Inductively Coupled Plasma Mass Spectrometry System Research Articles

A Novel and Simple Method for Elements Determination in Aerobiological Samples by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) Analysis

The identification of heavy metals in the atmosphere has increased a strong and growing interest. Thereby, monitoring of elements in aerobiological samples could be a powerful tool for detection of environmental pollution. In this work, a simple and fast method for the determination of trace metals bound to aeroparticles such as pollen was optimized. A single-step procedure for the dissolution of aerobiological samples in nitric acid and further determination by inductively coupled plasma mass spectrometry (ICP-MS) with a high-efficiency sample introduction system was developed. The procedure involved low dilution and low detection limits with adequate precision and its direct introduction into the ICP-MS system. The novel method proposed was successfully applied to determine five elements in concentrations from 0.04 mg g−1 (U) to 14.1 mg g−1 (Mn) in aerobiological samples. Through this procedure, the most significant correlations between pollen of Cupressaceae, Ulmus, and Moraceae with Mn, and pollen of Moraceae with Pb were found. This methodology could be a very useful tool to assess air pollution. We are not only proposing a new strategy to analyze air samples particles but also giving new information of the elemental composition carried by pollen.

Coupling ion chromatography and inductively coupled plasma-mass spectrometry with ultrasonic nebulization for sulfur speciation in dry foods

This paper describes an ion chromatography (IC) inductively coupled plasma mass spectrometry (ICP-MS) method, coupled with ultrasonic nebulization, for the speciation analysis of sulfur-namely sulfite (SO32−), sulfate (SO42−), and thiosulfate (S2O32−). These ionic sulfur compounds were separated well within 4.5 min through IC when using a Hamilton PRP-X100 column as the stationary phase and a mobile phase comprising 60 mmol L−1 NH4NO3 and 0.1% (v/v) formaldehyde solution (pH 7.0). The analyses were performed using a dynamic reaction cell (DRC) ICP-MS system. The sulfur-selective chromatogram was recorded at m/z 48, representing the 32S16O+ ion, formed through reactions with O2 in the reaction cell. This approach of detecting 32S+ as its oxide ion 32S16O+ at m/z 48 avoided the effect of polyatomic isobaric interference towards the signal of 32S+ at m/z 32 caused by the ions 16O16O+ and 14N18O+. The limits of detection of the various species were in the range from 3.1 to 3.7 ng S mL−1(6.2 to 7.4 mg kg−1). Accuracy of the method was verified by comparing the sums of the concentrations of the individual sulfur compounds, as measured using this new procedure, with the total concentrations of sulfur in a standard reference material (NIST 1573a Tomato Leaves) and in several samples of dry foods purchased locally. After ultrasonication for 90 min, the sulfur species had leached quantitatively from the leaves and the dry foods into the mobile phase solution. The extraction efficiency was >95%. The spike recoveries of the various studied compounds ranged from 96 to 102%.

Using on-line solid phase extraction for in vivo speciation of diffusible ferrous and ferric iron in living rat brain extracellular fluid

Exploration of brain extracellular non-protein-bound/diffusible iron species remains a critically important issue in investigations of free radical biology and neurodegenerative diseases. In this study, a facile sample pretreatment scheme, involving poly(vinyl chloride)–metal ion interactions as a selective extraction procedure, was optimized in conjunction with microdialysis (MD) sampling and inductively coupled plasma mass spectrometry (ICP-MS) in cool-plasma mode for in vivo online monitoring of rat brain extracellular Fe(II) and Fe(III) species. Optimization of the system provided detection limits in the range 0.9–6.9 μg Fe L−1, based on a 12-μL microdialysate, for the tested iron species; relative standard deviations of the signal intensities during 7.8 h of continuous measurement were less than 9.4%—sufficient to determine the basal concentrations of rat brain extracellular Fe(II) and Fe(III) species and to describe their dynamic actions. The method's applicability was verified through (i) spike analyses of offline-collected rat brain microdialysates, (ii) determination of the basal Fe(II) and Fe(III) concentrations of living rat brain extracellular fluids, and (iii) monitoring of the dynamic changes in the Fe(II) and Fe(III) concentrations in response to perfusion of a high-K+ medium. This proposed sample pretreatment scheme, based on polymer–metal ion interactions and hyphenation to an MD sampling device and an ICP-MS system, appears to have great practicality for the online monitoring of rat brain extracellular diffusible iron species.

