Low Ppb Levels Research Articles

Fill, Fold, Photo: Preconcentration and Multiplex Detection of Trace Level Heavy Metals in Water.

Heavy metal contamination is an increasing global threat to human and environmental health, particularly in resource-limited areas. Traditional platforms for heavy metal detection are labor intensive and expensive and require lab facilities. While paper-based colorimetric sensors offer a simpler approach, their sensitivity limitations prevent them from meeting legislative requirements for many metals. Existing preconcentration systems, on the other hand, can achieve lower detection limits but typically focus on analyzing only one metal, making comprehensive monitoring difficult. We address these limitations by introducing a low-cost preconcentration system coupled with colorimetric analysis for the simultaneous detection of seven metal ions at low ppb levels without the need for external equipment outside a smartphone. The system achieved detection limits of 15 ppb (Ni(II)), 7 ppb (Cu(II)), 2 ppb (Fe(III)), 20 ppb (Cr(VI)), 13 ppb (Pb(II)), 26 ppb (Hg(II)), and 15 ppb (Mn(II)) with six out of seven limits of detection values falling well below EPA regulatory guidelines for drinking water. The user-friendly Fill, Fold, Photo approach eliminates complex pretreatment steps. Smartphone-based detection offers portable quantification within seconds. Employing masking strategies ensured higher selectivity for each assay on the card, while our packaging protocols enable system stability for over 4 weeks of study, facilitating mass production and deployment within a realistic time frame. To validate the sensor's performance in real-world scenarios, the sensor was tested with environmental water samples. The sensor demonstrated good recovery, ranging from 77% to 94% compared to the standard ICP-MS method. Furthermore, spike recovery analysis confirmed the sensor's accuracy, with a relative standard deviation (RSD) of less than 15%. This technology holds significant promise for future development as a convenient, portable solution for field-based monitoring of a broad spectrum of water contaminants, including pesticides, PFAS, fertilizers, and beyond.

Doping control analysis of myo-inositol trispyrophosphate and 10 bisphosphonates in equine plasma by ion chromatography-mass spectrometry and its application to clodronic acid horse administration.

Bisphosphonates and myo-inositol trispyrophosphate (ITPP) are two classes of difficult-to-detect polar drugs that are prohibited under the rules of racing. ITPP is a drug capable of increasing the amount of oxygen in hypoxic tissues, and studies have shown that administration of ITPP increases the maximal exercise capacity in mice. The properties of ITPP make it an ideal candidate as a doping agent to enhance performance in racehorses. In recent years, ITPP had indeed been detected in racehorses and confiscated items. As for bisphosphonates, it is especially critical to control their use as since February 2019, the International Agreement on Breeding, Racing and Wagering (IABRW) by the International Federation of Horseracing Authorities (IFHA) had identified specific conditions on which bisphosphonates should not be administered to a racehorse. A recent review of literature shows that there is yet a simultaneous screening method for detecting ITPP and bisphosphonates in equine samples. This paper describes an efficient ion chromatography high-resolution mass spectrometry (IC-HRMS) method for the simultaneous detection of ITPP and 10 bisphosphonates at sub-parts-per-billion (ppb) to low-ppb levels in equine plasma after solid-phase extraction (SPE) and its application to an administration study of clodronic acid in horses.

A dilute-and-inject liquid-gas chromatography-mass spectrometry method for the analysis of sixteen polycyclic aromatic hydrocarbons in extra-virgin olive oil

