Uranium Single Particle Analysis for Simultaneous Fluorine and Uranium Isotopic Determinations via Laser-Induced Breakdown Spectroscopy/Laser Ablation-Multicollector-Inductively Coupled Plasma-Mass Spectrometry.

Uranyl fluoride (UO2F2) particles (<20 µm) were subjected to first-of-its-kind analysis via simultaneous laser-induced breakdown spectroscopy (LIBS) and laser ablation multi-collector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS). Briefly, a nanosecond pulsed high-energy laser was focused onto the sample (particle) surface. In a single laser pulse, the UO2F2 particle was excited/ionized within the microplasma volume, and the emission of light was collected via fiber optics such that emission spectroscopy could be employed for the detection of uranium (U) and fluorine (F). The ablated particle was simultaneously transported into the MC-ICP-MS for high precision isotopic (i.e., 234U, 235U, and 238U) analysis. This method, LIBS/LA-MC-ICP-MS was optimized and employed to rapidly measure 80+ UO2F2 particles, which were subjected to different calcination processes, which results in varying degrees of F loss from the individual particles. In measuring the particles, the average F/U ratios for the populations treated at 100 and 500 °C were 2.78 ± 1.28 and 1.01 ± 0.50, respectively, confirming loss of F through the calcination process. The average 235U/238U on the particle populations for the 100 and 500 °C were 0.007262 (22) and 0.007231 (23), which was determined to be <0.2% from the expected value. The 234U/238U ratios on the same particles were 0.000053 (11) and 0.000050 (10) for the 100 and 500 °C, respectively, <10% from the expected value. Notably, each population was analyzed in under 5 min, demonstrating the truly rapid analysis technique presented here.

Quantification of [99Tc]TcO4- in urine by means of anion-exchange chromatography-aerosol desolvation nebulization-inductively coupled plasma-mass spectrometry.

To sensitively determine 99Tc, a new method for internal quantification of its most common and stable species, [99Tc]Tc O 4 - , was developed. Anion-exchange chromatography (IC) was coupled to inductively coupled plasma-mass spectrometry (ICP-MS) and equipped with an aerosol desolvation system to provide enhanced detection power. Due to a lack of commercial Tc standards, an isotope dilution-like approach using a Ru spike and called isobaric dilution analysis (IBDA) was used for internal quantification of 99Tc. This approach required knowledge of the sensitivities of 99Ru and 99Tc in ICP-MS. The latter was determined using an in-house prepared standard manufactured from decayed medical 99mTc-generator eluates. This standard was cleaned and preconcentrated using extraction chromatography with TEVA resin and quantified via total reflection X-ray fluorescence (TXRF) analysis. IC coupled to ICP-MS enabled to separate, detect and quantify [99Tc]Tc O 4 - as most stable Tc species in complex environments, which was demonstrated in a proof of concept. We quantified this species in untreated and undiluted raw urine collected from a patient, who previously underwent scintigraphy with a 99mTc-tracer, and determined a concentration of 19.6 ± 0.5 ng L-1. The developed method has a high utility to characterize a range of Tc-based radiopharmaceuticals, to determine concentrations, purity, and degradation products in complex samples without the need to assess activity parameters of 99(m)Tc.

Capabilities of simultaneous 193 nm - LIBS/LA-ICP-MS imaging for microplastics characterization.

Microplastics (MPs) are currently one of the major environmental challenges within our society. With the awareness of the impact of MPs on the environment increasing over the last years, the need for increased monitoring as well as comprehensive analysis to better understand the fate and impact of MPs has become more and more important. A major aspect of MP characterization is the assignment of the polymer type of individual particles. Here, per- and poly-fluoroalkyl substances (PFAS), originating from fluor-containing polymers, have gained a lot of attention due to the severe environmental impact. Additionally, quantitative analysis of the metal content is of great interest in the field, since MPs are prone to either leaching (in)organic additives into the environment or taking up and accumulating hazardous components (e.g., heavy metals). In this work we demonstrate the capabilities of a simultaneous LIBS/LA-ICP-MS setup for the analysis of MPs. In the first part, we demonstrate the potential of targeted LIBS analysis for the imaging of fluor-containing polymers. Using a laser spot size of 5 µm combined with highly sensitive ICCD detection enables analysis of particles in the low µm range. In the second part we combine the polymer-identification capabilities of LIBS with the high sensitivity of ICP-MS to perform matrix-matched quantification of the metal content of individual MPs. In this case we use a spot size of 50 µm facilitating polymer classification with a broadband spectrometer, resulting in detection limits of 0.72 µg/g for Pb and 9.5 µg/g for Sn simultaneously measured using ICP-MS.