Arsenic in rice and diets of children

Levels of arsenic in Australian and imported rice (n = 36) were evaluated using inductively coupled plasma mass spectrometry (ICP-MS) for total arsenic and a hyphenated high-performance liquid chromatography ICP-MS system for arsenic species. The study also assessed the daily intake of total As from diets of healthy children (n = 15), collected over three consecutive days. A wide variation of total As levels (range: <0.05–0.42 mg/kg) in Australian and imported rice was found. The mean level of total As (0.24 ± 0.09 mg/kg, n = 10) in the Australian rice was relatively higher than imported rice from other countries (0.09 ± 0.04 mg/kg, n = 26). The mean level (0.25 ± 0.08 mg/kg, n = 7) of dimethylarsenic acid was considerably higher than that of inorganic As (III) (0.07 ± 0.03 mg/kg, n = 7) in the Australian rice. Children’s daily intakes of total As varied widely, ranging from 1.7 to 31.2 (11.5 ± 8.9 µg/day), which was comparable to other countries.

Detection and characterization of silver nanoparticles in chicken meat by asymmetric flow field flow fractionation with detection by conventional or single particle ICP-MS

A method of analysis of silver nanoparticles (AgNPs) in chicken meat was developed. The homogenized chicken meat sample, which was spiked with AgNPs, was subjected to enzymolysis by Proteinase K for 40 min at 37 °C. Transmission electron microscopy and inductively coupled plasma mass spectrometry (ICP-MS) in single particle mode were used to characterize the number-based size distribution of AgNPs in the meat digestate. Because similar size distributions were found in the meat digestate and in the aqueous suspension of AgNPs used for spiking the meat, it was shown that no detectable dissolution of the AgNPs took place during the sample preparation stage. The digestate was injected into the asymmetric flow field flow fractionation (AF(4)) -ICP-MS system, which enabled fractionation of nanoparticles from the remaining meat matrix, and resulted in one large peak in the fractograms as well as two smaller peaks eluting close to the void volume. The recovery of silver contained in the large AgNP peak was around 80%. Size determination of AgNPs in the meat matrix, based on external size calibration of the AF(4) channel, was hampered by non-ideal (early elution) behavior of the AgNPs. Single particle ICP-MS was applied for determination of the number-based particle size distribution of AgNPs in collected fractions. The presented work describes for the first time the coupling of AF(4) and ICP-MS for AgNP separation in a food matrix.

Simultaneous speciation of arsenic, selenium, and chromium: species stability, sample preservation, and analysis of ash and soil leachates

An analytical method using high-performance liquid chromatography separation with inductively coupled plasma mass spectrometry (ICP-MS) detection previously developed for the determination of Cr(III) and Cr(VI) has been adapted to allow the determination of As(III), As(V), Se(IV), Se(VI), Cr(III), and Cr(VI) under the same chromatographic conditions. Using this method, all six inorganic species can be determined in less than 3 min. A dynamic reaction cell (DRC)-ICP-MS system was used to detect the species eluted from the chromatographic column in order to reduce interferences. A variety of reaction cell gases and conditions may be utilized with the DRC-ICP-MS, and final selection of conditions is determined by data quality objectives. Results indicated all starting standards, reagents, and sample vials should be thoroughly tested for contamination. Tests on species stability indicated that refrigeration at 10 °C was preferential to freezing for most species, particularly when all species were present, and that sample solutions and extracts should be analyzed as soon as possible to eliminate species instability and interconversion effects. A variety of environmental and geological samples, including waters and deionized water [leachates] and simulated biological leachates from soils and wildfire ashes have been analyzed using this method. Analytical spikes performed on each sample were used to evaluate data quality. Speciation analyses were conducted on deionized water leachates and simulated lung fluid leachates of ash and soils impacted by wildfires. These results show that, for leachates containing high levels of total Cr, the majority of the chromium was present in the hexavalent Cr(VI) form. In general, total and hexavalent chromium levels for samples taken from burned residential areas were higher than those obtained from non-residential forested areas. Arsenic, when found, was generally in the more oxidized As(V) form. Selenium (IV) and (VI) were present, but typically at low levels.