BackgroundPolycyclic aromatic hydrocarbons (PAHs) represent a diverse group of organic compounds characterized by the fusion of two or more benzene rings arranged in various structural forms. Due to their harmful effects on human health, it is essential to implement monitoring systems and preventive measures to regulate human exposure. Given the affinity of PAHs for lipids, extensive research has been focused on their presence in vegetable oils. This study aimed to develop an on-line liquid-gas chromatography (LC-GC) method (using tandem mass spectrometry) with minimized solvent consumption for the determination of 16 PAHs in extra-virgin olive oil (EVOO). ResultsA side-by-side comparison of the selected-ion-monitoring and the pseudo multiple-reaction-monitoring (p-MRM) acquisition modes was performed, in terms of specificity and detectability. The results obtained using the p-MRM mode were superior, and for this reason it was selected. The method was linear over the concentration range 1–200 μg kg−1 (except in five cases, over 2–200 and 5–200 μg kg−1 ranges). Accuracy (at the 2 μg kg−1 and 20 μg kg−1 concentration levels) was in the 86.9–109.3 % range, with an RSD <10 %. Intra-day and inter-day precision (at 2 μg kg−1 and 20 μg kg−1 concentration levels) were in the 1.2–9.7 % and 3.2–10.8 % ranges, respectively. For all the PAHs, a negative matrix effect was observed. Three out of sixteen PAHs were detected in three EVOOs (among ten samples), albeit at the low ppb level. Limits of quantification were satisfactory in relation to EU legislation on the presence of PAHs in vegetable oils. SignificanceA dilute-and-inject LC-GC-tandem mass spectrometry method is herein proposed fulfilling EU legislation requirements; sample preparation was very simple, inasmuch that it involved only a dilution step, thus avoiding extraction, clean-up, and thus a high consumption of organic solvents. In fact, considering both oil dilution and the LC mobile phase, less than 8 mL of solvents were used.

Flow-modulation comprehensive two-dimensional enantio-gas chromatography: A valid and flexible alternative to heart-cutting multidimensional enantio-gas chromatography

The present research is focused on the proposal of use of flow-modulation comprehensive two-dimensional enantio-gas chromatography (FM eGC × GC) as a valid, flexible, and possibly superior alternative to heart-cutting multidimensional enantio-GC (eMDGC). The latter, a technique of demonstrated utility, is used specifically for the targeted separation of chiral compounds, whereas FM eGC × GC can produce both targeted and high-resolution untargeted information in a single run. It is clearly possible to use eMDGC for untargeted analysis, often with a flame ionization detector (stand-by analysis), to monitor a first-dimension (1D) separation, of much lower peak capacity compared to FM eGC × GC. If eMDGC is used with mass spectrometry (MS), it is normally exploited to monitor the second-dimension (2D) separation.The analytical instrument consisted of automated solid-phase microextraction (SPME), and a low duty-cycle FM eGC × GC system (with time-of-flight MS), equipped with an enantioselective 1D column (2,3-di-O-methyl-6-t-butyl silyl β-cyclodextrin derivative) and a 2D polyethylene glycol one. Ten Marsala wines were subjected to analysis, for the determination of chiral lactones (many at the low ppb level, due to the high concentration capacity of SPME) and for general analyte profiling. In many instances, highly complex chromatograms were attained, with statistical analysis (ANOVA-simultaneous component analysis and partial least squares discriminant analysis) used for sample differentiation.

Achieving One Part Per Billion Hydrogen Sulfide (H2S) Level Detection through Optimizing Composition and Crystallinity of Gold-Decorated Tungsten Trioxide (Au-WO3) Nanofibers.

As a common environmental pollutant and an important breath biomarker for several diseases, it is essential to develop a hydrogen sulfide gas sensor with a low-ppb level detection limit to prevent harmful gas exposure and allow early diagnoses of diseases in low-resource settings. Gold doped/decorated tungsten trioxide (Au-WO3) nanofibers with various compositions and crystallinities were synthesized to optimize H2S-sensing performance. Systematically experimental results demonstrated the ability to detect 1 ppb H2S with a response value (Rair/Rgas) of 2.01 using a 5 at % Au-WO3 nanofibers with average grain sizes of around 15 nm. Additionally, energy barrier difference of sensing materials in air and nitrogen (ΔEb) and power law exponent (n) were determined to be 0.36 eV and 0.7, respectively, at 450 °C indicating that O- is predominately ionic oxygen species and adsorption of O- significantly altered the Schottky barrier between the grain. Such quantitative analysis provides a comprehensive understanding of H2S detection mechanism.

