Direct atomic absorption mercury determination in oil and oil products
Determination of mercury in oil and petroleum hydrocarbon is currently a vital probl em due to the fact that the regulations for the mercury content in emission s from thermal power plants are becoming ever more stringent, and mercury poisons catalysts used in oil re fining.
Complex organic matrix of oil and low mercury content (average concentration does not exceed 30 μ g/kg, the highest concentration being 20,000 μ g/kg) make oil one of the most difficult objec ts for quantitative analysis for mercury. Practically all the AA and AF methods of mercury determination in oil involve the stage of the oil decomposition with acids, which increases the detecti on limit and time of analysis, and gives rise to errors.
This method of mercury determination in crude oil and oil products is based on the atomization of mercury contained in the sample in a PYRO-915+ attachment and subsequent mercury determination by flameless AAS in a mercury analyzer RA-915M (RA-915+). The mercury AAS analyzer RA-915M (RA-915+) with the Zeeman background correction equipped with a thermal decomposition attachment PYRO-915+ allows determination of mercury in oil, food and other samples with organic matrix without sample preparation and mercury accumulation on a sorbent. Mercury content in the sample is determined from the integrated analytical signal with due account of the preset calibration coefficient (from any reference mercury sample).
The two-section atomizer PYRO-915+ consists of evaporator, in which evaporation of liquid samples and hydrolysis of solid samples are carried out, and of the heated reactor, in which catalytic destruction of the sample matrix compounds proceeds. After the pyrolyzer, the gas flow heated to 800 OC directly enters the cell of the analyzer with the Zeeman correction. The effect of the remaining impurity compounds is eliminated due to the high selectivity of the RA-915M (RA-915+) analyzer.
Even if the optical density of the non-selective absorption is high (more than 2), no false signals appear, which allows a considerable increase of the sample weight (without accumulating mercury on the sorbent) and thereby lowering the concentration detection limit. The absence of cold ducts and smoke traps between the pyrolyzer and the cell makes it possible to avoid mercury sorption on them and thereby to improve the analysis reproducibility and correctness.