LOW LEVEL SELENIUM DETERMINATIONS IN BIOLOGICAL SAMPLES USING HYDRIDE GENERATION SAMPLE INTRODUCTION TO INDUCTIVELY COUPLED MASS SPECTROMETRY

Authors: Lacher, Craig; Sims, Rodger

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2005
Publication Date: 9/12/2005
Citation: Lacher, C.P., Sims, R.L. 2005. Low level selenium determinations in biological samples using hydride generation sample introduction to inductively coupled mass spectrometry. [Abstract]. 119th Association of Analytical Chemists Annual Meeting and Exposition.

Interpretive Summary: Determination of very low concentrations of selenium in most biological samples is difficult to achieve. Graphite furnace atomic absorption spectroscopy (GFAA) has detection limits for selenium concentrations of 0.4 ng/ml. Conventional inductively coupled plasma mass spectrometry (ICP-MS) can detect selenium at 0.1 ng/ml. To maximize analytical sensitivity and determine sub-ppb levels (0.01ppb) of selenium, we developed a method using a continuous flow hydride generation system coupled to an ICP-MS. The analytical method uses a Perkin-Elmer FIAS model 400 flow injection system, a Perkin-Elmer AS-93Plus autosampler and a Perkin-Elmer ELAN-DRCII ICP-MS. Hydride generation utilizes the property that certain elements such as selenium form covalent gaseous hydrides which can be generated from an acidic (HCl) solution and introduced directly to the argon plasma torch assembly. Typical ICP-MS analysis must incur total dissolved solids (TDS) of <1-2% by sample introduction through a diluting spray chamber and nebulizer. However by using the hydride generation method we can avoid the dissolved solids problem entirely and enhance available signal by providing a clean, gaseous, undiluted sample with direct injection to the ICP/MS. We have shown improvements of 100 times in the measurements of three sigma detection limits for selenium determinations. The 74Se isotope was measured at more than 500 cps (counts per second) with a concentration of 10.0 parts per trillion (ppt). The RSD (relative standard deviation) for the 74Se determination was <2.0% indicating a much lower detection limit of sub ppt. Selenium was accurately determined by ICP-MS hydride generation in a biological reference material (Seronorm Plasma Standard). The obtained values were 79.3 and 79.5 with <2% RSD of a 1/1000 dilution of an 81 ppb traceable standard. The advantages of our method include improved sensitivity and detection of selenium using concentrated sample introduction, interference free samples and the use of alternative low intensity masses.

Technical Abstract: Determination of very low concentrations of selenium in most biological samples is difficult to achieve. Graphite furnace atomic absorption spectroscopy (GFAA) has detection limits for selenium concentrations of 0.4 ng/ml. Conventional inductively coupled plasma mass spectrometry (ICP-MS) can detect selenium at 0.1 ng/ml. To maximize analytical sensitivity and determine sub-ppb levels (0.01ppb) of selenium, we developed a method using a continuous flow hydride generation system coupled to an ICP-MS. The analytical method uses a Perkin-Elmer FIAS model 400 flow injection system, a Perkin-Elmer AS-93Plus autosampler and a Perkin-Elmer ELAN-DRCII ICP-MS. Hydride generation utilizes the property that certain elements such as selenium form covalent gaseous hydrides which can be generated from an acidic (HCl) solution and introduced directly to the argon plasma torch assembly. Typical ICP-MS analysis must incur total dissolved solids (TDS) of <1-2% by sample introduction through a diluting spray chamber and nebulizer. However by using the hydride generation method we can avoid the dissolved solids problem entirely and enhance available signal by providing a clean, gaseous, undiluted sample with direct injection to the ICP/MS. We have shown improvements of 100 times in the measurements of three sigma detection limits for selenium determinations. The 74Se isotope was measured at more than 500 cps (counts per second) with a concentration of 10.0 parts per trillion (ppt). The RSD (relative standard deviation) for the 74Se determination was <2.0% indicating a much lower detection limit of sub ppt. Selenium was accurately determined by ICP-MS hydride generation in a biological reference material (Seronorm Plasma Standard). The obtained values were 79.3 and 79.5 with <2% RSD of a 1/1000 dilution of an 81 ppb traceable standard. The advantages of our method include improved sensitivity and detection of selenium using concentrated sample introduction, interference free samples and the use of alternative low intensity masses.