•First report on levels of metals and metalloids in APM collected simultaneously in two cities; Buenos Aires and Tokyo.•The elemental distribution within six size fractions μm was assessed in the Tokyo samples.•Temporal variability was studied in the Buenos Aires samples.•Potential contributing sources using groups of specific elements as chemical markers is obtained.In the framework of a collaborative project, a comprehensive chemical characterisation of urban fine aerosols collected in the antipodal cities of Buenos Aires and Tokyo was performed. Twenty three elements namely, Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Sb, Se, Ti, V and Zn were determined by plasma-based techniques after microwave-assisted digestion of the airborne particulate matter. An acid mixture containing HNO3, H2O2 and HF (6:1:3) was used for sample treatment. In samples collected in Buenos Aires concentrations varied between 0.1 μg g− 1 equivalent to 0.001 ng m− 3 (Be) and 36,000 μg g− 1 equivalent to 480 ng m− 3 (Na) while in Tokyo minimum and maximum determined concentrations varied from 0.6 μg g− 1 equivalent to 0.01 ng m− 3 (Co) to 52,000 μg g− 1 equivalent to 1200 ng m− 3 (Na). For both cities, significantly high enrichment factors (EFs > 100) were identified for Se > Sb > Cd > Zn > Pb > As, indicating the anthropogenic origin of these elements.

To investigate elemental fractionation during laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) we measured mass fractions of ablated particles and chemical composition of ablated particles in this study. Temporal changes of fractionation indexes (FIs) were investigated under laser defocus conditions which caused a large variation of size distribution of abated particles. It was a useful technique for understanding the relationship between temporal changes of FIs and the size of ablated particles. Ablated particles were fractionated by aerodynamic diameters (<0.06, 0.06–0.22, 0.22–2.2, and >2.2 μm) with a low-pressure impactor and were digested with HNO3 and HF; then As, Rb, Rh, La, Gd, Yb, W, Re, and Th were measured by ICPMS. Under 0.5 mm defocus and 1.0 mm defocus conditions, the mass fractions (ablated particle mass at 1–5 min divided by that at 0–1 min) of ablated particles larger than 0.22 μm were larger than the mass fractions of ablated particles smaller than 0.22 μm. Volatile elements such as As and Rb were enriched in particles smaller than 0.22 μm, owing to the large aspect ratio of the crater under defocus conditions. However, the magnitude of the enrichment for volatile elements did not change as ablation progressed. Therefore, we concluded that large particles could not be decomposed completely in the ICP and the FI peak observed at 2–3 min was caused by changes in elemental behavior due to changes in ablated particles larger than 0.22 μm.

Particles sampled by means of laser ablation in liquid (LAL) can be analyzed by inductively coupled plasma mass spectrometry (ICPMS) after acid digestion or slurry nebulization. The LAL sampling process is simple, and a standard solution can be used for calibration. In this study, we investigated elemental fractionation during LAL by using a standard glass reference material, NIST 610. NIST 610 was placed in an open-top chamber, and ultrapure water was added until the surface of the glass was 3 mm below the water surface. LAL sampling was carried out in line-scanning mode. The LAL-sampled particles were divided into two size classes by filtration through a polycarbonate filter: particles larger than 0.4 μm were collected on the filter, and particles smaller than 0.4 μm passed into the filtrate. Both sizes of particles were digested with acid and analyzed by ICPMS. Volatile elements were enriched in the smaller particles and depleted in the larger particles. That is, elemental fractionation related to the size of the ablated particles was observed during the LAL-sampling process. When the LAL-sampled particles were introduced into the ICP, the large particles did not decompose completely. Volatile elements in the larger particles were vaporized more easily than calcium. Therefore, positive elemental fractionation was observed when the LAL-sampled particles were analyzed by slurry nebulization ICPMS. Comparison between slurry nebulization and acid digestion revealed that particle size-related elemental fractionation in the ICP was larger than that observed during LAL sampling.

