Determination of beta-carboline alkaloids in foods and beverages by high-performance liquid chromatography with electrochemical detection at a glassy carbon electrode modified with carbon nanotubes.
Simple and sensitive methods for the separation and quantification of beta-carboline alkaloids in foods and beverages by HPLC with electrochemical detection at carbon nanotubes-modified glassy carbon electrodes (CNTs-GCE) are reported. Electrode modification with multi-wall CNTs produced an improved amperometric response to beta-carbolines, in spite of the working medium consisting of methanol:acetonitrile: 0.05 mol L(-1) Na(2)HPO(4) solution of pH 9.0 (20:20:60). On the contrary to that observed at a bare GCE, a good repeatability of the amperometric measurements carried out at +900 mV versus Ag/AgCl (R.S.D. of 3.2% for i(p), n=20) was achieved at the CNTs-GCE. Using an Ultrabase C(18) column and isocratic elution with the above mentioned mobile phase, a complete resolution of the chromatographic peaks for harmalol, harmaline, norharmane, harmane and harmine, was achieved. Calibration graphs over the 0.25-100 microM range with detection limits ranging between 4 and 19 ng mL(-1), were obtained. The HPLC-ED at CNTs-GCE method was applied to the analysis of beer, coffee and cheese samples, spiked with beta-carbolines at concentration levels corresponding to those may be found in the respective samples. The steps involved in sample treatment, such as extraction and clean-up, were optimized for each type of sample. Recoveries ranging between 92 and 102% for beer, 92 and 101% for coffee, and 88 and 100% for cheese, at sub-microg mL(-1) or g(-1) analytes concentration levels were achieved.
Agüí
Lourdes
L
Department of Analytical Chemistry, Faculty of Chemistry, University Complutense of Madrid, 28040-Madrid, Spain.
Peña-Farfal
Carlos
C
Yáñez-Sedeño
Paloma
P
Pingarrón
José M
JM
D000470:Alkaloids / Q000737:chemistry*; D001515:Beer; D002138:Calibration; D002243:Carbolines / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D002611:Cheese; D002625:Chemistry, Organic / Q000379:methods*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003069:Coffee; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D005504:Food Analysis / Q000379:methods; D005506:Food Contamination / Q000032:analysis; D037742:Nanotubes, Carbon / Q000737:chemistry*; D012997:Solvents
D000470:Alkaloids; D002243:Carbolines; D003069:Coffee; D037742:Nanotubes, Carbon; D012997:Solvents; D002244:Carbon