Species-dependent uptake of gadolinium in Chlamydomonas reinhardtii algae.

Single cell-inductively coupled plasma-mass spectrometry (sc-ICP-MS) was used in this study as a valuable tool to assess the species-dependent uptake of metallopharmaceuticals into algal cells. Chlamydomonas reinhardtii algae were incubated for 24 h with four Gadolinium-based contrast agents (GBCAs) and GdCl3. A species dependency towards the uptake of the tested Gd species was observed. Using single cell-ICP-MS, a Gd signal corresponding to single cell events was detected for GdCl3 and the linear GBCAs Omniscan® (Gadodiamide, Gd-DTPA-BMA) and Magnevist® (Gadodiamide, Gd-DTPA). For the macrocyclic complexes Dotarem® (Gadoteric acid, Gd-DOTA) and Gadovist® (Gadobutrol, Gd-BT-DO3A), no such Gd signal was visible. Total Gd analysis via ICP-MS confirmed the presence of Gd in the cells only after incubation with GdCl3 and the linear GBCAs, while only small amounts of Gd were detected for the incubations with macrocyclic GBCAs. Furthermore, the results showed that more Gd is bound to cell structures or macromolecules, while smaller amounts are present in the lysate. Using hydrophilic interaction liquid chromatography (HILIC)-ICP-MS, the soluble Gd species in the lysate were analyzed to determine if the initial Gd complexes were still intact. Surprisingly, no intact GBCAs were detected in the lysates of any incubation solution, possibly due to a change in Gd speciation. Further research is needed to assess which Gd species are present in the lysate, while "free" Gd ions or adducts with cell constituents are the most likely explanation. This study highlights the need for species-dependent investigation of elements in aquatic organisms. Moreover, the uptake of linear GBCAs and their species alteration raises the question of a potential accumulation of Gd in the food chain.

Single Cell-ICP-ToF-MS for the Multiplexed Determination of Proteins: Evaluation of the Cellular Stress Response.

An automated and straightforward detection and data treatment strategy for the determination of the protein relative concentration in individual human cells by single cell-inductively coupled plasma-time-of-flight mass spectrometry (sc-ICP-ToF-MS) is proposed. Metal nanocluster (NC)-labeled specific antibodies for the target proteins were employed, and ruthenium red (RR) staining, which binds to the cells surface, was used to determine the number of cell events as well as to evaluate the relative volume of the cells. As a proof of concept, the expression of hepcidin, metallothionein-2, and ferroportin employing specific antibodies labeled with IrNCs, PtNCs, and AuNCs, respectively, was investigated by sc-ICP-ToF-MS in human ARPE-19 cells. Taking into account that ARPE-19 cells are spherical in suspension and RR binds to the surface of the cells, the Ru intensity was related to the cell volume (i.e., the cell volume is directly proportional to (Ru intensity)3/2), making it possible to determine not only the mass of the target proteins in each individual cell but also the relative concentration. The proposed approach is of particular interest in comparing cell cultures subjected to different supplementations. ARPE-19 cell cultures under two stress conditions were compared: a hyperglycemic model and an oxidative stress model. The comparison of the control with treated cells shows not only the mass of analyzed species but also the relative changes in the cell volume and concentration of target proteins, clearly allowing the identification of subpopulations under the respective treatment.

Analysis of the elemental species-dependent uptake of lanthanide complexes in Arabidopsis thaliana plants by LA-ICP-MS.

