Evaluation of atomic fluorescence, absorption and emission techniques for the determination of mercury

Summary Atomic fluorescence (AFS), absorption (AAS) and emission (AES) systems were evaluated for the determination of inorganic mercury. Identical vapour generation and amalgamation procedures were used to permit direct comparison of the performance of a commercial long-path AAS instrument to laboratory constructed non-dispersive AFS as well as He-MIP based AES instruments. Instrumental noise-limited detection limits (LOD) were 0.94, 2.4, 2.8 pg for AAS, AES and AFS techniques, respectively. Methodological LOD's were found to be blank controlled and similar for all three instruments, viz. 9, 25 and 16 pg for AAS, AFS and AES, respectively. All three systems produced accurate results at the low ng/l concentration, as verified by the analysis of a certified river water reference material (NRCC ORMS-1).     

Electrothermal vaporization inductively coupled plasma mass spectrometric detection of As, Sb, Se, Bi and Sn following preconcentration by in situ collection of their hydrides

Volatile hydrides of As, Se, Sb, Sn and Bi were generated from aqueous sample solutions using a tetrahydroborate reductant. The gaseous analytes were transferred to the inner wall of an electrothermal vaporizer (graphite furnace) and preconcentrated on a 1.25 μg thin-film of reduced palladium at 400°C. The furnace comprised the sample introduction unit of an inductively coupled plasma mass spectrometric detection system. Absolute limits of detection (3σ_B) were 2.9, 3.3, 54, 5 and 1980 pg for As, Sb, Sn, Bi and Se, respectively. System efficiency for the generation and sequestration of the hydrides averaged, with the exception of Se, better than 75%. Multielement determinations of As, Se and Bi were possible using the same experimental conditions, those for Sn and Sb were accomplished in a separate run. The efficacy of this analytical approach was verified by the analysis of several marine reference materials using simple calibration standards prepared in the same manner as the samples. Good agreement with certified values was achieved for As, Sn, Sb and Se; no reference materials were available for assessment of accuracy in the case of Bi.     

Headspace single-drop microextration for the detection of organotin compounds

The performance of single-drop microextraction (SDME), coupled with gas chromatography/mass spectrometry, was assessed for the determination of tributyltin compounds in water and solid samples. Experimental parameters impacting the performance of SDME, such as microextraction solvent and sampling and stirring time, were investigated. Analytical results obtained by SDME were compared with those generated by conventional solid phase microextraction (SPME) and liquid-liquid extraction (LLE) for the determination of TBT in PACS-2 sediment certified reference material (CRM).     

Status and future prospects for use of the graphite furnace for elemental trace analysis of liquids and solids

Summary An overview of the versatility and use of the graphite furnace for elemental trace analysis of liquids and solids using spectrochemical detection is presented. The analytical performance of conventional graphite furnace atomic absorption spectrometry is compared to other popular state of the art spectrochemical techniques with respect to detection power, precision, sample compatibility and throughput. Some applications of the graphite furnace to practical problem solving in trace analysis are highlighted, including its use with atomic absorption, coherent forward scattering, laser excited atomic fluorescence, laser enhanced ionization and coupled methodologies. Prospects for future use and evaluation are given.     

The graphite furnace and its role in atomic spectroscopy

The diversity of applications of the graphite furnace is extraordinary, encompassing the fields of physics, thermochemistry, spectroscopy and analytical chemistry. In this respect, the graphite furnace has been used on a continuous basis as a research tool for nearly a century. Following its introduction as an atomization source for atomic absorption spectrometry by Lvov in 1959, its role in atomic spectrometry expanded considerably to encompass analytical applications in emision, fluorescence, absorption and mass spectrometry. In addition to its conspicuous use as an atomization source in these areas, it is frequently employed as a vaporizer when used in the format of combined and tandem sources with other instrumentation. The unique physico-chemical micro-environment which can be attained within the graphite furnace has also been used to advantage in a number of investigations, including the determination of gas- and solid-phase diffusion coefficients of high-temperature metal vapours, the heats of sublimation of refractory metals, fundamental optical constants and the measurement of the heats of desorption of adatoms from high-temperature surfaces. The range of such applications remains to be more fully explored. The attractive features of this source, viz., the high atomization/vaporization efficiency, comparatively long atomic vapour residence times, controllable chemical and thermal environment and its ability to handle high dissolved solids content samples (100%) serve to ensure its place in analytical atomic spectroscopy for years to come.     

Mass shifting roles of negative kernel mass in density estimation

f(x) is a univariate density in C ⁴ with bounded support. For any n and sufficiently small kernel bandwidths, the symmetric appendage of any negative mass, –U, to any smooth unimodal symmetric kernel of order p=2 shifts expected estimator mass from regions where f(x)>0 to regions where f(x)<0. For large n, the mean automatic kernel adaptation induced by –U is analyzed in the simplest MISE reduction scenario: The symmetric appendage of –U to the uniform kernel K(x, X) over MISE-optimal bandwidths reduces MISE by shifting K(x, X) mass asymmetrically across the observation X in the direction of decreasing |f(x)|.     

Determination of trace metals in estuarine sediments by graphite-furnace atomic absorption spectrometry

A simple and rapid acid digestion method for the decomposition of estuarine sediments is described. Quantitative recovery of Cd, Pb, Cu, Ni, Co, Be and Co is demonstrated. Sensitive, precise and accurate determination of these trace metals by graphite-furnace atomic absorption spectrometry in combination with the L'vov Platform provides an interference-free technique that permits calibration with simple aqueous solutions of metal standards. The accuracy of the method has been confirmed by analysis of two marine sediment reference materials, MESS-1 and BCSS-1.     

Application of edta to direct graphite-furnace atomic absorption analysis for cadmium in sea water

A method is described for the direct determination of cadmium in undiluted sea water by graphite-furnace atomic absorption spectrometry. The addition of EDTA ( 1 mg ml^-1) reduces the temperature of atomization of cadmium to far below that of volatilization of other matrix components. The need for very careful temperature control and accurate background compensation is thus minimized. Sea water was analyzed by the method of standard additions. A detection limit of 0.01 μg l^-1, a sensitivity of 0.034 μg l^-1 and a precision of ±10% at the 0.05 μg l^-1 level were obtained for 20-μl injections.     

UV light‐mediated alkylation of inorganic selenium

In the presence of low molecular weight organic acids (formic, acetic, propionic and malonic), inorganic selenium(IV) is converted by UV irradiation to volatile selenium carbonyl, dimethylselenide and diethylselenide, depending on the acid used. Gas chromatography–mass spectrometry analysis of the volatile products shows that, in 0.7 M formic acid solution, approximately 60–70% (v/v) SeH₂ and 30–40% (v/v) SeCO are formed. The presence of nitrate ion appears to increase threefold the formation of SeCO while completely suppressing formation of SeH₂. Copyright © 2003 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.