Spectrophotometric Determination of Cr(VI) Ions Using New Benzothiazolyl azo Compound 2-[(6–Methyl–2-Benzothiazolyl) azo] -4-Chlorophenol

Abstract

The new reagent 2-[ ( 6 – Methyl – 2 – Benzothiazolyl ) azo ] – 4 - Chlorophenol
(6-MeBTAClP) organic was synthesized, and used in the spectrophotometric
determination of Cr (VI) ion . Sensitive, selective and rapid method was proposed.
The reaction between the reagent and Cr(VI) ion occurs at pH = 7.4 , and the
absorbance of the resultant solution remains stable for over 24 h.
The method allows for the determination of Cr(VI) over the range 0.2-9.0μg.ml-1,
with molar absorptivity of 0.772x104 L.mol-1.cm-1 in chloroform solvent, and a
detection limit of 0.16 μg.ml-1 . Recovery and relative error values of precision and
accuracy of method were found to be R.S.D%=0.449 , Re%=98.67 ,and Erel%=1.33.
Study of complex nature showed that metal: reagent ratio was 1:2 at pH=7.4 ,and the
stability constant of (7.67 x 109) l2. mol-2, the interferences of ions (Cu2+, Pb2+, Hg2+,
Zn2+, Cd2+, Ni2+, MoO42-, WO4 2-) and masking agents effect on absorbance
were also studied.
The above mentioned procedure was applied in the determination of total
chromium in residual water of alnajaf dibajat factory as chromium(VI). Results came
in agreement with those obtained by flame atomic absorption method for
determination of Cr (VI).