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United States Department of Agriculture

Agricultural Research Service

Title: Comparison of a Cross-Flow and Microconcentric Nebulizer for Chemical Speciation Measurements Using Cze-Icp-Ms

Authors
item Baker, Scott
item Miller-Ihli, Nancy

Submitted to: Journal of Applied Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 22, 1998
Publication Date: N/A

Interpretive Summary: Chemical speciation is important because the form of the element determines it's adsorption, absorption, toxicity, etc. Chemical speciation measurements require the combination of a separation method and a detection method. In this case, capillary zone electrophoresis (CZE) is combined with inductively coupled plasma mass spectrometry (ICP-MS) for the efficient separation and detection of metal species in metallothionein samples. Cd was determined using 2 different nebulizer designs (cross-flow and microconcentric). Both proved suitable for CZE-ICP-MS, with the microconcentric providing better sensitivity, but it lacked ruggedness due to clogging, while the higher capacity cross-flow nebulizer never clogged. Alternative designs of microconcentric nebulizers will be evaluated in the future. The detection limits for the cross flow nebulizer (90 ng/g) and the microconcentric (MCN-100; 10 ng/g) were both adequate for quantification of the Cd content of the various metallothionein samples. This work is of particular importance to researchers and instrument companies interested in trace element speciation measurements. Colleagues at NIH, FDA, NIST, Perkin-Elmer and EPA will benefit as well as academic researchers interested in micro sampling techniques.

Technical Abstract: A standard cross-flow nebulizer and commercially available microconcentric nebulizer (MCN-100) have been compared for capillary zone electrophoresis (CZE) ICP-MS measurements. Metallothionein samples were separated and detected to characterize the performance of the two nebulizers for chemical speciation measurements. The MCN-100 offered improved sensitivity and lower detection limits compared to the cross- flow nebulizer, but provided slightly poorer resolution. The detection limit for 114Cd in metallothionein solutions was 90 ng/g with the cross-flow nebulizer and 10 ng/g with the MCN-100 for about 4 nL injections. These values correspond to absolute detection limits of 360 fg Cd in the injected sample with the cross-flow nebulizer and 40 fg Cd for the MCN-100. Quantitation of Cd in metallothioneins (rabbit liver and horse kidney) using a well-characterized rabbit liver metallothionein sample as the calibration standard is reported. Measured Cd concentrations agreed with results obtained by both graphite furnace AAS and solution nebulization ICP-MS.

Last Modified: 8/22/2014
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