D7321_11 V2

Thoroughly clean the outside of the sample container in the region of the cap by wiping it with a damp, lint-free cloth. Shake the container vigorously for about 1 minute. Remove the cap, and remove any external contaminant that may be present in the threads. Complete assembly of the receiving flask, pre-weighed filter, and funnel as a unit. See figure 1 of the written standard. To minimize operator exposure to fumes, the filtering procedure should be performed in a fume hood. Important-- the entire contents of the sample container shall be filtered through the glass fiber filter to ensure a correct measure of the particulate contamination in the sample. Some fuels may filter reasonably rapidly during transfer of the total contents of the sample container through a single glass fiber filter. However, some fuels, due to the quantity or nature of the particulates, or both, may plug the filters during filtration and require use of multiple successive filtrations. To facilitate the latter, it is advisable to use smaller, cleaned graduated transfer cylinders of 100 milliliter capacity. Pour fuel from the sample container to the graduated cylinder, start the vacuum, and then transfer 100 milliliters of fuel to the filter funnel. Continue transferring 100-milliliter increments of fuel to the filter funnel. When all the fuel from the sample container has been filtered or if filtration slows so that 100 milliliters of sample requires greater than 10 minutes for complete filtration, then remove the filter support, filter funnel from the receiving flask, and pour the filtered fuel into a clean graduated cylinder, and record the volume of fuel in milliliters that was filtered-- v sub f. Keep the fuel sample filtrate separate from the solvent washings filtrate. This allows the fuel to be used for additional analyses. If all the fuel has been filtered, thoroughly rinse the sample container and the graduated cylinder with one or more portions of filtered flushing fluid, and pour the rinses into the funnel, and proceed to 11.6 of the written standard. If all the fuel has not been filtered, then proceed to 11.6 and 11.8 of the written standard, and then repeat from 11.1 of the written standard. Wash down the inside of the funnel and the outside of the joint between the funnel and the filter base filtered with flushing fluid. Use two washes with approximately 50 milliliters each of washing flushing fluid. With the vacuum applied, carefully separate the funnel from the filter base. Wash the periphery of the glass fiber filter by directing a gentle stream of filtered flushing fluid from the edge to the center, exercising care not to wash any of the particulate from the surface of the glass fiber filter. The volume of the solvent required is recommended to be approximately 50 milliliters. However, the rate of filtration may dictate the solvent volume. Take care not to wash particles from the filter, particularly at the stage when the funnel has been removed. The volume of the solvent used to wash the filter should be sufficient to rinse any particles onto the filter paper. A final wash of approximately 20 milliliters of methanol or isopropanol, [? propintanol, ?] is applied with the use of a pipette to remove trace of fuel while taking care to minimize the risk of dislodging any particles on the filter. A Pasteur pipette has been found suitable for the final wash. Maintain vacuum after the final washing for 10 seconds to 15 seconds to remove excess filtered flushing fluid from the glass fiber filter. Using clean forceps, carefully remove the glass fiber filter from the filter base, and place it on clean glass support rods or watch glass in a clean, covered Petri dish. Dry and reweigh the glass fiber filter as described in 10.5 of the written standard, taking care not to disturb the particulate on the surface of the glass fiber filter. Record the glass fiber filter mass to the nearest 0.0001 gram for each filtration. If after removing the filter from the drying oven the filter is observed to have discoloration on the filter indicating fuel on the outer edges, gently rinse the filter with more solvent, rinsing gently from the outer edges inward so as to not disturb any particulate matter filtered and repeat 11.8.