Electrothermal Vaporization Inductively Coupled Plasma Mass Spectrometry Research Articles

Preconcentration and Separation of Gold Nanoparticles from Environmental Waters Using Extraction Techniques Followed by Spectrometric Quantification.

The quantification of gold nanoparticles (AuNP) in environmental samples at ultratrace concentrations can be accurately performed by sophisticated and pricey analytical methods. This paper aims to challenge the analytical potential and advantages of cheaper and equally reliable alternatives that couple the well-established extraction procedures with common spectrometric methods. We discuss several combinations of techniques that are suitable for separation/preconcentration and quantification of AuNP in complex and challenging aqueous matrices, such as tap, river, lake, brook, mineral, and sea waters, as well as wastewaters. Cloud point extraction (CPE) has been successfully combined with electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma mass spectrometry (ICP-MS), chemiluminescence (CL), and total reflection X-ray fluorescence spectrometry (TXRF). The major advantage of this approach is the ability to quantify AuNP of different sizes and coatings in a sample with a volume in the order of milliliters. Small volumes of sample (5 mL), dispersive solvent (50 µL), and extraction agent (70 µL) were reported also for surfactant-assisted dispersive liquid–liquid microextraction (SA-DLLME) coupled with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). The limits of detection (LOD) achieved using different combinations of methods as well as enrichment factors (EF) varied greatly, being 0.004–200 ng L−1 and 8–250, respectively.

Determination of metal uptake in single organisms, Corophium volutator, via complementary electrothermal vaporization/inductively coupled plasma mass spectrometry and laser ablation/inductively coupled plasma mass spectrometry.

(Eco-)toxicological effects are mostly derived empirically and are not correlated with metal uptake. Furthermore, if the metal content is determined, mostly bulk analysis of the whole organism population is conducted; thus, biological variability is completely disregarded, and this may lead to misleading results. To overcome this issue, we compared two different solid sampling techniques for the analysis of single organisms. In this study, complementary electrothermal vaporization/inductively coupled plasma mass spectrometry (ETV/ICP-MS) ⇔ laser ablation/inductively coupled plasma mass spectrometry (LA/ICP-MS)-based methods for the analysis of individual organisms were developed and the results obtained were compared with the concentrations obtained after digestion and measured using ICP-MS. For this purpose, a common (eco-)toxicological test organism, the mud shrimp Corophium volutator, was selected. As proof-of-concept application, these organisms were incubated with environmentally relevant metals from galvanic anodes, which are often used for protection against metal corrosion in, for example, offshore wind farms. The bulk analysis revealed that large quantities of the incubated elements were detectable. Using the ETV/ICP-MS method, we could identify a high biovariability within the population of organisms tested. Using the LA/ICP-MS method, it could be determined that the large quantities of the elements detected were due to adsorption of the metals and not due to uptake, which correlates well with the absence of (eco-)toxicological effects. The results obtained imply the efficiency of complementary methods to explain the absence or presence of (eco-)toxicological effects. In particular, methods that allow for single-organism analysis or provide even a spatial resolution support the interpretation of ecotoxicological findings.

Using electrothermal vaporization inductively coupled plasma mass spectrometry to determine S, As, Cd, Hg, and Pb in fuels

In this study the levels of S, As, Cd, Hg, and Pb in fuels were determined through electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). The fuel samples were injected into a graphite furnace in the form of emulsions containing 3% (m/v) fuel, 0.5% (m/v) tartaric acid, 1% (m/v) Triton X-100, and 0.5% (v/v) HNO3. Pd (1 μg) was used as a modifier. Analyses were performed using dynamic reaction cell (DRC) ICP-MS with O2 as the reaction gas. The method obviated the effects of polyatomic isobaric interference at m/z 32 and 75 by detecting 32S+ and 75As+ as their oxide ions 32S16O and 75As16O at m/z 48 and 91, respectively with much less interference. The developed method was applied to the determination of S, As, Cd, Hg, and Pb in three fuel samples obtained locally. The analytical results were in good agreement with those of digested samples analyzed through membrane desolvation sample introduction DRC ICP-MS, with 95% confidence according to Student's t-test. The precision between sample replicates was better than 8% when using the ETV-ICP-MS method. The detection limits for S, As, Cd, Hg, and Pb in the original fuel samples, obtained from standard addition curves, were 39, 0.07, 0.1, 0.07, and 0.07 ng g−1, respectively.

