Dayue Shang

Chemical fingerprinting of naphthenic acids and oil sands process waters—A review of analytical methods for environmental samples

This article provides a review of the routine methods currently utilized for total naphthenic acid analyses. There is a growing need to develop chemical methods that can selectively distinguish compounds found within industrially derived oil sands process affected waters (OSPW) from those derived from the natural weathering of oil sands deposits. Attention is thus given to the characterization of other OSPW components such as oil sands polar organic compounds, PAHs, and heavy metals along with characterization of chemical additives such as polyacrylamide polymers and trace levels of boron species. Environmental samples discussed cover the following matrices: OSPW containments, on-lease interceptor well systems, on- and off-lease groundwater, and river and lake surface waters. There are diverse ranges of methods available for analyses of total naphthenic acids. However, there is a need for inter-laboratory studies to compare their accuracy and precision for routine analyses. Recent advances in high- and medium-resolution mass spectrometry, concomitant with comprehensive mass spectrometry techniques following multi-dimensional chromatography or ion-mobility separations, have allowed for the speciation of monocarboxylic naphthenic acids along with a wide range of other species including humics. The distributions of oil sands polar organic compounds, particularly the sulphur containing species (i.e., OxS and OxS2) may allow for distinguishing sources of OSPW. The ratios of oxygen- (i.e., Ox) and nitrogen-containing species (i.e., NOx, and N2Ox) are useful for differentiating organic components derived from OSPW from natural components found within receiving waters. Synchronous fluorescence spectroscopy also provides a powerful screening technique capable of quickly detecting the presence of aromatic organic acids contained within oil sands naphthenic acid mixtures. Synchronous fluorescence spectroscopy provides diagnostic profiles for OSPW and potentially impacted groundwater that can be compared against reference groundwater and surface water samples. Novel applications of X-ray absorption near edge spectroscopy (XANES) are emerging for speciation of sulphur-containing species (both organic and inorganic components) as well as industrially derived boron-containing species. There is strong potential for an environmental forensics application of XANES for chemical fingerprinting of weathered sulphur-containing species and industrial additives in OSPW.

Toxicity of naphthenic acid fraction components extracted from fresh and aged oil sands process-affected waters, and commercial naphthenic acid mixtures, to fathead minnow (Pimephales promelas) embryos.

Naphthenic acids (NAs) are constituents of oil sands process-affected water (OSPW). These compounds can be both toxic and persistent and thus are a primary concern for the ultimate remediation of tailings ponds in northern Albertas oil sands regions. Recent research has focused on the toxicity of NAs to the highly vulnerable early life-stages of fish. Here we examined fathead minnow embryonic survival, growth and deformities after exposure to extracted NA fraction components (NAFCs), from fresh and aged oil sands process-affected water (OSPW), as well as commercially available NA mixtures. Commercial NA mixtures were dominated by acyclic O2 species, while NAFCs from OSPW were dominated by bi- and tricyclic O2 species. Fathead minnow embryos less than 24h old were reared in tissue culture plates terminating at hatch. Both NAFC and commercial NA mixtures reduced hatch success, although NAFCs from OSPW were less toxic (EC50=5-12mg/L, nominal concentrations) than commercial NAs (2mg/L, nominal concentrations). The toxicities of NAFCs from aged and fresh OSPW were similar. Embryonic heart rates at 2 days post-fertilization (dpf) declined with increasing NAFC exposure, paralleling patterns of hatch success and rates of cardiovascular abnormalities (e.g., pericardial edemas) at hatch. Finfold deformities increased in exposures to commercial NA mixtures, not NAFCs. Thus, commercial NA mixtures are not appropriate surrogates for NAFC toxicity. Further work clarifying the mechanisms of action of NAFCs in OSPW, as well as comparisons with additional aged sources of OSPW, is merited.

Rapid and sensitive method for the determination of polycyclic aromatic hydrocarbons in soils using pseudo multiple reaction monitoring gas chromatography/tandem mass spectrometry.