In inductively coupled plasma (ICP) mass spectrometry, signal enhancement by co-existing carbon results from multiple factors. To elucidate the signal enhancement factors, we compared the effects of co-existing carbon and co-existing bromine, which have similar ionization energies (C, 11.26 eV; Br, 11.81 eV). We eliminated the effect of sample introduction efficiency changes, which are considered to be one reason for signal enhancement, by using two nebulizers. The intensities of the P, I, S, As, Se and B signals were enhanced when a multi-element solution was introduced into the ICP from one nebulizer and a carbon solution was introduced from the other. No signal enhancement was observed by co-existing bromine. We focused on the bond energies of the oxides as a possible explanation for the difference between the results for carbon and bromine. Carbon oxide has a higher bond energy than bromine oxide, and therefore carbon reduces analyte oxides more readily than bromine does. We also considered the effects of the bond energies of the analyte oxides, as well as the effects of the degree of analyte ionization in the ICP, on signal enhancement. Signal enhancement was observed for analytes that were less than 60% ionized in the ICP and whose oxide bond energies exceeded 450 kJ mol−1. Iodine was an exception; signal enhancement was observed for I (ionization degree, 29.85%), even though the bond energy of iodine oxide is only 240 kJ mol−1. Therefore, charge transfer could not be eliminated as a cause of signal enhancement.

The organic Se compounds (particularly selenomethionine [SeMet]) in plants and yeasts are very effective chemoprotectants for mammalian cancer. To characterize the dynamics of selenomethionine utilization pathways, we intravenously injected 82Se-enriched SeMet into mice under different nutritional states (Se-adequate and Se-deficient mice) and then measured their endogenous and exogenous 82Se levels. Furthermore, we quantified Se compounds and selenoproteins in liver, kidneys, plasma, and urine. The average recoveries of exogenous 82Se from solid tissues, urine, and feces were 81% for Se-adequate mice and 84% for Se-deficient mice. Exogenous 82Se was distributed in the hepatic and renal cytosols as cellular glutathione peroxidase (cGPx), selenosugar, and SeMet within 1 h after injection. Synthesis of cGPx was maintained until 72 h after injection, regardless of the Se nutritional status. Whereas plasma levels of exogenous 82Se as selenoprotein P (Sel-P) peaked at 6 h after injection, those of Se-containing albumin (SeAlb), extracellular GPx, and SeMet peaked at 1 h after injection. These results suggest three Se transport pathways in mice injected with SeMet: SeAlb (within 1 h after injection); SeMet (from 1 to 72 h after injection); and Sel-P (from 6 to 72 h after injection). The amount of Sel-P in Se-deficient mice was 1.5 times that of Se-adequate mice, and this increase was much larger than Se-containing compounds other than Sel-P. Our results indicate that Sel-P has an important role in Se transport when the nutritional supply of Se is insufficient.

A new calibration system for real-time determination of trace elements in airborne particulates was developed. Airborne particulates were directly introduced into an inductively coupled plasma mass spectrometer, and the concentrations of 15 trace elements were determined by means of an external calibration method. External standard solutions were nebulized by an ultrasonic nebulizer (USN) coupled with a desolvation system, and the resulting aerosol was introduced into the plasma. The efficiency of sample introduction via the USN was calculated by two methods: (1) the introduction of a Cr standard solution via the USN was compared with introduction of a Cr(CO)6 standard gas via a standard gas generator and (2) the aerosol generated by the USN was trapped on filters and then analyzed. The Cr introduction efficiencies obtained by the two methods were the same, and the introduction efficiencies of the other elements were equal to the introduction efficiency of Cr. Our results indicated that our calibration method for introduction efficiency worked well for the 15 elements (Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Mo, Sn, Sb, Ba, Tl and Pb). The real-time data and the filter-collection data agreed well for elements with low-melting oxides (V, Co, As, Mo, Sb, Tl, and Pb). In contrast, the real-time data were smaller than the filter-collection data for elements with high-melting oxides (Ti, Cr, Mn, Ni, Cu, Zn, Sn, and Ba). This result implies that the oxides of these 8 elements were not completely fused, vaporized, atomized, and ionized in the initial radiation zone of the inductively coupled plasma. However, quantitative real-time monitoring can be realized after correction for the element recoveries which can be calculated from the ratio of real-time data/filter-collection data.Highlights► APs were directly introduced into ICP-MS and real-time analysis was performed. ► The real-time data were calibrated by a multi-element standard solution from USN. ► During real-time analysis, APs simultaneously collected on a filter were analyzed. ► Element recovery was calculated by the real-time data/the filter-collection data. ► Quantitative real-time data could be realized by correcting the element recovery.

