Trace Organic Analysis Research Articles

What if using certified reference materials (CRMs) was a requirement to publish in analytical/bioanalytical chemistry journals?

Certified reference materials (CRMs) are routinely used by analytical chemists to validate new analytical methods and to demonstrate the quality of their quantitative measurements. Even though CRMs for trace element and trace organic analysis have been available and widely used for over 50years, the majority of papers published in analytical chemistry journals do not mention the use of CRMs. What if analytical/bioanalytical chemistry journals required the use of CRMs to publish a paper? This feature article attempts to address this question by providing examples of recent papers that have made exceptional use of CRMs to validate new analytical methods and to describe novel, alternative uses of CRMs that provide new characterization of the CRM. The potential benefits of using a CRM even when it does not have certified values for the analytes of interest are presented.

Geochemical Evidence for the Origin of the Daranna Manganese Deposit, Kebbi State, Nigeria

Inorganic and organic geochemical and geostatistical studies of manganese ore deposits exposed at Daranna, near Kaoje have been carried out with the aim of characterizing and delineating the origin of the manganese ore deposits. Data were obtained from field observations and chemical analyses of 12 ore samples. Major and trace elements and organic geochemical analyses were conducted with Energy Dispersion X-ray Fluorescence Spectrometer and Rock-Eval pyrolysis method at Geo-data GmbH Garbsen, Germany. Results of the Major and trace elements, total organic carbon content abundances and the correlation among them imply that Daranna mineralizations are mainly of hydrothermal origin with little contribution from contemporaneous volcanic materials and this is confirmed by high Fe/Mn (8.274 to 24.066 wt%) and low Co/Zn ratios and trace element patterns. The significant geochemical characteristics such as high Mn content (22.660 to 62.330 wt%; average 45.919 wt%), low concentration of Fe (2.590 to 3.310 wt%; average 3.008 wt%) reveal a primary distal hydrothermal source for mineralization. The position of samples on Ni–Zn–Co and (Co/Zn)–(Co + Ni + Cu) diagrams and evaluation of these data reveals that hydrothermal activity was the main process with sedimentary influence responsible for mineralization in the Daranna manganese deposit.

The mysterious oil spill in the northeastern coast of Brazil: tracking offshore seawater and the need for improved vessel facilities

A scientific cruise between November 15 and December 18, 2019 aboard R/V Vital de Oliveira collected offshore seawater samples at 59 stations between the states of Ceará and Bahia. The objective was to identify hydrocarbon levels potentially associated with the mysterious oil spill that reached the northeastern coast of Brazil. Median concentrations of aliphatic hydrocarbons (AHs, 0.79 µg L-1) and polycyclic aromatic hydrocarbons (PAHs, 5.39 ng L-1) do not indicate contamination by crude oil and are comparable to baseline levels previously found in other areas of the Brazilian continental margin. The detailed composition of both groups of hydrocarbons revealed that some samples were contaminated during sampling and/or handling on-board. The data set presented herein highlights the difficulty in tracking small oil patches spread over a huge ocean area and, more importantly, the need for improving protocols of national research vessels used to collect seawater samples for trace organic analyses.

Analysis of trace organics and its correlation with COD in condensate from natural gas to hydrogen production.

Qualitative and quantitative analysis of trace organics in the condensate and its correlation with chemical oxygen demand (COD) is the key to the research on the reuse technology of condensate (condensate) from natural gas to hydrogen production process. The contents of anions, COD, total organic carbon (TOC) and total nitrogen (TN) were measured by ion chromatography and the TOC analyzer. Trace organics in the condensate and its correlation with COD was investigated in this paper. Results show that the contents of COD and TOC is 74.1 and 17.81 mg/L, respectively, and the anions in the condensate are mainly Cl-, I-, and SO4 2-, etc. The condensate mainly contains small molecule organics including methanol, ethanol and formic acid with the content of 41.4, 2.1 and 3.2 mg/L, respectively. The spiked recovery of methanol, ethanol and formic acid is 96.1%, 100.2% and 103.9% by high performance liquid chromatography (HPLC) and gas chromatography (GC), respectively. Methanol is the main source of COD in the condensate, and the contribution rate reaches up to 83.8%. The removal of trace methanol can significantly reduce the COD of the condensate. This work might provide basic data for reasonable recovery and utilization of condensate in the hydrogen production process.