Gadolinium-based contrast agents (GBCAs) are found increasingly in different water bodies, making the investigation of their uptake and distribution behavior in plants a matter of high interest to assess their potential effects on the environment. Depending on the used complexing agent, they are classified into linear or macrocyclic GBCAs, with macrocyclic complexes being more stable. In this study, by using TbCl3, Gd-DTPA-BMA, and Eu-DOTA as model compounds for ionic, linear, and macrocyclic lanthanide species, the elemental species-dependent uptake into leaves of Arabidopsis thaliana under identical biological conditions was studied. After growing for 14 days on medium containing the lanthanide species, the uptake of all studied compounds was confirmed by means of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Furthermore, the uptake rate of TbCl3 and the linear Gd-DTPA-BMA was similar, with Tb and Gd hotspots colocated in the areas of hydathodes and the trichomes of the leaves. In contrast, in the case of the macrocyclic Eu-DOTA, Eu was mainly located in the leaf veins. Additionally, Eu was colocated with Tb and Gd in the hydathode at the tip of the leave. Removal of the lanthanide species from the medium led to a decrease in signal intensities, indicating their subsequent release to some extent. However, seven days after the removal, depositions of Eu, Gd, and Tb were still present in the same areas of the leaves as before, showing that complete elimination was not achieved after this period of time. Overall, more Eu was present in the leaves compared to Gd and Tb, which can be explained by the high stability of the Eu-DOTA complex, potentially leading to a higher transport rate into the leaves, whereas TbCl3 and Gd-DTPA-BMA could interact with the roots, reducing their mobility.

Towards Automated and High-Throughput Quantitative Sizing and Isotopic Analysis of Nanoparticles via Single Particle-ICP-TOF-MS.

The work described herein assesses the ability to characterize gold nanoparticles (Au NPs) of 50 and 100 nm, as well as 60 nm silver shelled gold core nanospheres (Au/Ag NPs), for their mass, respective size, and isotopic composition in an automated and unattended fashion. Here, an innovative autosampler was employed to mix and transport the blanks, standards, and samples into a high-efficiency single particle (SP) introduction system for subsequent analysis by inductively coupled plasma-time of flight-mass spectrometry (ICP-TOF-MS). Optimized NP transport efficiency into the ICP-TOF-MS was determined to be >80%. This combination, SP-ICP-TOF-MS, allowed for high-throughput sample analysis. Specifically, 50 total samples (including blanks/standards) were analyzed over 8 h, to provide an accurate characterization of the NPs. This methodology was implemented over the course of 5 days to assess its long-term reproducibility. Impressively, the in-run and day-to-day variation of sample transport is assessed to be 3.54 and 9.52% relative standard deviation (%RSD), respectively. The determination of Au NP size and concentration was of <5% relative difference from the certified values over these time periods. Isotopic characterization of the 107Ag/109Ag particles (n = 132,630) over the course of the measurements was determined to be 1.0788 ± 0.0030 with high accuracy (0.23% relative difference) when compared to the multi-collector-ICP-MS determination.

Determination and localization of specific proteins in individual ARPE-19 cells by single cell and laser ablation ICP-MS using iridium nanoclusters as label.

Single cell-inductively coupled plasma-mass spectrometry (sc-ICP-MS) and laser ablation (LA)-ICP-MS have been complementary employed to develop a comprehensive study of APOE and claudin-1 expression in ARPE-19 cells submitted to a glucose treatment (100 mM, 48 h) that induces oxidative stress conditions. Results were compared with control cells. The determination of the two proteins by ICP-MS was sequentially carried out using specific immunoprobes labelled with IrNCs that offer a huge amplification (1760 ± 90 atoms of Ir on average). A novel sample introduction system, the microFAST Single Cell set-up, was employed for sc-ICP-MS analysis. This introduction system resulted in a cellular transport efficiency of 85 ± 9% for ARPE-19 cells (91 ± 5% using a PtNPs standard). After the proper immunocytochemistry protocol with the specific IrNCs immunoprobes in cell suspensions (sc-ICP-MS), the mass of APOE and claudin-1 in individual ARPE-19 cells was obtained. Average detection limits per cell by sc-ICP-MS were 0.02 fg of APOE and 3 ag of claudin-1. The results of sample analyses obtained by sc-ICP-MS were validated with commercial ELISA kits. The distribution of both target proteins in individual cells (fixated in the chamber wall) was unveiled by LA-ICP-MS. The high amplification provided by the IrNCs immunoprobes allowed the identification of APOE and claudin-1 within individual ARPE-19 cells. High resolution images were obtained using a laser spot of 2 × 2 µm.

Determination of fluorine distribution in shark teeth by laser-induced breakdown spectroscopy.

