12 and 0.40 µg mL⁻¹, respectively. Linear dynamic range was 0.5–100 µg mL⁻¹, and coefficient of determination (R²) was 0.9998. The relative standard deviation (RSD) was 2.20% when the standard solution concentration was 1.0 µg mL⁻¹. The fact that the determination coefficient obtained from the calibration curve was greater than 0.9998 gives information about the accuracy of the method. Also, in order to determine the accuracy of the developed method, selected coffee samples were spiked with 25 and 50 µg mL⁻¹ caffeine.

Graphical abstract

KEYWORDS:

• Caffeine
• liquid phase microextraction
• deep eutectic solvents
• coffee

Acknowledgments

I would like to thank Assoc. Prof. Hasan Çabuk and Assoc. Prof. Ayhan Tozluoğlu for their valuable contributions. This work was presented at 1st International Congress on Analytical and Bioanalytical Chemistry (1st ICABC 2019) as full text presentation.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by a grant from Duzce University Research Project Foundation (Project no: 2018.07.06.803).