Optimization of electrochemical detection in the high-performance liquid chromatography of lignin phenolics from lignocellulosic by-products.
Free phenolic acids and aldehydes (p- and o-hydroxyphenylacetic acid, p-hydroxybenzoic acid, p-hydroxybenzaldehyde, vanillic acid, vanillin, syringic acid, p-coumaric acid, syringaldehyde and ferulic acid) were detected in wheat straw extracts by high-performance liquid chromatography with a dual-cell electrochemical detector operated in the redox mode. Phenolics were oxidized with coulometric efficiency in the first cell (+ 1.00 V), then detected by reduction in the second cell (-0.20 V). Compared with the oxidative mode, the reductive detection mode has the advantage of being unaffected by large amounts of interferents eluting at the front of the chromatogram that interfere with the detection of small and early eluting compounds. Hydrodynamic voltammograms in the oxidative, reductive and screen-out modes are presented and the corresponding detection limits for real sample are discussed. Perfect linearity of response was found in the range 5 x 10(-7) - 5 x 10(-5) M and detection limits were of the order of 50-500 fmol injected.
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Centro di Studio per la Conservazione dei Foraggi, CNR, Bologna, Italy.
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D000447:Aldehydes / Q000032:analysis; D002482:Cellulose / Q000032:analysis* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004563:Electrochemistry; D062385:Hydroxybenzoates / Q000032:analysis; D008031:Lignin / Q000032:analysis* / Q000378:metabolism
D000447:Aldehydes; D062385:Hydroxybenzoates; C036909:lignocellulose; D002482:Cellulose; D008031:Lignin; C017616:phenolic acid