Selecting and Preparing the Reagents. Reagent grade chemicals shall be used in all tests. Unless otherwise
indicated, it is intended that all reagents shall conform to the specifications of the Committee on Analytical
Reagents of the American Chemical Society, where such specifications are available. Other grades may be
used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without
lessening the accuracy of the determination. Reagents for this test method consist of the following:
Water - understood to be reagent water as defined by Type III of Specification D-1193
Isopropyl alcohol. Isopropyl alcohol is flammable.
Liquid detergent - water soluble.
Flushing fluids - petroleum spirit (aka, petroleum ether or IP Petroleum Spirit 40/60).
Filtered fluid (use 0.45-micron membrane filter)
Preparing the Sample Containers.
Clean all components of the filtration apparatus, petri dishes, sample containers and their closures.
Remove any labels, tags, etc.
Wash with warm tap water containing detergent.
Rinse thoroughly with warm tap water.
Rinse thoroughly with reagent water. Container caps should only be handled externally with clean
laboratory crucible tongs during this and subsequent rinsing.
Rinse thoroughly with filtered isopropyl alcohol.
Rinse thoroughly with filtered flushing fluid.
Keep a clean piece if plastic film rinsed with filtered flushing fluid over the top of the sample container
until the closure is installed. Similarly protect the funnel opening of the assembled filtration apparatus
with clean plastic film until ready for use.
Preparing the Test and Control Membrane Filters. Two 47-mm membrane filters of nominal pore size 0.8-um
are required: a test and a control membrane filter. Matched-weight membrane filters may be used if so desired.
If matched-weight filters are used, it is unnecessary to carry out the procedures detailed in this section because
they had been carried out previously by the membrane filter supplier. The two membrane filters used for each
individual test should be identified by marking the petri dishes used as a container.
Wash two petri dishes and supports with warm water containing detergent. Rinse with warm water; rinse
with distilled water; rinse with filtered isopropyl alcohol; and do a final rinse with filtered petroleum ether
or 1,1,2-trichloro-1,2,2-trifluoroethane. Drain the petri dishes and air or oven dry.
Using forceps, place the test and control membrane filters side by side in the clean petri dishes (mark the
dishes to identify test from control). To facilitate handling, the membrane filters should rest on clean
glass support rods in the petri dish.
Place the petri dishes with lids slightly ajar in an oven at 90 + 5 degrees Celsius for 30 minutes.
Remove the petri dishes from the oven and place them near the balance. The covers should remain
slightly ajar, but still protect the membrane filters from being contaminated. Allow 30 minutes for the
membrane filters to come to equilibrium with the ambient air temperature and humidity.
Remove the control membrane filter form its petri dish with forceps, handling by the edge only, and place
it in the center of the weighing pan. Weigh it and return it to its petri dish.
Repeat the weighing procedure for the test filter.
Using clean forceps, place the weighed test membrane filter on top of the membrane filter. Place the
weighed test membrane filter on top of the control membrane filter. Install the funnel. Do not remove
the plastic film from the funnel opening until ready to start filtration.
Perform the Test Procedure.
Take precautions to minimize apparatus contamination from airborne dust. Use a protective hood or
cover. Clean all equipment used for handling samples and membrane filters before use.
With the membrane filters in place, perform a continuity test using a multimeter between the funnel and
the filter holder. The meter shall read 10 ohms or less.
The assembled apparatus shall be grounded by connecting a wire to the laboratory ground from the
locking ring of the filtration assembly to the support stand and to the sample container. Another ground
wire is required from the inside of the receiving and safety flasks, and from the sample container.
Thoroughly clean the outside of the sample container in the region of the closure by washing with
detergent in water and rinsing with tap water and filtered isopropyl alcohol. Shake the container
3-6
QM 5183
Previous Page