Chemical vapor generation sample introduction for the determination of As, Cd, Sb, Hg, and Pb in nail polish by inductively coupled plasma mass spectrometry

This paper describes a flow injection vapor generation (VG) method using inductively coupled plasma mass spectrometry (ICP-MS) for determining As, Cd, Sb, Hg, and Pb in nail polish. The samples for VG were prepared as aqueous slurries of a nail polish (0.5%m/v), thiourea (1%m/v), Co(II) (0.75μgmL−1), and HCl (1.2%v/v). Chemical VG of As, Cd, Sb, Hg, and Pb ions, by reduction with tetrahydroborate (3%m/v in 0.2%m/v NaOH), enabled their separation from the slurry. With VG sample introduction, As, Cd, Sb and Hg signals were increased by 1–2 orders (except Pb) compared to solution nebulization due to better sample introduction. Quantifications were performed by VG ICP-MS using isotope dilution and standard addition methods as slopes of calibration plots of analytes in the slurries were higher. Using the reported procedure, samples of three nail polishes purchased locally were analyzed for their levels of As, Cd, Sb, Hg, and Pb. The results obtained were in good agreement with those measured using electrothermal vaporization ICP-MS. In the original nail polish sample, the detection limits, calculated as 3σ of blank measurements, for As, Cd, Sb, Hg, and Pb, estimated from standard addition curves, were 0.06, 0.12, 0.14, 0.2, and 12ngg−1, respectively.

Dispersive micro-solid phase extraction combined with dispersive liquid-liquid microextraction for speciation analysis of antimony by electrothermal vaporization inductively coupled plasma mass spectrometry

A method was developed for speciation analysis of antimony by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) after preconcentration/separation using dispersive micro-solid phase extraction (DMSPE) and dispersive liquid-liquid micro-extraction (DLLME). In DMSPE, titanium dioxide nanofibers were used for preconcentration and separation of analytes. The upper aqueous phase and elution solution from DMSPE were used for further preconcentration and separation of Sb(III) and Sb(V) by DLLME without any pre-oxidation or pre-reduction operation, respectively. The extracts from DLLME were used for ETV-ICP-MS determination with APDC as a chemical modifier. Under optimal conditions, the detection limits of this method were 0.019 and 0.025pgmL−1 with relative standard deviations of 5.7% and 6.9% for Sb(III) and Sb(V) (c=1.0ngmL−1, n=9), respectively. This method was applied for speciation analysis of Sb and its distribution in the tea leaves and the tea infusion, including total, suspended, soluble, organic and inorganic Sb as well as Sb(III) and Sb(V). The results showed that the contents of Sb are 62.7, 12.9 and 47.3ngg−1 in the tea leaves, tea residue and tea soup, respectively; those of soluble, organic, inorganic, Sb(III) and Sb(V) are 0.41, 0.11, 0.29, 0.21 and 0.07ngmL−1 in the tea soup, respectively. A certified reference material of tea leaves (GBW 07605) was analyzed by this method with satisfactory results.

Ultra-trace determination of gold nanoparticles in environmental water by surfactant assisted dispersive liquid liquid microextraction coupled with electrothermal vaporization-inductively coupled plasma-mass spectrometry

A new method by coupling surfactant assisted dispersive liquid liquid microextraction (SA-DLLME) with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) was proposed for the analysis of gold nanoparticles (AuNPs) in environmental water samples. Effective separation of AuNPs from ionic gold species was achieved by using sodium thiosulphate as a complexing agent. Various experimental parameters affecting SA-DLLME of AuNPs, such as the organic solvent, organic solvent volume, pH of the sample, the kind of surfactant, surfactant concentration, vortex time, speed of centrifugation, centrifugation time, and different coating as well as sizes of AuNPs were investigated carefully. Furthermore, the interference of coexisting ions, dissolved organic matter (DOM) and other metal nanoparticles (NPs) were studied. Under the optimal conditions, a detection limit of 2.2ngL−1 and an enrichment factor of 152-fold was achieved for AuNPs, and the original morphology of the AuNPs could be maintained during the extraction process. The developed method was successfully applied for the analysis of AuNPs in environmental water samples, including tap water, the East Lake water, and the Yangtze River water, with recoveries in the range of 89.6–102%. Compared with the established methods for metal NPs analysis, the proposed method has the merits of simple and fast operation, low detection limit, high selectivity, good tolerance to the sample matrix and no digestion or dilution required. It provides an efficient quantification methodology for monitoring AuNPs' pollution in the environmental water and evaluating its toxicity.

