In-torch Vaporization Research Articles

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.

68Zn isotope exchange experiments reveal an unusual kinetic lability of the metal ions in the di-zinc form of IMP-1 metallo-β-lactamase

The apparently paradoxical behaviour of facile exchange (kinetic lability) of tightly bound (thermodynamic stability) zinc ions in the enzyme IMP-1 metallo-beta-lactamase with Zn-68 and cadmium ions, as indicated by in-torch vaporization inductively-coupled plasma mass spectrometry (ITV-ICP-MS) and electrospray-ionization mass spectrometry (ESI-MS), is consistent with the involvement of a third metal ion in promoting Lewis acid/base type exchange processes.

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.

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).

Lead in micro-samples of whole blood by Rhenium-cup in-torch vaporization-inductively coupled plasma-atomic emission spectrometry (ITV-ICP-AES).

A method is described for screening of lead in diluted micro-samples of whole blood by a Re-cup, in-torch vaporization (ITV) sample introduction system for inductively coupled plasma-atomic emission spectrometry (ICP-AES). The method required minimum sample preparation. For example, blood was diluted with water and Triton X-100 in 0.5% HNO3 and, 5 microL were deposited on the Re-cup of the ITV sample introduction system. Samples were dried and charred in-situ prior to vaporization. Levels 1, 2, 3 and 4 (Pb concentration: 4.04, 10.3, 20.59 and 39.36 microg/dL) of NIST Standard Reference Material 955b 'lead in bovine blood' were used to test accuracy and precision. Accuracy was acceptable and precision was below 10% for levels 2-4 and 15% for level 1.

Rhenium-cup in-torch vaporization inductively coupled plasma atomic emission spectrometry for liquid, slurry or solid micro-samples

In rhenium-cup in-torch vaporization (ITV) sample introduction for inductively coupled plasma atomic emission spectrometry (ICP-AES), a rhenium (Re) cup, which is formed from a thin Re foil, acts as the sample-carrying probe. The sample-carrying probe is inserted in a vaporization chamber which clips onto a typical ICP torch. The effect of carrier gas (Ar–∼3%H2 mixture) flow rate and cup insertion position on analyte emission characteristics were examined for several elements (e.g., Pb, Zn, Cd, Mn, Mg, V, Sr, and Be) that had different vaporization characteristics and emission lines that covered a wide spectral range. Calibration curves were linear, precision ranged between 2.4 and 4.7% (peak heights) and between 1.2 and 6.0% (peak areas) and detection limits were in the pg to fg range. Due to the use of cups, ITV-ICP-AES can now be used with µL volumes of liquids and for direct (i.e., minimum sample pre-treatment) elemental analysis of slurries or solid micro-samples as well.

The influence of true simultaneous internal standardization and background correction on repeatability for laser ablation and the slurry technique coupled to ICP emission spectrometry

Micro-samples of human fingernails were analyzed for lead using Rhenium-cup, in-torch vaporization (ITV) sample introduction and inductively coupled plasma atomic emission spectrometry (ICP-AES). Lead concentrations were found to be in agreement with those reported in the literature. Direct elemental analysis of micro-samples of fingernails, minimum sample pre-treatment and, overall, increased speed of analysis are the main advantages of the approach.

Elemental analysis of micro-samples of liquids or slurries by coiled-filament in-torch vaporization-inductively coupled plasma atomic emission spectrometry (ITV-ICP-AES)

In coiled-filament in-torch vaporization (ITV) sample introduction for inductively coupled plasma atomic emission spectrometry (ICP-AES), a sample is placed onto a coiled filament (e.g., a Re wire) and the sample carrying filament is inserted into a vaporization chamber which is attached to an ICP torch. In this study, six vaporization chambers were tested using in-situ generated smoke. Of these, a 6.5 cm 3 (internal volume) chamber was chosen. An Ar-H 2 (≈3% v/v) carrier gas was used and the effect of flow rate and filament insertion position was determined for several elements (e.g., Zn, Pb, Cd, Mn, Mg, V, Be and Sr) that covered a range of wavelengths and vaporization characteristics. Analytical performance characteristics were also obtained and calibration graphs were linear over several orders of magnitude. Detection limits were in the pg to sub-pg range. Coiled-filament ITV-ICP-AES was also briefly tested with powdered solids as slurries using a biological standard reference material and Mn and Zn as test elements.

