Vaporization Sample Introduction Research Articles

Electrothermal Vaporization Sample Introduction for Spaceflight Water Quality Monitoring via Gas Chromatography-Differential Mobility Spectrometry.

In the history of manned spaceflight, environmental monitoring has relied heavily on archival sampling. However, with the construction of the International Space Station (ISS) and the subsequent extension in mission duration up to one year, an enhanced, real-time method for environmental monitoring is necessary. The station air is currently monitored for trace volatile organic compounds (VOCs) using gas chromatography-differential mobility spectrometry (GC-DMS) via the Air Quality Monitor (AQM), while water is analyzed to measure total organic carbon and biocide concentrations using the Total Organic Carbon Analyzer (TOCA) and the Colorimetric Water Quality Monitoring Kit (CWQMK), respectively. As mission scenarios extend beyond low Earth orbit, a convergence in analytical instrumentation to analyze both air and water samples is highly desirable. Since the AQM currently provides quantitative, compound-specific information for air samples and many of the targets in air are also common to water, this platform is a logical starting point for developing a multimatrix monitor. Here, we report on the interfacing of an electrothermal vaporization (ETV) sample introduction unit with a ground-based AQM for monitoring target analytes in water. The results show that each of the compounds tested from water have similar GC-DMS parameters as the compounds tested in air. Moreover, the ETV enabled AQM detection of dimethlsilanediol (DMSD), a compound whose analysis had proven challenging using other sample introduction methods. Analysis of authentic ISS water samples using the ETV-AQM showed that DMSD could be successfully quantified, while the concentrations obtained for the other compounds also agreed well with laboratory results.

Diode laser thermal vaporization ICP MS with a simple tubular cell for determination of lead and cadmium in whole blood

A low-cost diode laser thermal vaporization sample introduction system to ICP MS for determination of lead and cadmium in whole blood.

Taking part of the lab to the sample: On-site electrodeposition of Pb followed by measurement in a lab using electrothermal, near-torch vaporization sample introduction and inductively coupled plasma-atomic emission spectrometry

An electrodeposition method for preconcentration and separation of labile Pb from liquid samples with a complex matrix is described. For the first time, Pb was electrodeposited on-site on Re coiled-filament assemblies that were developed for use with an electrothermal, near-torch vaporization (NTV) sample introduction system and inductively coupled plasma-atomic emission spectrometry (ICP-AES). The coiled-filament assemblies (or simply coils) were purposely designed to be removable and were fabricated to have identical coupling-mechanisms so that they can be used interchangeably. In addition to their small size (2.75cm long and 0.65cm wide), coiled-filament assemblies weighed only 1.4g, which made them portable for on-site use. The detection limit from diluted seawater Certified Reference Material (CRM) and NTV-ICP-AES was 25pg/mL following a 3min electrodeposition. This detection limit represents a 40-fold improvement as compared to the detection limit obtained by pipetting 5μL of dilute Pb standard solution directly on the coil. The detection limit improved by 400-times (to 2pg/mL) when the electrodeposition time was increased to 60min. Lead from very hard tap water was electrodeposited on coiled filaments on-site using a shirt-pocket size, battery-operated potentiostat and portable electrodeposition instrumentation. Concentration was determined in the lab using NTV-ICP-AES. The Pb concentration was used to test for compliance with the Pb–Cu rule set by the United States Environmental Protection Agency (US EPA). Overall, on-site electrodeposition permitted determination of Pb at the environmental conditions (e.g., pH, temperature) recorded at the time of sampling. On-site electrodeposition also opens the possibility for shipping portable coils with Pb electrodeposited on them to the lab rather than shipping large volumes of sample, thus reducing shipping, handling and storage costs.

