Hg Speciation in Petroleum Hydrocarbons with Emphasis on the Reactivity of Hg Particles

Abstract

Particulate HgS is generally thought to be the most abundant Hg species in stored petroleum hydrocarbons stocked onshore. It is also assumed that due to its high stability constant, HgS is chemically inert. However, results from the current study would suggest otherwise. Firstly, a comparison study of the analytical performance of ICP-MS and CV-AFS with respect to matrix effect, showed no significant difference in the measured Hg concentrations in studied samples when CV-AFS is used in the alkali mode. Subsequently, the suitability of three quantification methods during Hg speciation was investigated. Both external calibration and standard addition methods resulted troublesome with the former showing matrix dependence and the latter being hindered by the formation of an emulsion during the derivatisation step. Results from species-specific isotope dilution (SS-ID-GC-ICP-MS), on the other hand, performed at different equilibration times, showed a random variation in the calculated Hg 2+ concentration (RSD 32%), 2 suggesting that factors independent of equilibration time cause the observed variation. Further sedimentation of Hg particulate by means of ultracentrifugation improved the precision of SS-ID-GC-ICP-MS by 10-fold. These results would suggest that Hg particles in petroleum products are reactive at low temperature during Grignard alkylation.

Recent Studies on the Speciation and Determination of Mercury in Different Environmental Matrices Using Various Analytical Techniques

“…Following water samples, the most frequently analyzed material for mercury was seafood samples, such as fish, shrimp, and seaweed. A few studies reported the determination of mercury in various environmental samples, such as petroleum hydrocarbons [ 88 ], human hair [ 89 , 90 ], phosphate fertilizers [ 53 ], glycerin [ 91 ], sediments [ 55 , 92 , 93 ], cosmetics [ 94 ], living cells [ 66 , 95 ], and tobacco [ 67 ]. However, a few methods [ 74 , 81 , 87 , 96 – 101 ] did not report their applicability to natural samples.…”

“…In this respect, electrochemical methods had a higher degree of selectivity and did not suffer from interference from other ions. Determination of the level of interference was not performed by a large number of authors [ 45 – 47 , 53 , 55 , 59 , 60 , 62 , 63 , 69 , 88 , 91 , 92 , 102 – 106 ] who determined mercury with spectrometric instruments. However, those using electrochemical instruments, spectrophotometers, or spectrofluorometers largely reported the level of interfering ion(s).…”

“…Speciation studies revealed the exact toxicity of mercury in environmental samples. However, very few authors [ 88 , 90 , 92 , 107 ] reported the speciation of mercury, and most authors determined the level of inorganic mercury. More than 90% of studies using electrochemical methods or spectrophotometry and spectrofluorometry techniques determined divalent inorganic mercury and did not report speciation.…”

AF4-UV-MALS-ICP-MS/MS, spICP-MS, and STEM-EDX for the Characterization of Metal-Containing Nanoparticles in Gas Condensates from Petroleum Hydrocarbon Samples

“…For this reason, there is a need to identify exactly which species of mercury are present. The total amount of Hg should fulfil the following mass balance equation 8 :…”

GC-ICP-MS/MS Instrumental Setup for Total and Speciation Sulfur Analysis in Gasolines using Generic Standards

“…Nevertheless, direct liquid total analysis of petroleum samples by ICP-MS requires conscientious selection of the introduction technique to prevent large quantities of carbon arriving to the plasma, either by low-flow nebulizers, cooled spray chambers or alternative procedures. [11][12][13] Direct injection by thermal vaporization and ICP-MS was also employed. Unfortunately, matrix effects and signal-drifts caused by co-elution of hydrocarbons demanded for the application of isotope dilution using 34 S-labelled volatile standards.…”