Douglas M. Goltz

Removal of reactive red-120 and 4-(2-pyridylazo) resorcinol from aqueous samples by Fe3O4 magnetic nanoparticles using ionic liquid as modifier.

The nanoparticles of Fe(3)O(4) as well as the binary nanoparticles of ionic liquid and Fe(3)O(4) (IL-Fe(3)O(4)) were synthesized for removal of reactive red 120 (RR-120) and 4-(2-pyridylazo) resorcinol (PAR) as model azo dyes from aqueous solutions. The mean size and the surface morphology of the nanoparticles were characterized by TEM, DLS, XRD, FTIR and TGA techniques. Adsorption of RR-120 and PAR was studied in a batch reactor at different experimental conditions such as nanoparticle dosage, dye concentration, pH of the solution, ionic strength, and contact time. Experimental results indicated that the IL-Fe(3)O(4) nanoparticles had removed more than 98% of both dyes under the optimum operational conditions of a dosage of 60mg, a pH of 2.5, and a contact time of 2min when initial dyes concentrations of 10-200mg L(-1) were used. The maximum adsorption capacity of IL-Fe(3)O(4) was 166.67 and 49.26mg g(-1) for RR-120 and PAR, respectively. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The Langmuir adsorption constants were 5.99 and 3.62L mg(-1) for adsorptions of RR-120 and PAR, respectively. Both adsorption processes were endothermic and dyes could be desorbed from IL-Fe(3)O(4) by using a mixed NaCl-acetone solution and adsorbent was reusable.

Near-infrared spectroscopic imaging in art conservation: investigation of drawing constituents

AbstractThe remote-sensing technique of spectroscopic imaging has been adapted to the non-destructive examination of works of art.The principleof near-infrared reflectance spectroscopic imaging is explained, and our instrumentation for art examination described. The technique allowsthe art materials to be distinguished by their composition, and under-drawings revealed. The initial results indicate that even over limitedwavelength ranges (650–1040 nm) and with relatively coarse spectral resolution (10 nm) a number of pigments can be distinguished on thebasis of variations in spectral properties such as spectral slope and the presence or absence of absorption bands. Software adapted from theremote-sensing image-processing field has been used to successfully map areas of different brown and black pigments across a drawing.Non-destructive identification of pigments can be used to address issues of attribution, age dating, and conservation.An additional advantageof this technique is that it can be performed off-site using portable instrumentation, and under relatively benign lighting conditions. Thetechnique has been applied to the examination of a 15th-century drawing,Untitled (The Holy Trinity), in the collection of the Winnipeg ArtGallery. Multivariate image analysis produced a set of principal component (PC) images highlighting different materials’ aspects of thedrawing. A color composite image produced from the PC images provided a direct visualization of the compositional characteristics of thework. Features of the under-drawing have been exposed, and its material tentatively identified as charcoal, by comparison with reference data.© 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

Vaporization of acids and their effect on analyte signal in electrothermal vaporization inductively coupled plasma mass spectrometry

The vaporization properties of HCl and HNO3 under various furnace heating conditions were investigated. Drying-step temperatures of 140 °C (50 s) and pyrolysis-step temperatures of 400 °C (10 s) were effective in volatilizing most of the chloride from 10 µl of 1% v/v HCl, however, a small amount (40 ng) of acid was retained on the graphite even after pyrolysis at 400 °C. Under the same experimental conditions, HNO3 was completely volatilized from the graphite tube. The effect of a range of concentrations of HCl, HNO3, H2SO4 and H3PO4 on analyte signals was studied for Co, Cu, Ag, Cs, Pb, Bi and U. Analyte signals were enhanced by as much as a factor of two in the presence of 1% v/v HNO3 and H2SO4. Phosphoric acid suppressed analyte signals for Ag and Bi and the use of HCl resulted in relatively small changes in analyte sensitivity. The use of a pyrolysis step in the heating programme reduced the effects associated with acid matrices, but at the expense of signal intensity. A mixed modifier–carrier reduced the matrix effects associated with H2SO4 and H3PO4 and essentially eliminated them for HNO3 and HCl.

