LaMotte SMART Spectro Spectrophotometer - Manual (Page 247)

APPLICATION: Drinking, surface, and saline waters; domestic and
industrial wastes.
RANGE: 0.00–1.00 ppm Sulfi de
MDL: 0.02 ppm
METHOD: Under suitable conditions the sulfi de ion reacts
with p-aminodimethylaniline and ferric chloride to
produce methylene blue in proportion to the sulfi de
concentration. Ammonium phosphate is added to
remove the color due to the ferric iron.
SAMPLE HANDLING
& PRESERVATION:
Samples must be taken with a minimum of aeration
since sulfi de is volatilized by aeration and any oxygen
which is taken up will destroy sulfi des by chemical
action. Samples that are used for total sulfi de
concentrations may be preserved by adding 2M
zinc acetate solution at a dosage of 2 mL per liter of
sample. This precipitates sulfi de as inert zinc sulfi de.
Determination of dissolved sulfi des in samples not
preserved with zinc acetate must be started within 3
minutes of sampling.
INTERFERENCES: Strong reducing agents such as sulfi te, thiosulfate,
and hydrosulfi te prevent the formation of the color or
diminish its intensity. High concentrations of sulfi de will
inhibit the reaction, but dilution of the sample prior to
analysis eliminates this problem.
SULFIDE SMART Spectro Test Procedures 2.11
Test P
rocedures