2.6. Filter extraction for total metal analysis
A microwave extraction was done to remove metals from the
smoke-saturated filters. Both filters from a single session were cut in
half with a ceramic knife. The filter halves were weighed into 5.0 mL,
12 x 75 mm acid washed borosilicate glass vessels with 0.5 mL concen-
trated trace metal grade HNO3, 2.0 mL DDIW, and 50.0 μL internal stan-
dard. Two SRM vessels (DORM-3, 30.0 mg, used for a visual digestion
reference; certificate values are valid for a minimum of 0.250 g) and
three DDIW blank vessels (2.0 g) were also digested during each micro-
wave run. There were three steps to the temperature program — first
the sample vessels were ramped for 20 min to 250 °C, then held for
20 min, and finally ramped down for another 20 min to 60 °C at
1500 W and a pressure of 60 bar. The vessels were then centrifuged
for 5.0 min at RCF of 190 g. Then the filters were removed and the ex-
tract was transferred into another vial and diluted to 15.0 mL with
DDIW.
2.6. Filter extraction for total metal analysisA microwave extraction was done to remove metals from thesmoke-saturated filters. Both filters from a single session were cut inhalf with a ceramic knife. The filter halves were weighed into 5.0 mL,12 x 75 mm acid washed borosilicate glass vessels with 0.5 mL concen-trated trace metal grade HNO3, 2.0 mL DDIW, and 50.0 μL internal stan-dard. Two SRM vessels (DORM-3, 30.0 mg, used for a visual digestionreference; certificate values are valid for a minimum of 0.250 g) andthree DDIW blank vessels (2.0 g) were also digested during each micro-wave run. There were three steps to the temperature program — firstthe sample vessels were ramped for 20 min to 250 °C, then held for20 min, and finally ramped down for another 20 min to 60 °C at1500 W and a pressure of 60 bar. The vessels were then centrifugedfor 5.0 min at RCF of 190 g. Then the filters were removed and the ex-tract was transferred into another vial and diluted to 15.0 mL withDDIW.
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