Quantifying the chemical composition of fast-growing hard tissues in the environment can shed valuable information in terms of understanding ecosystems both prehistoric and current. Changes in chemical composition can be correlated with environmental conditions and can provide information about the organism's life. Sharks can lose 0.1 to 1.1 teeth/day, depending on species, which offers a unique opportunity to record environmental changes over a short duration of time. Shark teeth contain a biomineral phase that is made up of fluorapatite [Ca5(PO4)3F], and the F distribution within the tooth can be correlated to tooth hardness. Typically, this is determined by bulk acid digestion, energy-dispersive X-ray spectroscopy (EDS), or wavelength-dispersive spectroscopy. Here we present laser-induced breakdown spectroscopy (LIBS) as an alternative and faster approach for determining F distribution within shark teeth. Using a two-volume laser ablation chamber (TwoVol3) with innovative embedded collection optics for LIBS, shark teeth were investigated from sand tiger (Carcharias Taurus), tiger (Galeocerdo Cuvier), and hammerhead sharks (Sphyrnidae). Fluorine distribution was mapped using the CaF 603 nm band (CaF, Β 2Σ+ → X 2Σ+) and quantified using apatite reference materials. In addition, F measurements were cross referenced with EDS analyses to validate the findings. Distributions of F (603 nm), Na (589 nm), and H (656 nm) within the tooth correlate well with the expected biomineral composition and expected tooth hardness. This rapid methodology could transform the current means of determining F distribution, particularly when large sample specimens (350 mm2, presented here) and large quantities of specimens are of interest.

Fast and automated monitoring of gadolinium-based contrast agents in surface waters.

Gadolinium-based contrast agents (GBCAs) are frequently used for magnetic resonance imaging to improve image contrast. These inert complexes are excreted unmetabolized from the human body and pass through wastewater treatment plants almost unaffected, leading to a significant release of anthropogenic Gd into the environment. However, long-term ecotoxicological effects of GBCAs are mainly unknown and thus powerful methods of speciation analysis are required to monitor their distribution and fate in aquatic systems. In this work, a rapid and efficient monitoring method was developed utilizing a fully automated single platform system for total metal analysis and syringe-driven chromatography in combination with inductively coupled plasma-mass spectrometry (ICP-MS). An anion-exchange chromatography (IC) method was developed and applied to achieve a rapid separation and sensitive detection of the five complexes Gd-HP-DO3A, Gd-BT-DO3A, Gd-DOTA, Gd-DTPA, and Gd-BOPTA that are commonly administered in the European Union. Furthermore, the use of an automated inline-dilution function allowed a fast-external calibration from single stock standards. A chromatographic run time of less than 2 min and species-specific detection limits between 11 and 19 pmol L-1 on a quadrupole ICP-MS proved to be competitive compared to previously published methods, but without the use of aerosol desolvation and/or sector field ICP-MS to enhance sensitivity. The automated IC-ICP-MS method was applied for quantitative GBCA monitoring in a multitude of surface water samples that were obtained in the German state of North Rhine-Westphalia. The complexes Gd-HP-DO3A, Gd-BT-DO3A, and Gd-DOTA, were detected and quantified. In addition, the occurrence of an unidentified Gd species was observed for one of the sampled river systems.

A fast and automated separation and quantification method for bromine speciation analyzing bromide and 5-bromo-2'-deoxyuridine in enzymatically digested DNA samples via ion chromatography-inductively coupled plasma-mass spectrometry.

A fast and automated separation and quantification method for bromide and the artificial nucleoside 5-bromo-2'-deoxyuridine (5-BrdU) via hyphenation of ion exchange chromatography (IC) and inductively coupled plasma-mass spectrometry (ICP-MS) is presented. The analysis of these two species is relevant to monitor the transfer of electrons along metal-mediated DNA base pairs. Charge transfer in DNA is of high interest for the implementation in nanotechnological applications like molecular wires. 5-BrdU as part of the DNA sequence releases bromide upon one electron reduction after efficient electron transfer along the DNA. The concentrations of 5-BrdU and bromide in enzymatically digested DNA samples can therefore be used as a marker for the efficiency of electron transfer along the DNA helix. A large number of samples was analyzed using an automated IC system. This platform enables time-efficient external calibration by inline dilution of a stock solution. Due to the fast separation of the two bromine species in less than 90 s, the developed method is suitable for screening applications with a multitude of samples. Despite the isobaric interferences and a low degree of ionization for bromine detection via ICP-MS the method has a limit of detection (LOD) of 30 ng/L which is approximately an order of magnitude lower than a comparable method using reversed phase high performance liquid chromatography (RP-HPLC) and ICP-MS.

