Sensitive and selective determination of phenolic compounds from aromatic plants using an electrochemical detection coupled with HPLC method.
BACKGROUND
Phenolic compounds contained in essential oils from plants are responsible for their anti-oxidant capacity. The natural extract from each aromatic plant is characterised by a typical ratio of phenolic components, so each one of the essential oils shows different properties.


OBJECTIVE
The development of a simple reversed-phase high-performance liquid chromatographic (RP-HPLC) method for the determination of phenolic compounds from aromatic plants using spectrophotometric detection with a diode-array and electrochemical detection with amperometric and coulometric detectors.


METHODS
Chromatographic conditions are optimised to separate vanillin, eugenol, thymol and carvacrol using spectrophotometric detection. Acetonitrile and methanol are studied as mobile-phase organic modifiers. The hydrodynamic curves are obtained for both electrochemical detection modes and the principal values of merit are calculated. The proposed methodology is applied to determine the four analytes in real samples.


RESULTS
The shortest elution times and the highest electrochemical signals are achieved using 65% methanol solution in 0.1 mol/L acetic acid-acetate buffer as the mobile phase. Potential values of 0.925 V for amperometric detection and 0.500 V for coulometric detection are chosen as working potentials. The limits of detection (LOD) for the compounds studied ranged between 9.7-17 µg/L and 0.81-3.1 µg/L in amperometric and coulometric detection modes, respectively. In general, the obtained LODs are better than those previously reported.


CONCLUSIONS
The low LODs obtained using coulometric detection make this methodology very competitive and adequate for quality control of these phenolic compounds in comparison with others, such as GC-MS, that are more expensive and complicated to use than the RP-HPLC method with coulometric detection.
Department of Analytical Chemistry and Instrumental Analysis, Sciencies Faculty, Avda. Francisco Tomás y Valiente, 7, Autonoma University of Madrid, E-28049, Madrid, Spain.
Alberto
A
Cantalapiedra
M Jesús
MJ
Gismera
M Teresa
MT
Sevilla
Jesús R
JR
Procopio
D001547:Benzaldehydes / Q000737:chemistry / Q000302:isolation & purification; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D000081007:Cymenes; D055664:Electrochemical Techniques; D005054:Eugenol / Q000737:chemistry / Q000302:isolation & purification; D036142:Mentha piperita / Q000737:chemistry; D015394:Molecular Structure; D039821:Monoterpenes / Q000737:chemistry / Q000302:isolation & purification; D018649:Ocimum basilicum / Q000737:chemistry; D009822:Oils, Volatile / Q000737:chemistry / Q000302:isolation & purification*; D031341:Origanum / Q000737:chemistry; D010636:Phenols / Q000737:chemistry / Q000302:isolation & purification*; D018515:Plant Leaves / Q000737:chemistry; D010938:Plant Oils / Q000737:chemistry / Q000302:isolation & purification*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D027842:Syzygium / Q000737:chemistry; D013943:Thymol / Q000737:chemistry / Q000302:isolation & purification
D001547:Benzaldehydes; D000081007:Cymenes; D039821:Monoterpenes; D009822:Oils, Volatile; D010636:Phenols; D010938:Plant Oils; D013943:Thymol; D005054:Eugenol; C073316:carvacrol; C100058:vanillin
Amperometric detection; coulometric detection; high-performance liquid chromatography; phenolic compounds