Size characterization and quantification of silver nanoparticles by asymmetric flow field-flow fractionation coupled with inductively coupled plasma mass spectrometry

A method for determining the size of silver nanoparticles and their quantification by asymmetric flow field-flow fractionation coupled with inductively coupled plasma mass spectrometry (ICP-MS) is proposed and was tested in consumer products. Experimental conditions were studied in detail to avoid aggregation processes or alteration of the original size distributions. Additionally, losses from sorption processes onto the channel membrane were minimized for correct quantification of the nanoparticles. Mobile phase composition, injection/focusing, and fractionation conditions were evaluated in terms of their influence on both separation resolution and recovery. The ionic strength, pH, and the presence of ionic and nonionic surfactants had a strong influence on both separation and recovery of the nanoparticles. In general, better results were obtained under those conditions that favored charge repulsions with the membrane. Recovery values of 83 ± 8% and 93 ± 4% with respect to the content of silver nanoparticles were achieved for the consumer products studied. Silver nanoparticle standards were used for size calibration of the channel. The results were compared with those obtained by photon correlation spectroscopy and images taken by transmission electron microscopy. The quantification of silver nanoparticles was performed by direct injection of ionic silver standard solutions into the ICP-MS system, integration of the corresponding peaks, and interpolation of the fractogram area. A limit of detection of 5.6 μg L(-1) silver, which corresponds to a number concentration of 1×10(12) L(-1) for nanoparticles of 10 nm, was achieved for an injection volume of 20 μL.

Open-channel chip-based solid-phase extraction combined with inductively coupled plasma-mass spectrometry for online determination of trace elements in volume-limited saline samples

In this study, we used an automated online chip-based solid-phase extraction (SPE)–inductively coupled plasma-mass spectrometry (ICP-MS) system for analyzing trace elements in small-volume saline samples (∼15 μL). The proposed method involved the adsorption of trace metal ions in the interior of a functionalized poly(methyl methacrylate) (PMMA) channel in order to separate these ions from saline matrices. The adsorption of transition metal ions was presumably dominated by the surface complexation between the carboxylate moieties in the interior of the PMMA channel and the metal ions, which facilitated the formation of metal–carboxylate complexes. The components of the proposed online analytical system used for the simultaneous detection of multiple trace metals in saline samples involved microdialysis (MD) sampling, an established chip-based SPE procedure, and ICP-MS. The SPE–ICP-MS hyphenated system was optimized, and then, the analytical reliability of this system was further confirmed by using it to analyze the certified reference materials—SRM 2670 (human urine) and SRM 1643e (artificial saline water). The satisfactory analytical results indicated that the proposed on-chip SPE device could be readily used as an interface for coupling the MD probe with the ICP-MS system. The dramatically reduced consumption of chemicals and “hands-on” manipulations enabled the realization of a simplified and relatively clean procedure with extremely low detection limits in the range of 5.86–76.91 ng L −1 for detecting Mn, Co, Ni, Cu, and Pb in 15-μL samples by ICP-MS. The effectiveness of an online MD–chip-based SPE–ICP-MS technique for continuous monitoring of trace elements in a simulated biological system was also demonstrated. To the best of our knowledge, this is the first paper to report the direct exploitation of a PMMA chip as an SPE adsorbent for online sample pretreatment and trace metal preconcentration prior to ICP-MS measurement.

