OR/14/067 Hydrogen peroxide ‘polishing’

Lapworth, D J, Surridge, B, Williams, P J, Heaton, T H E, and Gooddy, D C. 2014. Method for analysing phosphate 18O/16O ratios for waters with high C:P ratios. British Geological Survey Internal Report, OR/14/067.

The final step is to clean the silver phosphate crystals with hydrogen peroxide to remove any residual organic material.

0.5 ml of 15% hydrogen peroxide solution was added slowly (so as to avoid excessive bubbling) to all sample vials. The sample vials were then placed back in the oven at 50°C and left until all the hydrogen peroxide had evaporated. This step usually visibly improves the colour of the crystals, bleaching them from a dark brown to a lighter shade.

After the cleaning procedure, the vials are reweighed and a final sample weight determined. This sample weight was used to calculate the phosphate yield from the original sample.