Assessment of the Halogen Content of Brazilian Inhalable Particulate Matter (PM10) Using High Resolution Molecular Absorption Spectrometry and Electrothermal Vaporization Inductively Coupled Plasma Mass Spectrometry, with Direct Solid Sample Analysis.

Halogens in the atmosphere play an important role in climate change and also represent a potential health hazard. However, quantification of halogens is not a trivial task, and methods that require minimum sample preparation are interesting alternatives. Hence, the aim of this work was to evaluate the feasibility of direct solid sample analysis using high-resolution continuum source molecular absorption spectrometry (HR-CS MAS) for F determination and electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICP-MS) for simultaneous Cl, Br, and I determination in airborne inhalable particulate matter (PM10) collected in the metropolitan area of Aracaju, Sergipe, Brazil. Analysis using HR-CS MAS was accomplished by monitoring the CaF molecule, which was generated at high temperatures in the graphite furnace after the addition of Ca. Analysis using ETV-ICP-MS was carried out using Ca as chemical modifier/aerosol carrier in order to avoid losses of Cl, Br, and I during the pyrolysis step, with concomitant use of Pd as a permanent modifier. The direct analysis approach resulted in LODs that were proven adequate for halogen determination in PM10, using either standard addition calibration or calibration against a certified reference material. The method allowed the quantification of the halogens in 14 PM10 samples collected in a northeastern coastal city in Brazil. The results demonstrated variations of halogen content according to meteorological conditions, particularly related to rainfall, humidity, and sunlight irradiation.

Simultaneous speciation of inorganic arsenic, selenium and tellurium in environmental water samples by dispersive liquid liquid microextraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry

A new method based on dispersive liquid liquid microextraction (DLLME) combined with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) was developed for the simultaneous speciation of inorganic arsenic (As), selenium (Se) and tellurium (Te) with sodium diethyldithiocarbamate (DDTC) as both chelating reagent and chemical modifier. As(III), Se(IV) and Te(IV) were transformed into DDTC-chelates at pH 7 and extracted into the fine droplets formed by injecting the binary solution of bromobenzene (extraction solvent) and methanol (dispersive solvent) into the sample solution. After phase separation by centrifugation, As(III), Se(IV) and Te(IV) preconcentrated in the organic phase were determined by ETV-ICP-MS. Total inorganic As, Se and Te were obtained by reducing As(V), Se(VI) and Te(VI) to As(III), Se(IV) and Te(IV) with l-cysteine, which were then subjected to the same DLLME-ETV-ICP-MS process. The concentration of As(V), Se(VI), Te(VI) were calculated by subtracting the concentration of As(III), Se(IV) and Te(IV) from the total inorganic As, Se and Te, respectively. The main factors affecting the microextraction efficiency and the vaporization behavior of target species were investigated in detail. Under the optimal conditions, the limits of detection were 2.5, 8.6 and 0.56ngL−1 for As(III), Se(IV) and Te(IV), respectively, with the relative standard deviations (n=7) of 8.5–9.7%. The developed method was applied to the speciation of inorganic As, Se and Te in Certified Reference Materials of GSBZ50004-88, GBW(E)080395 and GBW(E)080548 environmental waters, and the determined values are in good agreement with the certified values. The method was also successfully applied to the simultaneous speciation of inorganic As, Se and Te in different environmental water samples with the recoveries in the range of 86.3–107% for the spiked samples.