Concentrations of 14 rare earth elements (REEs) in six size classes of airborne particulate matter (APM) (<0.43, 0.43–0.65, 0.65–1.1, 1.1–2.1, 2.1–11, and >11 μm) and in two different phases (suspended particulate and dissolved) in rainwater were determined by inductively coupled plasma mass spectrometry (ICP-MS). Positive Eu and Tb anomalies were observed in size-classified APM. These anomalies may be due to large emissions of Eu and Tb to the atmosphere resulting from the recent change in Japan from the use of cathode-ray tubes to plasma displays in television sets (Eu and Tb) and from the widespread use of magneto-optical disks (Tb). The light REEs were enriched in fine APM particles (diameter < 1.1 μm). Because compositions of La/Ce/Sm in fine APM (diameter < 1.1 μm) were similar to those in automobile catalyst, the light REE enrichment was attributed to automobile emissions. In contrast, the REE distribution pattern in the suspended particulate phase in rainwater was similar to that in coarse APM (diameter > 2.1 μm), and a positive Tb anomaly was observed, suggesting that coarse particles easily become trapped in rain droplets. A negative Eu anomaly was observed in the dissolved phase in rainwater, but not in APM or in the suspended particulate phase in rainwater. Unlike other REEs, Eu can exist as both bivalent and trivalent ions in nature, and Eu-selective dissolution from or adsorption onto the trapped particles of Eu might account for the negative anomaly. These results show that atmospheric REE cycling is affected by the physico-chemical properties of APM.

The selenoprotein, cellular glutathione peroxidase (cGPx), has an important role in protecting organisms from oxidative damage through reducing levels of harmful peroxides. The liver and kidney in particular, have important roles in selenium (Se) metabolism and Se is excreted predominantly in urine and feces. In order to characterize the dynamics of these pathways we have measured the time-dependent changes in the quantities of hepatic, renal, urinary, and fecal Se species in mice fed Se-adequate and Se-deficient diets after injection of 82Se-enriched selenite. Exogenous 82Se was transformed to cGPx in both the liver and kidney within 1 h after injection and the synthesis of cGPx decreased 1 to 6 h and continued at a constant level from 6 to 72 h after injection. The total amount of Se associated with cGPx in mice fed Se-deficient diets was found to be less than in mice fed Se-adequate diets. This finding indicated that cGPx synthesis was suppressed under Se-deficient conditions and did not recover with selenite injection. Excess Se was associated with selenosugar in liver and transported to the kidney within 1 h after injection, and then excreted in urine and feces within 6 h after injection. Any excess amount of Se was excreted mainly as a selenosugar in urine.

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Airborne particulate matter (APM) is a major air pollutant, and the effect on human health of fine APM (PM2.5) deposited deep inside the lungs has recently become a serious concern. Moreover, soluble constituents may leach from APM, and intensify some health disorders. To identify the soluble chemical constituents of APM, size-classified APM was sampled in central Tokyo, and the elemental compositions of the water-soluble, acid-soluble and insoluble fractions were investigated. The extraction procedure was validated by calculating the mass balance of soluble and insoluble fractions of a standard APM reference material (NIST SRM 1648). Among the major elements, Fe and Ti in APM of all size classes and K in coarse APM were distributed primarily in the insoluble fraction and were inferred to be present as oxides or silicates, whereas Na and Mg in all size classes and K in fine APM were primarily in the water-soluble fraction and were inferred to be have originated mainly from sea salt. Among the trace elements, Zn and Cd in the fine APM (d < 2 µm) had large enrichment factors, indicating an anthropogenic origin, and were distributed primarily in the water-soluble fraction. When fine anthropogenic APM enters into the lungs, leached toxic elements, such as Cd, may adversely affect health. The higher the bonding energy of the monoxide molecule of the element was, the higher its distribution ratio was in the water-soluble fraction. Therefore, many metallic elements in APM were inferred to be present as oxygen-bonded compounds.

