Optimization of a method for determination of phenolic acids in exotic fruits by capillary electrophoresis.
In this work, the separation of nine phenolic acids (benzoic, caffeic, chlorogenic, p-coumaric, ferulic, gallic, protocatechuic, syringic, and vanillic acid) was approached by a 3(2) factorial design in electrolytes consisting of sodium tetraborate buffer (STB) in the concentration range of 10-50 mmol L(-1) and methanol in the volume percentage of 5-20%. Derringer's desirability functions combined globally were tested as response functions. An optimal electrolyte composed by 50 mmol L(-1) tetraborate buffer at pH 9.2, and 7.5% (v/v) methanol allowed baseline resolution of all phenolic acids under investigation in less than 15 min. In order to promote sample clean up, to preconcentrate the phenolic fraction and to release esterified phenolic acids from the fruit matrix, elaborate liquid-liquid extraction procedures followed by alkaline hydrolysis were performed. The proposed methodology was fully validated (linearity from 10.0 to 100 microg mL(-1), R(2)>0.999; LOD and LOQ from 1.32 to 3.80 microg mL(-1) and from 4.01 to 11.5 microg mL(-1), respectively; intra-day precision better than 2.8% CV for migration time and 5.4% CV for peak area; inter-day precision better than 4.8% CV for migration time and 4.8-11% CV for peak area; recoveries from 81% to 115%) and applied successfully to the evaluation of phenolic contents of abiu-roxo (Chrysophyllum caimito), wild mulberry growing in Brazil (Morus nigra L.) and tree tomato (Cyphomandra betacea). Values in the range of 1.50-47.3 microg g(-1) were found, with smaller amounts occurring as free phenolic acids.
Fukuji
Tatiana S
TS
Institute of Chemistry, University of Sao Paulo, 05513-970 Sao Paulo, SP, Brazil.
Tonin
Fernando G
FG
Tavares
Marina F M
MF
D001881:Borates / Q000032:analysis; D001938:Brazil; D002021:Buffers; D004573:Electrolytes / Q000032:analysis; D019075:Electrophoresis, Capillary / Q000295:instrumentation / Q000379:methods*; D005638:Fruit / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D062385:Hydroxybenzoates / Q000032:analysis* / Q000737:chemistry; D000432:Methanol / Q000032:analysis; D015394:Molecular Structure; D010936:Plant Extracts / Q000032:analysis / Q000737:chemistry; D012015:Reference Standards; D015203:Reproducibility of Results; D012997:Solvents / Q000032:analysis; D013997:Time Factors; D014867:Water / Q000737:chemistry
D001881:Borates; D002021:Buffers; D004573:Electrolytes; D062385:Hydroxybenzoates; D010936:Plant Extracts; D012997:Solvents; D014867:Water; C010634:sodium borate; C017616:phenolic acid; D000432:Methanol