A HIGHLY SELECTIVE AND SENSITIVE SPECTROFLUORIMETRIC METHOD FOR THE DETERMINATION OF CERIUM AT NANO-TRACE LEVELS IN SOME REAL, ENVIRONMENTAL, BIOLOGICAL, SOIL, FOOD AND BONE SAMPLES USING N-ACETYL-4-AMINOPHENOL

M. Jamaluddin Ahmed*, M. Didarul Alam Choudhury, and Prosenjit Ray

ABSTRACT

A very simple, rapid, ultra-sensitive, highly selective and non-extractive spectrofluorimetric method for the determination of cerium at nano-trace levels, based on the oxidative reaction between cerium(IV) and N-acetyl-4-aminophenol (paracetamol) has been developed. The fluorescent species is an oxidation product of paracetamol in a slightly acidic (0.05 – 0.15 molL-1 H2SO4) aqueous solution and has, excitation and emission maxima at λex = 255 and λem = 366 nm, respectively. The fluorescence intensity of oxidized product reaches a constant value (after heating in a thermostatically controlled water bath at (45 ±5) 0C for 5 min) within 15 minutes remains stable over 24 h. Linear calibration graphs were obtained for 0.01 – 400-μgL-1 of Ce(IV), having a detection limit of 1.3-ngL-1; the quantification limit of the reaction system was found to be13-ngL-1; the RSD was 2% and the correlation coefficient, R2 = 0.9998. A large excess of over 60 cations, anions and complexing agents (like, chloride, phosphate, azide, tartrate, oxalate, SCN- etc.) do not interfere in the determination. The developed method was successfully applied in the determination of cerium in several Standard Reference Materials (alloys, steels, noodles, ores and sediments) as well as in some environmental waters (potable and polluted), biological fluids (human blood, urine and milk), soil samples, food samples (vegetable, fruit, rice, corn and wheat), bone samples (human, cow, bull, fish, hen, goat, sheep), solutions containing both cerium(III) and cerium(IV) and complex synthetic mixtures. The results of the proposed method for biological and food analyses were comparable with that of ICP-MS and were found to be in an excellent agreement. The method has high precision and accuracy (s = ± 0.01 for 0.5-μgL-1).

Keywords: Spectrofluorimetry; cerium determination; alloys; environmental; biological; bone samples.