Analytical Method: Nickel (Total) in Electrophoretic Paints

Instruments and Reagents

• Product No. 173016 Spectroquant^® VIS Spectrophotometer Prove 100 or
• Product No. 173017 Spectroquant^® UV/VIS Spectrophotometer Prove 300 or
• Product No. 173018 Spectroquant^® UV/VIS Spectrophotometer Prove 600 or
• Product No. 109748 Spectroquant^® Photometer NOVA 30 or
• Product No. 109751 Spectroquant^® Photometer NOVA 60 or
• Product No. 173632 Spectroquant^® Colorimeter Move 100
• Product No. 114946 Rectangular cells 10 mm and/or
• Product No. 114947 Rectangular cells 20 mm and/or
• Product No. 114944 Rectangular cells 50 mm
• Product No. 114554 Spectroquant^® Nickel Cell Test
• Product No. 114785 Spectroquant^® Nickel Test
• Product No. 100731 Sulfuric acid 95 - 97 % for analysis
• Product No. 107210 Hydrogen peroxide 30 % (Perhydrol^®) for analysis
• Product No. 105590 Sodium hydroxide solution 32 %
• Product No. 109535 MColorpHast^TM Universal indicator strips pH 0 - 14
• Product No. 116754 Water for analysis

Sample Preparation

In a 400-mL glass beaker add 10 mL homogenized paint sample to 10 mL of sulfuric acid 95 - 97 % for analysis, swirling to mix. For complete solubilisation of the sedimented resins, heat the mixture on the steambath to

100 °C. After addition of 2 mL Perhydrol^®, the dark-brown solution is decolorized. When foaming has subsided, add once more 2 mL of Perhydrol^®, followed by a slow and cautious warming. After this add further 2 mL Perhydrol^® and heat to boiling (glass beads, as anti-bump medium).

If the mixture remains clear and colorless after 10 minutes heating, allow to cool to room temperature. Should the color remain brown, repeat the treatment with 2 mL Perhydrol^® with a further 10 minutes heating.

Dilute the cooled solution to 100 mL with water for analysis and adjust the pH (pH-meter) to 4, using sodium hydroxide solution 32 % and transfer to a 200-mL standard volumetric flask. Fill up to volume with water for analysis and mix well.

Analysis

Determine with the above mentioned test kits.

Calculation

Using the 1+99 sample dilution the analysis value corresponds directly to the nickel (total) content in mg/l.