LaMotte SMART Spectro Spectrophotometer - Manual (Page 145)

APPLICATION: Low level concentrations in drinking and surface waters;
domestic and industrial waters. This method determines
only those cyanides amenable to chlorination.
RANGE: 0.00–0.500 ppm Cyanide
MDL: 0.05 ppm
METHOD: Cyanides react with a chlorine donor to form cyanogen
chloride, which subsequently reacts with Pyridine
and Barbituric Acid to form a red-blue compound in
proportion to the amount of cyanide originally present.
The concentration of the red-blue compound is
determined spectrophotometrically.
SAMPLE HANDLING &
PRESERVATION:
Cyanide solutions tend to be unstable and should
be analyzed as soon as possible. Samples can be
stabilized by adjusting the pH to greater than 12 with
NaOH. However, the pH will have to be readjusted to
pH 10.5 before performing the test.
INTERFERENCES: Oxidizing agents and aldehydes can react with cyanide,
while reducing agents, such as sulfi te, react with the
chlorine donor; both can cause negative interferences.
Thiocyanate and cyanogen chloride both react as
cyanide in this test and will give a positive interference.
Color and turbidity can also interfere.
CYANIDE SMART Spectro Test Procedures 2.11
Test P
rocedures