A simple spectrophotometric method for the determination of molybdenum in real, environmental, biological and soil samples using 1, 5-diphenylcarbohydrazide

A very simple, ultra-sensitive and highly selective non-extractive spectrophotometric method for the determination of trace amount of molybdenum(VI) using 1,5-diphenylcarbohydrazide (DPCH) has been developed. 1,5-diphenylcarbohydrazide (DPCH) reacts in slightly acidic media (0.01 - 0.06M H/sub 2/SO/sub 4/) of 50% 1,4-dioxane with molybdenum(VI) to give a red-violet chelate which has an absorption maximum at 520 nm. The average molar absorption co-efficient and Sandell's sensitivity were found to be 4.85 x 10/sup 4/ L mol/sup -1/ cm/sup -1/ and 15 ng cm/sup -2/ of Mo/sup vi/, respectively. Linear calibration graphs were obtained for 0.1-60 micro g mL/sup -1/. The stoichiometric comparison of the chelate is 1:3 (mo : DPCH). The absorbance intensity of the metal chelate reaches at constant value (after heating of 10 minutes at 60 plus minus 5 degree C) within 3/4 hour and remain unchanged for over 48 hours. Large excess of 60 cations, anions and complexing agents (like tartarate, oxalate, chlorate, phosphate thio-urea, SCN etc.) do not interfere in the Mo determination. The development method was successfully used in assaying in several standard reference materials (alloys and steels) as well as in some environmental waters (inland and surface), biological samples (human blood and urine), soil samples and complex mixtures. The methods has high precision and accuracy (s= plus minus 0.01 for 5 micro g mL/sup -1/). (author)