Ingeniero quimico industrial

ANALYTICAL SCIENCES SEPTEMBER 2002, VOL. 18
2002 © The Japan Society for Analytical Chemistry

1027

Novel Sensitive Spectrophotometric Method for the Trace
Determination of Cyanide in Industrial Effluent
Padmarajaiah NAGARAJA,*† Mattighatta S. HEMANTHA KUMAR,** Hemmige S. YATHIRAJAN,*
and Jainara S. PRAKASH*
*Department of Studies in Chemistry, University of Mysore, Manasagangotri,Mysore-570 006, India
**Department of Studies in Environmental Sciences, University of Mysore,
Manasagangotri, Mysore-570 006, India

The high toxicity of the cyanide ion at low concentration necessitates its analysis in a variety of environmental samples
with a very low cyanide content. A new sensitive spectrophotometric method has been developed for the trace
determination of cyanide withninhydrin (NH) in an alkaline medium. Beer’s law is obeyed in the range of cyanide
concentration 0.04 – 0.24 µg cm–3, and the molar absorptivity at 590 nm is 2.20 × 105 dm3 mol–1 cm–1. The Sandell’s
sensitivity of the product is 0.000118 µg cm–2. The optimum reaction conditions and other important analytical
parameters have been investigated. The results obtained by using the proposed method forenvironmental samples agree
well with those obtained by the Aldridge standard method.
(Received March 19, 2002; Accepted July 19, 2002)

Introduction
Although cyanides are present in small concentrations in plants
and micro-organisms,1,2 their large-scale presence in the
environment is attributed to human activities, because cyanide
compounds are extensively used in industry. The cyanidesare
widely used in electroplating, in precious metal refining, the
manufacture of organic chemicals and in many other processes.3
The analytical considerations are important for cyanides,
because these easily form complexes with many materials.4,5
Cyanides form complexes with different affinities. Complex
cyanide is generally less toxic, while free cyanide is the most
toxic of all the cyanidespecies.5 In wastewater, the total
cyanide, which includes both complexed and uncomplexed
forms of cyanide, is analyzed by the standard distillation
method.4 Spectrophotometric methods6–8 for the determination
of cyanide are far more superior to the other methods, such as
titrimetric,9 polarographic,10 fluorometric11 and chromatographic
techniques.12 A trace amount of cyanide is oftendetermined by
spectrophotometry by the pyridine-benzidine method of
Aldridge,6 the pyridine-pyrazolone method of Epstein,7 the
pyridine-barbituric acid method of Asmus and Garschagen13 and
the pyridine-p-phenylenediamine method of Bark and Higson.8
However, these methods have certain drawbacks, such as the
carcinogenic properties of benzidine, the instability of the
pyridine-pyrazolone reagent,the slow color development in the
pyridine-p-phenylenediamine method and the rapid fading of
color in the pyridine-barbituric acid method.14 Most of the
methods suffer from a narrow range of determination,15 lengthy
procedures16,17 and interference by common ions.18 Ninhydrin
(NH) was first discovered in 1910, and has established itself as
† To whom correspondence should be addressed.E-mail: nagarajap@mailcity.com

an important analytical tool in the fields of chemistry,
biochemistry and forensic science.19 It has been used for the
detection of amino acids20 and amines for almost fifty years.
Ninhydrin is also known as triketohydrindene hydrate, Rumen’s
reagent or, more systematically, as 2,2-dihydroxy-1,3indanedione.
In this work, a simple and sensitive spectrophotometricmethod was developed for the trace determination of cyanide in
industrial wastewater, based on the reaction between cyanide
and ninhydrin in an alkaline medium. The experimental
variables affecting color formation and the possible interference
of co-existing ions were thoroughly studied. The optimum
conditions established were incorporated in the recommended
procedure, which was applied to...