Se-containing proteins play an important role in human metabolic processes such as antioxidant action. However, speciation analysis of Se-containing proteins in biological samples is challenging because of their small amounts. In order to determine selenoprotein P (Sel-P) in human plasma, separation performance was compared between size exclusion chromatography and affinity chromatography. It was found that affinity chromatography showed better separation performance for Sel-P. Micro-affinity chromatography coupled with low flow ICP-MS was developed, which enabled separation analysis of Sel-P in sub-μl samples. Standard solution flow rate ranges for low sample consumption and total consumption nebulizers were investigated. Moreover, the stability analysis for each nebulizer with the change in composition of the mobile phase was investigated. Finally, using the developed micro-affinity chromatography coupled with the low flow ICP-MS, Sel-P and the other Se-containing proteins in sub-μl samples of human plasma were determined.

APM was collected and trace elements existing in the particles were monitored since May 1995 in this study. APM sample was collected separately by size (d < 2 μm, 2–11 μm and >11 μm) on the roof of the university building (45 m above ground) in the campus of Faculty of Science and Engineering, Chuo University, Tokyo, Japan, using an Anderson low volume air sampler. The collected sample was digested by HNO3, H2O2 and HF using a microwave oven, and major elements (Na, Mg, Al, K, Ca and Fe) were measured by ICP-AES, and trace elements (Li, Be, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sb, Ba and Pb) were measured by ICP-MS. It was observed that the APM concentration was higher between the winter and the spring, compared to during the summer. The enrichment factor was calculated for each element in each set of APM (d < 2 μm, 2–11 μm and >11 μm). Seasonal trends of enrichment factors were examined, and the elements were classified into 3 groups according to the common seasonal behavior. It is likely that the elements in the same group have common origins. Toxic pollutant elements (Sb, Se, Cd, Pb and As) were found in small particles with d of <2 μm in concentrated levels. Antimony (Sb) had the highest enrichment factor, and the results suggested that Sb level in APM was extremely high. The origins of Sb were sought, and wastes from plastic incineration and brake pad wears of automobiles were suspected. Each set of APM (d < 2 μm, 2–11 μm and >11 μm) was classified by the shape, and the shape-dependent constituents of a single APM particle were quantitatively measured by SEM-EDX. High concentration of Sb was found in APM <2 μm and square particles. Particles less than 2 μm and square shaped particles were major particles produced by actual car braking experiments. From these experimental results it was concluded that the source of Sb in squared APM <2 μm is considered to be from brake pad wear.

A sensitive and robust method for the determination of five inorganic and organic Se species in human urine by reversed-phase liquid chromatography with mixed ion-pair reagents coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) is described in this paper. A good separation for anionic, cationic and neutral Se species, namely selenate [Se(VI)], selenourea (SeUr), selenomethionine (SeMet), selenoethionine (SeEt), and trimethylselenonium ion (TMSe+), was achieved within 15 min on a LiChrosorb RP 18 reversed-phase column by using mixed ion-pair reagents of 2.5 mM sodium 1-butanesulfonate and 8 mM tetramethylammonium hydroxide, with isocratic elution at a flow rate of 1.0 mL min−1. The detection limits of the five Se species obtained by HPLC-ICP-MS ranged from 0.6 to 1.5 ng Se mL−1 using an injection volume of 20 µL. It is noteworthy that the urine sample can be directly injected into the analytical system without any pre-treatment, except a filtration with a 0.45 µm membrane filter, and that the determination of Se species was free from chloride-induced matrix interference. In addition, no serious deterioration in column performance or decrease in the sensitivity of ICP-MS was observed for the experimental period of three months. In Japanese urine samples, no detectable SeMet, SeUr, and SeEt could be found, even if the total Se concentration was higher than 100 ng Se mL−1. On the contrary, TMSe+ and two unknown Se species (U1 and U2) were detected in the urine. The major unknown, U1, was found in all of the measured urine samples, suggesting that it might be one of the important Se metabolites.

The effect of laser defocusing on analytical performance of laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) was studied by varying laser focus conditions with respect to the surface of a low-alloy steel and a powdered sediment pellet. Laser-induced plasma (LIP) and LA-ICP-AES emission signals and LIP excitation temperatures (LIP Tex) were determined and compared for different laser defocus conditions. LIP Fe and LA-ICP-AES Fe emission signals and LIP Tex decreased when the laser was defocused for the low-alloy steel. On the other hand, when the sediment pellet was ablated, LIP Tex decreased when the laser was defocused. However, LA-ICP-AES Fe emission signals increased at first, then decreased when the laser was defocused more. It was concluded that LIP Tex and LIP and LA-ICP-AES Fe emission signals are dependent on laser shot conditions (focus–defocus), and are also dependent on sample type (texture, mineralogy, hardness, conductivity and heat capacity).