Method comparison for 241Am emergency urine bioassay

241Am is one of the high-risk radionuclides that might be used in a terrorist attack. 241Am in urine bioassay can identify the contaminated individuals who need immediate medical intervention and decontamination. This paper compares three methods for the measurement of 241Am in urine, namely liquid scintillation counting (LSC), inductively coupled plasma mass spectrometry (ICP-MS) and gamma spectrometry (GS), at two levels, 20 and 2 Bq l(-1). All three methods satisfied the ANSI N13.30 radio-bioassay criteria for accuracy and repeatability. ICP-MS offered the best sensitivity and fastest sample turnaround; however, the ICP-MS system used in this work may not be available in many bioassay laboratories. LSC and GS are more commonly available instruments. GS requires minimal or no sample preparation, which makes it a good candidate method. Moreover, the sample throughput can be significantly improved if the GS and LSC methods are automated.

Development of a Species-Unspecific Isotope Dilution GC−ICPMS Method for Possible Routine Quantification of Sulfur Species in Petroleum Products

Inductively coupled plasma mass spectrometry (ICPMS) hyphenated with capillary gas chromatography was applied for sulfur multispecies determination in petroleum products by species-unspecific isotope dilution mass spectrometry (IDMS). To guarantee a stable and continuous addition of the spike into the GC-ICPMS system, a special dosing unit was designed and synthesis of a (34)S-labeled dimethyldisulfide spike from (34)S-enriched elemental sulfur in the milligram range was developed. The sample was mixed with an internal standard for spike mass flow calibration. From the mass flow chromatogram obtained by species-unspecific GC-ICP-IDMS, determination of all separated sulfur species and of the total sulfur content was possible without any matrix influence by coeluting hydrocarbons. The accuracy of the developed method was evaluated by determining reference material SRM-2296 certified for three sulfur species and by comparison of results obtained by species-specific GC-ICP-IDMS. The total sulfur concentration determined for all separated species agreed well with the sulfur content in the original samples which demonstrated that all sulfur species have been covered. Structural characterization of sulfur species was carried out by corresponding sulfur standards and by applying electron ionization ion trap mass spectrometry. The low detection limit of 9 ng sulfur per gram sample, independent of results on coeluting hydrocarbons, and the robust instrumental design of the continuous spike flow dosing unit qualifies this species-unspecific GC-ICP-IDMS method for accurate and sensitive sulfur multispecies determinations also on a routine basis.

Trace amounts of rare earth elements in high purity samarium oxide by sector field inductively coupled plasma mass spectrometry after separation by HPLC

Today there is an increasing need for high purity rare earth compounds in various fields, the optical, the electronics, the ceramic, the nuclear and geochemistry. Samarium oxide has special uses in glass, phosphors, lasers and thermoelectric devices. Calcium chloride crystals treated with samarium have been employed in lasers, which produce light beams intense enough to burn metal. In general, the inductively coupled plasma mass spectrometry (ICP-MS) presents some advantages for trace element analysis, due to high sensitivity and resolution, when compared with other analytical techniques such as ICP optical emission spectrometry (ICP-OES). In this work, sector field inductively coupled plasma mass spectrometry was used. Sixteen elements (Sc, Y and 14 lanthanides) were determined selectively with the ICP-MS system using a concentration gradient method. The detection limits with the ICP-MS system were about 0.2 (La) pg mL −1 to 8 (Gd) pg mL −1. The %R.S.D. of the methods varying between 0.9 and 1.5% for a set of five ( n = 5) replicates was found for the IPEN's material and for the certificate reference sample. Determination of trace REEs in two high pure samarium oxides samples (IPEN and JMC) was performed. IPEN's material is highly pure (>99.99%) and was successfully analyzed without spectral interference (MO + and MOH +).

