APPENDIX A: CLEANING PROCEDURE FOR SILVER MEMBRANE FILTERS
NOTE: Some lots of silver membrane filters contain extremely high chloride background levels. If
excessively high this cleaning procedure will not remove all of the chloride, even if repeated
several times. Screening is necessary for each lot before being used for this method.
Screening may be done by following this procedure at least twice, or by analyzing by XRD.
1. Place each filter in a 30-mL, wide-mouth bottle, and add 3 mL 6 m M Na2S2O3.
2. Allow to stand for a minimum of 10 min with occasional swirling.
3. Discard solution and rinse thoroughly with deionized water. Allow the filters to stand in last rinse for
a few minutes.
4. Remove filters from bottles and dry between layers of absorbent laboratory towels.
5. Store cleaned filters between paper disks in manufacturer's container. Filters are stable for at least
8 months.