Contributions on the Use of Bismuth as Internal Standard for Lead Determinations Using ICP-Based Techniques

Bismuth was evaluated as internal standard for Pb determinations and showed usefulness to minimize variations due to changes in the experimental conditions of the inductively coupled plasma optical emission spectrometry (ICP OES), inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). Thirty four samples were analyzed and the Pb contents obtained by ICP-MS and ETV-ICP-MS were in agreement at 95% confidence level. Plant, biological tissue and soil reference materials were also analyzed and the results were close to certified values upon the use of the internal standard. Recoveries for Pb spikes (ICP OES: 95-110%; ICP-MS: 95-106%; ETV-ICP-MS: 92-119%) were better than those obtained with external calibration (ICP OES: 56-91%; ICP-MS: 36-136%; ETV‑ICP-MS: 5-123%). The relative standard deviations (n = 12) was improved from 1-9% to 0.2-6% (ICP OES), from 0.5-11% to 0.1-7% (ICP-MS) and from 0.4-7% to 0.1-4% (ETV‑ICP‑MS) by using external and internal standard calibrations, respectively.

Determination of rare earth elements in graphite by solid sampling electrothermal vaporization-inductively coupled plasma mass spectrometry

Determination of rare earth elements in graphite samples was performed by direct solid sampling electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICP-MS).

Evaluation of electrothermal vaporization as a sample introduction technique for the determination of trace elements in biological samples by inductively coupled plasma mass spectrometry, following dispersive liquid–liquid microextraction

This work describes the method development process involved in the determination of Ag, Cd, Cu and Pb in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS), following dispersive liquid–liquid microextraction (DLLME). The parameters associated with DLLME such as HNO3 and diethyldithiophosphate (DDTP) concentrations, as well as the volumes of disperser (ethanol) and extracting (chloroform) solvents, were evaluated. The ICP-MS operating parameters (carrier gas flow rate and RF power) were also optimized. Several distinct approaches involving investigation on chemical modifiers (W, Ru, Pd and combinations), aerosol carriers (Na2SO4, ascorbic acid and diethyldithiophosphate – DDTP) and the effect of insertion of a L'vov platform on the transport efficiency from the ETV to the ICP and overall analytical performance were evaluated. The results suggest that the use of a platform and chemical modifiers lead to increased thermal stability, although the sensitivity is generally reduced when compared to the absence of modifiers and wall vaporization. Several calibration approaches were evaluated, including the combination of chemical modifiers and the use or absence of a L'vov platform inside the graphite tube. Accurate results were achieved for all elements upon the use of palladium as the aerosol carrier in combination with W and Ru as permanent chemical modifiers, demonstrating that the effective transportation of the analytes and equalization of the transport efficiency between samples and calibration solutions are carrier-dependent. To verify the accuracy of the proposed methodology, four certified reference biological materials were analyzed, with good agreement between certified and determined values. ‘Real’ samples were also analyzed following the optimized procedure. The proposed method resulted in detection limits between 0.001 and 0.09 μg g−1 and enhancement factors between 35 and 59, with appreciable analytical sensitivity.

Dual dispersive extraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry for determination of trace REEs in water and sediment samples

A simple and efficient two-step method based on dispersive solid phase extraction (D-SPE) and dispersive liquid–liquid microextraction (DLLME) has been developed for the separation and preconcentration of 15 rare earth elements (REEs) from environmental water and sediment samples, followed by electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICP-MS) detection. With Chelex 100 as the adsorbent of D-SPE, target REEs were firstly extracted and the retained REEs were then desorbed by 0.1 mol L−1 HNO3. After 125 mmol L−1 Tris and 40 mmol L−1 1-phenyl-3-methyl-4-benzoylpyrazolone (PMBP) were added into the above elution solution, target REEs were further preconcentrated into CCl4 by DLLME. The developed dual extraction technique exhibited high enrichment factors (234 to 566-fold) and good anti-interference ability. Various parameters affecting the extraction of target REEs by D-SPE and DLLME were investigated in detail. Under the optimal conditions, the limits of detection (LODs, 3σ) for target REEs were in the range of 0.003–0.073 ng L−1 with the relative standard deviations (CY,La,Ce,Pr,Nd,Gd,Dy = 1.0 ng L−1, CSm,Eu,Tb,Ho,Er,Tm,Yb,Lu = 0.2 ng L−1, n = 7) ranging from 6.7 to 11.5%. The proposed method of D-SPE-DLLME-ETV-ICP-MS was successfully applied to the determination of 15 REEs in water and sediment samples with the recoveries of 78–115% and 75–117% for the spiked water and sediment samples, respectively. To validate the accuracy of the method, a Certified Reference Material of GBW07301a stream sediment was analyzed and the determined values were in good agreement with the certified values.

