Glass Standard Reference Material Research Articles

Trace element analysis of scheelite by excimer laser ablation-inductively coupled plasma-mass spectrometry (ELA-ICP-MS) using a synthetic silicate glass standard

Concentrations of W and trace elements in scheelites (CaWO 4) associated with Archean lode-gold deposits in Western Australia were determiined by ArF (193 run) excimer laser ablation-ICP-MS with external calibration against a silicate glass standard reference material, NIST 610. The excimer laser beam drilled well-defined pits in both scheelite and silicate glass. With internal standardization against Ca alone, W measurements for the scheelites fall within 5% of the concentrations expected from electron microprobe measurements. A matrix effect between scheelite and silicate glass is apparent in the behaviour of W during; laser ablation: W is progressively fractionated from Ca in the glass but not in the scheelite. Proper data reduction, therefore, requires use of the early maximum count rates for W and Ca rather than the mean count rates during ablation. W isotopic ratios measured in the scheelites and an in-house generated silicate glass, ANU 252, are both within ∼2.5% of the accepted values for the natural ratios and are reproducible to ∼1%, if data for the first ∼11 s of ablation are excluded. Using the same data reduction techniques employed for W, concentrations of Sr, Y, Mo, REE and Pb, present at ppm levels in the scheelites, were measured with a precision of 4% or less. Measurements on Th and U, present at the 5–10 ppb level, and P, Mn, Nb and Ta are less precise (∼5–40%) and concentrations of Rb, Zr, Ba, Sn, Hf, TI and Bi are, for the most part, below detection limits. For Sr, Sm and Nd, replicate ELA-ICP-MS measurements made on 80-μm wide spots in scheelite largely encompass the concentrations determined by ID-TIMS on bulk samples. REE patterns determined by ELA-ICP-MS for the scheelites vary smoothly as a function of atomic number. Most of the patterns are hump-shaped but others are rather flat except for positive Eu anomalies. This suggests that the hydrothermal fluids that formed the scheelites did not have a common composition and source.

Chemical fractionation during infrared and ultraviolet laser ablation inductively coupled plasma mass spectrometry—implications for mineral microanalysis

The silicate glass standard reference material NIST SRM 610 has been repeatedly analysed by UV and IR laser ablation ICP-MS in procedures designed to mimic typical analytical procedures adopted during mineral analysis. Trace element fractionation during both IR and UV laser ablation is observed and relationships between fractionation trends and ionic radius, charge and melting temperature of the elements determined are defined and discussed. In particular the high field strength elements (e.g., Nb, Ta, Zr, Hf) all show decreasing fractionation trends with respect to Si in the NIST SRM 610 glass during repeated laser ablation, whilst the low field strength and large ion lithophile elements (e.g., Rb, Sr, Pb, Ba, Ca) all show increasing trends with respect to Si. For IR laser ablation the degree of fractionation observed in the analysis of the REEs is strongly correlated to their ionic radii. In all the analytical procedures studied, fractionation arising from IR laser ablation is considerably greater than UV laser ablation and simple changes to analytical procedure to reduce trace element fractionation are suggested. For UV laser ablation, the effect of laser focus on analytical precision is assessed. Active focussing of the laser during ablation under computer control significantly improves analytical precision.

Ceramic glaze analysis by simultaneous in-beam PGAA and XRFS

Twenty-one ready-to-use hobby glazes, of which 18 were labeled “safe for food containers” (SFFC), were analyzed for Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Gd, Hf, K, Mn, Na, Pb, Si, Sm, Sr, Ti, Zn, and Zr by neutron capture prompt γ-ray activation analysis (PGAA). Simultaneously, Pb was also determined by X-ray fluorescence spectrometry (XRFS) using Pb K X-rays induced by the γ-ray component of the neutron beam. The XRFS limits of detection were 200–400 μg Pb·g−1 (dry weight), a factor of ∼ 100 better than those for PGAA. Pb concentrations (by dry weight; with weight losses ranging from 28 to 49% after air-drying) found were 0.16–27.2% in the SFFC glazes and 0.86–32% in the other glazes. The SFFC glazes contained from <0.6 to 202 μg Cd·g−1, and Co, Cr, and Cu (elements which may enhance Pb leaching from fired glazes) were found in concentrations up to 1.2, 2.7, and 5.6%, respectively. Method accuracy was demonstrated with the analysis of soil, fly ash, and glass standard reference materials.

