Lumex Instruments Group

Determination of the mercury concentration in naphtha

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". Mercury determination in naphtha and light petroleum products (condensate, gasoline and diesel fuel) at a level below 5 ppb is a vital problem for the oil refining and petrochemical industry. Complex organic matrix impedes conventional quantitative analysis for mercury.

The proposed method of direct mercury determination in naphtha, condensate, and light 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 with a mercury analyzer RA-915M.

At the mercury concentration above 1–5 ppb (µg/kg), the analysis is made directly without any sample preparation and mercury accumulation on a sorbent. The sample of 50–200 µl is sufficient for mercury determination in a range of 5 ppb to 100 ppm. The analysis takes 1–2 min.

If the mercury concentration is below 1–5 ppb, a preconcentration step is required. Mercury is extracted to a special solid sorbent from a sample of 1–5 ml that reduces the limit of detection down to 0.02 ppb. The analysis takes 5–6 min.