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The CCQM-P106 pilot study was organized by the inorganic working group of the Comite Consultatif pour la Quantite de Matiere (CCQM) as a feasibility comparison to study the applicability of different analysis methods to the polypropylene sample and test the abilities of the participants for measuring the Cd, Cr, Hg and Pb in polypropylene. National Institute of Metrology P.R. China (NIM) acted as the coordinating laboratory of this pilot study. There were 21 laboratories that submitted the final results. The median values of the mass fraction of Cd, Cr, Hg and Pb were 36.12 mg kg−1 (the median absolute deviation about the median (MADe) = 0.46 mg kg−1), 252.5 mg kg−1 (MADe = 3.4 mg kg−1), 387.0 mg kg−1 (MADe = 10.1 mg kg−1) and 466.2 mg kg−1 (MADe = 8.9 mg kg−1), respectively. Isotope dilution mass spectrometry (IDMS), inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma-optical emission spectrometry (ICP-OES), atomic absorption spectrometry (AAS), instrumental neutron activation analysis (INAA) and X-ray fluorescence (XRF) measurement methods were used, and microwave digestion was used by the most of the participants. In general, very good agreement of the results was observed. Moreover, compared to the results of other methods, the results of IDMS still showed less spread amongst laboratories and had a smaller uncertainty. In addition, the results of some analytes used by XRF and INAA also got satisfactory agreement with the median value.

Owing to the absence of readily available certified particulate reference materials (RMs), most analytical methods used to determine particulate contaminant levels in workplace or other environments are validated using solution RMs, which do not assess the robustness of the digestion step for all forms and sizes of particles in a sample. A library of particulate RMs having a range of chemical forms and particle sizes is needed to support a shift in method evaluation strategies to include both solution and particulate RMs. In support of creating this library, we characterized bulk and physically size separated fractions of beryllium oxide (BeO) particles recovered from the machining fluid sludge of an industrial ceramic products grinding operation. Particles were large agglomerates of compact, crystalline BeO primary particles having diameters on the order of several micrometers. As expected, the particle surface area was independent of sieve size, with a range from 3.61 m(2)/g (53-63-microm fraction) to 4.82 m(2)/g (355-600-microm fraction). The density was near the theoretical value (3.01 g/cm(3)). The data support more detailed characterization of the sludge materials for use as size-selective RMs. This work illustrates an approach that can be used to develop RMs that are difficult to digest.

A commercial inductively coupled plasma (ICP) mass spectrometer was modified to employ an air-hydrogen flame in place of the ICP as an ion source. A liquid nitrogen trap was placed in the vacuum line to remove water. A very simple intrinsic mass spectral background was obtained with the hydrogen flame ionization mass spectrometry (FIMS). Molecular ions such as K(H 2 O) + , Na(H 2 O) + , Ca(H 2 O) + and CaOH(H 2 O) x + (x=0-2) were observed when solutions containing Na, K or Ca were aspirated. Although the presence of the molecular ions complicated the mass spectra, it also provided a wider choice of analytical masses for an analyte. Isotope ratio measurements of Ca were made with both Ca + and CaOH + species at masses 40, 44, 57 and 61. Better isotope ratio precision was obtained at CaOH + masses relative to those for Ca + because the sensitivity was about 10 times higher. Isotope ratio measurement of K was made at masses 39 and 41. A ratio precision of about 0.2 and 0.5% was obtained for K and Ca, respectively. The results suggest that the FIMS is suitable for the isotope ratio measurement of K and Ca in simple matrices, and that the air-hydrogen flame is a more desirable ion source than an air-acetylene flame for FIMS.

Experiments were carried out to explore the effect of an electric field upon atomic species introduced into a flame. The study involves components from a conventional flame atomic absorption apparatus with 10 × 10-cm parallel plate electrodes as the cathode and the 5-cm slot burner head as the anode. A marked decrease in the emission and absorption of many atomic species was observed, and quantification of the effect was carried out. The effect has been interpreted as a disturbance of the equilibrium, Me ≈ Me+ + e−. Relative decreases in absorption and emission were found to be functions of applied voltage and analyte concentration at low voltages, and constant for high voltages (≍ −2000 V). Temporal behavior of the effect has been investigated by observation of the speed of restoration of the emission signal from Na (589.16 nm), Sr (460.86 nm), and Sr+ (407.89 nm) after rapid elimination of the electric field. The effects were also studied as a function of viewing position in the flame for optimization of the position and comparison of the temporal behavior with the speed of the flame gases.

