F. Adams

A computer analysis of X-ray fluorescence spectra

Abstract A method is presented for the non-linear least-squares analysis of low-energy X-ray spectra obtained by tube-excited X-ray fluorescence analysis. The method is based on a description of the full energy peaks as Gaussian distributions and the background as a polynomial. System constraints are used to keep peak position and resolution consistent with predetermined calibration expressions. The least-squares routine is based on the Marquardt algorithm but parameters are confined within predetermined physically significant intervals. The method is implemented in the computer program AXIL written in Fortra IV for a PDP 11/45 system. Tests are described which prove that the program is able to provide reliable values for the parameters.

Use of microscopic XRF for non‐destructive analysis in art and archaeometry

The various application possibilities of microscopic x-ray fluorescence and associated methods for the characterization and provenance analysis of objects and materials of cultural heritage value are discussed by means of a number of case studies. They include the trace analysis of historic glass, the analysis of corroded coins and statues in bronze and silver and the study of inks on historical documents. These studies are conducted by means of micro-XRF instruments installed at synchrotron beamlines and by means of laboratory equipment, some of which is easily transportable to the museum or archaeological site where the objects of interest are located. Copyright

Determination of cadmium, copper and lead in environmental samples. An evaluation of flow injection on-line sorbent extraction for flame atomic absorption spectrometry

Abstract A flow injection on-line sorbent extraction system was studied in conjunction with flame atomic absorption spectrometry to determine cadmium, copper and lead in digest solutions of solid environmental samples using octadecyl functional groups (C18) bonded silica gel as sorbent with diethylammonium-N,N-diethyldithiocarbamate (DDDC) or ammonium diethyldithiophosphate (DDPA) as complexing agent and methanol as eluent. Using DDDC as complexing agent, citric acid was used as masking agent for iron and manganese. The complexing agent DDPA selectively extracts cadmium, copper and lead at pH values 1 to 3. Using DDPA as complexing agent with citric acid at pH 1.0, the results of the analysis of five environmental standard reference materials, including coal fly ash (CRM 038), calcareous loam soil (CRM 141), lake sediment (CRM 280), river sediment (CRM 320) and estuarine sediment (CRM 277) after digestion were in good agreement with the certified values except cadmium in the river sediment with a very high iron content. With a 20-s sample loading at 8.7 ml min−1, detection limits (3σ) were 0.8, 1.4 and 10.0 μg l−1 respectively for cadmium, copper and lead.

Metal speciation in the environment

Assessment of Metal Mobility in Sludges and Solid Wastes.- The Complexation of Metal Ions by Humic Substances in Natural Waters.- Complexation of Paramagnetic Metal Ions by Aquatic Fulvic Acids.- Study of Lead Fulvic Acid Interactions by Voltammetric Methods.- Isotachophoretic Investigations into the Speciation of Niobium(V) and Plutonium(IV) in the Presence of Citrate.- The Effect of Caffeic Acid on the Speciation of Metal Ions in Plant Nutrient Solutions.- Complexes of Monosaccharides with Metal Ions: Some Bioinorganic and Environmental Inorganic Chemistry Aspects.- Kinetic Studies on the Interaction of Metals between Water and Clay Mineral.- The Occurrence of Heavy Metals in Antarctic and Greenland Ancient Ice and Recent Snow.- Elemental Species Analyses with Isotope Dilution Mass Spectrometry.- Speciation of Trace Elements in Serum or Plasma.- Chemical Sensors in Environmental Analysis: Ammonium and Cadmium Sensors.- Use of ICP-Spectrometry for Environmental Analysis.- Preconcentration of Refractory Elements for Inductively Coupled Plasma Atomic Fluorescence Spectrometry.- HPLC-AAS Interfaces for the Determination of Ionic Alkyllead, Alkyltin, Arsonium and Selenonium Compounds.- Coupling of HPLC and Chemical Reaction Detectors for Trace Analysis of Alkyllead Species.- Speciation of Organolead Compounds by GC-AAS.- Analysis of Mercury - Species in Sediments.- Stability Study of Cr(III) and Cr(VI) in Water for Production of an Aqueous Chromium Reference Material.- Organic Arsenic Compounds in Petroleum and Natural Gas.- Application of Polarographic and Voltammetric Techniques in Environmental Analysis.- Metal Speciation in Flue Gases, Work Place Atmospheres and Precipitation.- Evaluation of New Organic Phase Extraction Procedures for Studying the Role of Terrestrial Humic Substances in the Speciation of Iron and Plutonium.- Development and Improvement of Analytical Methods for Specification Scheme of Al in the Mobile Soil Phase.- The Analysis of Arsenic in Turkish Coals and Ashes by Photometric Methods and MECA.- The Ecological Role of Aquatic Organic and Inorganic Components, deduced from their Nature, Circulation and Interactions.- Exchange of Heavy Metals Between Sediment Components and Water.- Biogeochemical Cycling of Atmospheric Selenium.- Partitioning of Trace Metals in Sediments and its Relationship to their Accumulation in Benthic Organisms.- Environmental Chemistry of the Actinide Elements.- Accumulation and Distribution of 99Tc in three Bean Plant Varieties.- Heavy Metals in Sediments of Turkish River Systems - Natural Background and Anthropogenic Effects.- Chromium Treatment of Wastewaters by Chemical Methods.- Bacterial Response to Copper in the Environment: Copper Resistance in Escherichia Coli as a Model System.- Panel Discussions.- K. IRGOLIC Speciation.

