The determination of trace amount of sulfide based on the addition reaction of sulfide with malachite green at pH= 7.5 and 25 ºC has been
investigated in micellar media. Surfactants studied include non-ionic surfactant, Trition-x-100, anionic surfactant, sodium dodecyl sulfate
(SDS), cationic surfactant, cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC). The reaction is followed
spectrophotometrically by measuring the decrease in absorbance of the indicator at max= 630 nm by the fixed time method. The reaction in
the presence of Trition-x-100 is faster than in the absence of surfactant in medium. No significant change was observed with SDS, CTAB
and CPC. Under the optimum experimental conditions decreases in the absorbance of malachite green is proportional to the concentration
of sulfide in the range 25-1750 ng ml-1 with a fixed time method at the first 5, 15 and 25 seconds from initiation of the reaction. The
detection limit and quantification limit of the proposed kinetic method were 0.166, 0.207and 0.281 μg ml-1
(t=5, 15 and 25 s )and 0. 555,
0.692and 0.959 μg ml-1
(t=5, 15and 25) respectively. To confirm the usefulness of the proposed method, sulfide was determined in river,
spring, fish farm, and tap water wastewater samples without any purification or using masking reagents
Key words: Kinetic spectrophotometry; sulfide determination; malachite green; micelle.
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