Vaporization and atomization of uranium in a graphite tube electrothermal vaporizer: a mechanistic study using electrothermal vaporization inductively coupled plasma mass spectrometry and graphite furnace atomic absorption spectrometry

Abstract The mechanism of vaporization and atomization of U in a graphite tube electrothermal vaporizer was studied using graphite furnace atomic absorption spectrometry (GFAAS) and electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). Graphite furnace AAS studies indicate U atoms are formed at temperatures above 2400°C. Using ETV-ICP-MS, an appearance temperature of 1100°C was obtained indicating that some U vaporizes as U oxide. Although U carbides form at temperatures above 2000°C, ETV-ICP-MS studies show that they do not vaporize until 2600°C. In the temperature range between 2200°C and 2600°C, U atoms in GFAAS are likely formed by thermal dissociation of U oxide, whereas at higher temperatures, U atoms are formed via thermal dissociation of U carbide. The origin of U signal suppression in ETV-ICP-MS by NaCl was also investigated. At temperatures above 2000°C, signal suppression may be caused by the accelerated rate of formation of carbide species while at temperatures below 2000°C, the presence of NaCl may cause intercalation of the U in the graphite layers resulting in partial retention of U during the vaporization step. The use of 0.3% freon-23 (CHF3) mixed with the argon carrier gas was effective in preventing the intercalation of U in graphite and U carbide formation at 2700°C.

Vaporization and atomization of boron in the graphite furnace investigated by electrothermal vaporization inductively coupled plasma mass spectrometry

Abstract The vaporization and atomization of boron in the graphite furnace were investigated using both electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) and graphite furnace atomic absorption spectrometry (GFAAS). The results show that the majority of the boron is vaporized in molecular form and removed from the furnace at temperatures well below the appearance temperature of atomic boron. The effect of nickel nitrate chemical modifier on the vaporization of boron was also studied. The modifier is largely ineffective in preventing loss of boron from the graphite furnace prior to atomization. The extent of this preatomization loss, both in the presence and absence of the modifier, is reported. For the determination of boron by ETV-ICP-MS, the optimum sensitivity is obtained at a vaporization temperature of about 1800°C, i.e. well below the maximum possible vaporization temperature. This sensitivity is enhanced by the addition of the nickel modifier.

Mechanism of vaporization of yttrium and rare earth elements in electrothermal vaporization inductively coupled plasma mass spectrometry

The mechanism of vaporization of yttrium and the rare earth elements (REEs) has been studied using graphite furnace atomic absorption spectrometry (GFAAS) and inductively-coupled plasma mass spectrometry (ICP-MS). The appearance temperatures for Y and the REEs obtained by GFAAS were generally identical to the appearance temperatures obtained using ETV-ICP-MS. At lower temperatures, Y and the REEs are predominantly vaporized in atomic form or as oxides, while at temperatures above 2500°C, the elements are vaporized as oxides and/or carbides. This accounts for the very high sensitivity of ETV-ICP-MS compared to GFAAS for the determination of these elements. Absolute limits of detection for Y and all of the REEs using ETV-ICP-MS ranged from 0.002 pg for Tm to 0.2 pg for Ce. The use of freon as a chemical modifier was effective in controlling analyte carbide formation and reducing memory effects.

A microwave dissolution technique for the determination of arsenic in soils

A procedure has been developed for rapid dissolution of soil samples by heating with various acid mixtures in sealed vessels in a microwave oven, without risk of loss of arsenic through volatilization.

Temperature-controlled ionic liquid-based dispersive liquid-phase microextraction, preconcentration and quantification of nano-amounts of silver ion by using disulfiram as complexing agent

