Sample Uptake Research Articles

Utilizing Low Sample Uptake Rates and A Nitrogen Mixed-gas Plasma for the Elimination of Oxide-based Interferences in ICPMS Analyses

Utilizing Low Sample Uptake Rates and A Nitrogen Mixed-gas Plasma for the Elimination of Oxide-based Interferences in ICPMS Analyses

Single particle inductively coupled plasma mass spectrometry and its variations for the analysis of nanoparticles.

Single particle inductively coupled plasma mass spectrometry (spICPMS) can count and weigh metal-containing nanoparticles (NPs), enabling their sizing if their geometry, density, and composition are known. With a nebulizer and a spray chamber for sample introduction, both the sample uptake rate and the transport efficiency must be determined when calibrating with solutions. In contrast, flow injection (FI) and mono-segmented flow analysis (MSFA) coupled to spICPMS do not need determination of the transport efficiency and sample uptake rate for accurate NP mass measurement. Correcting for the significant settling time on some instruments is also discussed, as well as calibration through signal integration instead of averaging, which eliminates the need to measure the transport efficiency when seeking NP mass. Nitrogen added to the outer plasma gas can reduce the background for the determination of P, S, Ca and Fe. Infrared heating of the sample introduction system provides 100% transport efficiency, enabling accurate particle mass and concentration measurements without measurement of transport efficiency.

Comparing Equilibrium Concentrations of Polychlorinated Biphenyls Based on Passive Sampling and Bioaccumulation in Water Column Deployments.

Biomonitoring at contaminated sites undergoing cleanup, including Superfund sites, often uses bioaccumulation of anthropogenic contaminants by field-deployed organisms as a metric of remedial effectiveness. Bioaccumulation studies are unable to assess the equilibrium status of the organisms relative to the contaminants to which they are exposed. Establishing equilibrium provides a reproducible benchmark on which scientific and management decisions can be based (e.g., comparison with human dietary consumption criteria). Unlike bioaccumulating organisms, passive samplers can be assessed for their equilibrium status. In our study, over a 3-year period, we compared the bioaccumulation of selected polychlorinated biphenyls (PCBs) by mussels in water column deployments at the New Bedford Harbor Superfund site (New Bedford, MA, USA) to codeployed passive samplers. Based on comparisons to the calculated passive sampler equilibrium concentrations, the mussels were not at equilibrium, and the subsequent analysis focused on evaluating approaches for estimating equilibrium bioaccumulation. In addition, a limited evaluation of metal bioaccumulation by the exposed mussels and a metal passive sampler was performed. In general, mussel and passive sampler accumulation of PCBs was significantly correlated; however, surprisingly, agreement on the magnitude of accumulation was optimal when bioaccumulation and passive sampler uptake were not corrected for nonequilibrium conditions. A subsequent comparison of four approaches for estimating equilibrium mussel bioaccumulation using octanol-water partition coefficients (KOW ), triolein-water partition coefficients (KTW ), and two types of polymer-lipid partition coefficients demonstrated that field-deployed mussels were not at equilibrium with many PCBs. A range of estimated equilibrium mussel bioaccumulation concentrations were calculated, with the magnitude of the KOW -based values being the smallest and the polymer-lipid partition coefficient-based values being the largest. These analyses are intended to assist environmental scientists and managers to interpret field deployment data when transitioning from biomonitoring to passive sampling. Environ Toxicol Chem 2023;42:317-332. Published 2022. This article is a U.S. Government work and is in the public domain in the USA.

The efficiency of Hg cold vapor generation and its influence on Hg isotope analysis by MC-ICP-MS

Non-quantitative Hg cold-vapor generation can compromise the accuracy of Hg isotope analysis, and it should be monitored and optimized by performing matrix separation, adopting the design of gas–liquid separators, and tuning the sample uptake rate.