A method for the rapid determination of 18 polycyclic aromatic hydrocarbons (PAHs) in soil has been established based on a simplified solvent extraction and GC/MS/MS operated in pseudo multiple reaction monitoring mode (PMRM), a technique where the two quadrupoles mass monitor the same m/z. The PMRM approach proved superior to the classic single quadrupole technique, with enhanced sensitivity, specificity, and significant reduction in time consuming sample clean-up procedures. Trace level PAHs could be readily confirmed by their retention times and characteristic ions. The limit of quantitation in soil was observed to be 20ng/g for 16 EPA-priority PAHs and 2 additional PAHs specific to Environment Canada. The developed method was linear over the calibration range 20-4000ng/g in soil, with observed coefficients of determination of >0.996. Individual PAH recoveries from fortified soil were in the range 58.1 to 110.1%, with a precision between 0.3 and 4.9% RSD. The ruggedness of the method was demonstrated by the success of an inter-lab proficiency test study organized by the Canadian Association for Laboratory Accreditation. The present method was found to be applicable as a rapid, routine screening for PAH contamination in soil, with significant savings in terms of preparation time and solvent usage.

Triclosan exposure alters postembryonic development in a Pacific tree frog (Pseudacris regilla) Amphibian Metamorphosis Assay (TREEMA)

The Amphibian Metamorphosis Assay (AMA), developed for Xenopus laevis, is designed to identify chemicals that disrupt thyroid hormone (TH)-mediated biological processes. We adapted the AMA for use on an ecologically-relevant North American species, the Pacific tree frog (Pseudacris regilla), and applied molecular endpoints to evaluate the effects of the antibacterial agent, triclosan (TCS). Premetamorphic (Gosner stage 26-28) tadpoles were immersed for 21 days in solvent control, 1.5 μg/L thyroxine (T(4)), 0.3, 3 and 30 μg/L (nominal) TCS, or combined T(4)/TCS treatments. Exposure effects were scored by morphometric (developmental stage, wet weight, and body, snout-vent and hindlimb lengths) and molecular (mRNA abundance using quantitative real time polymerase chain reaction) criteria. T(4) treatment alone accelerated development concomitant with altered levels of TH receptors α and β, proliferating cell nuclear antigen, and gelatinase B mRNAs in the brain and tail. We observed TCS-induced perturbations in all of the molecular and morphological endpoints indicating that TCS exposure disrupts coordination of postembryonic tadpole development. Clear alterations in molecular endpoints were evident at day 2 whereas the earliest morphological effects appeared at day 4 and were most evident at day 21. Although TCS alone (3 and 30 μg/L) was protective against tadpole mortality, this protection was lost in the presence of T(4). The Pacific tree frog is the most sensitive species examined to date displaying disruption of TH-mediated development by a common antimicrobial agent.

Development of a rapid liquid chromatography tandem mass spectrometry method for screening of trace naphthenic acids in aqueous environments

Over the past 20 years, oil sands exploration and processing in Canada have grown steadily, leading to the development of intensive large-scale operations in Alberta, Canada. Naphthenic acids (NAs), a complex mixture of aliphatic and alicyclic carboxylic acids, are by-products of oil sands processing and are known to be toxic. While oil sands processing water (OSPW) is contained in tailings ponds, potential seepage and leaking of OSPW and its contaminants into surrounding surface water systems is a concern. The ability to quantify NAs and their isomers in OSPW surrounding water is essential for monitoring these spills. Unfortunately, quantification of NAs and their isomers is challenging due to the complexity of the NA mixtures, the lack of commercially available standards, and interference from naturally occurring NA compounds. Techniques such as FT-IR and GC/MS are currently used to analyse NAs, but are limited by poor sensitivity and specificity in the case of FT-IR and long sample preparation and instrument run time for GC/MS. To tackle these issues, a rapid LC/MS method was developed which can quickly quantify NAs in surface water with much better sensitivity and specificity than current methods. This method uses large volume injection, ESI negative mode and a Poroshell LC column to improve the method limits of detection (LOD) and quantitation (LOQ). The method is robust and has no complicated sample preparation steps. The method detection limit (MDL) is 0.01 mg/L (10 ppb) and low limit of quantitation (LLOQ) of 0.1mg/L (100 ppb), both for surface water. The developed method was tested with samples from the oil sands producing region, and demonstrated its applicability for fast screening of surface water samples before resorting to costly high accuracy and high resolution mass spectrometry determination. This is the first very rapid LC/MS method using large volume single column direct injection for quantitative determination of naphthenic acids in surface water.

