Three separate analyses are performed in this package.
- ICP-MS analysis on the partial digestion
- ICP-OES analysis for major and minor elements on the near-total digestion
- ICP-MS analysis for trace elements on the near-total digestion
Aqua Regia “Partial” Digestion – ICP-MS
A 0.5 g sample is digested in aqua regia at 90 °C in a microprocessor controlled digestion block for 2 hours. Digested samples are diluted and analyzed by Perkin Elmer Sciex ELAN 6000, 6100 or 9000 ICP-MS. One blank is run for every 68 samples. An in-house control is run every 33 samples. Digested standards are run every 68 samples. After every 15 samples, a digestion duplicate is analyzed. Instrument is recalibrated every 68 samples.
ICPMS1 – Aqua Regia “Partial” Digestion ICP-MS Elements and Detection Limits (ppm)
4-Acid “Near-Total” Digestion – ICP-OES Portion
A 0.25g sample is digested with four acids beginning with hydrofluoric, followed by a mixture of nitric and perchloric acids, heated using precise programmer controlled heating in several ramping and holding cycles which takes the samples to incipient dryness. After incipient dryness is attained, samples are brought back into solution using aqua regia.
With this digestion, resistate minerals are not digested and certain phases may be only partially solubilized. These phases include zircon, monazite, sphene, gahnite, chromite, cassiterite, rutile and barite. Ag greater than 100 ppm and Pb greater than 5000 ppm should be assayed as high levels may not be solubilized. Only sulphide sulfur will be solubilized.
The samples are then analyzed using a Varian ICP. QC for the digestion is 14% for each batch, 5 method reagent blanks, 10 in-house controls, 10 samples duplicates, and 8 certified reference materials. An additional 13% QC is performed as part of the instrumental analysis to ensure quality in the areas of instrumental drift.
ICPMS1 – 4-Acid “Near-Total” Digestion ICP Elements and Detection Limits (%)
4-Acid “Near-Total” Digestion – ICP-MS Portion
Additional elements are determined by ICP-MS on the multi-acid digest solution above. The samples are diluted and analyzed on a Perkin Elmer Sciex ELAN 6000, 6100 or 9000 ICP-MS. One blank is run for every 40 samples. In-house control is run every 20 samples. Digested standards are run every 80 samples. After every 15 samples, a digestion duplicate is analyzed. Instrument is recalibrated every 80 samples.
ICPMS1 – 4-Acid “Near-Total” Digestion ICP-MS Elements and Detection Limits (ppm)