Determination of Cu, As, Hg and Pb in vegetable oils by electrothermal vaporization inductively coupled plasma mass spectrometry with palladium nanoparticles as modifier

The determination of Cu, As, Hg and Pb in vegetable oils by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) was investigated. The oils were injected in the form of emulsions containing 5% m/v vegetable oil, 1.5% v/v Triton X-100 and 50 μg mL(-1) ascorbic acid. Palladium nanoparticles (Pd-NPs) were used as modifier. The interference of (40)Ar(35)Cl(+) at arsenic mass m/z 75 was reduced significantly using dynamic reaction cell (DRC). Standard addition and isotope dilution methods were used for the quantifications. The method reported has been applied to the determination of Cu, As, Hg and Pb in selected vegetable oil samples purchased from a local market. The analytical results obtained were in good agreement with those of digested samples analyzed by pneumatic nebulization ICP-MS with 95% confidence according to Student t-test (except for Cu). Precision between sample replicates was better than 10% with the ETV-ICP-MS method. The detection limits obtained from standard addition curves were 0.4, 0.5, 1.1 and 0.4 ng g(-1) for Cu, As, Hg and Pb, respectively, in the original oil samples.

Dispersive liquid liquid microextraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry for the speciation of inorganic selenium in environmental water samples

A novel method based on dispersive liquid liquid microextraction (DLLME) followed by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) determination was proposed for the speciation of inorganic selenium by using 5-mercapto-3-phenyl-1,3,4-thiadiazole-2-thione potassium salt (Bismuthiol II) as both chelating reagent and chemical modifier. In this method, 500μL ethanol (as disperser solvent) containing 70μL chloroform (as extraction solvent) and 0.2gL−1 Bismuthiol II (as chelating reagent) was rapidly injected into a sample solution to form cloudy solution. The complex of Se(IV) with Bismuthiol II was rapidly extracted into the extraction solvent at pH 2.0, while Se(VI) was remained in the aqueous solutions. Thus, the separation of Se(IV) and Se(VI) could be realized. After centrifugation, the complex of Se(IV) and Bismuthiol II concentrated in the extraction solvent was introduced into the ETV-ICP-MS for determination of Se(IV). Se(VI) was reduced to Se(IV) prior to determination of total selenium, and its assay was based on subtracting Se(IV) from total selenium. The main factors influencing the DLLME and the vaporization behavior of selenium in ETV were investigated systematically. Under the optimal conditions, the limit of detection (LOD) for Se(IV) was 0.047ngmL−1. The relative standard deviation (RSD) was 7.2% (CSe(IV)=1.0ngmL−1, n=8) with an enhancement factor of 64.8-fold from only 5mL of water sample. The proposed method was successfully applied to the speciation of inorganic selenium in different environmental water samples with recoveries ranging from 94.8 to 108% for the spiking samples. In order to validate the proposed method, a Certified Reference Material of Environment Water (GBW(E)080395) was analyzed, and the determined value obtained was in good agreement with the certified value.

Tungsten coil electrothermal matrix decomposition and sample vaporization to determine P and Si in biodiesel by inductively coupled plasma mass spectrometry

A tungsten coil extracted from commercially available microscope light bulbs is used to decompose the organic matrix and vaporize biodiesel samples for P and Si determination by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). The vaporization cell is connected to a modified sheath gas tube so that sample vapors are mixed with a continuous aerosol flow exiting the ICP-MS nebulization chamber. Helium and H2 are used with a collision–reaction interface (CRI) to minimize spectral interferences and obtain low baseline spectra. These strategies contribute to improving repeatability and accuracy. A small solid state constant current power supply is used to resistively heat the vaporizer and 10 μl sample aliquots are introduced manually on the coil with a micropipette. Limits of detection of 0.4 and 0.1 mg kg−1 are obtained for P and Si, respectively. Reference biodiesel samples are used to check the accuracy of the procedure for P. A spike experiment is carried out to assess accuracy in Si determinations. No statistically significant differences are observed for reference and determined values by applying a t-test at a 95% confidence level. The direct analysis of biodiesel by tungsten coil ETV-ICP-MS is a fast and effective alternative to determine challenging elements like P and Si.

