DETERMINATION OF NARINGIN IN GRAPEFRUIT JUICE BY CATHODIC STRIPPING DIFFERENTIAL-PULSE VOLTAMMETRY AT THE HANGING MERCURY DROP ELECTRODE

A highly sensitive cathodic stripping voltammetric method for the dete rmination of naringin is presented. It is based on the formation and a ccumulation of two naringin-mercury complexes at the electrode surface , followed by reduction of the surface species during a differential p ulse voltammetric scan. The cathodic stripping responses at -0.25 V an d -0.42 V, are evaluated with respect to various experimental conditio ns, such as composition and pH of the supporting electrolyte, naringin concentration, accumulation potential and preconcentration time. The new method is suitable for the determination of naringin concentration s between 0.1 mg l(-1) (1.72x10(-7) mol l(-1)) and 40 mg l(-1) (6.88x1 0(-5) mol l(-1)). A 3 sigma limit of detection of 32 mu g l(-1) (55 nm ol l(-1)) can be reached. The relative standard deviation (r.s.d.) is <1.5%. Recovery experiments yielded a mean recovery of 97% (r.s.d.=4.1 %). The application of the procedure to the selective determination of naringin in grapefruit juice is demonstrated. (C) 1998 Elsevier Scien ce B.V.