Derivatization gas chromatography negative chemical ionization mass spectrometry for the analysis of trace organic pollutants and their metabolites in human biological samples.

Gas chromatography negative chemical ionization mass spectrometry (GC-NCI-MS) is a preferred instrumental approach for the trace and ultra-trace analysis of various toxic organics and their metabolites in human biological fluids. Specifically, the method has played an important role in the highly sensitive and specific quantitative detection of persistent highly halogenated compounds in environmental matrices and biota during the past few decades. However, for the analysis of toxic metabolites with active hydrogen atoms, such as acids, alcohols, and phenolic compounds, from biological matrixes or organics without electronegative atoms or groups, a derivatization step is often needed prior to GC analysis. Such derivatization aims to change the properties of targets to improve their separation, increase their volatility, and enhance the sensitivity of instrumental detection. This review summarizes three derivatization strategies commonly used for GC methods, i.e., alkylation, silylation, and acylation, together with their application combined with GC-NCI-MS for the high sensitivity analysis of toxic organic metabolites in the human body. The advantages and disadvantages of each derivatization method and potential directions for future applications are discussed. Given the broad variety of applications as well as the compound-specific sensitivity for the ultra-trace analysis of target xenobiotics in human biological fluids, subsequent studies are required to develop convenient, faster derivatization procedures and reagents better suited for routine analysis. Graphical abstract.

A powerful combination of quadruple isotope dilution strategy with dispersive magnetic solid phase extraction for the accurate and precise multi-analyte determination of tadalafil, sildenafil, avanafil and vardenafil in human plasma and urine samples using LC-ESI-Tandem MS

Trace organic analysis in biological matrices plays a critical role in clinical studies. To achieve a reliable evaluation of clinical practice, many analytical improvements have been introduced to overcome the difficulties/errors in the steps of the analysis procedure. In this study, quadrupole isotope dilution mass spectrometry was combined with dispersive magnetic solid phase extraction to achieve inherent accuracy and precision at trace levels. The lower limits of detection and quantification values of analytes ranged between 0.42–0.84 ng/g and 1.39–2.80 ng/g, respectively with percent relative standard deviations (%RSDs) of 0.65–1.24%. The combined method was applied for simultaneous determination of selected erectile drugs including sildenafil, tadalafil, vardenafil and avanafil in human urine and plasma samples by using commercially available isotopic analogues of these compounds. Great percent recovery values between 97.50–99.57% and 98.26–100.92% with%RSDs of 1.19–1.96% and 0.49–1.95% respectively for plasma and urine samples were obtained. The proposed method is simple, environmentally friendly, requires less laborious sampling and provides superior accuracy and precision at low levels of analytes. Furthermore, the proposed method also provides economical advantages. The synthesis procedure of magnetic sorbent is easy, low cost and does not require high consumption of toxic chemicals. Additionally, the isotopically enriched standards of target compounds are accessible, do not have high costs and the method requires only small amounts of these chemicals.

The Role of Reactive Nitrogen Species in Sensitized Photolysis of Wastewater-Derived Trace Organic Contaminants.

