Analytical Method: Lead in Waste Water with High Concentrations of Calcium

Instruments and Reagents:

173016 Spectroquant^® VIS Spectrophotometer Prove 100 or
173017 Spectroquant^® UV/VIS Spectrophotometer Prove 300 or
173018 Spectroquant^® UV/VIS Spectrophotometer Prove 600 or
109748 Spectroquant^® Photometer NOVA 30 or
109751 Spectroquant^® Photometer NOVA 60 or
173632 Spectroquant^® Colorimeter Move 100

114946 Rectangular cells 10 mm and/or
/TW/en114947 Rectangular cells 20 mm and/or
114944 Rectangular cells 50 mm

114833 Spectroquant^® Lead Cell Test
109717 Spectroquant^® Lead Test
106689 Sodium diethyldithiocarbaminate trihydrate for analysis
100983 Ethanol for analysis
109966 Nitric acid 1 mol/L
109137 Sodium hydroxide solution 1 mol/L
109535 MColorpHast^TM Universal indicator strips pH 0 - 14
116754 Water for analysis
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 the sample solution, shake and aspirate into a 10 mL-PE syringe. Pass the syringe contents through a 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.

Analyze:

Determine with the above mentioned test kits.

Calculation:

Lead content in mg/L Pb = analysis value in mg/L Pb x 0.5