Electrically heated wire-loop, in-torch vaporization (ITV) sample introduction system for ICP-AES with photomultiplier tube detection and ICP-MS

In this first report on an electrically heated, Re wire-loop in-torch vaporization (ITV) sample introduction system for ICP-AES with photomultiplier tube detection and ICP-MS, some preliminary results obtained for Pb, Cd, Zn and Sr are presented. An un-optimized, manually operated ITV system and 10 μl volumes have been used. Estimated absolute detection limits are (in pg) Zn (26), Pb (25), Cd (41) and Sr (0.12) for ITV-ICP-AES and Zn (0.04), Pb (0.12), Cd (0.11) and Sr (0.32) for ITV-ICP-MS.

Correlation-based detection of spectral information using microliter volumes, in-torch vaporization (ITV) sample introduction and inductively coupled plasma atomic emission spectrometry with photodiode array detection

The application of Fourier transform-based cross-correlation techniques for automatic detection of spectral information using 10 μl volumes is presented. The basic approach involves interrogation of a spectral pattern from a multielement mixture for the presence of spectral features obtained by running single element standard(s). In essence, the multielement mixture is “interrogated” for the presence of the sought-for element and, thus, automatic interpretation of spectral information is obtained. Spectral patterns from 10 μl volumes of single element standards and multielement mixtures were acquired using an electrically heated wire-loop, in-torch vaporization (ITV) sample introduction system and an inductively coupled plasma (ICP) spectrometer equipped with a photodiode array detector (Leco Plasmarray). The wavelength region from about 280 nm to about 410 nm was covered. Spectral patterns for 10 elements (Al, Be, Co, Ni, Sc, Sr, V, Y, Yb and Zr) obtained using 10 μl volumes of single element standards were converted to spectral interference-free and noise-free binary software masks. Cross-correlation of these binary software masks with spectral patterns obtained from 10 μl volumes of multielement mixtures is discussed and a graphical user interface that utilizes a color-coded periodic table to present the likely composition (i.e. qualitative and semi-quantitative analysis) of a mixture on the computer screen is described.

Electrically heated wire-loop, in-torch vaporization sample introduction system for inductively coupled plasma atomic emission spectrometry with photodiode array detection

A new sample introduction system that can be used for the analysis of microliter volumes of liquids by inductively coupled plasma atomic emission spectrometry (ICP-AES) is described. The system consists of an electrically heated W wire-loop which is attached to a thermocouple ceramic insulator. Ceramic and wire-loop are inserted manually into the central tube of a modified ICP torch, with the top of the wire-loop positioned about 10 cm below the plasma. An inexpensive variac, which plugs into a wall socket, is used as a power supply. This in-torch vaporization (ITV) sample introduction system was characterized using an ICP optical emission spectrometer with a photodiode array detector. In this pilot study aimed at testing the validity of the approach, spectral interference effects arising from W emission lines are documented for Be, Cu, Mn, Sc, Sr, V, Y and Zn and preliminary analytical performance characteristics using an unoptimized wire-loop/torch design are presented. Calibration curves were linear for over three orders of magnitude for Sr, Y and Be; the non-linear calibration curves obtained for Cu were attributed to contamination from the power transfer cables, for Mg to contamination from the ceramic and for Ca to airborne particles adhering to the wire-loop. As well, Au-coated W wire-loops proved to be sensitive to Hg 0-vapor in air. Precision varied between 1.9 and 4.5% (10 μl injection of single element standards) and, estimated absolute detection limits were (in pg) Zn (710), V (20), Mn (10), Y (10), Sc (9), Be (1) and Sr (0.4).

Determination of mercury vapor in air using electrically heated, gold-coated wire-loops, in-torch vaporization sample introduction and inductively coupled plasma atomic emission spectrometry with photodiode array detection

A method for the determination of Hg 0 vapor in ambient air using an electrically heated, Au-coated wire-loop, in-torch vaporization (ITV) sample introduction and inductively coupled plasma atomic emission spectrometry (ICP-AES) spectrometry with photodiode array detection is described. Tungsten wire-loops were coated with gold using sputtering methodology developed for scanning electron microscopy (SEM). Mecury vapor formed an amalgam with Au on the wire-loop, the wire-loop was inserted into a modified ICP torch about 10 cm below the plasma and electrical power was applied to the loop, thus thermally releasing mercury. Atomic emission was monitored using an ICP spectrometer equipped with a photodiode array detector. Calibration curves were constructed using a variation of the reduction-aeration method and were linear for about two-and-a-half orders of magnitude. Mercury vapor levels determined close to a polarography apparatus compared favorably with measurements taken at the same location using cold vapor atomic absorption spectrometry (CVAAS). The possibility of using a Au-coated wire-loop system as an integrating personal dosimeter is postulated.