Precipitation of BaSO4 for 34S analysis.
Isotope Science Laboratory (ISL)
University of Calgary
BaSO4 should be precipitated from natural waters (groundwater and/or
surface waters) as follows:
1. Filter 1L of water through a glass fiber filter (~0.7 um pore size)
2. Acidify the water to just below pH 2 by adding ~5mL of 3N
environmental grade HCl (this can be adjusted depending on the
alkalinity of the samples). Wait ~10 minutes to ensure that the DIC
is driven out of solution (give it a stir or swish to aid)
3. Add 5mL of saturated BaCl2 solution
4. Allow BaSO4 precipitate to settle (pure BaSO4 is a clean, white
precipitate)
5. Recover precipitate on 0.45um nitrocellulose membranes (use
Millipore HAWP02500 or HAWP04700 because they are ashless)
6. While the filter is still in the filter apparatus, rinse the precipitate
with at least 500 ml of distilled water (ideally warm) to remove any
residual BaCl2
7. Place filter in a scintillation vial or watch glass and dry in a
dessicator
By acidifying the samples before adding the BaCl2 there should be no
BaCO3 formed. Also, any detrital CaCO3 will have been dissolved.
The BaSO4 samples are captured on nitrocellulose filter membranes so
that if the amount of precipitate is very small, the filter paper can be fused
(muffle furnace @ 500 ºC ~1hour). In such cases, it is best to dry the
sample, fold the filter paper with the sample carefully and send it all in a
capped scintillation vial to the ISL-UofC. We will perform the fusing. Care
must be taken not to lose any sample during fusing.
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