Automated Chiral Analysis of Amino Acids Based on Chiral Derivatization and Trapped Ion Mobility-Mass Spectrometry.

A fast and fully automated method for chiral analysis has been developed by combining a chiral derivatization approach with high-resolution trapped ion mobility separation. Although the presented approach can be potentially applied to diverse types of chiral compounds, several benchmark amino acids were used as model compounds, focusing on the smallest amino acid alanine. An autosampler with an integrated chromatography system was used for inline chiral derivatization with (S)-naproxen chloride and subsequent preseparation. Afterwards, derivatized amino acids were directly introduced into the electrospray interface of a trapped ion mobility-mass spectrometer for rapid diastereomer separation in the gas phase. This unique combination of preseparation and trapped ion mobility spectrometry separation in the negative ion mode enabled rapid chiral analysis within 3 min per sample. Furthermore, the diastereomer separation proved to be independent of alkali salts or other metal ions, offering robustness with regard to samples containing high amounts of salts. Highly sensitive detection of amino acid diastereomers was possible down to the lower nanomolar concentration range, and enantiomeric ratios could be readily determined from the recorded mobilograms with excellent reproducibility and precision. To demonstrate the general applicability of our method, alanine and other amino acids were analyzed from soy sauces and seasonings, which revealed extraordinarily high d-Ala contents of up to 99% in all samples.

LC-ICP-MS method for the determination of "extractable copper" in serum.

Copper is an essential element for biological functions within humans and animals. There are several known diseases associated with Cu deficiency or overload, such as Menkes disease and Wilson disease, respectively. A common clinical method for determining extractable Cu levels in serum, which is thought to be potentially dangerous if in excess, is to subtract the value of tightly incorporated Cu in ceruloplasmin from total serum Cu. In this work, an automated sample preparation and liquid chromatography (LC) system was combined with inductively coupled plasma-mass spectrometry (ICP-MS) to determine bound Cu and extractable Cu in serum. This LC-ICP-MS method took 250 s for sample preparation and analysis, followed by a column recondition/system reset, thus, a 6 minute sample-to-sample time including sample preparation. The method was validated using serum collected from either control (Atp7b+/-) or Wilson disease rats (Atp7b-/-). The extractable Cu was found to be 4.0 ± 2.3 µM Cu in healthy control rats, but 2.1 ± 0.6 µM Cu in healthy Wilson rats, and 27 ± 16 µM Cu in diseased Wilson rats, respectively. In addition, the extractable Cu/bound Cu ratio was found to be 6.4 ± 3.5%, 38 ± 29%, and 34 ± 22%, respectively. These results suggest that the developed method could be of diagnostic value for Wilson disease, and possibly other copper related diseases.

Coupling of Laser Ablation and the Liquid Sampling-Atmospheric Pressure Glow Discharge Plasma for Simultaneous, Comprehensive Mapping: Elemental, Molecular, and Spatial Analysis.

The spatial distributions of elemental and molecular species are vital pieces of information for a broad number of applications such as material development and bio/environmental analysis. There is currently no single analytical method that can simultaneously acquire elemental, molecular, and spatial information from a single sample. This paper presents the coupling of an NWR213 laser ablation (LA) system to the liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma for combined atomic and molecular (CAM) analysis. The work demonstrates a fundamental balance that must be considered between the extent of fragmentation of molecules and ionization of atoms for CAM analysis. Detailed studies showed that the interelectrode gap to be a critical parameter for controlling the ionization efficiency of atomic and molecular species. Utilizing Design-of-Experiment (DoE) procedures, the discharge current was also found to be a significant parameter to control. Elemental lead, caffeine, and simultaneous lead and caffeine analysis via LA-LS-APGD-MS was made possible through improved understanding of the influence of plasma parameters on the product mass spectra of laser-ablated particles. Finally, a chemical map of elemental lead and molecular caffeine, from lead nitrate and caffeine residues, was generated, demonstrating the comprehensive mapping capabilities of LA-LS-APGD-MS. The practical relevance of the capabilities is demonstrated by mapping glutamic acid from a cryosectioned chicken breast with a thallium spike deposited within the tissue. It is believed that the LA-LS-APGD-MS could be a valuable methodology for the simultaneous mapping of elemental and molecular species from a variety of samples.

Evaluation and Specifications for In-Line Uranium Separations Using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) Detection for Trace Elemental Analysis.