Transformation of zinc acetate into ZnO nanofibers for enhanced NOx gas sensing: Cost-effective strategies and additive-free optimization

Gas sensors based on ZnO nanocomposites have been widely investigated for the detection of various gases. However, few studies have reported electrospun ZnO for NOx gases, especially NO (nitrogen monoxide), due to its high tendency for oxidation upon contact with air. The development of gas sensors that operate at temperatures below 300°C is challenging for metal oxide gas sensors, as decreasing the temperature can lead to lack of sensitivity and very long recovery times. In this study, the operating temperature was improved to 200°C while achieving a high response to a low concentration of 0.5 ppm gas, with recovery times of 572s and 105s for NO and NO2 (nitrogen dioxide), respectively. Detecting NO and NO2 at low ppm and ppb levels is a major demand and challenge for the development of metal oxide-based gas sensors, especially for health monitoring portable sensors. This study focuses on the design and performance of a NOx gas sensor based on ZnO nanofibrous material with precise structural optimization. The study optimizes the precursor for electrospinning without using any additives. The sensing materials proportion were optimized by changing the ratio of ZnAc:PVA in the precursor of electrospinning solution. Choosing ZnAc:PVA = 1.5 as the optimum precursor for synthesizing ZnO nanofibers resulted in the highest response of 27 and 16 (Ohm/Ohm) for 0.5 ppm NO and NO2, respectively, at 200°C and relative humidity of 50%. Additionally, reproducible sensors were developed, which is crucial for mass production. This remarkable sensitivity in low concentration indicates that the design of material structure and the control of zinc acetate amount in the electrospun solution has great practical applications to detect both gases.

Delafossite CuGaO2 nanomaterial-based room temperature H2S selective gas sensor

To minimize harmful gas exposure and enable early disease diagnoses in low-resource settings, it is crucial to create an H2S gas sensor that can detect low ppb levels at room temperature (RT).

Facile engineering of TiO2@Pd based hybrid heterogeneous nanostructures for enhanced NO2 gas sensing at room temperature under UV activation.

Highly sensitive sub-ppb level NO2 gas sensors based on hybrid heterostructures made out of metal nanoparticles (NPs) and porous metal oxide semiconductors are of great significance in environmental monitoring and medical diagnosis. Herein, we report the successful synthesis of a Pd nanoparticle decorated porous TiO2 nanostructure-based hybrid Schottky heterostructure and its application in room temperature (RT ∼ 30 °C) low-ppb level NO2 detection under UV activation. The optimized TiO2@Pd 50 hybrid heterogeneous nanostructures (HNs) showed an excellent NO2 (100 ppm) gas sensing response of 175.42%, excellent cycling stability, outstanding selectivity, low detection limit (∼82 ppb) and fast response/recovery speed (48/72 s) under UV illumination. Moreover, the as-prepared hybrid sensor demonstrates reliable reproducibility and robust sensing responses under various elevated temperatures (30-200 °C) and relative humidity conditions (0-80% RH) towards NO2. The excellent RT NO2 gas sensing properties of TiO2@Pd 50 HNs are primarily attributed to the improved surface area, enhanced oxygen vacancies, low charge carrier recombination, and catalytic effect triggered by the hot electrons induced, from the localized plasmonic resonance effect of Pd NPs, resulting in effective NO2 adsorption/desorption dynamics. The Schottky junction formation at the hybrid TiO2@Pd 50 HNs interface effectively aids in the separation of charge carriers via band bending, leading to excellent charge transfer between the NO2 molecules and the heterointerface under UV light, yielding substantial sensitivity and selectivity to NO2. The present work is expected to provide a strategic route for designing and fabricating sub-ppb level high-performance NO2 sensors based on hybrid heterostructures.

Sulfur Impurities in COx Feed Gases of Solid Oxide Cells: Effect on Degradation and Removal Strategies

High-temperature solid oxide cells (SOC) offer unrivaled Faradaic and energetic efficiencies for carbon dioxide electrolysis. However, it is yet unclear which contaminant level in carbon monoxide and carbon dioxide feed gases are tolerable to achieve low degradation rates in commercial applications. In the present work, electrolyte-supported cells (ESC) with Ni/Gadolinia-doped ceria (Ni/CGO) fuel electrodes were exposed to CO/CO2 gas mixtures at open circuit voltage and in electrolysis operation. The resistance evolution over time was monitored by means of electrochemical impedance spectroscopy. With this approach it is shown that a severe reversible degradation over time periods of up to 72 h occurs. X-ray photoemission spectroscopy (XPS) and high-resolution secondary ion mass spectrometry (SIMS) imaging techniques were used to show that this degradation effect is related to sulfur impurities on the Ni surface. Inlet gas composition variations were carried out to show that sulfur impurities most likely in the low ppb level are present in both industrial CO and CO2 feed gases. The efficacy of different gas cleaning units at room temperature was investigated to identify a suitable desulfurization solution. The results demonstrate the importance of feed gas purity for the commercialization of high-temperature CO2 electrolysis.