Bringing part of the lab to the field: On-site chromium speciation in seawater by electrodeposition of Cr(III)/Cr(VI) on portable coiled-filament assemblies and measurement in the lab by electrothermal, near-torch vaporization sample introduction and inductively coupled plasma-atomic emission spectrometry

A field-deployable electrochemical approach to preconcentration, matrix clean up and selective electrodeposition of Cr(III) and Cr(III)+Cr(VI) in seawater is described. Using portable, battery-operated electrochemical instrumentation, Cr species in seawater were electrodeposited in the field on portable coiled-filament assemblies made from Re. Assemblies with dried residues of Cr(III) or Cr(III)+Cr(VI) on them were transported to the lab for concentration determination by electrothermal, near-torch vaporization (NTV) sample introduction and inductively coupled plasma-atomic emission spectrometry (ICP-AES).Electrodeposition offers selective species deposition, preconcentration and matrix clean up from seawater samples. For selective deposition, free Cr(VI) was electrodeposited at −0.3V and Cr(III)+Cr(VI) at −1.6V (both vs Ag/AgCl). Interestingly, at 0V (vs Ag/AgCl) and in the absence of an electrodeposition potential only Cr(VI) was spontaneously and selectively adsorbed on the coil and reasons for this are given. Due to preconcentration afforded by electrodeposition, the detection limits obtained after a 60s electrodeposition at the voltages stated above using buffered (pH=4.7) artificial seawater spiked with either Cr(III) or Cr(VI) were 20pg/mL for Cr(III) and 10pg/mL for Cr(VI). For comparison, the detection limit for Cr obtained by pipetting directly on the coil 5μL of diluted standard solution was 500pg/mL, thus it was concluded that electrodeposition offered 40 to 60 fold improvements. Matrix clean up is required due to the high salt content of seawater and this was addressed by simply rinsing the coil with 18.2MΩ water without any loss of Cr species. Reasons for this are provided. The method was validated in the lab using buffered artificial seawater and it was used in the field for the first time by sampling seawater, buffering it and immediately electrodepositing Cr species on portable assemblies on-site.Electrodeposition in the field addressed species transformation during sample pre-treatment. Such transformations occur due to sample acidification and may take place during transport and possibly storage prior to analysis. Thus, electrodeposition in the field is more reflective of Cr species concentration at the environmental conditions (e.g., temperature) at the time of sampling. It also opens up the possibility for shipping to the lab portable assemblies with Cr species on them rather than shipping large volumes of sample to the lab, thus also reducing shipping, handling and storage costs.

Micro- and nano-volume samples by electrothermal, near-torch vaporization sample introduction using removable, interchangeable and portable rhenium coiled-filament assemblies and axially-viewed inductively coupled plasma-atomic emission spectrometry

An electrothermal, near-torch vaporization (NTV) sample introduction for micro- or nano-volume samples is described. Samples were pipetted onto coiled-filament assemblies that were purposely developed to be removable and interchangeable and were dried and vaporized into a small-volume vaporization chamber that clips onto any ICP torch with a ball joint. Interchangeable assemblies were also constructed to be small-size (e.g., less than 3cm long with max diameter of 0.65cm) and light-weight (1.4g) so that they can be portable. Interchangeable assemblies with volume-capacities in three ranges (i.e., <1μL, 1–10μL and 10–100μL) were fabricated and used.The horizontally-operated NTV sample introduction was interfaced to an axially-viewed ICP-AES (inductively coupled plasma-atomic emission spectrometry) system and NTV was optimized using ICP-AES and 8 elements (Pb, Cd, Zn, V, Ba, Mg, Be and Ca). Precision was 1.0–2.3% (peak height) and 1.1–2.4% (peak area). Detection limits (obtained using 5μL volumes) expressed in absolute-amounts ranged between 4pg for Pb to 0.3fg (~5million atoms) for Ca. Detection limits expressed in concentration units (obtained using 100μL volumes of diluted, single-element standard solutions) were: 50pg/mL for Pb; 10pg/mL for Cd; 9pg/mL for Zn; 1pg/mL for V; 0.9pg/mL for Ba; 0.5pg/mL for Mg; 50fg/mL for Be; and 3fg/mL for Ca.Analytical capability and utility was demonstrated using the determination of Pb in pg/mL levels of diluted natural water Certified Reference Material (CRM) and the determination of Zn in 80nL volumes of the liquid extracted from an individual vesicle. It is shown that portable and interchangeable assemblies with dried sample residues on them can be transported without analyte loss (for the concentrations tested), thus opening up the possibility for “taking part of the lab to the sample” applications, such as testing for Cu concentration-compliance with the lead–copper rule of the Environmental Protection Agency. It is also shown that interchangeable assemblies with volume-capacities in the ranges mentioned above can be used interchangeably in the same calibration curve, thus in some cases and for on-site applications, volume-of-sample can be substituted for sample-dilution.