Chip-based liquid phase microextraction combined with electrothermal vaporization-inductively coupled plasma mass spectrometry for trace metal determination in cell samples

Metal determination in precious biological samples is critical to metallomics research. Microfluidic chips provide an excellent platform for the miniaturization of extraction. In this work, a chip-based liquid phase microextraction (chip-based LPME) device was fabricated and combined with electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the determination of trace Cu, Zn, Cd, Hg, Pb and Bi in cell samples and human serum samples. With sodium diethyldithiocarbamate (DDTC) as both the chemical modifier for low-temperature ETV-ICP-MS and the extracting reagent for the chip-based LPME, the chip parameters influencing the extraction efficiency including central channel width, branch channel ratio and central channel length were optimized by orthogonal design experiments. Under the optimized conditions, the limits of detection (LODs) are in the range of 6.6–89.3 pg mL−1 with the RSDs ranging from 4.23–8.15% (n = 7, c = 1 ng mL−1) for the target metal ions. The linear range covers three magnitudes with correlation coefficients higher than 0.99. The proposed method was validated by analyzing the target metal ions in certified reference materials of GBW07605 human hair and GBW09152 human serum, and metal determination in HepG2 cells, Jurkat T cells and a human serum sample were achieved with the recoveries in the range of 86.6–119%. The developed method is fast, has a low sample and reagent consumption and is highly sensitive, thus it is quite suitable for the analysis of precious biological samples such as cells.

Phase transfer hollow fiber liquid phase microextraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of trace heavy metals in environmental and biological samples

A new method of phase transfer hollow fiber liquid phase microextraction (PT-HF-LPME) combined with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) has been developed for the determination of trace Co, Pd, Cd and Bi in environmental and biological samples. In PT-HF-LPME, an intermediate solvent (1-butanol) was added into the sample solution to ensure the maximum contact area between the target metal ions and the chelating reagent (8-hydroxyquinoline, 8-HQ), which accelerated the formation of 8-HQ-metal complexes and their subsequent extraction by extraction solvent (toluene). The experimental parameters affecting the extraction efficiency of PT-HF-LPME for the target metals were studied by simplex optimization and orthogonal array design (OAD) experiments. Under the optimized conditions, the enrichment factors for Co, Pd, Cd and Bi were 110, 393, 121 and 111-fold, respectively, the limits of detection (LODs, 3σ) ranged from 3.7 to 8.3ngL−1. The relative standard deviations (RSDs, c=0.5ngmL−1, n=7) were 8.7, 6.2, 12.4 and 12.9% for Co, Pd, Cd and Bi, respectively. To validate the accuracy of the proposed method, two Certified Reference Materials of GSBZ50009-88 Environment Water and GBW09103 Human Urine were analyzed, and the results obtained for Cd were in good agreement with the certified values. Finally, the developed method was successfully applied to the analysis of Co, Pd, Cd and Bi in lake water and human urine samples.

Nanoparticle labelling-based magnetic immunoassay on chip combined with electrothermal vaporization - inductively coupled plasma mass spectrometry for the determination of carcinoembryonic antigen in human serum

A sensitive and selective on chip magnetic immunoassay method, based on a sandwich-type immunoreaction with PbS nanoparticle (NPs) labels in combination with electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICP-MS), was proposed for the determination of carcinoembryonic antigen (CEA). We designed and fabricated a microfluidic chip for magnetic immunoassay, and the prepared iminodiacetic acid modified silica coated magnetic nanoparticles (IDA-SCMNPs) were packed into the central microchannel to form a solid phase column by self-assembly under the magnetic field. After completion of the immunoreaction involving a primary antibody, CEA and a secondary antibody labeled with PbS NPs on a magnetic solid phase packed-column, ETV-ICP-MS was used to determine the concentration of Pb that was released from the captured PbS NPs using an acid-dissolution step. The concentrations of CEA can be correlated with that of Pb. The established method demonstrated a limit of detection of 0.058 μg L(-1) for CEA, with a relative standard deviation (RSD) of 6.7% (c = 10 μg L(-1), n = 7). A linearity ranging from 0.2 μg L(-1) to 50 μg L(-1) and a 2-fold enrichment factor (from 60 μL sample solution to 30 μL eluent) were achieved. The proposed method was further validated by analyzing CEA in human serum. The results were in good agreement with those obtained by chemiluminescent immunoassay, which is currently used as a clinical method. Overall, this method offers the advantages of high speed, high sensitivity, high selectivity, low sample/reagents consumption, high integrity and versatility. Moreover, it can be easily applied to other biological and medical assays.