Simultaneous determination of low molecular weight nitrosamines in pharmaceutical products by fast gas chromatography mass spectrometry

Control of N-nitrosamines has been in the focus of health authorities in recent years because many of these compounds are probable human carcinogens. In July 2018 the U.S. Food and Drug Administration (FDA) announced a recall for valsartan-containing medicines due to contamination with the carcinogenic low molecular weight nitrosamine, N-nitrosodimethylamine (NDMA). It has become clear that the problem can not only exist in the case of sartans, but in any active pharmaceutical ingredient (API)/drug product in which secondary or tertiary amines are present (as API or as impurities) and a nitrosating agent is available. The decision was made by regulators, according to which manufacturers of pharmaceutical products are obliged to perform a risk assessment for the potential presence of nitrosamines in active pharmaceutical ingredients and drug products. This resulted in a high demand for validated analytical methods that are able to quantify N-nitrosamines at low ppb levels in pharmaceutical products.In this work we have developed and validated a generic fast GC-MS method suitable for the quantitative determination of a wide range of low molecular weight nitrosamines, which include N-nitrosodiethylamine (NDEA), N-nitrosodimethylamine (NDMA), N-nitroso-diphenylamine (NDPh), N-nitrosodipropylamine (NDPA), N-nitrosomethylethylamine (NMEA), N-nitrosomorpholine (NMOR), N-nitrosopiperidine (NPIP), N-nitroso-ethylisopropylamine (EIPNA), N-nitroso-diisopropylamine (DIPNA), N-nitroso-N-methylaniline (NMPA), 1-Methyl-4-nitrosopiperazine (MeNP) and N-nitroso-pyrrolidine (NPYR). The advantage of the method is that it is possible to screen low molecular weight nitrosamines in low concentrations with a short analysis time in a wide range of APIs and drug products.

An electromembrane microextraction-based green method for the determination of trace copper in natural waters.

Driven by the search for an environmentally-friendly methodology, electromembrane extraction (EME) has recently emerged as a green and versatile tool for the analysis of trace pollutants in water samples, being mainly applied to the preconcentration and determination of organic compounds. Recently, EME has also shown its applicability to the analysis of inorganic species, allowing a considerable reduction in both reagent consumption and extraction times, and without loss of efficacy, in comparison with other liquid phase microextraction techniques. In this study, an EME system for trace copper analysis in natural waters has been optimised by the modified simplex method. A chemical modifier, di-2-pyridyl ketone benzoylhydrazone (dPKBH) was synthesized and dissolved in 1-nonanol, to be used as an organic phase impregnated into the pores of a polymeric hollow fibre. With only 15 min of extraction, an enrichment factor of 77.1 ± 10.8 was obtained for a wide salinity range (0-35), allowing its application in a variety of different waters, including seawater. Optimum operating conditions were a sample pH of 6.26, an electric potential of 95 V, 0.08 M nitric acid as the acceptor phase, 4.01 mM dPKBH in 1-nonanol as the organic phase and a stirring rate of 1500 rpm. A LOD of 0.004 μg L-1 was obtained, and the system was successfully applied to the analysis of several water samples containing copper at low ppb levels (tap water and river water) or even at sub-ppb levels (seawater).