Analysis of microsamples of biological fluids via inductively coupled plasma-tandem mass spectrometry using a micro-flow injection system coupled to a high-efficiency sample introduction setup

In many fields, the sample volume available is the limiting factor for ultra-trace elemental analysis, and thus, the development of novel methods that can extract more information from lower sample amounts is a topic that deserves attention. In this work, the performance of a micro-flow injection system coupled to either (1) a traditional or (2) a high-efficiency sample introduction system has been evaluated for the analysis of liquid microsamples using inductively coupled plasma-mass spectrometry (ICP-MS). The figures of merit with each sample introduction system have been studied in a wide range of sample volumes and sample uptake rates. The use of a high-efficiency low-volume sample introduction system provided a > 4-fold enhanced sensitivity as compared to the traditional one, while the former setup was demonstrated being capable of accurately delivering volumes as low as 5 or 10 μL to the ICP. Even for such low sample amounts, good linearity (>0.9998) and repeatability (RSD down to 0.2%) were experimentally demonstrated, while matrix effects were lower with the high-efficiency sample introduction system. The use of an internal standard adequately corrected for changes in sample introduction conditions, allowing quantitative results to be obtained by using a single set of calibration data obtained at fixed operating conditions (sample volume and sample uptake rate), with a bias <15% (typical acceptance criterion for clinical QC analysis). The set-up characterized was successfully applied to the analysis of microsamples of biological fluids (down to 0.4 μL of sample volume). Tandem ICP-MS (ICP-MS/MS) was used to overcome spectral overlap (chemical resolution with a mixture of NH3/He) affecting the determination of six clinically relevant metals (Co, Cr, Mn, Ni, Ti and V) at ultra-trace concentration levels. No significant differences were found between the results obtained in this work and the reference values, even when using different sample introduction conditions for the measurement of calibration standards and samples.

Further insight into analyte transport processes and water vapor, aerosol loading in ICP-OES and ICP-MS

Simple concepts that control the amount of analyte, solvent aerosol and solvent vapor that enter the plasma are used to explain changes in analyte transport efficiency as a function of sample uptake rate in pneumatic nebulizer/spray chamber sample introduction systems. These include droplet-droplet collision/coalescence, evaporation of solvent from the sample aerosol and droplet impact on the walls of the spray chamber. We show that even small (2 to 5 μm diameter) droplets have a poor (<12%) transport efficiency through the spray chamber when the sample uptake rate is 1 mL/min. A dual nebulizer system and video are used to assess the role of droplet-droplet collisions/coalescence and aerosol evaporation in controlling sample transport efficiency as a function of sample uptake rate. The impact of water vapor that evaporates from the wall of the spray chamber and from evaporation of solvent from the sample aerosol are described with experimental evidence. Sample transport efficiencies for “conventional” nebulizers and micronebulizers are found to be similar when compared at the same sample uptake rates from 0.02 to 1.0 mL/min. The stability of signals when using “conventional” and micronebulizers at sample uptake rates less than 0.05 mL/min are compared. The impact of water vapor loading and water aerosol loading are investigated using a heated sample introduction system that efficiently evaporates the solvent from aerosol droplets and a vibrating mesh nebulizer than can provide virtually 100% aerosol transport efficiency at aerosol transport rates up to 0.3 mL/min, respectively.

Integrating Instead of Averaging Signal Intensity to Simplify Nanoparticle Mass Measurement by Single Particle Inductively Coupled Plasma Mass Spectrometry.

The use of single particle inductively coupled plasma mass spectrometry has been rapidly expanding for the analysis of nanoparticles (NPs). When external calibration with standard solutions is done to find the mass of NPs, the average signal intensity for each standard solution is typically used, which requires measurement of the transport efficiency of solutions through the spray chamber. However, if the signal is integrated over a constant time period for all standards and samples, then there is no need to determine the transport efficiency to measure NP mass, as the mass of analyte aspirated can be directly found by multiplying the analyte concentration in each standard by the sample uptake rate and the integration time. The line of best fit through the calibration curve of integrated signal versus mass is then used to find the total mass of NPs nebulized during the integration time, the mass of each NP then corresponding to the fraction of the total integrated signal caused by the NP. Measurement of the transport efficiency is only required if the concentration of NPs is desired.

