OR/14/067 Reagent required for silver phosphate precipitation

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.

Initial preparation

Dowex 1X8–200 anion exchange resin (Sigma Aldrich) Approx. 50 g per sample
Dax-8 resin (Supelco, Supelite) Approx. 50 g per sample
Methanol (Analar) For preparing and cleaning Dax-8 resin — volume needed can be estimated according to requirements
Hydrochloric acid (Aristar) For preparing and cleaning Dowex anion exchange resin — volume needed can be estimated according to requirements
Potassium Chloride (Analar) 44.73 g required to make up 1litre — Two litres needed ideally just to elute for PO₄
Potassium phosphate (KH₂PO₄) used to make up a PO₄ standard

Acetic acid, glacial (Analar) At least 2 ml per sample
Nitric acid (Arsitar) At least 1 ml per sample
Potassium acetate (Analar) Approx. 0.49 g needed to make up 0.5 M solution for 10 samples
Potassium hydroxide (may be necessary for adjusting pH)
Cerium (III) nitrate hexahydrate (From Merck described as ‘Extra pure’) 400 mg per sample

Dowex 50W X-8 cation exchange resin (Sigma Aldrich) Approx. 4 g per sample
Nitric acid (Aristar) For preparing and cleaning Dowex cation exchange resin — volume needed can be estimated according to requirements

Silver nitrate (AgNO₃) (Analar) Approx. 2.54 g required to make up solution per 10 samples
Ammonium nitrate (NH₄NO₃) (Analar) Approx. 4.3 g required to make up solution per 10 samples
Ammonium hydroxide (NH₄OH) (Analytical grade — From Fluka described as ‘for trace analysis’) Approx. 7–8 ml required per 10 samples