Under conditions typically encountered in the aquatic environment, the absorption of sunlight by nitrite and nitrate leads to the transformation of trace organic contaminants. In addition to the well understood mechanism through which hydroxyl radical (·OH) produced by nitrate and nitrite photolysis oxidizes contaminants, absorption of light also results in the formation of reactive nitrogen species that transform organic contaminants. To assess the importance of this process on the fate of trace organic contaminants, radical quenchers and transformation product analysis were used to discriminate among potential reaction pathways. For sulfamethoxazole, an antibiotic that is frequently detected in municipal wastewater effluent, nitrate and nitrite-sensitized photolysis pathways resulted in production of transformation products that were not detected during direct photolysis or reaction with ·OH. The reactivity of sulfamethoxazole with the reactive species produced when nitrite absorbed sunlight was affected by the presence of hydroxyl radical scavengers, indicating the likely involvement of nitrogen dioxide, which forms when nitrite reacts with hydroxyl radical. Reactive nitrogen species also reacted with emtricitabine, propranolol, and other trace organic contaminants commonly detected in wastewater effluent, indicating the potential importance of this process to the fate of other trace organic contaminants. A kinetic model indicated that reactive nitrogen species could be important to the phototransformation of trace organic contaminants when relatively high concentrations of nitrite are present (e.g., in surface waters receiving reverse osmosis concentrate from potable water reuse projects or in agricultural runoff).

High Flow-Rate Sample Loading in Large Volume Whole Water Organic Trace Analysis Using Positive Pressure and Finely Ground Sand as a SPE-Column In-Line Filter.

By using an innovative, positive pressure sample loading technique in combination with an in-line filter of finely ground sand the bottleneck of solid phase extraction (SPE) can be reduced. Recently published work by us has shown the proof of concept of the technique. In this work, emphasis is put on the SPE flow rate and method validation for 26 compounds of emerging environmental concern, mainly from the 1st and 2nd EU Watch List, with various physicochemical properties. The mean absolute recoveries in % and relative standard deviations (RSD) in % for the investigated compounds from spiked pure water samples at the three investigated flow rates of 10, 20, and 40 mL/min were 63.2% (3.2%), 66.9% (3.3%), and 69.0% (4.0%), respectively. All three flow rates produced highly repeatable results, and this allowed a flow rate increase of up to 40 mL/min for a 200 mg, 6 mL, reversed phase SPE cartridge without compromising the recoveries. This figure is more than four times the maximum flow rate recommended by manufacturers. It was indicated that some compounds, especially pronounced for the investigated macrolide molecules, might suffer when long contact times with the sample glass bottle occurs. A reduced contact time somewhat decreases this complication. A very good repeatability also held true for experiments on both spiked matrix-rich pond water (high and low concentrations) and recipient waters (river and wastewater) applying 40 mL/min. This work has shown that, for a large number of compounds of widely differing physicochemical properties, there is a generous flow rate window from 10 to 40 mL/min where sample loading can be conducted. A sample volume of 0.5 L, which at the recommended maximum flow rate speed of 10 mL/min, would previously take 50 min, can now be processed in 12 min using a flow rate of 40 mL/min. This saves 38 min per processed sample. This low-cost technology allows the sample to be transferred to the SPE-column, closer to the sample location and by the person taking the sample. This further means that only the sample cartridge would need to be sent to the laboratory, instead of the whole water sample, like today’s procedure.

Chemical characterization and toxicity of particulate matter emissions from roadside trash combustion in urban India