Field- and model-based calibration of polyurethane foam passive air samplers in different climate regions highlights differences in sampler uptake performance

Abstract Polyurethane foam (PUF) passive air samplers (PAS) are widely used for measurements of persistent organic pollutants (POPs) and other semi-volatile organic compounds (SVOCs) in large-scale monitoring networks as well as in case studies around the globe. Calibration of PUF-PAS is performed by field-based calibration studies or passive sampler uptake models, but both these are typically performed and/or validated in temperate zones, while the sampling rates are more widely applied, including in tropical and polar zones. Here, we present field-based calibrations results for MONET PUF-PAS from a subtropical and tropical site (Nairobi, Kenya and Accra, Ghana) based on side-by-side deployment of PUF-PAS and active air samplers (AAS), as well as model PAS uptake from available passive sampler uptake models. By comparing these results with a similar calibration from a temperate site (Brno, Czech Republic), we show that the higher ambient temperatures result in higher effective sampling rates for intermediate molecular weight SVOCs (logKOA of 7–11) as a result of lower particle-bound fraction, and in lower sample volumes for lighter SVOCs (logKOA

Time integrative sampling properties of Speedisk and silicone rubber passive samplers determined by chemical analysis and in vitro bioassay testing

Compared to grab samples, passive samplers have the advantage that they sample over a longer time period and can detect lower compound concentrations in water quality monitoring campaigns. To allow the determination of time-weighted average concentrations, however, sampler uptake should remain linear in time over the entire sampling period. Therefore, the time integrative or linear uptake properties of adsorption-based Speedisks and partitioning-based silicone rubber samplers were assessed with respect to chemically analyzed single compounds and measured bioactivity in in vitro bioassays. Both sampler types were deployed in consecutive and overlapping time series in a WTTP effluent and in the river Meuse up to 105 days. Extracts were chemically analyzed for PCBs, PAHs and pesticides and tested in the Aliivibrio fischeri and DR-LUC bioassays. Speedisks showed time integrative sampling for the detected pesticides as well as for bioassay responses at both sampling locations for the entire sampling period. The silicone rubber samplers showed poor linear uptake in time for the unknown compounds causing bioassay responses. The bioassay results indicate that conversion of a bioassay response to a passive sampler extract into a time-weighted average bioactivity per liter water seems justified for Speedisks, confirming that concentrations in the samplers correspond to a single volume of sampled water for all compounds. The bioassay results also indicate that a similar conversion for silicone rubber extracts should be interpreted with caution. In principle, it is actually impossible, because the concentration of each compound contributing to the bioassay response corresponds to a different sampled water volume.

Single particle inductively coupled plasma mass spectrometry with and without flow injection for the characterization of nickel nanoparticles

This work compares the performance of transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), single particle inductively coupled plasma mass spectrometry (spICPMS) and flow injection (FI) coupled to spICPMS for the characterization of synthetic ferromagnetic Ni nanoparticles (NPs) prepared with and without polyvinylpyrrolidone (PVP) stabilizer. Whereas single NPs measurement by XRD yielded nominal diameters of 13.7 and 16.6 nm with and without PVP respectively, a diameter of 100–130 nm was obtained by TEM and SEM with or without PVP, indicating extensive agglomeration during preparation for microscopy. In contrast, without PVP stabilization, mean and mode sizes of respectively 35 ± 18 and 21 nm by spICPMS and 33 ± 15 and 20 nm by FI-spICPMS were obtained for suspensions of Ni NPs using external calibration with Ni standard solutions. With PVP stabilization, the mean and mode sizes respectively decreased to 27 ± 12 and 18 nm by spICPMS and 25 ± 10 and 16 nm by FI-spICPMS. Mass balance taking into account the amount of dissolved Ni was verified in all cases. No degradation in performance resulted from using FI-spICPMS instead of spICPMS, even though measurement of NPs mass by FI-spICPMS is done without knowledge of the transport efficiency and the sample uptake rate. This is the first time that spICPMS and FI-spICPMS are demonstrated to be suitable for the characterization of ferromagnetic NPs.