In this work, a complexation effect of Sb compounds with citric acid was observed using electrospray mass spectrometry (ES-MS). It was found that both Sb(III) and Sb(V) could form complexes readily with citric acid in an aqueous solution at room temperature. These complexes were found to be very stable in various matrices (moat water and aqueous extracts of airborne particulate matter), therefore, a novel HPLC-ICP-MS analytical method for the speciation of Sb(III) and Sb(V) in environmental samples was developed by using the observed complexation effect. Sb(III)- and Sb(V)-citrate complexes were separated on a PRP-X100 anion-exchange column with 10 mmol l−1 EDTA–1 mmol l−1 phthalic acid (pH 4.5) as a mobile phase. All complexes were retained on the separation column, and none of them eluted in the solvent front. Low detection limits of 0.05 µg l−1 and 0.07 µg l−1 were achieved for Sb(III) and Sb(V), respectively. The calibration curves were linear over the range of 1.0–250 µg l−1 for the investigated Sb species. The precisions, evaluated by using the relative standard deviation (%RSD) with a 2 µg l−1 standard solution, were 1.8% and 3.3% for Sb(III) and Sb(V), respectively. Several advantages of the developed method, such as improving chromatographic separation, stabilizing Sb compounds in a water sample, and preventing Sb(III) from oxidizing to Sb(V) during the ultrasonic-assisted and microwave-assisted extraction of an airborne particulate matter (APM) sample using 26 mmol l−1 citric acid as an extraction solvent, and alleviating the adsorption of Sb compounds on the sample surface, were observed. The developed method enabled us to detect the most toxic Sb specie, Sb(III), in an APM sample for the first time.

Positive- and negative ion electrospray mass spectra of commonly encountered organic antimony compounds, i.e., trimethylantimony dichloride (TMSbCl2) and trimethylantimony dihydroxide [TMSb(OH)2], and inorganic antimony compounds, i.e., potassium hexahydroxyantimonate [Sb(V)] and potassium antimonyl tartrate [Sb(III)] have been obtained using electrospray time-of-flight mass spectrometry (ES-TOF-MS). By operating the ES-TOF-MS instrument at high sample cone voltage (100 V), fragmentation information of TMSbCl2 and TMSb(OH)2 was obtained. Positive ion electrospray mass spectra have been found to be more useful for the identification of organic antimony compounds, TMSbCl2 and TMSb(OH)2, whereas negative ion electrospray mass spectra are more suitable for the identification of inorganic antimony compounds, Sb(V) and Sb(III). Based on the ES-MS results, a solution chemistry of TMSbCl2 and TMSb(OH)2 was proposed. Peaks at m/z 183 and 185 corresponding to [(CH3)3SbOH]+ can be considered as a characteristic fingerprint for the identification of trimethylantimony species (TMSb) in an aqueous solution when using a positive ion ES-MS technique. The characteristic fingerprint was applied for the identification of TMSbCl2, following its elution from a size-exclusion chromatography (SEC) column.

There is a considerably increasing concern about the speciation of antimony because anthropogenic emission has resulted in an increasing concentration of antimony in the environment. Apart from inorganic Sb species, methylated Sb species have been detected in a variety of environmental samples. However, little is known about the distribution of Sb species in airborne particulate matter (APM). The speciation of Sb species in APM was performed using both anion-exchange and size-exclusion HPLC-ICP-MS detection. A Japanese quality control sample for APM (AS-1, 92 μg g−1 Sb) and an APM sample collected in Tokyo (APM sample, 56 μg g−1 Sb) were investigated. In aqueous extracts of APM sample and AS-1, apart from the major Sb(V) species (ca. 80%), trimethylantimony species (TMSb) and several hydride active unknown Sb species were for the first time detected.