Hybrid Carbon Nanotubes/Gold Nanoparticles Composites for Trace Nitric Oxide Detection over a Wide Range of Humidity

Composites of functionalized single walled carbon nanotubes (SWCNTs) and gold nanoparticles (Au NPs) of ≈15 nm diameter were drop-cast on a printed circuit board (PCB) substrate equipped with interdigitated electrodes to make a hybrid thin film. Addition of Au NPs decorated the surface of SWCNTs networked films and acted as catalysts which resulted into an enhanced sensitivity and low ppb concentration detection limit. The compositions of the film were characterized by scanning electron microscope (SEM). SWCNTs clusters were loaded with various amount of Au NPs ranging from 1–10% (by weight) and their effect on Nitric oxide (NO) sensitivity was studied and optimized. Further, the optimized composite films were tested in both air and nitrogen environments and as well as over a wide relative humidity range (0–97%). Sensors were also tested for the selectivity by exposing to various gases such as nitrous oxide, ammonia, carbon monoxide, sulfur dioxide and acetone. Sensitivity to NO was found much higher than the other tested gases. The advantage of this sensor is that it is sensitive to NO at low ppb level (10 ppb) with estimated response time within 10 s and recovery time around 1 min, and has excellent reproducibility from sensor to sensor and works within the wide range of relative humidity (0–97%).

Highly Sensitive Oxygen Sensing Characteristics Observed in IGZO Based Gasistor in a Mixed Gas Ambient at Room Temperature.

Oxygen (O2) sensing in trace amounts and mixed gas is essential in many types of industries. Semiconductor sensors have proven to be invaluable tools for the O2 measurements in a wide concentration range, but the sensors are only able to quantify O2 in a concentration range of subppm, thus far, especially in mixed gas. We present in this paper a new concept for O2 sensing with incomparable sensitivity using IGZO-films with oxygen vacancy-based conducting filaments (CFs). O2 sensing relies on rupturing of the CFs, and the proposed device quickly recovers to the initial state using a pulse of 0.6 V/90 μs after the sensing. The proposed device has a high sensitivity of 14 even at an O2 concentration of 500 ppb, a detection limit of 150 ppb for O2 at RT, and excellent selectivity for O2 in mixed gas, which is remarkable compared to other gas sensors. The proposed device can be widely used in gas sensors especially for detecting O2 at a low ppb level, which is due to excellent sensing characteristics.

Ordered large-pore mesoporous ZnCr2O4 with ultrathin crystalline frameworks for highly sensitive and selective detection of ppb-level p-xylene

Highly sensitive and selective detection of toxic and harmful gases especially at low-ppb (part per billion) level is of great significance to human health and air quality, although it remains a great challenge in gas sensor applications. Herein, for the first time, we present an ordered mesoporous ZnCr2O4 with both large mesopore of 11 nm and ultrathin crystalline framework of 3–5 nm for highly sensitive and selective detection of p-xylene at low ppb levels. The resultant ordered large-pore mesoporous ZnCr2O4 with ultrathin framework exhibits a higher specific surface area of up to 168 m2 g−1 than those for its mesoporous counterpart with thick framework (60 m2 g−1) and bulk ZnCr2O4 particle (48 m2 g−1), which also exhibits the highest response value (Rgas/Rair−1 = 26.8) toward 1 ppm of p-xylene at 270 °C and is nearly 8 and 10 times higher than those for its mesoporous counterpart with thick framework (3.32) and bulk ZnCr2O4 particle (2.65) respectively. Notably, the ordered mesoporous ZnCr2O4 also has a rather low limit of detection (<2 ppb) as well as good selectivity and would be potential in gas sensors.

Characterization of a modular microfluidic photoionization detector

Photoionization detectors with a small ionization chamber can contribute to overall gas analyser miniaturization. This work reports the characterization of a microfluidic photoionization detector prototype (μPID) which is constructed to be modular for easy replacement of the components and maintenance. The device is fabricated by micromilling and electrical discharge machining, dispensing clean room fabrication techniques. The μPID ionization chamber is a microchannel and four channel designs are presented and tested in experiments in order to evaluate the influence of the geometrical parameters on the detector performance. The chamber volumes of the channel designs range from 1.1 to 6.7 μL. Experimental characterization of the prototype is performed when it is used without and with a portable gas chromatograph (GC) for volatile organic compounds (VOCs) analysis. When a sample of 100 ppm toluene is injected directly into the μPID, it can generate a current signal up to ∼4 nA. When used without a GC, the device showed a linear response for an injection of toluene gas concentrations ranging from 1 to 100 ppm. A combination of high illumination area and electrode area resulted in the highest signal in the μPID with a detection limit of ∼40 ppb of toluene. When integrated to the portable GC, the detection limit reached for toluene is ∼140 ppb. The detection limit for toluene was further reduced to low ppb levels (∼5 ppb) when a preconcentrator was integrated into the sampling loop of the portable GC.