Development and Field Application of a Passive Sampler for Atmospheric Mercury

In this study, a passive sampler for gaseous elemental mercury (GEM) was developed and applied to field monitoring. Three Radiello® diffusive bodies with iodineimpregnated activated carbon (I-IAC) as a Hg adsorbent were placed in an opaque acrylic external shield with a stainless steel lid. The performance of the passive sampler was evaluated at seven monitoring sites in South Korea. Hg uptake mass by the passive sampler linearly increased as the deployment time increased up to four months. The reproducibility of the sampler uptake mass for the different deployment periods was also good, and the average relative standard deviation calculated for the three adsorbents in one passive sampler was 9%. Using the Hg concentration measured by an active sampler, an experimental sampling rate (SR) of 0.082 m3 day−1 was obtained. It was shown that the experimental SR was significantly affected by meteorological parameters, and a calibration equation was successfully derived based on wind speed, temperature, and relative humidity. With the calibrated SRs, there was a significant correlation between the active and passive Hg concentrations. When the passive samplers were deployed in an industrial district, the GEM concentration showed very large spatial variation, suggesting its potential for application in future field monitoring.

How much aqueous sample can an inductively coupled plasma withstand?

An inductively coupled plasma can withstand the total introduction of 250 μL min−1 if infrared heating first pre-evaporates the aerosol.

Calibration and field application of an innovative passive sampler for monitoring groundwater quality

This study describes the development of a novel Empore™ disk-based passive sampler specially adapted to groundwater monitoring. The sampler was calibrated in the laboratory using conditions that corresponded to groundwater (i.e. matrix medium, water temperature, flow rate and water flow across the disks). The retention and elution performance for sixteen semi-polar and polar pollutants on the Empore™ disk (47 mm diameter, SDB-XC) was evaluated. Recoveries were ~80% for the majority of compounds. Sampler uptake kinetics were measured over fourteen days at three concentrations (10, 100 and 500 ng L−1) and the sampling rate (RS) calculated for four compounds. There was no influence of concentration of the test analyte on the uptake profile; with mean RS varying between 0.018 ± 0.007 L day−1 and 0.047 ± 0.001 L day−1. Passive samplers were deployed in twelve characterized groundwater wells near Lyon (France). Atrazine, atrazine-desethyl and diuron were the main pollutants found with a maximum time-weighted concentration of 61 ± 3, 62 ± 24 and 127 ± 49 ng L−1 respectively.

Calibration parameters for the passive sampling of organic UV filters by silicone; diffusion coefficients and silicone–water partition coefficients

In recent years, organic ultraviolet filters (UVFs) received considerable attention as a group of emerging contaminants, including in Australia where the use of UVFs is particularly relevant. Passive sampling using polymers has become widely used for routine monitoring of chemicals in the aquatic environment. Application of passive samplers for monitoring chemicals in the water relies on calibration data such as chemical's polymer-water partition coefficient (Kpw) and diffusion coefficients in the sampling material (Dp), for understanding uptake and kinetic limitations. In the present study, Kpw and Dp for nine UVFs were estimated. Kpw values were determined in different water – polymer partition experiments where (1) a given mass of chemicals was dosed into the water and (2) into the polymer. Diffusion coefficients were determined using the stacking method. The estimated log Kpw and log Dp ranged from 2.9 to 6.4 L kg−1 and -11.1 to −10.5 m2s-1, respectively. The sufficient high Dp allows application of kinetic models that only consider water boundary-controlled uptake for converting silicone sampler uptake into an aqueous phase concentration using the presented Kpw.

