Analytical Sciences

A Rapid Spectrophotometric Method forthe Determination of Molybdenum in Industrial, Environmental, Biologicaland Soil Samples Using 5,7-Dibromo-8-hydroxyquinoline

M. Jamaluddin AHMED  andM. Enamul HAQUE

Laboratory of Analytical Chemistry,Department of Chemistry, University of Chittagong, Chittagong-4331,Bangladesh

A very simple, ultra-sensitive and highlyselective non-extractive spectrophotometric method for the determination oftrace amount of molybdenum(VI) using 5,7-dibromo-8-hydroxyquinoline (DBHQ)has been developed. 5,7-Dibromo-8-hydroxyquinoline reacts in a slightlyacidic solution (0.05 - 1.0 M H₂SO₄) withmolybdenum(VI) to give a deep greenish-yellow chelate which has anabsorption maximum at 401 nm. The reaction is instantaneous and theabsorbance remains stable for over 24 h. The average molar absorptioncoefficient and Sandell$BCT(B sensitivity were found to be 4.13 x10³ L mol^-1 cm^-1 and 7 ng cm^-2of molybdenum(VI), respectively. Linear calibration graphs were obtainedfor 0.1 - 50 ug mL^-1 of molybdenum(VI). The stoichiometriccomposition of the chelate is 1:3 (Mo:DBHQ). A large excess of over 50cations, anions and some common complexing agents (e.g. EDTA,oxalate, citrate, phosphate, thiourea, SCN^-) do not interferewith the determination. The method was successfully used in thedetermination of molybdenum in several Standard Reference Materials(alloys, steels and waters) as well as in some environmental waters (inlandand surface), biological samples (human blood and urine), soil samples,solution containing both molybdenum(V) and molybdenum(VI) and complexsynthetic mixtures. The method has high precision and accuracy (S =± 0.01 for 0.5 ug mL^-1).

J-STAGE: View this article in J-STAGE