Arsenic, antimony, and tellurium are determined at part-per-million concentration levels in bullet lead, lead-base alloy, and high purity lead using electrothermal atomization atomic absorption spectrometry (ETAAS) with Zeeman-effect background correction. A spectral interference by lead absorption lines resulting from excited state transitions is observed on both primary arsenic analysis lines, at 193.696 nm and 197.197 nm. Analytical bias caused by the interference at 197.197 nm is eliminated by using temperature programming and temporal resolution.

Sodium atoms in an air-hydrogen flame at atmospheric pressure have been selectively ionized by laser-enhanced ionization (LEI) spectroscopy, and the resulting ions have been drawn into a vacuum and detected by quadrupole mass spectrometry. A commercial inductively coupled plasma-mass spectrometer, modified for use with a flame rather than an ICP, was used to sample and detect the LEI ions. Following double-resonance LEI using pulsed dye lasers, the detected sodium ion signal was enhanced by a factor of 350 over that induced by thermal ionization alone. Using a 5 mm laser beam diameter, the LEI signal pulse was found to last for 0.54 ms (FWHM). Spatial studies in which the position of the laser beam relative to the mass spectrometer sampler cone was varied, demonstrated that the ions produced by LEI travel with the flame velocity into the mass spectrometer, with no significant losses due to recombination from as far as 13 mm from the interface.

Liquid chromatography (LC) and laser-enhanced ionization spectrometry (LEI) have been combined to provide a very sensitive method for the measurement of organolead species. Measurement is possible in environmental and biological matrices, which often contain high levels of easily ionized elements that normally interfere with LEI measurements. However, LC is able to resolve the interferents from the analytes, and LEI is sensitive enough to counterbalance the increase in detection limits that results from the use of LC. The method has been applied to the determination of organolead compounds in National Institute of Standards and Technology Standard Reference Material 1566a, Oyster Tissue. Trace levels of trimethyllead were observed in the Oyster Tissue, but concentrations were variable among the samples tested.

A technique has been developed which can determine where within a flame laser-enhanced ionization (LEI) actually takes place, thus forming an image of the LEI active volume. The method is based upon spatial control of the flame volume sampled by the ionization detection electrodes by variation of the applied voltage. As and example, this procedure has been used to observe anomalous contributions to LEI caused by scattering or fluorescence from the laser beam to other regions in the flame

Random signal fluctuations of simultaneously detected laser-enhanced ionization (LEI) and laser-induced fluorescence (LIF) were investigated and analyzed for correlation with each other and with laser power fluctuations. A greater degree of noise correlation was found between LEI and LIF than between either technique and laser power fluctuations. A background correction method is proposed which subtracts the LIF signal of the background-inducing interfering element from the combined LEI signals from analyte and interferant. Noise correlation between LEI and LIF can be utilized to cancel the noise in the interfering background signal. Broadband spectral interference due to wing excitation of sodium LEI was used as an example to demonstrate the method. Excitation spectra and laser power dependencies of sodium LEI and LIF were also studied, and found to be identical.

Laser-induced fluorescence of iron atoms during the plasma-off cycle of a power-modulated inductively coupled plasma has been performed. The low plasma background emission, and absence of radio-frequency interference, 1.4 ms after complete interruption of power to the ICP, results in an excellent environment for fluorescence detection. With the use of a simple nondispersive detection system, a limit of detection of 5 µg Fe/L was achieved. The iron atom population was found to remain constant for 1.2 ms after power interruption, indicating that the chemical environment during this period is inert. A spatial profile and ICP power study were conducted as diagnostic aids for optimization of the power-modulated ICP for both fluorescence and ionization detection.