Automated introduction platforms integrated with inductively coupled plasma optical emission spectroscopy (ICP-OES) systems are continuously being improved. Expanding on the introduction systems, a newly developed automated ion chromatography system was explored for performing rapid in-line separations coupled to ICP-OES for the detection of trace elements in uranium. Trace elements are separated from a uranium material and the analytes are directed into the ICP-OES for subsequent detection. Detection parameters such as exposure time frequency, wavelength selection, and settling times were explored to gain insight on optimal detection schemes for in-line trace elemental analysis. The methodology was applied in the analysis of a uranium oxide (U3O8) certified reference material, CRM-124. It was found here that the sensitivity and uncertainty of the technique are greatly affected by how the ICP-OES is employed to collect data. Overall it was determined that faster exposure replicates can provide greater peak resolution with higher fidelity measurements but are limited with respect to the total analysis time (i.e., limited in detection timely separations). Zeta scores, which combine accuracy and uncertainty of certified values and experimental values, were used to validate the ICP-OES modes of operation.

Trace elemental analysis of bulk uranium materials using an inline automated sample preparation technique for ICP-OES.

An automated inline method for the separation of trace element impurities from uranium matrices using a 200 µL column packed with UTEVA resin is presented here utilizing an Elemental Scientific, Inc. prepFAST IC in combination with a Perkin Elmer Avio 500 ICP-OES. This method reduces human exposure to highly concentrated acids and uranium-rich samples by automating the chemistry and introduction to the ICP. Calibration standards were prepared using inline dilutions requiring a single stock standard. The separation of trace elements from uranium matrices requires samples to be prepared in 8 M HNO3, which can be detrimental to the ICP, thus a post-column dilution step was employed to dilute the eluent matrix to 4 M HNO3. The method was optimized for a sample-to-sample time of < 9 min and monitored 21 elements in total. Proof of concept experiments for 1 µg mL-1 trace elements spiked into 0.1 vol%, 0.5 vol%, and 1.0 vol% uranium matrices resulted in < 5% relative difference and < 10% relative standard deviation for triplicate measurements of each uranium matrix analyzed. Inline dilutions (pre-column) of 2 vol% uranium + 20 µg mL-1 trace elements resulted in accurate and precise measurements using dilution factors of 2×, 4×, 5×, and 20×. Method detection limits for the 21 elements (Al, B, Ba, Be, Cd, Ca, Co, Cu, Fe, Li, Pb, Mg, Mn, Ni, K, Sr, Na, V, Zn, Zr, and U) analyzed for ranged from 7 to 326 ng mL-1 for 70 µL volume injections.

An automated micro-separation system for the chromatographic removal of uranium matrix for trace element analysis by ICP-OES.

An automated, miniaturized, off-line separation technique is presented here using an Elemental Scientific Inc. microFAST MC system with UTEVA resin to extract the uranium matrix from its trace element impurities in aqueous media. The collected fractions were analyzed for ~ 30 trace elements using inductively coupled plasma - optical emission spectroscopy. Ten replicate samples were processed with a single column resulting in precision ranging from 3.3% to 6.2% relative standard deviation with regards to the trace element recoveries. Accuracy, with respect to trace element concentrations in the U3O8 Certified Reference Material 124-1, resulted in an average of 13.9% relative deviation while accuracy to the Canadian U3O8 reference material, CUP-2, resulted in an average relative deviation of 8.6%. The total separation time of this automated process was reduced to ~ 30 min per sample while employing a 0.5 mL UTEVA chromatographic resin bed and 2.5 mg of uranium.

A study on the in vitro percutaneous absorption of silver nanoparticles in combination with aluminum chloride, methyl paraben or di-n-butyl phthalate.

Some reports indicate that the silver released from dermally applied products containing silver nanoparticles (AgNP) (e.g. wound dressings or cosmetics) can penetrate the skin, particularly if damaged. AgNP were also shown to have cytotoxic and genotoxic activity. In the present study percutaneous absorption of AgNP of two different nominal sizes (Ag15nm or Ag45nm by STEM) and surface modification, i.e. citrate or PEG stabilized nanoparticles, in combination with cosmetic ingredients, i.e. aluminum chloride (AlCl3), methyl paraben (MPB), or di-n-butyl phthalate (DBPH) was assessed using in vitro model based on dermatomed pig skin. The inductively coupled plasma mass spectrometry (ICP-MS) measurements after 24h in receptor fluid indicated low, but detectable silver absorption and no statistically significant differences in the penetration between the 4 types of AgNP studied at 47, 470 or 750µg/ml. Similarly, no significant differences were observed for silver penetration when the AgNP were used in combinations with AlCl3 (500µM), MPB (1250µM) or DBPH (35µM). The measured highest amount of Ag that penetrated was 0.45ng/cm2 (0.365-0.974ng/cm2) for PEG stabilized Ag15nm+MPB.

