Submitted to: Journal of Applied Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 22, 1995
Publication Date: N/A
Interpretive Summary: Direct analysis of solid materials is important to avoid time-consuming sample preparation and avoid contamination prior to trace element analysis. By preparing a slurry, solid material may be injected directly into an electrothermal atomizer using an autosampler. Ultrasonic slurry sampling (USS) was developed in the author's lab and has been developed into a commercial product which allows fully automated direct solids analysis. Ultrasonic slurry sampling (USS) has been used with electrothermal vaporization (ETV) which has been coupled with inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS) to provide rapid, sensitive, multielement determinations, with isotopic information. This work evaluates the suitability of using Pd as a carrier and using oxygen ashing to get rid of any organic matrix to better match the transport efficiency of slurries and solutions so that calibration may be achieved with aqueous standards. The mechanisms affecting transport efficiency are of interest to the analytical spectroscopic community. Rapid, multielement isotopic direct analysis of solids will be of significant interest to the biological, geological, and environmental analysis communities, especially government agencies.
Technical Abstract: Mass transport efficiency of both aqueous solutions and slurry samples were studied using ultrasonic slurry electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS). The elements studied include: V, Mn, Ni, Cu, and Pb and the materials analyzed include: NIST SRM 1548 Total Diet, SRM 1632a Coal, SRM 1566a Oyster Tissue and NRCC LUTS-1 Lobster Hepatopancreas. The effect of microgram amounts of Pd on analyte transport efficiency as well as the effect of oxygen ashing were studied. Slurry samples were found to have increased transport efficiencies compared to aqueous solutions when no physical carriers are added. Under these experimental conditions, the determined slurry concentrations were apparently high when quantified using external calibration. Microgram amounts of Pd were used to investigate if a match in transport efficiency between slurry samples and aqueous standards was possible. The use of microgram amounts of Pd resulted in signal intensity attenuation. Such a signal reduction could be related to the presence of space charge effects or losses of analyte due to condensation of the physical carrier together with the analyte on different parts of the ETV cell or the transfer line. However, quantitation for slurry samples was improved by the use of Pd. With oxygen ashing, slurry samples behaved more similarly to aqueous solutions facilitating quantitation with aqueous standards.