Simultaneous Determination of Caffeine and Phenolic Compounds in Tea and Coffee - Caffeine: Chemistry, Analysis, Function and Effects - page 151

acids, hydroxycinnamic acids, hydrolyzable tannins and lignins, among others.
The flavonoid class includes flavanols, flavonones, flavones, isoflavones,

proanthocyanins and anthocyanins.
Extraction: Sample preparation procedure used to separate target analytes
from the sample matrix to be later analyzed. Usually involves contact between
the sample and some type of solvent.
Ultrasound-assisted extraction: This technique is based on the cavitation of the
bubbles created by the passage of ultrasonic waves (.20 kHz ) through the
extraction medium. It enhances contact between the solvent and sample,
improving extraction efficiency. It also may affect sample structure, which can
release target analytes to the extraction medium.
Supercritical fluid extraction: This technique consists of separating sample
components using a supercritical fluid as the extracting solvent. The most
commonly used supercritical fluid is carbon dioxide (CO 2 ), which is capable of
dissolving non-polar or moderately polar compounds.
Supercritical fluids: Any substance submitted to temperature and pressure
above their thermodynamic critical point.
Critical point: In thermodynamics, a critical point specifies the conditions
(temperature and pressure) at which a phase boundary ceases to exist.
Pressurized liquid extraction: Extraction based on a combination of elevated
temperature (50-200 uC) and moderate pressures (100-140 atm) of liquid
solvents. High temperature is used to improve extraction efficiency, while
pressure is used to maintain the solvent in the liquid phase.
Microwave-assisted extraction: This technique is based on the molecular
movement caused by electromagnetic waves with wavelengths ranging from 1
mm to 1 m, or frequencies between 300 MHz and 300 GHz.
High performance liquid chromatography: It is an analytical technique based on
the selective retention of analytes by a stationary phase that is carried by the
mobile phase. Once analytes are separated, they are individually detected by
different types of detectors. There is usually a correlation between the signal
generated and the concentration.
Isocratic:

d n 0 t 2 n g | 0

A separation in which the mobile phase composition remains

constant throughout the procedure.
Gradient: A separation in which the mobile phase composition does not
remains constant throughout the procedure.

List of Abbreviations
DAD Diode array detection

HPLC High-performance liquid chromatography

MAE Microwave-assisted extraction

PLE Pressurized liquid extraction

SFE Supercritical fluid extraction

UHPLC Ultra high performance liquid chromatography

UAE Ultrasound-assisted extraction