A Review of Tungsten Coil Electrothermal Vaporization as a Sample Introduction Technique in Atomic Spectrometry

Tungsten coil electrothermal vaporization has served as an alternative sample introduction method in atomic spectroscopy for some time and is easily employed in a laboratory because of its mass production, ease of use, and small requirement for power. This review will focus on the use of the tungsten coil as an electrothermal vaporization sample introduction source in atomic absorption, emission, and fluorescence spectrometry over the past decade. Analyzed samples have both biological and industrial significance, illustrating the versatility of the technique. Since its conception 40 years ago, tungsten coil electrothermal vaporization continues to provide users with innovative options for spectroscopic analysis.

Simultaneous electrothermal vaporization and nebulizer sample introduction system for inductively coupled plasma mass spectrometry

The novel analytical application of the combination of an inline electrothermal vaporization (ETV) and nebulization source for inductively coupled plasma mass spectrometry (ICP-MS) has been studied. Wet plasma conditions are sustained during ETV introduction by 200 mL/min gas flow through the nebulizer, which is merged with the ETV transport line at the torch. The use of a wet plasma with ETV introduction avoided the need to change power settings and torch positions that normally accompany a change from wet to dry plasma operating conditions. This inline-ETV source is shown to have good detection limits for a variety of elements in both HNO 3 and HCl matrices. Using the inline-ETV source, improved limits of detection (LOD) were obtained for elements typically suppressed by polyatomic interferences using a nebulizer. Specifically, improved LODs for 51V and 53Cr suffering from Cl interferences ( 51ClO + and 53ClO + respectively) in a 1% HCl matrix were obtained using the inline-ETV source. LODs were improved by factors of 65 and 22 for 51V and 53Cr, respectively, using the inline-ETV source compared to a conventional concentric glass nebulizer. For elements without polyatomic interferences, LODs from the inline-ETV were comparable to conventional dry plasma ETV-ICP time-of-flight mass spectrometry results. Lastly, the inline-ETV source offers a simple means of changing from nebulizer introduction to inline-ETV introduction without extinguishing the plasma. This permits, for example, the use of the time-resolved ETV-ICP-MS signals to distinguish between an analyte ion and polyatomic isobar.

Ultratrace determination of Pb, Se and As in wine samples by electrothermal vaporization inductively coupled plasma mass spectrometry

The determination of Pb, Se and As in wine has a great interest due to health risks and legal requirements. To perform the analysis of wine, two considerations must be taken into account: (i) the low concentration level of the analytes; and (ii) the risk of interferences due to wine matrix components. The goal of this work is to evaluate electrothermal vaporization (ETV) sample introduction for ultratrace determination of Pb, Se and As in wine samples by inductively coupled plasma mass spectrometry (ICP-MS). The results obtained with ETV-ICP-MS were compared to those obtained with conventional liquid sample introduction in ICP-MS and electrothermal atomic absorption spectrometry (ETAAS). Analytical figures of merit of ETV sample introduction strongly depend on the amount of wine sample, on the modifier nature (i.e. Pd, ascorbic acid or citric acid) and concentration and on the temperature program. Wine matrix components exert a great influence on analyte transport efficiency. Due to this fact, the analysis of wine cannot be performed by means of external calibration but the standard addition methodology should be used. The determination of Pb and Se in wine by ETV-ICP-MS provides similar results as conventional liquid sample introduction ICP-MS. For As, the concentration values obtained with ETV sample introduction were between two and four times lower than with the conventional system. These differences are related to the lower intensity of polyatomic interferences (i.e. 40Ar 35Cl + vs. 75As +) obtained for ETV sample introduction when compared to the conventional system. Finally, no differences for Pb determination were observed between ETV sample introduction and ETAAS. Unfortunately, the limits of detection for As and Se in ETAAS were not low enough to quantify these elements in the wine samples tested.