MAJOR AND TRACE ELEMENT DETERMINATIONS ON NIST GLASS STANDARD REFERENCE MATERIALS 611, 612, 614 AND 1834 BY INDUCTIVELY COUPLED PLASMA‐MASS SPECTROMETRY

We report on the major and trace element composition and homogeneity of NIST (National Institute of Standards and Technology) glass standard reference materials 611, 612, 614, and 1834 for use as microanalytical trace element standards in laser ablation‐inductively coupled plasma‐mass spectrometry. The four analyzed NIST glasses were not designed as microanalytical standards, but their availability and careful preparation made them obvious candidates. Our data indicate that NIST 1834 is inhomogeneous on a scale of 100 mg with respect to several trace elements. Within analytical uncertainty, NIST 611, 612, and 614 are apparently homogeneous.

Trace elemental analysis at nanometer spatial resolution by parallel-detection electron energy loss spectroscopy

Parallel-detection electron energy loss spectroscopy (EELS) combined with scanning transmission electron microscopy (STEM) and a field emission source provides an unprecedented sensitivity for elemental microanalysis. By deflecting the energy loss spectrum across a parallel detector and computing the difference spectrum from sequentially collected energy-shifted spectra, the effects due to detector pattern noise are nearly eliminated so that signals less than 0.1% of the background can be readily detected. Measurements on a series of glass standard reference materials show that EELS provides both high spatial resolution and trace sensitivity at the 10 atomic ppm level for a wide range of elements including the alkaline earths, 3-d transition metals, and the lanthanides. For analytical volumes with dimensions of the order of 10 nm, this translates into near-single atom detectability.

Trace analysis of transition elements and rare earths by parallel EELS

It has been realized for some years that electron energy loss spectroscopy (EELS) offers the potential for a highly sensitive microanalytical technique. Here, we present measurements from some NIST glass standard reference materials showing that EELS provides both high spatial resolution and trace sensitivity for a wide range of elements including the 3-d transition metals and the lanthanides.Specimens were prepared by grinding the glass and depositing the powder on to thin carbon support films. The energy loss spectra were collected by means of a Gatan 666 parallel-detection spectrometer attached to a VG Microscopes HB501 scanning transmission electron microscope (STEM) operating at 100 keV beam energy. This arrangement gave an energy resolution of approximately 0.4 eV limited by the spread of the field-emission source. Large spectral intensities were obtained by setting the probe current to about 8 nA and the collection semi-angle to 20 mrad. In order to eliminate possible hydrocarbon contamination the specimens were cooled to -160 C.

Surface characterization of a National Bureau of Standards glass reference material by californium-252 particle desorption mass spectrometry

National Bureau of Standards glass Standard Reference Materials have been characterized by particle desorption mass spectrometry (PDMS). Surface cleaning procedures, such as etching with HF or kiloelectronvolt ion sputtering, allow the detection of low-level dopants. Differences observed in the PDMS spectra before versus after sputter removal or surface hydration layers reflect the sensitivity of this technique to the chemical environment of the sample region from which the analytical signal originates. The small number of particles (ca. 10/sup 5/) needed to obtain a useful spectrum minimizes sample charging problems often encountered in surface analysis of insulating materials. Li, Be, Rb, and Cs were detected in NBS glass, nominally doped at the 500-ppm level. Only Li was detected in the 50-ppm doped glass. Therefore, the detection limits range between 50 and 500 pp, The use of a dual grid assembly for the acceleration of the desorbed ions resulted in increased efficiency of the time-of-flight mass spectrometer.

Thermal expansion of solids from −261°C to 173°C using strain gauges

The resistance foil strain gauge technique was used to measure the thermal expansion of solids from −261 to 173°C. Type E (Chromel-constantan) thermocouples were used to measure the temperature. Measurements were made on copper and borosilicate glass standard reference materials obtained from the National Bureau of Standards, USA. The data obtained were compared to the certified values of thermal expansion reported by the NBS. In addition to the standard reference materials, Invar samples supplied by Texas Instruments Inc and Carpenter Technology Corp were tested and the results compared to those obtained using a Westinghouse fused silica tube dilatometer. The results obtained using the strain gauge technique are within ±5% of the true values.

Analysis of ancient and medieval glasses by INAA

A scheme for instrumental neutron activation analysis of ancient and medieval glasses is proposed. The combination of three irradiations (short time, pile and epithermal) enables the determination of 34 elements. The accuracy of the method is evaluated by analyzing two glass standard reference materials. Results from the analysis of three glasses from different times are presented.