Headspace trapping of the hydrides on a Pd(II)-coated graphite adsorptive bar as a microextraction method for ETV–ICP-MS determination of Se, Te and Bi in seawater and human hair samples

A new, simple and sensitive method by combining headspace Pd(II)-coated graphite bar microextraction (GBME) with electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICP-MS) was developed for the determination of trace Se, Te and Bi in seawater and human hair. In this method, the graphite bar was coated with Pd(II) and then used for headspace trapping of the hydrides of Se(IV), Te(IV) and Bi(III). The graphite bar with enriched hydrides of analytes was inserted directly into the graphite tube and subsequently determined by ETV-ICP-MS according to the established temperature program. The experimental parameters, which may affect the extraction and vaporization of target analytes, were systematically investigated and the optimal experimental conditions were established. Under the optimal conditions, the detection limits of the method were 8.6, 2.6 and 0.2 ng l(-1) and the relative standard deviations (RSDs) were 7.0%, 6.2% and 8.0% (C=0.20 microg l(-1), n=7) for Se, Te and Bi, respectively. Linearity was obtained over the range of 0.05-20.00, 0.01-5.00 and 0.01-20.00 microg l(-1) with the correlation coefficients of 0.9942, 0.9997 and 0.9976 for Se, Te and Bi, respectively. The proposed method was successfully applied for the determination of trace Se, Te and Bi in seawater and human hair samples. In order to validate the method, the proposed method has also been applied for the determination of trace Se, Te and Bi in the certified material of GBW07601 human hair, and the determined values were in good agreement with the certified values.

Magnetic solid phase microextraction on a microchip combined with electrothermal vaporization-inductively coupled plasma mass spectrometry for determination of Cd, Hg and Pb in cells

Quantitative analysis of trace levels of heavy metals in human cells is critical to environmental and toxicological research. We describe here a new strategy of determining ultratrace levels of cadmium, lead, and mercury in cultured cells. It involves the integration of cell sample introduction and magnetic nanoparticle solid phase microextraction (MSPME) on a microfluidic chip, combined with electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICP-MS) detection. γ-mercaptopropyltrimethoxysilane (γ-MPTS) modified silica-coated magnetic nanoparticles were synthesized and demonstrated for the microextraction of Cd, Pb, and Hg. Under an external magnetic field, these magnetic nanoparticles self-assembled in microchannels to form a solid phase packed column. The formation mechanism of the on-chip magnetic solid phase packed column and the main factors influencing the packing and analytical performance were investigated. Under the optimized conditions, MSPME enabled enrichment of Cd, Hg, and Pb by a factor of >40, and resulted in improved limits of detection for Cd (0.72 ng L−1), Hg (0.86 ng L−1), and Pb (1.12 ng L−1) using ETV-ICP-MS. Quantitative analyses of trace Cd, Hg and Pb in HepG2 cells were achieved by applying the microfluidic system that integrated cell rupture, mixing, magnetic extraction and elution into one device, followed by ultrasensitive detection by ETV-ICP-MS, which required only a microlitre amount of sample. Analysis of approximately 5000 cells revealed that the average amounts of Cd, Hg and Pb in a single HepG2 cell were of the order of a few femtograms, and that the cellular levels increased with increasing concentrations of these metals in cell cultures. The concentrations of Cd, Hg, and Pb detectable in HepG2 cells were several orders of magnitude lower than their IC50 values, suggesting that the technique is potentially useful for measuring these heavy metals in studies of chronic metal toxicity.