Multianion analysis, applications of ion chromatography - Determination of Anions in Natural and Treated Waters - page 684

12.6.4 Sulphide and cyanide
Bond et al. [21] have described a method for the simultaneous determination of down to
1mg L −1 free sulphide and cyanide by ion chromatography. with electrochemical
detection. These workers carried out considerable exploratory work on the development
of ion chromatographic conditions for separating sulphide and cyanide in a basic medium
(to avoid losses of toxic hydrogen cyanide and hydrogen sulphide) and on the
development of a suitable amperometric detector.
Reagents
Distilled deionised water, to prepare all standards and eluents.
Sulphide and cyanide standards. Prepare daily by dissolving sodium sulphide and
potassium cyanide respectively in 0.005mol L −1 sodium hydroxide. Prior to use filter the
eluents through a 0.45µm filter. Then degas before and during chromatographic runs with
high purity nitrogen.
Apparatus
Dionex (Sunnyvale, California) Model 10 ion chromatograph with supplied detector or
replaced by an electrochemical (amperometric) detector. A waters (Milford, MA) Model
6000A pump in conjunction with a Model U6K injector. Separator column, a Dionex
anion exchange column (internal diameter=3mm, length=250mm). Amperometric
detector, Tacussel (Villeurbanne, France) DELC−1 detector cell. Dropping mercury
electrode (preferred) and a mercury coated platinum working electrode. Mercury was
plated onto the platinum at −1.00V vs Ag/AgCl for 5min and then the electrode was
dipped into a mercury pool. Glassy carbon auxiliary and Ag/AgCl (3mol L −1 NaCl)
reference electrodes. Cathode ray oscilloscope to trace current time curves and hence
determine the drop time in the Tacussell cell F.G. & G.Princeton Applied Research
Corp., (P.A.R) Princeton, NJ. Model 310 polarographic detector cell with Model 303
static mercury drop electrode with auxiliary and reference electrodes as above.
Polarographic data recovered by use of a PAR Model 174A polarographic analyser,
with a PAR Model 303 static mercury drop electrode.
Voltammograms in a conventional electrochemical cell recorded by using 'mini
electrodes' obtained from Metrohm (Herisau, Switzerland) Gold working electrode,
glassy carbon auxiliary and Ag/AgCl (3mol L −1 ) reference electrode for voltammetry.
Procedure
All experiments were carried out in a controlled temperature laboratory at22±1°C