Ultrasound-assisted surfactant-enhanced emulsification microextraction and determination of caffeine and theophylline in human plasma and cocoa powder

A rapid and simple ultrasound-assisted surfactant-enhanced emulsification microextraction procedure with chloroform-decanoic acid (87:13 w/w) as the extractant mixture has been improved for the simultaneous preconcentration of caffeine and theophylline before their determination using high-performance liquid chromatography. The use of ultrasonic radiation and surfactant can enhance the dispersion of extraction solvent into an aqueous phase and simplify the emulsification process. The proposed method is an environmentally friendly pretreatment method because of its low solvent consumption. Various parameters influencing the efficiency of the method including pH, buffer, extraction solvent, extraction time, and interfering ions were studied. The linear calibration curves were obtained in the ranges of 0.5-150 and 2-150 ng mL(-1) with limits of detection of 0.22 and 0.15 ng mL(-1) for caffeine and theophylline, respectively. The proposed procedure was successfully utilized for the determination of caffeine and theophylline in cocoa powder and human plasma samples. Based on the obtained results, it can be concluded that the proposed method is potentially applicable as an efficient method for preconcentration and determination of caffeine and theophylline in real samples such as food and biological media.

Automated summary

A rapid and simple ultrasound-assisted surfactant-enhanced emulsification microextraction method has been improved for the determination of caffeine and theophylline. The method offers low solvent consumption and environmental friendliness, and can be successfully applied to real samples such as food and biological media.