Comparison of tungsten coil electrothermal vaporization and thermospray sample introduction methods for flame furnace atomic absorption spectrometry

Flame furnace atomic absorption spectrometry (FF-AAS) is a newly developed flame atomic absorption spectrometric technique based on arranging a flame furnace onto the top of the flame burner head. In this fundamental investigation, 25 elements were carefully tested by using either thermospray FF-AAS or tungsten coil electrothermal vaporization FF-AAS, of which 15 volatile and semi-volatile elements (Cd, Tl, Ag, Pb, Zn, Hg, Cu, Sb, Bi, Te, In, As, Se, Sn and Au) exhibited better limits of detection compared to those by conventional FAAS; however, non-volatile or refractory elements (Fe, Co, Ni, Cr, Mn, Pd, Pt, Al, Be and V) showed inferior sensitivities by the proposed methods.

Dry analyte introduction system for ICP-MS optimization utilizing a dry plasma

A solventless, multi-element, steady-state optimization system is presented. The device uses three parallel conduits that contain solid NbF5 and SnBr4 as well as a low wattage tungsten filament loaded with Pb to deliver dry vapors to an ICP. These are used to create a steady-state signal containing the following ions that can be used for tuning: 28Si+, 79Br+, 120Sn+, 184W+, and 208Pb+. In comparison to using a nebulizer for optimization, the dry plasma optimization produced an average enhancement of 4.5(±0.4)-fold for 26 elements when using electrothermal vaporization sample introduction.

Ti in dilute slurries of TiO 2 nanoparticles by in-torch vaporization sector field inductively coupled plasma-mass spectrometry☆

A Re coil-filament in-torch vaporization (ITV) sample introduction system was interfaced to a sector field inductively coupled plasma-mass spectrometry (SFICP-MS) system. In this first report on an un-optimized ITV-SF-ICP-MS system, detection limits were established using 5 μL volumes of 100 pg mL − 1 standard solutions, translating to 0.5 pg absolute. Such absolute amounts of a dried solution are near or below the detection limit of many ICP-based techniques. The absolute detection limits for Cd, Eu, Pb, Ti, U and Zn were in the 0.2–2 fg range (or, in the 10's of millions to millions of atoms for Pb, Cd, Zn and Ti, about one million atoms for U and about 800 thousand for Eu). These absolute detection limits along with the ability of ITV to handle minute amounts of discrete samples (thus eliminating memory effects from nanoparticles adhering to the walls of pneumatic nebulization sample introduction systems and from clogging of the mass spectrometer orifice), use of sonicated water-based slurries (that eliminated contamination from acid digestion reagents or from slurry stabilization reagents), and elimination of oxygen containing molecular ion interferences due to use of dry samples enabled concentration determinations of Ti (and consequently of TiO 2) in pg mL − 1 concentrations of slurries of manufactured, 20 nm diameter TiO 2 nanoparticles.