High purity elements can serve as a realization of the SI unit amount of substance for the specific element. Solutions prepared from high purity metals by applying gravimetric preparation and the concept of molar mass are used as 'calibration' solutions in many fields of analytical chemistry and provide the metrological basis in elemental analysis. Since ideal purity does not exist for real materials, the actual purity of the high purity material must be known with a specified uncertainty. As required uncertainties around 10?4 relative on the purity statement are not accessible in almost all cases by a direct measurement of the element in itself, the indirect approach is followed, where all elements excepting the matrix element itself are measured and their sum is subtracted from the value for ideal purity, which is 1 kg/kg. It was the aim of this comparison to demonstrate the capability of national metrology institutes and designated institutes to determine the purity of pure elements. In order to limit the effort within this comparison, only six metallic impurities (Ag, Al, Cd, Cr, Ni, Tl) in the low mg/kg range are considered in a zinc matrix. It has to be underlined here that the task was to measure the purity of zinc based on the determination of six analytes. The task is not trace analysis of specific analytes in zinc. This subtle distinction defines different measurands. The sample, pure Zn, was cut in pieces of cubic geometry for wet chemical analysis or of pin geometry for GDMS analysis and was sent to the participants. The comparison was run under the auspices of the Inorganic analysis Working Group (IAWG) of the CCQM and was piloted by the BAM Federal Institute for Materials Research and Testing, Berlin, Germany. The majority of the participants applied ICP-MS techniques and only two participants used additionally atomic absorption spectrometry. GDMS was used only by one participant. The observed spreads for the measurement results reported by the participants were significantly lower than those of the preceding study CCQM-P107 and were well below the target uncertainty of 30% relative. As a consequence, comparability within the participating laboratories is demonstrated to be established. The individual measurement results, mean values and medians derived were in all cases very consistent with the reference values obtained by IDMS and so the accuracy of the measurement results for the participating laboratories is as well demonstrated to be established. Especially with the results of CCQM-P62 and CCQM-P107 in mind, the outcome of CCQM-K72 can be considered as a big step forward in the community. CCQM is aware of the difference between a characterization based on only six analytes and a complete characterization. Therefore, the pilot study CCQM-P149 has been initiated and already started, which focuses on the fit-for-purpose approaches for the purity determination of metals (here: zinc) to be used as primary standards in elemental analysis. Another follow-up in the form of a pilot study on non-metal impurities is mandatory, because non-metal impurities such as oxygen, nitrogen and sulfur often make up the largest contributions. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

A point charge model based upon charge induction theory has been developed to describe the proposed detection mechanisms of laser-enhanced ionization (LEI). The model predictions are in good agreement with experimentally observed LEI electron and ion signal pulses. The predicted effects of alkali metal matrix concentration and laser beam position are also confirmed by experimental results. The development of this model provides a basis for establishing experimental methodology that is necessary for the development of LEI as a technique for trace metal analysis. 23 references, 8 figures, 2 tables.

We review atomic flame spectrometry of metals based on the selective laser-enhancement of the rate of atomic ionization. A discussion of basic principles, prior literature, and instrumentation is followed by an overview of analytical figures of merit for the technique, and a look at its present status and areas for future development.

Stepwise excitation laser-enhanced ionization spectroscopy utilizes two independently tunable dye lasers to populate high-lying excited states of atoms in flames. Two atomic resonances are required, with the upper level of the first-step transition coinciding with the lower level of the second-step transition. Efficient population of a high-lying atomic level is achieved, from which a high rate of collisional ionization can take place. The double-resonance aspect of such excitation adds an extra dimension of spectroscopic selectivity to the measurement. A computer-controlled dual-wavelength LEI spectrometer, including a Fizeau wave-meter for wavelength verification, is used to record three-dimensional spectra–ionization signal as a function of both first- and second-step wavelengths. Examples illustrate the accuracy advantage accorded by the three-dimensional survey.

The ionization spectrum of strontium atoms in an air/acetylene flame under pulsed laser excitation has been recently reported. Single-step as well as two-step excitation was provided by an excimer-pumped dye laser tuned in the blue region of the spectrum. The collisionally assisted ionization in the flame was measured with a water-cooled electrode immersed in the flame and negatively biased (–1300 V), while the charges produced were collected at the burner, converted into a voltage signal, and processed by a boxcar integrator.

A dye laser pumped by a Nd: YAG laser is used as a source for the excitation of nickel non-resonance atomic fluorescence in an air-acetylene flame. Detection limits are poorer than previous data from flashlamp-pumped dye laser experiments, but measurement precision is improved. Nickel is determined in a complex Standard Reference Material (NBS SRM 1645, River Sediment).

A double-beam thermal lensing experiment based upon a pulsed dye laser as the excitation beam and a He-Ne laser as a probe beam is described. The technique has been used to detect the small absorptions given by uranyl ions in aqueous solution. The system is capable of detecting absorption coefficients as low as 5 × 10–7 cm–1. Moreover, by changing several dyes, an absorption spectrum can be obtained at concentration levels (ca. 4 × 10–6M) far below (ca. 103×) those obtained by conventional absorption spectrophotometry, thereby allowing the direct study of the chemical equilibria involved. The sensitivity of the present apparatus is limited by short-term fluctuations of the probe laser.

Recent developments of laser-enhanced ionisation (LEI) spectroscopy are reviewed. This method utilises tunable dye lasers to enhance the rate of collisional ionisation of specific metal atoms in a flame or other atom reservoirs. It can be utilised for trace metal analysis, or for fundamental studies of flames and plasmas. Among the topics highlighted here is the use of double-resonance laser excitation methods to generate three-dimensional atomic LEI spectra. Also discussed are recent results on the use of laser-induced ionic fluorescence as an optical detection method for LEI. An updated list of LEI limits of detection compiled from the literature is included.