Roadside trash burning is largely unexamined as a factor that influences air quality, radiative forcing, and human health even though it is ubiquitously practiced across many global regions, including throughout India. The objective of this research is to examine characteristics and redox activity of fine particulate matter (PM2.5) associated with roadside trash burning in Bangalore, India. Emissions from smoldering and flaming roadside trash piles (n = 24) were analyzed for organic and elemental carbon (OC/EC), brown carbon (BrC), and toxicity (i.e. redox activity, measured via the dithiothreitol “DTT” assay). A subset of samples (n = 8) were further assessed for toxicity by a cellular assay (macrophage assay) and also analyzed for trace organic compounds. Results show high variability of chemical composition and toxicity between trash-burning emissions, and characteristic differences from ambient samples. OC/EC ratios for trash-burning emissions range from 0.8 to 1500, while ambient OC/EC ratios were observed at 5.4 ± 1.8. Trace organic compound analyses indicate that emissions from trash-burning piles were frequently composed of aromatic di-acids (likely from burning plastics) and levoglucosan (an indicator of biomass burning), while the ambient sample showed high response from alkanes indicating notable representation from vehicular exhaust. Volume-normalized DTT results (i.e., redox activity normalized by the volume of air pulled through the filter during sampling) were, unsurprisingly, extremely elevated in all trash-burning samples. Interestingly, DTT results suggest that on a per-mass basis, fresh trash-burning emissions are an order of magnitude less redox-active than ambient air (13.4 ± 14.8 pmol/min/μgOC for trash burning; 107 ± 25 pmol/min/μgOC for ambient). However, overall results indicate that near trash-burning sources, exposure to redox-active PM can be extremely high.

Increased electrospray ionization intensities and expanded chromatographic possibilities for emerging contaminants using mobile phases of different pH.

In this work the habitual behaviour of low pH in environmental organic trace analysis is challenged by investigating the full potential of building a multi-component UHPLC-ESI-MS/MS method adapted to cover common emerging contaminants of many different polarities, minimizing the elements of compromise in the performance of the final analytical separation and detection. Contributes have been made by taking advantage of common commercially available technology in understanding the impact from solvent components and the ionization of analytes which can facilitate future development of robust, sensitive and precise UHPLC-MS/MS methods. All contaminants were evaluated and optimized without prejudices regarding historical residence in terms of chromatographic conditions and ESI mode; increasing multi-method's flexibility that can be implemented in routine analysis in response to new requests as well as to emerging contaminants yet to be discovered. Our data strongly supports the questioning of the assumption that equilibrium concentrations of ions in solution reflect those produced during the electrospray process. ESI responses of [M+H](+) and limits of detection were comparable, or often better at high pH compared to acidic eluents. Presence of nitrogen basic groups such as tertiary and secondary amines in a compound increased the intensity of the ESI+ signal, and was even further elevated in basic eluent. The proton affinity probably changes for many nitrogen-containing compounds during the ionization process, making the gas-phase processes very important in generation of these ions by ESI+. There were also an unexpected large number of compounds showing their highest response at pH 7 and weak ionic strength. A flow optimized, buffert free, neutral UHPLC-MS/MS method enhanced the sensitivity for the environmental important synthetic hormone ethinyl estradiol significantly.

Enhancing performance of liquid sample desorption electrospray ionization mass spectrometry using trap and capillary columns

Desorption electrospray ionization mass spectrometry (DESI-MS) is a recent and important advance in the field that has extensive applications in surface analysis of solid samples but has also been extended to analysis of liquid samples. The liquid sample DESI typically employs a piece of fused silica capillary to transfer liquid sample for ionization. In this study, we present the improvement of liquid sample DESI-MS by replacing the sample transfer silica capillary with a trap column filled with chromatographic stationary phase materials (e.g., C4, C18). This type of trap column/liquid sample DESI can be used for trace analysis of organics and biomolecules such as proteins/peptides (in nM concentration) in high salt content matrices. Furthermore, when the sample transfer capillary is modified with enzyme covalently bound on its inside capillary wall, fast digestion (<6min) of proteins such as phosphoproteins can be achieved and the online digested proteins can be directly ionized using DESI with high sensitivity. The latter is ascribed to the freedom to select favorable spray solvent for the DESI analysis. Our data show that liquid sample DESI-MS with a modified sample transfer capillary has significantly expanded utility in bioanalysis.