Quantification of trace amounts of rare earth elements in high purity gadolinium oxide by sector field inductively coupled plasma mass spectrometry (ICP-MS)

In recent years, rare earth elements (REEs) have received much attention in the fields of geochemistry and industry. Gadolinium oxide is used for many different high technology applications such as infrared absorbing automotive glass, petroleum cracking catalyst, gadolinium–yttrium garnets, microwave applications, and color TV tube phosphors. It can also be used in optical glass manufacturing and in the electronic industry. Rapid and accurate determinations of the rare earth elements are increasingly required as industrial demands expand. In general, the inductively coupled plasma mass spectrometry (ICP-MS) presents some advantages for trace element analysis, due to high sensitivity and resolution, when compared with other analytical techniques. In this work, sector field inductively coupled plasma mass spectrometry was used. Sixteen elements (Sc, Y, and 14 lanthanides) were determined selectively with the ICP-MS system using a concentration gradient method. The detection limits with the ICP-MS system were about 0.2–8 pg ml −1. The recovery percentage ranged from 95 to 100% for different rare earth elements. The %R.S.D. of the methods varying between 1.5 and 2.5% for a set of five ( n=5) replicates was found for the IPEN’s material and for the certificate reference sample. Determination of trace REEs in two high pure gadolinium oxides samples (IPEN and JMC) was performed. IPEN’s material is highly pure (>99.99%) and was successfully analyzed without spectral interference.

Inductively coupled plasma mass spectrometric determination of heavy metals in sea-water samples after pre-treatment with a chelating resin disk by an on-line flow injection method.

A new on-line flow injection (FI) pre-treatment system using a disk-type chelating resin (5 mm diameter, 0.5 mm thickness) was developed for the simultaneous multi-element determination of trace metals in sea-water samples by inductively coupled plasma mass spectrometry (ICP-MS). A chelating resin possessing an iminodiacetate (IDA) functional group was used for the collection of trace elements and the elimination of alkali and alkaline earth metals in highly concentrated salt solution. A 1 ml volume of a sea-water sample (pH 5.5) was applied to the chelating resin disk. Considering the removal efficiency for Ca, 50 mM ammonium acetate buffer solution (pH 5.5) was chosen as a sample carrier. The enriched trace metals were eluted with 0.1 M nitric acid and the eluate flowed into the ICP-MS system. The processing time for one sample was < 6 min (350 s). One of the important observations is the possibility of working with a low recovery, even lower than 50%. For example, several elements such as Mn, Cr, As, Mo, Ba and U, the recovery of which was < 50% in a batch-wise method, showed good linearity and reproducibility. The proposed method was evaluated by analyzing two kinds of sea-water certified reference materials, CASS-4 and NASS-5. Analytical data for eight heavy metals, V, Mn, Co, Ni, Cu, Mo, Cd and U, obtained from the present study agreed well with the certified values.

A high-efficiency cross-flow micronebulizer interface for capillary electrophoresis and inductively coupled plasma mass spectrometry.

A pneumatic nebulizer interface for capillary electrophoresis (CE) and inductively coupled plasma mass spectrometry (ICPMS) is reported. The interface is constructed using a high-efficiency cross-flow micronebulizer (HECFMN) and has the following features. (1) Makeup solutions can be fed to the interface by nebulizer self-aspiration and liquid gravity pressurization. (2) The liquid dead volume of the interface is approximately 65 nL, much smaller than those (200-2500 nL) reported for other interfaces. (3) The interface can be stably operated at a liquid flow rate down to 5 microL/min with a high analyte transport efficiency up to 95% to the plasma and (4) does not induce noticeable laminar flow in the CE capillary at typical nebulizer gas flow rates of 0.8-1.2 L/min. Because of these features, baseline resolution of 10 lanthanides with a CE-ICPMS system using the HECFMN interface is achieved, and detection limits and peak asymmetry are 0.05-1 microg/L and 0.93-1.23, respectively, improved significantly over those reported previously for a CE-ICPMS system using a high-efficiency nebulizer interface. Peak precision for the 10 lanthanides is in the range of 6.2-12.3% RSD (N = 5). Peak widths are from 9.1 s for 139La to 17.9 s for 175Lu. The effects of nebulizer gas flow rate, makeup solution flow rate, and spray chamber volume on CE-ICPMS signal intensity and separation are also evaluated for the HECFMN interface by the separation of Cr3+ and Cr2O7(2-).