Biomass burning in Southern Africa: individual particle characterization of atmospheric aerosols and savanna fire samples

Ambient atmospheric aerosols and savanna fireparticulate emission samples from southern Africa werecharacterised in terms of particle classes and theirnumber abundance by electron probe X-ray microanalysis(EPXMA). About ten particle classes were identifiedfor each sample. The major classes werealuminosilicates and sea salts for ambient coarse(2–10 μm equivalent aerodynamic diameter (EAD))samples, and K-S and S-only particles for ambient fine(<2 μm EAD) samples. The K-S particles are oneof the major products of biomass burning. The EPXMAresults were found to be consistent with the resultsfrom bulk analyses on a sample by sample basis. Forsavanna fire fine samples, quantitative EPXMA revealedthat many particles had a composition of simple saltssuch as KCl. Some particles had a deviatingcomposition in the sense that more ionic species wereinvolved in sustaining the balance between cations andanions, and they were composite or mixed salts.Because of extensive processing during the atmospherictransport, the composition of the K-S particles in theambient samples was different from K2SO4,and such particles were enriched with S. The finepyrogenic KCl particles and the fine sea-saltparticles were much depleted in chlorine.

A method for the accurate description of the full-energy peaks in non-linear least-squares analysis of x-ray spectra☆

Abstract Accurate fitting of X-ray spectra obtained with Si(Li) detectors is accomplished by a model consisting of a Gauss function and numerical corrections. The procedure is incorporated into a non-linear least-squares fitting program used for the analysis of X-ray induced X-ray fluorescence spectra.

Two methods for the speciation analysis of mercury in fish involving microwave-assisted digestion and gas chromatography-atomic emission spectrometry

In this paper a novel approach for the speciation analysis of mercury (methyl mercury and mercury II) in fish tissue using gas chromatography-microwave induced plasma atomic emission spectromertry is described. Focused microwave-assisted digestion which has been used previously in speciation analysis only for the determination of organotin and organoselenium compounds, was applied for sample preparation, a technique which enables mild, quick and complete dissolution of the sample. The important parameters for the digestion of fish tissues were optimised for the given analytical problem. Since no experience was available for the further treatment of the produced sample solution two different derivatisation/injection procedures were examined: 1. (1) ethylation with sodium tetraethylborate, extraction into hexane and injection with a cooled injection system and 2. (2) hydride generation with sodium tetrahydroborate together with purge-and-trap injection. The latter reaction has not been used previously for the determination of mercury species in fish samples. The optimum parameters for both procedures were evaluated and the methods were validated by analysis of a standard reference material (CRM 464). The 3σ detection limits were (1) 3.0 pg g−1 and (2) 12.5 pg g−1.

Flow injection on-line preconcentration of palladium by ion-pair adsorption in a knotted reactor coupled with electrothermal atomic absorption spectrometry

A flow injection (FI) method for the preconcentration/separation of palladium, coupled with electrothermal atomic absorption spectrometry (ETAAS), is presented. The preconcentration was performed by on-line formation of an ion-pair between the positively charged potassium complex of 1,4,7,10,13,16-hexaoxacyclooctadecane (K+18-crown-6) and the palladium thiocyanate anion (Pd(SCN)42−) and its sorption on the inner walls of a PTFE knotted reactor (KR). The elution was achieved by methanol acidified with 1% (v/v) HNO3. An enhancement factor of 29 and a sampling frequency of 14 h−1 were obtained for a preconcentration time of 90 s and a sampling flow rate of 4.4 ml min−1. The detection limit (3σ) is 16 ng l−1 and precision (RSD) for 0.4 µg l−1 Pd is 2.3%. The method was validated by recovery measurements on spiked blood and road dust samples.

The fate of mercury species in a sub-arctic snowpack during snowmelt

An extensive mercury study was conducted in April 2002 prior to and during the annual melting of a snowpack in a sub-arctic site along the Hudson Bay (Canada). Gas-phase measurements show that the snowmelt coincides with an elemental mercury (Hg°) pulse in the snowpack air far above ambient levels. Additional measurements of inorganic mercury (Hg2+) and methylmercury (MeHg+) in snow pits, in surface snow and in a meltwater sample clearly reveal that most of Hg is removed from the snow during the first days of snowmelt. We estimate that gas-phase exchanges contribute poorly to remove Hg from the snowpack; consequently during a snowmelt day more than 90% of Hg present in the snow surface is likely released with the meltwater. In arctic areas, where Hg accumulates at an accelerated rate in the snow surfaces [Lu et al., 2001] during mercury depletion events (MDE), the discharge of this toxic and bio-accumulating pollutant in water systems could be a threat to ecosystems and local indigenous populations.

Surface characterization of artificial corrosion layers on copper alloy reference materials

Abstract This paper describes the surface characterization of artificial patina layers on five different copper alloys. The chemical composition of the examined bronzes covers the major families of archaeological copper alloys from antiquity until the Roman period. The patina layers of the five samples were formed under identical conditions by electrochemical means. Light microscopy, scanning electron microscopy with energy dispersive X-ray micro analysis (SEM–EDX) and Fourier transform infrared spectroscopy (FTIR) were used to describe the main properties of the patina layers. The results were interpreted and classified according to an existing corrosion model for copper alloys.