Multi-Pesticide Analysis in Sediment by GC-EI-MS/MS Using Programmed Temperature Vaporization–Large Volume Injection Technique

A sensitive, selective and high throughput gas chromatography–tandem mass spectrometry method using programmable temperature vaporization–large volume injection mode (PTV-LVI-GC-MS/MS) for the analysis of 30 organochlorine pesticides (OCPs) including toxaphenes in sediments was developed. The PTV-LV injection settings, viz. inlet temperature, split flow, injection phase time, and injection speed were optimized for 50 µL injection. A significant increase in sensitivity was accomplished as compared with that obtained by the conventional 1 µL cold splitless injection. Average LVI recoveries for OCPs were in the range 58–133 % with low % RSD in instrument precision (<12 %). The method detection limits achieved were 0.04–0.92 µg kg−1. The method recovery ranged from 80 to 120 % with <10 % RSD for more than 83 % of targeted analytes fortified at 10 µg kg−1 in sediments. The PTV-LVI-GC-MS/MS allows simultaneous determination and unambiguous confirmation of trace OCPs and toxaphene congeners, which significantly streamlines and improves the trace organic analysis in the environmental surveillance and monitoring.

Dripwater organic matter and trace element geochemistry in a semi-arid karst environment: Implications for speleothem paleoclimatology

A series of four short-term infiltration experiments which revealed hydrochemical responses relevant to semi-arid karst environments were carried out above Cathedral Cave, Wellington, New South Wales (NSW), Australia. Dripwater samples were collected at two sites for trace element and organic matter analysis. Organic matter was characterised using fluorescence and interpreted using a PARAFAC model. Three components were isolated that represented unprocessed, soil-derived humic-like and fulvic-like material, processed humic/fulvic-like material and tryptophan-like fluorescence. Principal Component Analysis (PCA) performed on the entire dataset comprising trace element concentrations and PARAFAC scores revealed two dominant components that were identified as soil and limestone bedrock. The soil component was assigned based on significant contributions from the PARAFAC scores and additionally included Ba, Cu, Ni and Mg. The bedrock component included the expected elements of Ca, Mg and Sr as well as Si. The same elemental behaviour was observed in recent stalagmite growth collected from the site. Our experiments demonstrate that existing paleoclimate interpretations of speleothem Mg and Sr, developed in regions of positive water balance, are not readily applicable to water limited environments. We provide a new interpretation of trace element signatures unique to speleothems from water limited karst environments.

Cotton-supported graphene functionalized with aminosilica nanoparticles as a versatile high-performance extraction sorbent for trace organic analysis

Cotton fibers were functionalized, following the coating of fibers with graphene oxide (GO), the covalent attachment of aminosilica nanoparticles and the reduction to the cotton-GR-aminosilica material. Employing the cotton-supported graphene (GR)-aminosilica material, a novel and easily applicable extraction mode was put forward. Several groups of analytes were employed such as PAHs, phthalates, musks, phenolic endocrine disrupters and haloacetic acids to test the applicability of the functionalized cotton for extraction purposes. The extraction yields ranged from 76% to 96% corroborating the high degree of affinity of the material for the above groups of compounds while the limits of detection were between 0.06 and 1.10μg/L using gas chromatography-electron capture detection for haloacetic acids and gas chromatography–mass spectrometry for the rest of the analytes. The accuracy of the method was evaluated in fortified lake water at a spiking level of three to ten times the lowest quantifiable concentration and the recoveries varied from 86% to 104% for all the studied analytes. The π–π and hydrophobic interactions, the hydrogen bonding between the functionalized cotton and analytes and the electron polarizability and ionizability of the chemical structures justify the extraction behavior.

