12. Procedure
12.1 Place crude oil sample containers in an ultrasonic homogenizer for approximately fifteen minutes just prior to analysis. Keep the water in the bath at ambient temperature by adding a few ice chips as the temperature rises. The homogenization step dissociates particulate mercury and promotes a more stable suspension.
12.2 Remove sample boat and reagents (if required) from muffle furnace and allow to cool to room temperature in a covered container.
12.3 Spread approximately 0.2 g of charcoal over the bottom of a cooled sample boat.
12.4 Shake the sample to mix just before withdrawing an aliquot. Open the cap and quickly withdraw sample in a clean, disposable transfer pipet. Weigh approximately 0.1 g of sample into the sample boat.
12.5 Choose the appropriate instrument parameters and heating mode for crude oil based upon manufacturer's instructions.
12.6 Open the inlet cover. Insert the sample boat into the combustion area of the furnace. Close the cover and start the analysis. Analyze a test specimen of the analysis sample in accordance with the manufacturer's instructions.
12.7 After analysis is complete, remove sample boat from furnace. Allow to cool before disposing of reagent material.
13. Calculation
13.1 Calculate the concentration of mercury, on the appropriate sample basis, as follows:
where:
A = ng/g of the analyte,
B = detector response for the analyte,
C = detector response for the reagent blank,
D = mass, ng per unit of detector response established for analyte during calibration, and
E = mass of test specimen, g.
13.2 The calculations can be provided automatically by the instrumental system used for this test method.