Doping control analysis of antipsychotics and other prohibited substances in equine plasma by liquid chromatography/tandem mass spectrometry

Antipsychotics are banned substances and considered by the Fédération Equestrian Internationale (FEI) to have no legitimate use in equine medicine and/or have a high potential for abuse. These substances are also prohibited in horseracing according to Article 6 of the International Agreement on Breeding, Racing and Wagering (published by the International Federation of Horseracing Authorities). Over the years, antipsychotics have been abused or misused in equestrian sports and horseracing. A recent review of literature shows that there is yet a comprehensive screening method for antipsychotics in equine samples. This paper describes an efficient liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the simultaneous detection of over 80 antipsychotics and other prohibited substances at sub-parts-per-billion (ppb) to low-ppb levels in equine plasma after solid-phase extraction (SPE).

Minimizing the impact of sample preparation on analytical results: In-tube solid-phase microextraction coupled on-line to nano-liquid chromatography for the monitoring of tribenuron methyl in environmental waters

The degradation kinetics and residual levels of the sulfonylurea herbicide tribenuron-methyl (TBM) in different environmental waters were studied using in tube-solid phase microextraction (IT-SPME) coupled on-line to nano-liquid chromatography (nanoLC) and UV diode array detection (DAD). This approach combines the high extraction efficiency of IT-SPME using polymeric coatings reinforced with metal oxide nanoparticles and the high sensitivity attainable by nanoLC, making possible the determination of TBM at low ppb levels (limit of detection, 0.25 ppb) without altering the sample matrix. The present study demonstrated that the preservation of the sample properties is essential to ensure accurate results at these concentration levels due to the high tendency of TBM to hydrolyze, particularly under the acidic conditions involved in most protocols used for sample treatment. The approach used in the present study was applied to evaluate the degradation of this herbicide under different conditions (UV radiation, pH), as well as to study the evolution of its concentration in different environmental waters, namely sea, river, ditch and transition waters. When the samples were exposed to identical conditions, significant differences in the degradation rate of TBM were found depending on the water matrix. The results obtained indicate that this herbicide can persist from several days to weeks depending on the type of water.

Under Deposit Corrosion in Steam Generators: Towards Understanding Critical Deposit Thresholds

Most significant industrial facilities operate large steam systems, including multiple steam generators. The steam produced may be used for power generation by steam turbines or for heating various equipment items and is usually critical to the overall operation of the plant. Each steam generator will typically contain hundreds of carbon steel tubes: the failure of such tubes by unpredicted corrosion represents a common cause of plant downtime, significant lost production, and an ongoing safety risk. The mechanism of UDC in these systems is not well-understood, and this is in part because of the experimental challenges of studying such systems [1-3]. However, some clear parametric observations have been made and it is now established that very low (ppb) levels of dissolved ferrous ions and micro-scale particles of magnetite are produced by flow-assisted corrosion in the steam generator feed-water systems, and that these are then deposited on to the heat transfer surfaces. Together with the presence of only trace (ppb) levels of bulk chloride contamination, these deposits can lead to extraordinarily rapid corrosion. Characteristic features of the damaged material include: the porous structure of the deposit layer; the presence of high local chloride concentrations within the deposits; and formation of a complex ‘multi-duplex’ layer of corrosion product that exhibits approximately linear growth kinetics. According to EPRI guidelines [4], 35 mg.cm-2 represents a critical threshold for deposit thickness after which interventional maintenance should be initiated. This nominal thickness is not based on mechanistic understanding and is often achieved in boilers within only a few years of operation, resulting in the need for expensive and time-consuming chemical cleaning to remove the deposits. Hence, it is necessary to better understand the various stages in the formation of these layers to improve prediction of UDC and help reduce conservatism in maintenance without compromising on safety. In this presentation, we will present a study of field-retrieved samples that were examined with optical and electron microscopy techniques, coupled with phase and chemical analyses. This will be compared with model experiments where deposits are formed under laboratory-controlled conditions [1], including both new and literature data. We will discuss these data in terms of a model for UDC in steam generators, with emphasis on the critical deposit thickness and the particular role of chloride in the formation of the characteristic multi-duplex scales. References Robertson, J. and Forrest, J.E., 1991, Corrosion Science, 32(5/6), 521-540.Howell, A.G., 2006, NACE – 06458, NACE international publication.Dooley, R.B. and Bursik, A., 2010, Boiler and HRSG tube failures - Hydrogen Damage, 12(2), 122-127.Dooley, R.B., 2005, EPRI Technical Report, 1-154.

