Silver-Ion Solid Phase Extraction Separation of Classical, Aromatic, Oxidized, and Heteroatomic Naphthenic Acids from Oil Sands Process-Affected Water

Abstract

The separation of classical, aromatic, oxidized, and heteroatomic (sulfur-containing) naphthenic acid (NA) species from unprocessed and ozone-treated oil sands process-affected water (OSPW) was performed using silver-ion (Ag-ion) solid phase extraction (SPE) without the requirement of pre-methylation for NAs. OSPW samples before SPE and SPE fractions were characterized using ultra performance liquid chromatography ion mobility time-of-flight mass spectrometry (UPLC-IM-TOFMS) to corroborate the separation of distinct NA species. The mass spectrum identification applied a mass tolerance of ±1.5 mDa due to the mass errors of NAs were measured within this range, allowing the identification of O2S-NAs from O2-NAs. Moreover, separated NA species facilitated the tandem mass spectrometry (MS/MS) characterization of NA compounds due to the removal of matrix and a simplified composition. MS/MS results showed that classical, aromatic, oxidized, and sulfur-containing NA compounds were eluted into individual SPE fractions. Overall results indicated that the separation of NA species using Ag-ion SPE is a valuable method for extracting individual NA species that are of great interest for environmental toxicology and wastewater treatment research, to conduct species-specific studies. Furthermore, the separated NA species on the milligram level could be widely used as the standard materials for environmental monitoring of NAs from various contamination sites.

Naphthenic acids in oil sands process waters: Identification by conversion of the acids or esters to hydrocarbons

“…Fractionation of the NA extract of sample #1 by Ag-Ion chromatography (as methyl esters; Scheme 1), produced 'alicyclic' (36 %), 'aromatic' (17 %) and 'aromatic/sulphur' (4 %) subfractions of OSPW. These contrasted with the proportions of sub-fractions of a commercial NA extract obtained from the refinement of petroleum (80.0 %, 6.4 % and 0.9 % respectively) but were consistent with the results of previous fractionation studies of OSPW NA analysed by liquid chromatography with ion mobility and high resolution mass spectrometry (Huang et al, 2016).…”

Utilization of Fe-Ethylenediamine-N,N′-Disuccinic Acid Complex for Electrochemical Co-Catalytic Activation of Peroxymonosulfate under Neutral Initial pH Conditions

“…The Fluka commercial NA mixture is composed of a complex class of NAs extracted from crude oil, and it has been extensively employed as a representative of organic pollutants in authentic oil and gas field wastewater samples in previous studies [37,43]. The composition of the Fluka NA mixture predominantly features classical NAs, characterized by a double-bond equivalent (DBE) number that spans the range of 0 to 6, and a carbon number that spans the range of 7 to 26.…”

Water Analysis: Emerging Contaminants and Current Issues

“…The use of barium ions allowed the formation of barium adducts, (M – H + Ba) + , which improved selectivity in complex samples, eliminating isobaric interferences from hydroxylated species. Huang et al reported another new method using Ag + -SPE to better separate classical, aromatic, oxidized, and heteroatomic NAs, which could be eluted into separate SPE fractions . UPLC-ion mobility (IM)-HR-TOF-MS was used for analysis, with a mass tolerance of ±1.5 mDa.…”

“…Huang et al reported another new method using Ag + -SPE to better separate classical, aromatic, oxidized, and heteroatomic NAs, which could be eluted into separate SPE fractions. 210 UPLC-ion mobility (IM)-HR-TOF-MS was used for analysis, with a mass tolerance of ±1.5 mDa. In an earlier paper by the same group, their UPLC-IM-TOF-MS method was described and used to measure NAs in the oil sands process water and ozone-treated process waters.…”