This document describes a method for analyzing metal content in chlorinated hydrocarbons during the petroleum production process. The method uses flame atomic absorption spectroscopy (FAAS), but evaporates the hydrocarbons to safe laboratory conditions instead of burning them directly. The method uses two solvents, 2% hydrochloric acid (2% HCl) and methyl isobutyl ketone (MIBK).
The document addresses the safety issues of aspirating chlorinated hydrocarbons directly into a flame atomic absorption spectrometer due to the formation of toxic organic compounds like phosgene. It proposes an alternate method where samples are evaporated under safe laboratory conditions, and the resulting residue is dissolved in a solvent for analysis.
Two primary solvents were investigated: 2% hydrochloric acid (HCl) and methyl isobutyl ketone (MIBK). The study evaluated the recovery rates and precision of aluminium, iron, and nickel using these solvents with the Agilent AA-975 instrument. Results indicated that while MIBK dissolved organic material well, it failed to quantitatively recover metals. Conversely, 2% HCl provided good recoveries for most metals, though concentrated acids were tested specifically to improve nickel recovery.
Chlorinated hydrocarbons break down into toxic organic compounds, such as phosgene, with flame combustion.
The study initially investigated 2% hydrochloric acid (2% HCl) and methyl isobutyl ketone (MIBK).
The use of acid to dissolve the residue, specifically 2% HCl or concentrated acids, is recommended over MIBK.