Studies on transport phenomena in electrothermal vaporization sample introduction applied to inductively coupled plasma for optical emission and mass spectrometry

In the present work electrothermal vaporization (ETV) was used in both inductively coupled plasma mass spectrometry (ICP-MS) and optical emission spectrometry (OES) for sample introduction of solution samples. The effect of (Pd + Mg)-nitrate modifier and CaCl 2 matrix/modifier of variable amounts were studied on ETV-ICP-MS signals of Cr, Cu, Fe, Mn and Pb and on ETV-ICP-OES signals of Ag, Cd, Co, Cu, Fe, Ga, Mn and Zn. With the use of matrix-free standard solutions the analytical curves were bent to the signal axes (as expected from earlier studies), which was observed in the 20–800 pg mass range by ICP-MS and in the 1–50 ng mass range by ICP-OES detection. The degree of curvature was, however, different with the use of single element and multi-element standards. When applying the noted chemical modifiers (aerosol carriers) in microgram amounts, linear analytical curves were found in the nearly two orders of magnitude mass ranges. Changes of the CaCl 2 matrix concentration (loaded amount of 2–10 μg Ca) resulted in less than 5% changes in MS signals of 5 elements (each below 1 ng) and OES signals of 22 analytes (each below 15 ng). Exceptions were Pb (ICP-MS) and Cd (ICP-OES), where the sensitivity increase by Pd + Mg modifier was much larger compared to other elements studied. The general conclusions suggest that quantitative analysis with the use of ETV sample introduction requires matrix matching or matrix replacement by appropriate chemical modifier to the specific concentration ranges of analytes. This is a similar requirement to that claimed also by the most commonly used pneumatic nebulization of solutions, if samples with high matrix concentration are concerned.

Simultaneous determination of the Cd and Zn total body burden of individual, nearly microscopic, nanoliter-volume aquatic organisms ( Hyalella azteca) by rhenium-cup in-torch vaporization (ITV) sample introduction and axially viewed ICP-AES.

The Cd and Zn total body burden of individual, up to 7-day-old aquatic organisms (Hyalella azteca benthic amphipod) with an average volume of approximately 100 nL was determined simultaneously by using rhenium-cup (Re-cup) in-torch vaporization (ITV) sample introduction and an axially viewed inductively coupled plasma atomic emission spectrometry (ICP-AES) system. The direct elemental analysis capabilities of this system (i.e., no sample digestion) reduced sample preparation time, eliminated contamination concerns from the digestion reagent and, owing to its detection limits (e.g., in the low pg range for Cd and Zn), vit enabled simultaneous determinations of Cd and Zn in individual, neonate and young juvenile specimens barely visible to the unaided eye (e.g., nearly microscopic). As for calibration, liquid standards and the standard additions method were tested. Both methods gave comparable results, thus indicating that in this case liquid standards can be employed for calibration, and in the process making use of the standard additions method unnecessary. Overall, the ITV-ICP-AES approach by-passed the time-consuming acid digestions, eliminated the potential for contamination from the digestion reagents, improved considerably the speed of acquisition of analytical information and enabled simultaneous determinations of two elements using individual biological specimens.

Determination of absolute transport efficiencies of Be, Cd, In, Pb and Bi for electrothermal vaporization sample introduction into an inductively coupled plasma using an in-line electrostatic precipitator

A novel laboratory-constructed electrostatic precipitator for the determination of analyte transport efficiencies from a tube furnace electrothermal vaporization (ETV) sample introduction system is described. This simple experimental set up captures the analyte electrostatically using a negative corona discharge. The absolute transport efficiencies using experimental conditions typical of those applied to real analysis by ETV–ICP-MS were determined for Be, Cd, In, Pb and Bi to be 26±3, 39±8, 35±1, 50±11 and 35±1%, respectively. Pd and NaCl were evaluated as ‘carriers’ and were found to only marginally increase analyte transport for the elements investigated. Pd enhanced efficiencies 20–50% for all but Bi, which decreased by 17%. The NaCl produced transport enhancements of 10–50% for all five analytes. However, uncertainties in the measurements made several of the individual improvements statistically insignificant. The mean precipitator collection efficiency of the aerosol leaving the ETV for the five elements studied was found to be greater than 90% and was determined using the ICP-MS signal with the in-line precipitator's voltage either on or off. While 30 ETV firings were used for a single efficiency determination, reasonable precision could be obtained with approximately 10 firings while still employing reasonable analyte masses, i.e. approximately 20 ng. The transport results are in good agreement with previous studies using similar ETV design and analyte masses.

