ASTM D7623 Standard Test Method for Total Mercury in Crude Oil Using Combustion-Gold Amalgamation and Cold Vapor Atomic Absorption Method
4. Summary of Test Method
4.1 Controlled heating of the analysis sample in oxygen is used to liberate mercury. The sample is heated to dryness in the instrument and then thermally (at about 700 °C) and chemically decomposed. The decomposition products are carried by flowing treated air to the catalytic section of the furnace (at about 850 °C), where oxidation is completed. The decomposition products are carried to a gold amalgamator that selectively traps mercury. After the system is flushed with oxygen to remove any remaining decomposition products other than mercury, the amalgamator is rapidly heated to about 600 °C, releasing mercury vapor. Flowing oxygen carries the mercury vapor through absorbance cells positioned in the light path of single wavelength cold vapor atomic absorption spectrophotometer. Absorbance peak height or peak area, as a function of mercury concentration, is measured at 253.65 m.
NOTE 1 - Mercury and mercury salts can be volatized at low temperatures. Precautions against inadvertent mercury loss should be taken when using this test method.
5. Significance and Use
5.1 The emission of mercury during crude oil refining is an environmental concern. The emission of mercury may also contaminate refined products and form amalgams with metals, such as aluminum.
5.2 When representative test portions are analyzed according to this procedure, the total mercury is representative of concentrations in the sample.