Simultaneous analysis of multiclass contaminants of emerging concern in sediments by liquid chromatography with tandem quadrupole mass spectrometry.

A quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based extraction and simultaneous dispersive solid-phase extraction (dSPE) clean-up method was developed for contaminants of emerging concern (CECs) in sediment samples. Hydration with a phosphate buffer (pH 2.0) and salting out with NaCl and MgSO4 facilitated the extraction and liquid-liquid portioning of the aqueous and organic phases. Cleanup of the extracts was achieved by florisil and C18 (1:1) sorbents in dSPE with minimal compromise of the analytes. The extracts were clean enough for determination by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The procedure was validated for preservatives, blood lipid regulators, analgesics and anti-inflammatory drugs, plasticizers, and other classes of CECs in sediment matrix spiked at 6 levels between 1- and 40-fold concentrations for CECs of varying analytical sensitivities. The recovery values were generally between approximately 27 and 120% and the relative standard deviation (%RSD) values were below 20% at 10- , 20- , and 40-fold spiking levels, albeit the recoveries for some analytes dropped at low spike concentrations. The method showed high sensitivity where the method detection limits (MDLs) were at low ppb levels for the majority of the analytes that ranged between 0.002 and 1.93 µg/kg. The method performance was also compared with well-established US Environmental Protection Agency (USEPA) Method 1694 by analyzing sediment samples collected from Yundang Lagoon (Xiamen, China) with field-incurred CEC residues. The sediment samples were detected with residues of parabens, gemfibrozil, ketoprofen, naproxen, fenoprofen, diclofenac, miconazole, carbamazepine, benzophenon-3, glibenclamide, sildinafil citrate, and some bisphenol analogues. Environ Toxicol Chem 2019;38:1409-1422. © 2019 SETAC.

Sorptive process and breakthrough behavior of odorous volatile compounds on inert surfaces

The use of glass impinger is an important device for sampling and handling when measuring volatile organic compounds (SVOCs). Thus, it is important to check for possible analyte losses to the inner glass surface when carrying out sample analysis with the aid of impinger system. In this research, we evaluated the sorptive loss patterns of vapor-phase semi-volatile organic compounds [SVOCs (n = 10): acetic acid (ACA), propionic acid (PPA), i-butyric acid (IBA), n-butyric acid (BTA), i-valeric acid (IVA), n-valeric acid (VLA), phenol (PhAl), p-cresol (p-C), indole (ID), and skatole (SK)] on inert surfaces of an impinger in reference to sampling bags. The gaseous standard of these SVOCs (48–406 ppb) in polyester aluminum (PEA) bags was passed through an empty impinger in 1 L steps. The exiting SVOCs were collected on three-bed sorbent tubes for subsequent analysis by thermal desorption-gas chromatography-mass spectroscopy (TD-GC-MS). Impinger wall sorption capacities ranged from 2.0 to 21.0 ng cm−2. The 10% breakthrough adsorption capacities on the impinger wall for acids, phenols, and indoles ranged from 1.21 ± 0.15 to 5.39 ± 0.79, 0.92 ± 0.12 to 13.4 ± 2.25, and 4.47 ± 0.42 to 5.23 ± 0.35 ng cm−2, respectively. The observed sorptive patterns suggest that the sorptive losses of the volatile fatty acids, phenols, and indoles can occur very effectively at low ppb levels onto a glass surface.