Trace analysis of total naphthenic acids in aqueous environmental matrices by liquid chromatography/mass spectrometry-quadrupole time of flight mass spectrometry direct injection

A rapid and sensitive liquid chromatography quadrupole time of flight method has been established for the determination of total naphthenic acid concentrations in aqueous samples. This is the first methodology that has been adopted for routine, high resolution, high throughput analysis of total naphthenic acids at trace levels in unprocessed samples. A calibration range from 0.02 to 1.0μgmL(-1) total Merichem naphthenic acids was validated and demonstrated excellent accuracy (97-111% recovery) and precision (1.9% RSD at 0.02μgmL(-1)). Quantitative validation was also demonstrated in a non-commercial oil sands process water (OSPW) acid extractable organics (AEOs) fraction containing a higher percentage of polycarboxylic acid isomers than the Merichem technical mix. The chromatographic method showed good calibration linearity of ≥0.999 RSQ to 0.005μgmL(-1) total naphthenic acids with a precision <3.1% RSD and a calculated detection limit of 0.0004μgmL(-1) employing Merichem technical mix reference material. The method is well suited to monitoring naturally occurring and industrially derived naphthenic acids (and other AEOs) present in surface and ground waters in the vicinity of mining developments. The advantage of the current method is its direct application to unprocessed environmental samples and to examine natural naphthenic acid isomer profiles. It is noted that where the isomer profile of samples differs from that of the reference material, results should be considered semi-quantitative due to the lack of matching isomer content. The fingerprint profile of naphthenic acids is known to be transitory during aging and the present method has the ability to adapt to monitoring of these changes in naphthenic acid content. The methods total ion scan approach allows for data previously collected to be examined retrospectively for specific analyte mass ions of interest. A list of potential naphthenic acid isomers that decrease in response with aging is proposed and a quantitative assay of an adamantane carboxylic acid is reported.

Specificity of high resolution analysis of naphthenic acids in aqueous environmental matrices

The determination of naphthenic acids to ultra-trace level is reported using liquid chromatography with quadrupole time-of-flight mass spectrometry detection (LC/QToF). The application of this method is in the rapid screening for low level oxygenated naphthenic acid species from potential oil sands process water (OSPW) spills and leakage from storage facilities into aquafers and waterways. During LC/QToF method optimization it was found to be essential to adjust sample pH to >10 prior to any sample container transfer or sub-sampling in order to avoid naphthenic acid losses. Under acidic conditions the loss of O4 species from AEOs was shown to range from 17% for earlier eluting C17 species, to 86% for a later C21 species. Despite application of high resolution mass spectrometry with a mass accuracy of 5 ppm, the potential for interference from environmental contaminants was demonstrated for recognized estrogenic contaminants, resin acids, and fatty acids. These contaminants occur in the environment from natural and human activity, for example fatty acids derived from the pulp and paper mill industry upstream of the Athabasca oil sands. In an effort to avoid potential false positive identifications at low NA concentration levels, formulae for Cn z-0 O2 fatty acids were excluded from total NA screening. It was further noted that OSPW-derived acid extractable organics (AEOs) and Merichem technical mixtures contained ∼2.5% and ∼1.8% respectively of compounds identified with formulae equivalent to both naphthenic and resin acids. The C20 resin acids, anticipated at higher levels in dystrophic water samples, were recommended for future exclusion. Similarly, estrogens, namely estrone, 17α-ethinylestradiol, and 17β-estradiol estrogens, were also identified as NA during screening but eluted at different retention times to the naphthenic acid homologs observed in NA technical mixtures. The potential for their erroneous inclusion in total naphthenic acid results is also discussed.

