Analytical Method: Lead in waste water with high concentrations of calcium

Instruments and Reagents:

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 or

Cat.No. 173632 Spectroquant® Colorimeter Move 100

Cat.No. 114946 Rectangular cells 10 mm and/or

Cat.No. 114947 Rectangular cells 20 mm and/or
Cat.No. 114944 Rectangular cells 50 mm
Cat.No. 114833 Spectroquant® Lead Cell Test
Cat.No. 109717 Spectroquant® Lead Test
Cat.No. 106689 Sodium diethyldithiocarbaminate trihydrate for analysis
Cat.No. 100983 Ethanol for analysis
Cat.No. 109966 Nitric acid 1 mol/l
Cat.No. 109137 Sodium hydroxide solution 1 mol/l
Cat.No. 109535 MColorpHast^TM Universal indicator strips pH 0 - 14
Cat.No. 116754 Water for analysis
Cat.No. 114724 Empty cells 16 mm with screw caps
Membranfilter 0.45 μm
Polyethylene syringe, 10 ml, with Luer cone
Thermoreactor

Sodium diethyldithiocarbaminate solution10 %:
Dissolve 5 g sodium diethyldithiocarbaminate trihydrate for analysis in 45 ml of water for analysis.

Waste water from the metal- and glass-processing industries are normally treated with milk of lime to precipitate metals. However, the resulting high concentrations of Ca²⁺ tend to interfere with the photometric determination of lead. The procedure described below avoids this type of interference.

Sample preparation:
Add 10 drops of a 10 % solution of sodium diethyldithiocarbaminate solution to 10 ml of sample solution, shake and aspirate into a 10 ml-PE syringe. Pass the syringe contents through an membrane filter, wash with 10 ml water for analysis and dispose of the filtrate and wash solution. Pass 5 ml ethanol through the same membrane filter. Collect the ethanolic filtrate in a 16-mm round cell, add 5 drops of nitric acid 1 mol/l and place in the thermoreactor at 100 °C for evaporation to dryness.
Add 5 ml of water for analysis to the residue in the round cell and adjust the pH to the required value of 3 - 6 with sodium hydroxide solution. This can be checked using universal indicator strips. This solution can now be used directly for the determination of lead.

Analyse:
Determine with the above mentioned test kits.

Calculation:
Lead content in mg/l Pb = analysis value in mg/l Pb x 0.5