Speciation of protein-binding zinc and copper in human blood serum by chelating resin pre-treatment and inductively coupled plasma mass spectrometry

A method for the speciation of zinc and copper binding with proteins in human serum was explored by chelating resin (Chelex-100) pre-treatment and inductively coupled plasma mass spectrometry (ICP-MS). It was shown by a SEC (size-exclusion chromatography)-ICP-MS system that albumin-zinc and albumin-copper (loosely-bound species) could be selectively removed from serum by adsorption on the Chelex-100 resin after the chelating resin pre-treatment, while alpha 2-macroglobulin-zinc and ceruloplasmin-copper (firmly-bound species) remained in the serum. The zinc and copper bound with alpha 2-macroglobulin and ceruloplasmin, respectively, were then determined by ICP-MS after batch treatment of the serum samples with the Chelex-100 resin. In addition, the total concentrations of zinc and copper were also determined by ICP-MS after a 20-fold dilution with 0.1 M HNO3. The albumin-zinc and -copper were estimated as the differences between the concentrations of total and firmly-bound species. The present batch pre-treatment method was applied to the speciation analysis of zinc and copper binding with proteins in sera donated from 25 healthy volunteers as well as from a pregnant woman and a myelodysplastic syndrome patient. The observed concentrations of alpha 2-macroglobulin-zinc and ceruloplasmin-copper were in the ranges 109-202 ng ml-1 (12.4-31.3% of total zinc) and 513-880 ng ml-1 (90.6-99.7% of total copper), respectively. The present method is simple (only addition of the chelating resin and centrifugation is required) and reproducible (average RSD = 2% for alpha 2-macroglobulin-zinc and 1% for ceruloplasmin-copper in intra-assay measurements, and 5% for alpha 2-macroglobulin-zinc and 4% for ceruloplasmin-copper in inter-assay measurements), and there is less risk of contamination during separation.

Determination of Continuous Size and Trace Element Distribution of Colloidal Material in Natural Water by On-Line Coupling of Flow Field-Flow Fractionation with ICPMS

The coupled technique here presented utilizes the size-separating capabilities of flow field-flow fractionation (FlFFF) and the high-sensitivity, multielement detection capabilities of inductively coupled plasma mass spectrometry (ICPMS). The system enables determinations of colloidal size and element distributions for 28 elements (including carbon) in natural waters. To cope with the low concentrations often found for colloids and trace elements in natural waters, the conventional FlFFF system has been modified to include an on-channel preconcentration procedure allowing injection of up to 50 mL of sample. The performance of the FlFFF−ICPMS system is further evaluated in terms of reproducibility and detection limits. The size distributions of six selected elements are given, and different colloidal distributions for the elements are discussed.

Development of accurate mass spectrometric routine and reference methods for the determination of trace amounts of iridium and rhodium in photographic emulsions