Simultaneous determination of hydride forming elements (As, Bi, Ge, Sb, Se) and Hg in biological and environmental reference materials by electrothermal vaporization–microwave induced plasma-optical emission spectrometry with their in situ trapping in a graphite furnace

The approach for the simultaneous determination of five hydride forming elements (As, Bi, Ge, Sb, Se) and Hg by microwave induced plasma optical emission spectrometry (MIP-OES) is described. The combination of hydride generation (HG) and in situ preconcentration of the analytes onto the Pd (for As, Bi, Ge, Sb, Se) or Au (for Hg) pretreated interior wall surfaces of a graphite furnace (GF) has been used as a collection technique. The furnace comprised the electrothermal vaporization (ETV) sample introduction unit of a MIP-OES detection system. Compromise conditions are established. The trapping temperature was 300 °C and the vaporization temperature 2100 °C. Calibration was achieved via the method of standard additions. Absolute limits of detection (3σblank criterion, peak height) were 3, 8, 15, 8, 20 and 10 ng for As, Bi, Ge, Hg, Sb and Se, respectively. System efficiency for the generation and sequestration of the hydrides averaged better than 55%. The HG-ETV-MIP-OES method was successfully applied to the determination of As, Bi, Ge, Hg, Sb and Se in several certified biological and environmental reference materials (hair, tissue, leaves, soil, sediment, fly ash) with a precision of 8–15% RSD at a concentration 50-fold above the LOD, following high pressure decomposition and dissolution of the samples by microwave heating in a mixture of acids. The results obtained by this method were in fair agreement with the reference value.

Generation of a square wave inductively coupled plasma scanning mass spectrometry signal using electrothermal vaporization sample introduction

A device was designed to convert the typical skewed gaussian shaped signal from an inductively coupled plasma mass spectrometer (ICP-MS) using electrothermal vaporization (ETV) into a square wave signal. The basis for such a transformation is centered on the assumption that the aerosol particles produced from ETV are aerodynamically small, and thus, have diffusive properties similar to gases, which makes them easy to mix and resistant to loss by settling. The ETV square wave signals were generated through the use of a stainless steel cylinder equipped with a motor driven piston assembly, which was used to trap the transient ETV signal and deliver a uniform density aerosol to the ICP-MS. The length of the signal was controlled by the rate of travel of the piston during expulsion of the sample aerosol. A constant flow rate was achieved and maintained using a pressure sensor feedback to the motor driving the piston. The system was evaluated by quantitative full mass scans on a variety of signal shapes including square wave signals, normal ETV signals, and broadened ETV signals generated with the use of a single bead string reactor (SBSR). The square wave signals yielded precisions for quantitative full mass scans of better than 10% RSD for most metals compared to approximately 15% for SBSR broadened signals and 40% for normal signals. The improved precision was attributed to an increased duty cycle, but the increase did not become significant until more than 100 masses were monitored due to the relatively small amount of “temporal overhead time” (fly-back time, amplifier settling time, etc.) relative to data collection periods. Because the ETV generated aerosol consists of aerodynamically small particles, there was only a minimal decrease (<2–11%) in the integrated signal area as a result of using the square wave generator.

Calcium content of individual, microscopic, (sub) nanoliter volume Paramecium sp. cells using rhenium-cup in-torch vaporization (ITV) sample introduction and axially viewed ICP-AES

The Ca content of individual Paramecium species (sp.) cells with an average volume of about 0.1 nL was determined by Re-cup in-torch vaporization (ITV) sample introduction and an axially viewed inductively coupled plasma atomic emission spectrometry (ICP-AES) system. Calcium contamination and, overall, sample preparation of live microscopic biological cells proved to be problematic. These problems were addressed using sub-boiled distilled, de-ionized, water, and by washing and manipulating cells under a microscope. Direct (i.e., minimum sample pre-treatment) Ca analysis of one microscopic cell at-a-time, and overall, an ability to discern small differences in the Ca content of individual cells are key advantages of this approach.