Source apportionment of atmospheric particulate carbon in Las Vegas, Nevada, USA

A study was conducted to quantify wintertime contributions of source types to carbonaceous PM2.5 at four urban sites in the Las Vegas Valley, one of the most rapidly growing urban areas in the southwestern United States. Twenty-four hour average ambient samples were collected for mass, ions, elements, organic carbon (OC), elemental carbon (EC), and trace organic markers analysis. Additional measurements were made to determine diurnal patterns in light-absorbing black carbon (BC) as a marker for combustion sources. Carbonaceous PM sources of on-road gasoline vehicles, on-road diesel vehicles, and off-road diesel engines were characterized with their chemical profiles, as well as fuel-based emission factors, using an In-Plume Sampling System. The Effective Variance Chemical Mass Balance (EV-CMB) source apportionment model was applied to the ambient samples collected, using source profiles developed in this study as well as profiles from other relevant studies. Four main sources contributed to PM2.5 carbon within the Las Vegas Valley: (1) paved road dust, (2) on-road gasoline vehicles, (3) residential wood combustion, and (4) on-road diesel vehicles. CMB estimated that on-road mixed fleet gasoline vehicles are the largest source for OC and EC at all the sites. The contribution of paved road dust to both OC and EC was 5–10% at the four sites. On-road diesel vehicles contribute 22% of the OC and 34% of the EC at a site near the city center, which is located immediately downwind of a major freeway. Residential wood combustion is a more important source than on-road diesel vehicles for two residential neighborhood sites. These results are consistent with our conceptual model, and the research methodology may be applied to studying other urban areas.

Solid Phase Micro-Extraction, a Versatile and Handy Tool in Environmental Trace Organic Analysis, Gets a New Class of Coatings, Polymeric Ionic Liquids

Solid Phase Micro-Extraction, a Versatile and Handy Tool in Environmental Trace Organic Analysis, Gets a New Class of Coatings, Polymeric Ionic Liquids

Recent advances in applications of single-drop microextraction: A review

During the past fifteen years since its introduction, single-drop microextraction has witnessed incessant growth in the range of applications of samples preparation for trace organic and inorganic analysis. This was mainly due to the array of modes that are available to accomplish extraction in harmony with the nature of analytes, and to use the extract directly for analysis by diverse instrumental methods. Whilst engineering of novel sorbent materials has expanded the sample capabilities of rival method of solid-phase microextraction, the single-drop microextraction – irrespective of the mode of extraction – uses common equipment found in analytical laboratories sans any modification, and in a much economic way. The recent innovations made in the field, as highlighted in this review article in the backdrop of historical developments, are due to the freedom in operational conditions and practicability to exploit chemical principals for optimum extraction and sensitive determination of analytes. Literature published till July 2011 has been covered.

Surface-enhanced Raman scattering using silver nanocluster on anodic aluminum oxide template sensor toward protein detection

The affordable surface-enhanced Raman scattering (SERS) substrates, with a structure consisting of densely distributed round-shape silver nanoclusters on anodic aluminum oxide (AAO) template, is fabricated by magnetron sputtering and anodization processes. The physical investigations show that the silver nanoclusters with size distribution ranging from 10 to 30 nm uniformly distributed on the top and in the bottom of the AAO nanochannels. The SERS activities from adsorbed probe molecules, i.e., methylene blue, on the SERS substrate surface indicate a high Raman enhancement factor for trace organic analysis. The SERS substrate is successfully utilized in the detection of a trace amount of three different proteins, bovin serum albumin, immunoglobulin G, and cardiac troponin T, also adsorbed on the substrate surface. Several spectral bands containing important molecular structures of these proteins are clearly observed and identified. The obtained results indicated a step forward to label-free biomolecular detections in chip-based biosensors.

Nonplasmonic surface enhanced Raman spectroscopy using silica microspheres

Surface enhanced Raman spectroscopy is presented using a nonplasmonic mechanism based on whispering gallery modes in silica microspheres. Sensitive Raman analysis of molecular films is demonstrated by using 5–10 μm sized silica spheres. The advantages of this nonplasmonic approach are the active substrate is chemically inert, thermally stable, and relatively simple to fabricate. Applications include trace organic analysis particularly for in situ planetary instruments that require robust sensors with consistent response.

In honor of Walter Giger: setting standards of excellence in environmental organic chemistry

In this issue of ES&T, we pay tribute to Walter Giger—a pioneer who advanced the field of trace organic analysis and its application to significant environmental problems.