Calibration and application of the Chemcatcher\xae passive sampler for monitoring acidic herbicides in the River Exe, UK catchment

Acidic herbicides are used to control broad-leaved weeds. They are stable, water-soluble, and with low binding to soil are found frequently in surface waters, often at concentrations above the EU Drinking Water Directive limit of 0.10 μg L−1. This presents a problem when such waters are abstracted for potable supplies. Understanding their sources, transport and fate in river catchments is important. We developed a new Chemcatcher® passive sampler, comprising a 3M Empore™ anion-exchange disk overlaid with a polyethersulphone membrane, for monitoring acidic herbicides (2,4-D, dicamba, dichlorprop, fluroxypyr, MCPA, MCPB, mecoprop, tricolpyr). Sampler uptake rates (Rs = 0.044–0.113 L day−1) were measured in the laboratory. Two field trials using the Chemcatcher® were undertaken in the River Exe catchment, UK. Time-weighted average (TWA) concentrations of the herbicides obtained using the Chemcatcher® were compared with concentrations measured in spot samples of water. The two techniques gave complimentary monitoring data, with the samplers being able to measure stochastic inputs of MCPA and mecoprop occurring in field trial 1. Chemcatcher® detected a large input of MCPA not found by spot sampling during field trial 2. Devices also detected other pesticides and pharmaceuticals with acidic properties. Information obtained using the Chemcatcher® can be used to develop improved risk assessments and catchment management plans and to assess the effectiveness of any mitigation and remediation strategies.

The influence of pH on sampler uptake for an improved configuration of the organic-diffusive gradients in thin films passive sampler

Recent literature has demonstrated the utility of the organic-diffusive gradients in thin films (o-DGT) device as an effective passive sampler for polar organics in aquatic environments. Here, a new configuration comprising a polyacrylamide diffusive gel and Sepra™ ZT sorbent was developed and calibrated under multiple pH conditions. Linear uptake (r2 > 0.9) was observed at pH ≈ 5 for a suite of 31 pharmaceuticals and pesticides over 25 days, suitable for typical passive sampler deployments. At pH ≈ 8.5, linear uptake (r2 > 0.9) was observed for many of the same compounds. Comparisons of the uptake rates between the two pH experiments generally agreed (14% average relative error), with only 6 compounds exhibiting marked reduction with pH (e.g. sulfonamide antibiotics). These discrepancies may be explained by changes in analyte-sorbent interaction (H-bonding) due to speciation changes at varying pH. Samplers performed well in field evaluations conducted in an impacted river system, showing close agreement with the previously validated agarose/HLB o-DGT configuration deployed simultaneously. This work illustrates that polyacrylamide diffusive gels are a more robust and resistant outer-membrane material compared to agarose used in earlier o-DGT configurations. Sepra™ ZT binding gels served as an effective binding resin, offering a cost effective and commercially available sorbent.

Calibration and field evaluation of the Chemcatcher® passive sampler for monitoring metaldehyde in surface water

Metaldehyde is a potent molluscicide. It is the active ingredient in most slug pellets used for crop protection. This polar compound is considered an emerging pollutant. Due to its environmental mobility, metaldehyde is frequently detected at impacted riverine sites, often at concentrations above the EU Drinking Water Directive limit of 0.1µgL−1 for an individual pesticide. This presents a problem when such waters are abstracted for use in the production of potable water supplies, as this chemical is difficult to remove using conventional treatment processes. Understanding the sources, transport and fate of this pollutant in river catchments is therefore important. We developed a new variant of the Chemcatcher® passive sampler for monitoring metaldehyde comprising a Horizon Atlantic™ HLB-L disk as the receiving phase overlaid with a polyethersulphone membrane. The sampler uptake rate (Rs) was measured in semi-static laboratory (Rs = 15.7mLday−1) and in-field (Rs = 17.8mLday−1) calibration experiments. Uptake of metaldehyde was linear over a two-week period, with no measurable lag phase. Field trials (five consecutive 14day periods) using the Chemcatcher® were undertaken in eastern England at three riverine sites (4th September-12th November 2015) known to be impacted by the seasonal agricultural use of metaldehyde. Spot samples of water were collected regularly during the deployments, with concentrations of metaldehyde varying widely (~ 0.03–2.90µgL−1) and often exceeding the regulatory limit. Time weighted average concentrations obtained using the Chemcatcher® increased over the duration of the trial corresponding to increasing stochastic inputs of metaldehyde into the catchment. Monitoring data obtained from these devices gives complementary information to that obtained by the use of infrequent spot sampling procedures. This information can be used to develop risk assessments and catchment management plans and to assess the effectiveness of any mitigation and remediation strategies.