A traceable reference for direct comparative assessment of total naphthenic acid concentrations in commercial and acid extractable organic mixtures derived from oil sands process water

ABSTRACT The advantage of using naphthenic acid (NA) mixtures for the determination of total NA lies in their chemical characteristics and identification of retention times distinct from isobaric interferences. However, the differing homolog profiles and unknown chemical structures of NA mixtures do not allow them to be considered a traceable reference material. The current study provides a new tool for the comparative assessment of different NA mixtures by direct reference to a single, well-defined and traceable compound, decanoic-d19 acid. The method employed an established liquid chromatography time-of-flight mass spectrometry (LC/QToF) procedure that was applicable both to the classic O2 NA species dominating commercial mixtures and additionally to the O4 species known to be present in acid extractable organics (AEOs) derived from oil sands process water (OSPW). Four different commercial NA mixtures and one OSPW-derived AEOs mixture were comparatively assessed. Results showed significant difference among Merichem Technical, Aldrich, Acros, and Kodak commercial NA mixtures with respect to “equivalent to decanoic-d19 acid” concentration ratios to nominal. Furthermore, different lot numbers of single commercial NA mixtures were found to be inconsistent with respect to their homolog content by percent response. Differences in the observed homolog content varied significantly, particularly at the lower (n = 9–14) and higher (n = 20–23) carbon number ranges. Results highlighted the problem between using NA mixtures from different sources and different lot numbers but offered a solution to the problem from a concentration perspective. It is anticipated that this tool may be utilized in review of historical data in addition to future studies, such as the study of OSPW derived acid extractable organics (AEOs) and fractions employed during toxicological studies.

Determination of polycyclic aromatic hydrocarbons in surface water using simplified liquid–liquid micro-extraction and pseudo-MRM GC/MS/MS

A simplified liquid–liquid micro-extraction (LLME) GC/MS/MS method was developed for the determination of 18 polycyclic aromatic hydrocarbons (PAHs) in surface water. This method utilizes a pseudo multiple reaction monitoring (PMRM) mode, a technique in which the third quadrupole monitors the same m/z as for the first quadrupole precursor ion. The use of helium as the only collision gas improved the sensitivity by significantly reducing both PAH compound fragmentation and baseline noise. For PAH determination, the PMRM approach proved superior to the classical quadrupole MRM technique in terms of enhanced sensitivity. With observed improvements in sensitivity, micro-extraction using only 4 mL of a novel binary solvent became possible, with corresponding reduction in time consuming sample preparation procedures and toxic solvent usage. Quantifying and qualifying ions, in addition to retention times, were used to verify trace level PAHs. During method validation, the limit of quantitation (LOQ) in surface water was observed to be 10 ng L−1 for the target PAHs. The recovery of individual PAHs was in the range of 80 to 114% from a water matrix, with a corresponding precision between 1.4 and 4.8% RSD. The robustness and accuracy of this method was demonstrated by its success in repeated proficiency test studies. The procedure has been successful during routine use in environmental sample testing and analysis of chemically enhanced water accommodated fraction (CEWAF) samples from toxicological LC50 (50% lethal concentration) bioassays, showing its applicability to situations in which both crude oil and oil spill dispersants are present.

Rapid and Sensitive LC/MS/MS Direct Injection Method for the Determination of Trace Level Corexit EC9500A Oil Dispersant in Seawater

A rapid and sensitive liquid chromatography tandem mass spectrometry (LC/MS/MS) method for the determination of trace dioctyl sulfosuccinate (DOSS) concentrations in seawater samples has been established. The method is well suited to aquatic environment impact monitoring following application of the dispersant Corexit EC9500A. Linearity of the method was demonstrated down to 0.05 ng/mL−1 (0.05 µgL−1) DOSS in seawater, with a 2.4% relative standard deviation precision for preparation replicates. A US EPA method limit of detection of <0.02 ng/mL−1 (<0.02 µgL−1) was calculated and specificity was confirmed by monitoring of two qualifier ions at 291.1 m/z and 227.1 m/z. These transitions were confirmed by QToF analysis to be associated with the DOSS precursor ion at 421.2 m/z. For application to seawater samples and samples containing oil particulates, a practical and repeatable calibration range of 0.5 ng/mL−1 (0.5 µgL−1) to 25.0 ng/mL−1 (25.0 µgL−1) DOSS is reported. The method was shown to have excellent precision and accuracy, with a consistent ≤1.6% relative standard deviation for system suitability standards at 0.5 ng/mL−1 (0.5 µgL−1) and linear weighted (1/x) regression coefficients of determination ≥0.995. The surfactant nature of the analyte is discussed in relation to detection limit and loss of analyte. Speculation of a relationship between DOSS in association or aggregation with divalent cations, such as Ca2+ present in salt water and hard water, is suggested. The consequent effects on cell ionic balance and membrane function are discussed.