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Common Operations
Metal Sample Prep
Sample Analysis Preparation
Thermo Scientific
Up until recently, sample preparation was not a big worry for XRF metals analysis, as the
LOD of the analyzer was seldom low enough for any but the most heavy contamination to be
intrusive; but recent developments such as He-purged analysis have brought analysis to a level
where even light surface contamination can skew an analysis.
You should always prepare your samples before analysis, especially when using He-purged
analysis, as these analyzers will see even trace amounts of contaminants. Oils from fingerprints
and other body contact, lint, oxidation materials, and abrasive materials used in cleaning can
all skew readings if not removed. Sample preparation is simple and not time consuming, and
usually well worth the effort.
The following is a list of problems that need correction before testing:
• Oxidation or Rust may produce an increase or decrease in one or more element test
values unless we remove the rust or oxidation and expose the raw metal.
• Paint may contain several elements which need to be tested at lower levels within
metal alloys (Ti & Zn in white paint, Fe in red paint, Cr in green paint).
• Oil, grease or lubricates may contain high levels of the following elements: lithium,
aluminum, barium, strontium, molybdenum or calcium.
Plated surfaces may have high levels of the following elements: zinc, chromium, nickel, or
copper.
CAUTION Anything on the metal surface will become part of your test results!
You need to clear the surface of your samples of any paint, plating, or any oxidation such as
rust or verdigris before analysis. In order to accomplish this, you need the following:
• Isopropyl alcohol - not rubbing alcohol, which contains oils.
• Lint-free paper.
• Diamond paper - P/N 179-1202- cut into 1 inch/2.5 cm squares. Never re-use this
paper, as it may transfer contaminants to the surface of the sample from previous
cleanings. Depending on the state of the sample, several squares may be needed per
sample.
5
Common Operations
Metal Sample Prep
Niton XL2 Analyzer User's Guide
47
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