Analytical method for total chromium and nickel in urine using an inductively coupled plasma-universal cell technology-mass spectrometer (ICP-UCT-MS) in kinetic energy discrimination (KED) mode.

Biomonitoring and emergency response measurements are an important aspect of the Division of Laboratory Sciences of the National Center for Environmental Health, Centers for Disease Control and Prevention (CDC). The continuing advancement in instrumentation allows for enhancements to existing analytical methods. Prior to this work, chromium and nickel were analyzed on a sector field inductively coupled plasma-mass spectrometer (SF-ICP-MS). This type of instrumentation provides the necessary sensitivity, selectivity, accuracy, and precision but due to the higher complexity of instrumentation and operation, it is not preferred for routine high throughput biomonitoring needs. Instead a quadrupole based method has been developed on a PerkinElmer NexION™ 300D ICP-MS. The instrument is operated using 6.0 mL min-1 helium as the collision cell gas and in kinetic energy discrimination mode, interferences are successfully removed for the analysis of 52Cr (40Ar12C and 35Cl16O1H) and 60Ni (44Ca16O). The limits of detection are 0.162 µg L-1 Cr and 0.248 µg L-1 Ni. Method accuracy using NIST SRM 2668 level 1 (1.08 µg L-1 Cr and 2.31µg L-1 Ni) and level 2 (27.7 µg L-1 Cr and 115 µg L-1 Ni) was within the 95% confidence intervals reported in the NIST certificate. Among-run precision is less than 10% RSDs (N = 20) for in house quality control and NIST SRM urine samples. While the limits of detection (LOD) for the new quadrupole ICP-UCT-MS with KED method are similar to the SF-ICP-MS method, better measurement precision is observed for the quadrupole method. The new method presented provides fast, accurate, and more precise results on a less complex and more robust ICP-MS platform.

Liquid sampling-atmospheric pressure glow discharge (LS-APGD) ionization source for elemental mass spectrometry: preliminary parametric evaluation and figures of merit.

A new, low-power ionization source for the elemental analysis of aqueous solutions has recently been described. The liquid sampling-atmospheric pressure glow discharge (LS-APGD) source operates at relatively low currents (<20 mA) and solution flow rates (<50 µL min(-1)), yielding a relatively simple alternative for atomic mass spectrometry applications. The LS-APGD has been interfaced to what is otherwise an organic, LC-MS mass analyzer, the Thermo Scientific Exactive Orbitrap without any modifications, other than removing the electrospray ionization source supplied with that instrument. A glow discharge is initiated between the surface of the test solution exiting a glass capillary and a metallic counter electrode mounted at a 90° angle and separated by a distance of ~5 mm. As with any plasma-based ionization source, there are key discharge operation and ion sampling parameters that affect the intensity and composition of the derived mass spectra, including signal-to-background ratios. We describe here a preliminary parametric evaluation of the roles of discharge current, solution flow rate, argon sheath gas flow rate, and ion sampling distance as they apply on this mass analyzer system. A cursive evaluation of potential matrix effects due to the presence of easily ionized elements indicate that sodium concentrations of up to 50 µg mL(-1) generally cause suppressions of less than 50%, dependant upon the analyte species. Based on the results of this series of studies, preliminary limits of detection (LOD) have been established through the generation of calibration functions. While solution-based concentration LOD levels of 0.02-2 µg mL(-1) are not impressive on the surface, the fact that they are determined via discrete 5 µL injections leads to mass-based detection limits at picogram to single-nanogram levels. The overhead costs associated with source operation (10 W d.c. power, solution flow rates of <50 µL min(-1), and gas flow rates <10 mL min(-1)) are very attractive. While further optimization in the source design is suggested here, it is believed that the LS-APGD ion source may present a practical alternative to inductively coupled plasma sources typically employed in elemental mass spectrometry.