For selenium speciation analysis, the hyphenation of chromatographic separation with element-specific detection has proved a useful technique. A powerful separation system, which is capable of resolving several biologically and environmentally important selenium compounds in a single column, is greatly needed. However, that has been difficult to achieve. In this paper eight selenium compounds, namely, selenite [Se(IV)], selenate [Se(VI)], selenocystine (SeCys), selenourea (SeUr), selenomethionine (SeMet), selenoethionine (SeEt), selenocystamine (SeCM) and trimethylselenonium ion (TMSe+), were separated by using mixed ion-pair reagents containing 2.5 mM sodium 1-butanesulfonate and 8 mM tetramethylammonium hydroxide as a mobile phase. The separation of these anionic, cationic and neutral organic selenium compounds on a LiChrosorb RP18 reversed-phase column took only 18 min at a flow-rate of 1.0 ml/min with isocratic elution, and baseline separation among the six organic Se compounds was achieved. Inductively coupled plasma mass spectrometry (ICP-MS) was employed as element-specific detection. A comparison of ICP-MS signal intensity obtained with a Barbington-type nebulizer and with an ultrasonic nebulizer (USN) was made. Different signal enhancement factors were observed for the various selenium compounds when a USN was used. The speciation technique was successfully applied to the study on chemical forms of selenium in a selenium nutritional supplement. Selenomethionine was found to be the predominant constituent of selenium in the supplement.

Se-containing proteins play an important role in human metabolic processes such as antioxidant action. However, speciation analysis of Se-containing proteins in biological samples is challenging because of their small amounts. In order to determine selenoprotein P (Sel-P) in human plasma, separation performance was compared between size exclusion chromatography and affinity chromatography. It was found that affinity chromatography showed better separation performance for Sel-P. Micro-affinity chromatography coupled with low flow ICP-MS was developed, which enabled separation analysis of Sel-P in sub-μl samples. Standard solution flow rate ranges for low sample consumption and total consumption nebulizers were investigated. Moreover, the stability analysis for each nebulizer with the change in composition of the mobile phase was investigated. Finally, using the developed micro-affinity chromatography coupled with the low flow ICP-MS, Sel-P and the other Se-containing proteins in sub-μl samples of human plasma were determined.

In inductively coupled plasma (ICP) mass spectrometry, signal enhancement by co-existing carbon results from multiple factors. To elucidate the signal enhancement factors, we compared the effects of co-existing carbon and co-existing bromine, which have similar ionization energies (C, 11.26 eV; Br, 11.81 eV). We eliminated the effect of sample introduction efficiency changes, which are considered to be one reason for signal enhancement, by using two nebulizers. The intensities of the P, I, S, As, Se and B signals were enhanced when a multi-element solution was introduced into the ICP from one nebulizer and a carbon solution was introduced from the other. No signal enhancement was observed by co-existing bromine. We focused on the bond energies of the oxides as a possible explanation for the difference between the results for carbon and bromine. Carbon oxide has a higher bond energy than bromine oxide, and therefore carbon reduces analyte oxides more readily than bromine does. We also considered the effects of the bond energies of the analyte oxides, as well as the effects of the degree of analyte ionization in the ICP, on signal enhancement. Signal enhancement was observed for analytes that were less than 60% ionized in the ICP and whose oxide bond energies exceeded 450 kJ mol−1. Iodine was an exception; signal enhancement was observed for I (ionization degree, 29.85%), even though the bond energy of iodine oxide is only 240 kJ mol−1. Therefore, charge transfer could not be eliminated as a cause of signal enhancement.

Particles sampled by means of laser ablation in liquid (LAL) can be analyzed by inductively coupled plasma mass spectrometry (ICPMS) after acid digestion or slurry nebulization. The LAL sampling process is simple, and a standard solution can be used for calibration. In this study, we investigated elemental fractionation during LAL by using a standard glass reference material, NIST 610. NIST 610 was placed in an open-top chamber, and ultrapure water was added until the surface of the glass was 3 mm below the water surface. LAL sampling was carried out in line-scanning mode. The LAL-sampled particles were divided into two size classes by filtration through a polycarbonate filter: particles larger than 0.4 μm were collected on the filter, and particles smaller than 0.4 μm passed into the filtrate. Both sizes of particles were digested with acid and analyzed by ICPMS. Volatile elements were enriched in the smaller particles and depleted in the larger particles. That is, elemental fractionation related to the size of the ablated particles was observed during the LAL-sampling process. When the LAL-sampled particles were introduced into the ICP, the large particles did not decompose completely. Volatile elements in the larger particles were vaporized more easily than calcium. Therefore, positive elemental fractionation was observed when the LAL-sampled particles were analyzed by slurry nebulization ICPMS. Comparison between slurry nebulization and acid digestion revealed that particle size-related elemental fractionation in the ICP was larger than that observed during LAL sampling.