Microextraction and preconcentration of Ag+ by using temperature-controlled ionic liquid-based dispersive liquid-phase microextraction (TCIL-DLPME) method is reported. It was found that tetraethylthiuram disulfide (disulfiram) dissolved in 1-hexyl-3-methylimidazolium hexaflorophosphate, [C6mim][PF6] was useful as extracting media. Graphite furnace atomic absorption spectroscopy was used to quantify Ag+. To improve extraction efficiency, different experimental factors, such as volume of ionic liquid phase, pH and volume of aqueous solution, cooling and centrifugation periods, and dissolving temperature were investigated. The calibration curve was linear in the concentration range of 6.0–100.0 ng l−1 of Ag+. Relative standard deviation (n = 7), detection limit, and preconcentration factor for determination of Ag+ were found to be 4.5%, 5.2 ng l−1, and 120, respectively. The method was successfully applied for determination of Ag+ in drinking water and hair samples. Percent recoveries for solutions containing Ag+ indicated that chemical interferences by selected anions (NO3−, Cl−, I−, Br− and citrate) or cations (Ni2+, Cu2+, Mg2+, Zn2+, Pb2+, Ca2+, Co2+, Hg2+, Na+ and Mn2+) in solution were minimal or non-existent.

Digital imaging of formation and dissipation processes for atoms and molecules and condensed-phase species in graphite furnace atomic absorption spectrometry : a review

Abstract This is a review of our recent work in the use of a CCD-based digital imaging system for the shadow spectral digital imaging (SSDI) of boron, aluminium (spike formation), and condensation of vapour of selected analytes, matrices, and chemical modifiers in graphite furnace atomic absorption spectrometry (GFAAS). The use of a charge-coupled device (CCD) camera has enabled a number of processes in the Massmann-type GFAAS to be more thoroughly investigated than has been previously possible. The SSDI technique has been used to obtain spatially and temporally resolved distributions of atoms, molecules and condensed-phase species generated in a graphite furnace as a result of processes such as vaporization, atomization and condensation. The application of this technique to the investigation of atomic and molecular species of boron has helped in elucidating the mechanism of vaporization and atomization of boron. Thermal dissociation of boron oxide species results in the formation of BO(g) and its loss from a graphite furnace at temperatures below the atomization temperature of boron. The atomic boron signal is the result of desorption of boron atoms from the decomposition of condensed-phase boron carbide. Studies using the CCD imaging of atomic and molecular species of aluminium in a graphite furnace have resulted in a mechanism being proposed for aluminium atom spike formation and for dissipation of aluminium atoms in the graphite furnace, aluminium atom spikes formed from gaseous Al 2 O precursors, this reaction being triggered by the formation of a condensed-phase Al 4 C 3 melt. Finally, the SSDI technique has been used to further our knowledge and understanding of light-scattering of microparticles produced by condensation of vapours of selected analytes, matrices and chemical modifiers. The spatial and temporal non-uniformity of condensed-phase particle clouds are attributed to thermal expansion of gas, gas flow patterns and temperature gradients in the vapour phase and in the heated graphite tube which develop in the Massmann-type graphite furnace.

Trace analysis of single zircons for rare-earth elements, U and Th by electrothermal vaporisation-inductively coupled plasma-mass spectrometry (ETV-ICP-MS)

Abstract A method is described for the trace analysis of single zircons for Y, La, Ce, Nd, Sm, Yb, Th and U by electrothermal vaporisation-inductively coupled plasma-mass spectrometry (ETV-ICP-MS). Zircons are cleaned by an abrasion process and dissolved in HNO 3 and HF in a pressure vessel. Following conversion to chlorides and evaporation to dryness, the dissolved zircon residue is re-dissolved in 500 μl of high-purity 2.5 M HNO 3 . Analyte concentrations were measured with a precision of ∼ ±6%. Agreement between found and reference values for BCS- 388 zircon reference material was excellent. Limits of detection for the analysis of a 10-μg zircon were 150 ng g −1 for Y, 90 ng g −1 for La, 115 ng g −1 for Ce, 65 ng g −1 for Nd,180 ng g −1 for Sm, 22 ng g −1 for Yb, 190 ng g −1 for Th and 80 ng g −1 for U. Absolute limits of detection for a 10-μl solution aliquot ranged from 4 to 36 fg (10 −15 g). Zircon solutions were analysed using external calibration by aqueous standards with the addition of a mixed component carrier (NASS-3 open ocean seawater). No matrix or spectroscopic interferences were observed from major-element matrix components. The analysis of a typical set of single zircons gave concentration levels well above the limit of detection for all elements except La.