Submitted to: Spectrochimica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 8, 1996
Publication Date: N/A
Interpretive Summary: Direct solids analysis is an important area of research today. Time consuming sample preparation procedures are eliminated, sample contaminating risks are minimized, and there is less generation of acid waste. Inductively coupled plasma mass spectrometry (ICP-MS) is a very powerful multielement technique which provides excellent sensitivity. Direct solids analysis can be achieved using electrothermal vaporization (ETV). An interesting aspect of direct solids analysis using biological slurry samples with organic matrix is that the carbon present in the sample acts as a carrier enhancing analyte transport resulting in improved sensitivity. This paper focuses on matrix effects, outlining strategies for selecting the most appropriate means of calibration for quantitative analyses.
Technical Abstract: Quantification of both digested and slurry samples were studied using ultrasonic slurry electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS). The results of external calibration using aqueous standards, method of additions, and In as an internal standard were compared. The elements studied include: Mn, Ni, and Cu. Pd was used as a physical carrier and oxygen ashing was used. Different degrees of matrix suppression effects were observed due to changes in para- meters such as skimmer-sampler separation, skimmer/sampler orifice align- ment, and separation between the skimmer sampling orifice and the first ion lens. Aging of the skimmer cone and loss of its circular symmetry results in differences in sampling of the ion beam and the degree of matrix effects observed. The presence of matrix suppression effects is evidenced by strong suppressions in the Ar2, C, and analyte signals. When matrix suppression effects were present external calibration provided low recoveries, there- fore it was necessary to use the method of additions to compensate provid- ing an average accuracy of 100+/-13%. When matrix effects were absent external calibration provided an average accuracy of 101+/-16%.