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University of California
Stable Isotope Laboratory
Earth and Planetary Sciences
1156 High Street Santa Cruz, CA 95064

Lab: (831) 459-5751
Office: (831) 459-5857
Fax: (831) 459-3074

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Silver Phosphate (Ag3PO4) Preparation for Apatite Samples

Preparation of Ag3PO4 in fossil biopatite (after Bassett et al., 2007)
1- Weigh between 1.5 mg and 2 mg of powdered sample in a 2 ml polypropylene vial with pointed bottom.
2- Add 100 µl of 0.5M HNO3. Use the Vortex Genie so the sample can totally dissolved. Leave overnight.
3- Add 75 µl of 0.5M KOH to neutralize the dissolution.
4- Add 200 µl of 0.36M KF so CaF2 can precipitate (along with other fluorides depending on the apatite composition).
5- Centrifuge the samples during ~ 7 minutes so the solid residue stick to the bottom of the vial.
6- Transfer the liquid from the vials to a new vial (don't forget to write the signature on this new vial!) with a pippete. BE CAREFUL in order to avoid the solid of the bottom!
7- Add 250 µl of silver amine (0.2M AgNO3, 0.35M NH4NO3, 0.74M NH4OH).
8- Leave the vials open in the oven at 50°C overnight. At this point the precipitation of Ag3PO4 should happen (formation of yellow crystals).
9- In order to recover the Ag3PO4, vials must be centrifuged 5 times during 10 minutes every time. 1 ml of Milli-Q water must be added in every rinse. Ag3PO4 crystals will remain stuck to the bottom of the vials. Use the Vortex Genie between every rinse.
10- The remaining liquid is removed and vials are left open drying in the oven at 50°C overnight.
11- Place vials in a dessicator and weigh between 200 µg and 300 µg of sample in pressed silver capsules.