Evaluating the Relationship between Equilibrium Passive Sampler Uptake and Aquatic Organism Bioaccumulation.

This Critcal Review evaluates passive sampler uptake of hydrophobic organic contaminants (HOCs) in water column and interstitial water exposures as a surrogate for organism bioaccumulation. Fifty-seven studies were found where both passive sampler uptake and organism bioaccumulation were measured and 19 of these investigations provided direct comparisons relating passive sampler uptake and organism bioaccumulation. Polymers compared included low-density polyethylene (LDPE), polyoxymethylene (POM), and polydimethylsiloxane (PDMS), and organisms ranged from polychaetes and oligochaetes to bivalves, aquatic insects, and gastropods. Regression equations correlating bioaccumulation (CL) and passive sampler uptake (CPS) were used to assess the strength of observed relationships. Passive sampling based concentrations resulted in log-log predictive relationships, most of which were within one to 2 orders of magnitude of measured bioaccumulation. Mean coefficients of determination (r2) for LDPE, PDMS, and POM were 0.68, 0.76, and 0.58, respectively. For the available raw, untransformed data, the mean ratio of CL and CPS was 10.8 ± 18.4 (n = 609). Using passive sampling as a surrogate for organism bioaccumulation is viable when biomonitoring organisms are not available. Passive sampling based estimates of bioaccumulation provide useful information for making informed decisions about the bioavailability of HOCs.

Flow Injection Single Particle Inductively Coupled Plasma Mass Spectrometry: An Original Simple Approach for the Characterization of Metal-Based Nanoparticles.

In recent years, single-particle inductively coupled plasma mass spectrometry (spICPMS) has emerged as a reliable tool that can both count metal-containing nanoparticles and measure their mass, thereby allowing sizing if their shape, density, and composition are known. However, the methodology associated with the current spICPMS approach for mass determination requires determination of both the sample uptake rate and the sample introduction efficiency of the nebulization system. In this paper, the proof of concept of a novel approach based on flow injection (FI) analysis coupled to ICPMS, i.e., FI-spICPMS, is presented. Unlike the established technique, this method does not require a determination of the transport efficiency and of the sample uptake rate for the accurate measurement of particle mass. It also only requires a measurement of the transport efficiency for determination of the particle number. Unlike the traditional spICPMS approach, the measurement of transport efficiency by FI-spICPMS is not affected by changes in sample uptake rate. The efficiency of FI-spICPMS is demonstrated through accurate determination of the particle number and size of 60 nm citrate-coated gold nanoparticles suspended in high-purity water. Despite being simpler, the method provides similar results to those obtained by the established spICPMS method. With a 5 ms dwell time and 200 μs settling time, the size detection limit is 20 nm, i.e., the same as with spICPMS.

Spilled Oils: Static Mixtures or Dynamic Weathering and Bioavailability?

Polynuclear aromatic hydrocarbons (PAHs) from sequestered MV Selendang Ayu oil were biologically available in 2008, 3.6 y after it was spilled along Unalaska Island, Alaska. Thermodynamically driven weathering was the most probable mechanism of organism exposure to PAHs. Alkane and PAH composition in oil changed over time as smaller constituents were preferentially lost, indicative of weathering. In contrast, composition of the largest compounds (biomarkers) including triterpanes, hopanes, and steranes remained unchanged. Smaller molecules (the PAHs) lost from stranded oil were observed in indigenous mussels and passive samplers deployed in July 2008. Concentration and composition of PAHs were significantly different than in a non-oiled reference area and patterns observed in mussels were repeated in passive samplers deployed in three zones (intertidal, subtidal, and water). Thus, hydrocarbons lost from one compartment (sequestered whole oil) were detectable in another (mussels and passive samplers) implying aqueous transfer. Quantities of mobile oil constituents were small, yielding uptake concentrations that are likely inconsequential for mussels, but the sensitivity provided by bioaccumulation and passive sampler uptake ensured that dissolved hydrocarbons were detectable.