Analytical Method: Mercury in water and wastewater

Extraction photometric determination with Michler's thioketone

Cat.No. 173016  Spectroquant® VIS Spectrophotometer Prove 100 or
Cat.No. 173017  Spectroquant® UV/VIS Spectrophotometer Prove 300 or
Cat.No. 173018  Spectroquant® UV/VIS Spectrophotometer Prove 600 or
Cat.No. 109748  Spectroquant® Photometer NOVA 30 or
Cat.No. 109751  Spectroquant® Photometer NOVA 60
Cat.No. 106268  Sodium acetate for analysis
Cat.No. 116754  Water for analysis
Cat.No. 100063  Acetic acid 100 % for analysis
Cat.No. 820162  Michler's thioketone (4.4'-Bis-(dimethylamino)-thiobenzophenone)
Cat.No. 101024  1-Propanol LiChrosolv®
Reagent 1:
Dissolve 17 g sodium acetate in 150 ml of water for analysis and then mix with 2.5 ml of acetic acid 100 %.
Reagent 2:
Dissolve 25 mg 4.4'-Bis-(dimethylamino)-thiobenzophenone in 50 ml 1-Propanol; in a dark glass bottle this solution is stable for about three days. From this parent solution the working solution has to be derived freshly every day by dilution of 5 ml parent solution with 15 ml 1-Propanol.
With Michler's thio-ketone in an acetate buffered medium, mercury(II) forms a red complex, which is soluble in a aqueous-alcoholic medium. The complex has an absorption peak at 560 nm and can be used for the photometric determination of mercury.
Measurement range:
Method no. 135
0.025 - 1.000 mg/l Hg at cell length of 50 mm and 565 nm
Analysis: Mix 5.0 ml of sample solution (pH 3 - 7) with 1.0 ml reagent 1 as well as 1.5 ml reagent 2. After 5 min waiting time determine the extinction against a blank.
In the photometers Prove 100, Prove 300, Prove 600, Pharo 100, Pharo 300 and NOVA 60the method is stored.
For the measurement select method no 135 in the instrument.
According to the literature mentioned below all noble metals (gold, silver, platinum, palladium, rhodium, iridium, ruthenium) interfere due to the same reaction; tin(II) interferes differently.
G. Ackermann, H. Röder: Talanta 24(1977)99-103


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