Analytical Method: Mercury in water and wastewater

Extraction photometric determination with Michler's thioketone

Instruments:
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
 
Reagents:
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.
 
Reaction:
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.
 
Measurement:
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.
 
Interferences:
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.
 
Literature:
G. Ackermann, H. Röder: Talanta 24(1977)99-103

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