Rhenium-cup, in-torch vaporization (ITV) sample introduction for axially viewed ICP-AES and its application to the analysis of a microscopic, ng-weight solid sample

A reported advantage of axial over radial plasma viewing is improvement of detection limits. In an attempt to capitalize on this advantage, a new, horizontally operated in-torch vaporization (ITV) sample introduction system was developed and was coupled to an axially viewed inductively coupled plasma-atomic emission spectrometry (ICP-AES) instrument. In ITV, a sample is placed into a cup made out of a thin rhenium (Re) foil and the sample-carrying cup is inserted in a small volume vaporization chamber that clips onto a typical ICP torch. The effect of carrier gas (Ar–∼3% H2) flow rate and cup insertion position on analyte emission characteristics was examined for several elements (e.g., Ba, Be, Ca, Cd, Mg, V, Pb and Zn) that had different vaporization characteristics and emission lines that covered a wide spectral range (e.g., from 213.856 to 455.403 nm). Calibration curves were linear over the (narrow) range of concentrations used in this work and precision ranged between 1.0 and 2% (peak height) and between 1.0 and 4.6% (peak area). Detection limits were in the pg range for Pb, Cd and Zn, in the sub-pg range for Ba, Mg and V, and in the fg and sub-fg range for Be and Ca. The improvement in detection limits enabled determinations of Ca and Mg in microscopic individual grains of pollen (10 pL volume, ∼8 ng weight).

Multiplexed electrothermal vaporization sample introduction system for inductively coupled plasma spectrometry

A multiplexed electrothermal vaporization (ETV) system for sample introduction into an inductively coupled plasma was designed in an effort to increase sample turn-around time. Tungsten filaments (300 W), originally designed for overhead projectors, were chosen for use as ETVs to avoid the high power requirements associated with other ETV devices, e.g. graphite furnaces (2–3 kW). In short, we have multiplexed the thermal stages have been multiplexed such that a vaporization event can take place every 20 s. This represents a significant increase in the throughput typically associated with ETV-ICPMS, which is normally approximately 20–30 samples/h. Evaluated with respect to common figure of merit criteria, the performance of the multiplexed ETV system is similar to that seen with conventional graphite furnace ETV systems. However, several mass spectral interferences can be introduced by the presence of W into the plasma, which hinder the analysis of certain metals (Hg, Mo, etc.). Thus, other low power vaporizers (e.g. Re, Ta) should be considered for use in future systems.

Peak broadening from an electrothermal vaporization sample introduction source into an inductively coupled plasma

Signal broadening using electrothermal vaporization with inductively coupled mass spectrometry (ETV-ICPMS) occurs at a rate much faster than would be predicted by simple longitudinal diffusion. A Monte Carlo simulation that focused on particle motion within the transport tubing was created to elucidate the causes of this dispersion within ETV-ICPMS. Several parameters, including the diffusion coefficient, tube diameter, transport tube length, and flow rate were varied to discern their role in signal broadening. Using typical instrumental parameters, the parabolic flow profile generated by laminar flow of the carrier gas was shown to be the primary cause of dispersion. Manipulating the aforementioned variables to lessen the effects of laminar flow led to a decrease in dispersion. Conversely, increasing the role of laminar flow promoted broadening. The broadening processes should be applicable to any transient introduction system where material must be transported to a detection system. Due to the difference in the rate of broadening expected for particles of different sizes, the simulation was used to calculate the average size of particles generated in the ETV using different mass amounts of sample. No change in particle size (∼1 nm) was seen for mass amounts ranging from 10–10 000 pg, which suggests that the particle number is increased with increasing sample mass rather than the average particle size. Using this method of determining particle size, it might be possible to further evaluate the mechanisms of physical ‘carrier’ action.