Airborne particulate matter (APM) is a major air pollutant, and the effect on human health of fine APM (PM2.5) deposited deep inside the lungs has recently become a serious concern. Moreover, soluble constituents may leach from APM, and intensify some health disorders. To identify the soluble chemical constituents of APM, size-classified APM was sampled in central Tokyo, and the elemental compositions of the water-soluble, acid-soluble and insoluble fractions were investigated. The extraction procedure was validated by calculating the mass balance of soluble and insoluble fractions of a standard APM reference material (NIST SRM 1648). Among the major elements, Fe and Ti in APM of all size classes and K in coarse APM were distributed primarily in the insoluble fraction and were inferred to be present as oxides or silicates, whereas Na and Mg in all size classes and K in fine APM were primarily in the water-soluble fraction and were inferred to be have originated mainly from sea salt. Among the trace elements, Zn and Cd in the fine APM (d < 2 µm) had large enrichment factors, indicating an anthropogenic origin, and were distributed primarily in the water-soluble fraction. When fine anthropogenic APM enters into the lungs, leached toxic elements, such as Cd, may adversely affect health. The higher the bonding energy of the monoxide molecule of the element was, the higher its distribution ratio was in the water-soluble fraction. Therefore, many metallic elements in APM were inferred to be present as oxygen-bonded compounds.

Concentrations of 14 rare earth elements (REEs) in six size classes of airborne particulate matter (APM) (<0.43, 0.43–0.65, 0.65–1.1, 1.1–2.1, 2.1–11, and >11 μm) and in two different phases (suspended particulate and dissolved) in rainwater were determined by inductively coupled plasma mass spectrometry (ICP-MS). Positive Eu and Tb anomalies were observed in size-classified APM. These anomalies may be due to large emissions of Eu and Tb to the atmosphere resulting from the recent change in Japan from the use of cathode-ray tubes to plasma displays in television sets (Eu and Tb) and from the widespread use of magneto-optical disks (Tb). The light REEs were enriched in fine APM particles (diameter < 1.1 μm). Because compositions of La/Ce/Sm in fine APM (diameter < 1.1 μm) were similar to those in automobile catalyst, the light REE enrichment was attributed to automobile emissions. In contrast, the REE distribution pattern in the suspended particulate phase in rainwater was similar to that in coarse APM (diameter > 2.1 μm), and a positive Tb anomaly was observed, suggesting that coarse particles easily become trapped in rain droplets. A negative Eu anomaly was observed in the dissolved phase in rainwater, but not in APM or in the suspended particulate phase in rainwater. Unlike other REEs, Eu can exist as both bivalent and trivalent ions in nature, and Eu-selective dissolution from or adsorption onto the trapped particles of Eu might account for the negative anomaly. These results show that atmospheric REE cycling is affected by the physico-chemical properties of APM.

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To investigate elemental fractionation during laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) we measured mass fractions of ablated particles and chemical composition of ablated particles in this study. Temporal changes of fractionation indexes (FIs) were investigated under laser defocus conditions which caused a large variation of size distribution of abated particles. It was a useful technique for understanding the relationship between temporal changes of FIs and the size of ablated particles. Ablated particles were fractionated by aerodynamic diameters (<0.06, 0.06–0.22, 0.22–2.2, and >2.2 μm) with a low-pressure impactor and were digested with HNO3 and HF; then As, Rb, Rh, La, Gd, Yb, W, Re, and Th were measured by ICPMS. Under 0.5 mm defocus and 1.0 mm defocus conditions, the mass fractions (ablated particle mass at 1–5 min divided by that at 0–1 min) of ablated particles larger than 0.22 μm were larger than the mass fractions of ablated particles smaller than 0.22 μm. Volatile elements such as As and Rb were enriched in particles smaller than 0.22 μm, owing to the large aspect ratio of the crater under defocus conditions. However, the magnitude of the enrichment for volatile elements did not change as ablation progressed. Therefore, we concluded that large particles could not be decomposed completely in the ICP and the FI peak observed at 2–3 min was caused by changes in elemental behavior due to changes in ablated particles larger than 0.22 μm.