Direct mercury determination in crude oil and oil products

INTRODUCTION

The mercury concentration in crude oil and petroleum products can vary in a wide range of less than 0.1 ppb to dozens ppm. Direct mercury determination in crude oil and petroleum products at the range above 5 ppb is covered by ASTM D7622-10(2015) "Standard test method for total mercury in crude oil using combustion and direct cold vapor atomic absorption method with Zeeman background correction"and SN/T 4429.2-2016 “Determination of total mercury in crude oil – Zeeman correction – Cold atomic absorption spectrometry”. The complex organic matrix impedes conventional quantitative analysis for mercury.

MEASURING METHOD

The Lumex Instruments method specifies a practical guidance for the standard method implementation for crude oil and petroleum products analysis using Lumex Instruments mercury analyzers.

The principle of the method is based on the reduction of Hg(II) to the atomic state due to the thermal decomposition of the mercury compounds and the follow-up transporting of mercury atoms into the analytical cell of the analyzer by the air flow. The mercury concentration is then determined from the absorption of the 254-nm resonance radiation by mercury atoms measured by the RA-915M or RA-915+ mercury analyzer combined with PYRO-915+ attachment or by RA-915F mercury analyzer using differential atomic absorption spectroscopy with Zeeman correction for background absorption.