Sample Contamination from Grinding and Sieving Determined by Emission Spectrometry

Abstract

The trace element contaminations, introduced by grinding or sieving samples of Specpure silica and calcium carbonate in various devices in common usage, have been measured using emission spectrometry. The tungsten carbide vial introduced large amounts of Co and Ti. The alumina mortar introduced Al, Cr, Fe, Ga, and Zr. The alumina-ceramic vial introduced Al, Cu, Fe, Ga, Li, Ti, B, Ba, Co, Mn, Zn, and Zr. The boron carbide mortar (except for B), the agate mortar, and the Lucite grinding vials introduced little or no contamination, as did sifting with nylon sieves. Stainless steel or brass sieves introduced appreciable levels of Co, Cu, Fe, Mn, Ni, Pb, Sn, and Zn. The contamination Cu, Pb, and Zn from sieving with the brass was greatest in the smaller size fraction. Pregrinding an aliquot of the sample is recommended. Greater reductions in contamination from the grinding material were noted by pregrinding with soft fine CaCO3 than with SiO2. Cross contamination from previously ground samples was demonstrated to be a major source of contamination. Grinding with the hard, more abrasive SiO2 removed more of the cross contaminants than did the CaCO3.

Trace element abundance in agate.

“…Because of its rigidity and purity, agate is considered as one of the best materials for grinding mortar. Thompson and Bankston (1970) investigated in detail the effect of variety of grinding and sieving materials. Contamination levels were de termined by the spark source-optical emission spectrometry.…”

“…Any zigzag pattern, how ever, can not be recognized clearly. Thompson and Bankston (1970) reported a few ppm level of contamination for B and Cu from agate mortar. We could not examine it for both B and Cu by the INAA employed here.…”

Explanatory Notes

“…Finally, powders were produced by grinding in a tungsten carbide shatterbox vessel for approximately 1-2 min. Sample contamination from the tungsten carbide shatterbox is significant for elements W, Co, and Ta (Thompson and Bankston, 1970). At these grinding times, however, niobium contamination is minimal (<l ppm).…”

Baseline geochemistry of soil and bedrock Tshirege Member of the Bandelier Tuff at MDA-P

“…Background samples of bedrock were prepared for chemical analysis by pulverizing in a tungsten carbide shatterbox, which introduces levels of contamination for Co (Thompson and Bankston, 1970) that overwhelms levels present in silicic rocks. Analysis has confirmed about 10% Co in the specific shatterbox used to pulverize the background samples.…”