For the determination of trace amounts of iridium and rhodium in photographic emulsions different sample treatment procedures were coupled with inductively coupled plasma mass spectrometry (ICP-MS) and, for iridium, also with negative thermal ionisation isotope dilution mass spectrometry (NTI-IDMS) and ICP-IDMS. IDMS determinations of iridium were carried out using an enriched 191 Ir spike solution. Elimination of the silver matrix was established for both mass spectrometric methods, which prevents corresponding memory effects in the ICP-MS system and is essential for the formation of IrO 2 – thermal ions, respectively. For NTI-MS measurements, the gelatine matrix of the emulsion must also be eliminated by decomposition with HNO 3 -H 2 O 2 . The detection limits for ICP-IDMS and NTI-IDMS are 0.1 and 10 ng iridium per gram of emulsion, respectively, so that all relevant photographic emulsions, doped with iridium, could be analysed. ICP-IDMS with silver matrix elimination is recommended as a routine method, while NTI-IDMS can be applied as an accurate reference method. Determinations of the mono-isotopic element rhodium cannot be carried out by IDMS. Photographic emulsions were therefore first dissolved in concentrated ammonia solution and rhodium was then directly measured by ICP-MS after dilution of the solution using an internal indium standard for calibration. This procedure has the advantage of a simple sample preparation technique but introduces high amounts of silver into the mass spectrometer and dilution of the sample restricts the detection limit. Because of the similar chemical and physical behaviour of Ru and Rh, ruthenium was used as an internal standard during matrix separation and subsequent ICP-MS measurements of trace amounts of rhodium. By determining the 103 Rh/ 99 Ru ratio of the separated sample, reliable results for the determination of trace amounts of rhodium were obtained, which was confirmed by the good agreement between the data obtained by the procedure with internal Ru calibration and those obtained without matrix separation and calibration by indium. The determination of trace amounts of iridium and rhodium in the range 0.5-650 ng g –1 was carried out in photographic emulsions with the different methods, which agreed well in their results. The relative standard deviations were usually in the range 3-10% and were substantially influenced by sample inhomogeneities.

Determination of arsenic in organic solvents and wines using microscale flow injection inductively coupled plasma mass spectrometry

S. Wangkarn and S. A. Pergantis, J. Anal. At. Spectrom., 1999, 14, 657 DOI: 10.1039/A900067D

Arsenic Speciation in Water and Human Urine by HPLC–ICP-MS and HPLC–MO–HG-AAS

Arsenite, arsenate, monomethylarsonate, dimethylarsinate, arsenobetaine, and arsenocholine have been successfully separated in one chromatographic run in a mixed mode column, Spherisorb ODS/NH2, using 5.0 mmol liter−1phosphate buffer at pH 5.0 as mobile phase and final detection by inductively coupled plasma mass spectrometry (ICP-MS) or microwave-assisted oven (MO) coupled with hydride generation atomic absorption spectrometry (HG-AAS). The detection limits achieved with the HPLC–ICP-MS coupling (0.04–0.28 ng) were about 20 times lower than those achieved by HPLC–MO–HG-AAS, which makes it suitable for determining these species at their naturally occurring concentration levels. The chloride present in the samples was chromatographically separated from the arsenic species, and the interferent signal from the40Ar35Cl formed on the ICP-MS system was insignificant. The proposed methods were successfully applied to the determination of six arsenic species in water and urine (after previous cleanup of the sample).

The determination of mercury and selenium in maternal and neonatal scalp hair by inductively coupled plasma-mass spectrometry.

As part of a prospective study to evaluate maternal and neonatal scalp hair mineral profiles in normal and pathological pregnancy cases, the suitability of inductively coupled plasma-mass spectrometry (ICP-MS) was evaluated for the quantitation of mercury and selenium as part of a multi-element determination procedure. Treatment of hair samples included a closed-system microwave-assisted digestion in screw-capped PTFE vials of 10-mL capacity with concentrated nitric acid (2 mL) as the matrix solubilization medium. A digestion time of 10 min at 40% microwave power yielded limpid digestates, which, after appropriate dilution with deionized water to give a final acid concentration of 20% (v/v), were used for direct ICP-MS measurements within a rectilinear calibration range from 0 to 10 micrograms/L. Analytical recovery results for mercury ranged from 97 to 102%, whereas those for selenium ranged from 96 to 101%. Results from concurrent analyses of a human hair reference material showed a high degree of concordance with certified values. The results obtained suggest that the closed-system microwave-assisted digestion procedure described was effective in minimizing the risk of volatility-associated losses that can be encountered in the assays of both metals. The results also indicated that the ICP-MS system used in this study was suitable for including both metals as part of a multi-element quantitation procedure. Using this method, analytical results were obtained for mercury and selenium levels from 100 pairs of maternal and neonatal scalp hair samples collected at the postnatal ward of Hull Maternity Hospital, Hull, United Kingdom.