Table of Contents
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Introduction
Inductively Coupled Plasma Atomic Emission Spectroscopy, ICP-AES, is a method to perform elemental analysis on a sample in solution (ODP Technical Note 29). This manual covers hard rock sample preparation for ICP-AES analysis. Hard rock samples are prepared via the 'flux fusion' approach. This technique ensures complete dissolution of sample allowing a full elemental analysis. Solutions are stable which allows further analysis, and involves no HF making it a safe and ideal method (ODP Technical Note 29).
Rock samples are crushed to a fine, talc-like powder using multiple cleaning, crushing and grinding procedures. After grinding, loss on ignition (LOI) is determined. Ignited material is fused with flux powder forming a glass sample bead. Fused beads are then dissolved in 10% HNO3 . This is further diluted and the resulting solution is processed by the ICP-AES machine.
The complete process (from sample table to ICP-AES machine) takes 3-4 days. Day 1 involves: polishing on the Diamond Wheel, cleaning, and drying samples overnight. Day 2: Crushing in the X-Press, grinding in the Shatterbox, a pre-ignition (for LOI) weight, and placing samples in the furnace overnight. Day 3-4: Taking a post-ignition (for LOI) weight, and fusing the sample bead. The beads are handed off to the chemistry technicians to continue ICP analysis.
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Note: The polycarbonate door sits on two interlock switches that enable operation. If the door is not fully closed or pressing down on these switches the machine will not work.
Crush the sample by continuously holding down the toggle switch (Figure 15 D). The motor and pump can be heard and the pressure will rise (Figure 15 E). Once the desired pressure is reached the toggle can be released and the sample will sit under that pressure. For most samples ~5 tons of pressure is enough force to crack it. If you find the need to go past 10 tons, try rotating the sample onto another side and apply pressure again.
Note: Always wear safety glasses. Do not stand directly in front of the X-Press while it is operating.
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The large grinding vessel holds between 20 – 60mLs of material and has five components: a container, puck, inner ring, O-Ring, and lid (Figure 18).
Figure 18. Large Vessel components. A. Container B. Inner Ring C. Puck D. O-Ring E. Lid
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When the time is set press the 'Start' button (Figure 28D). To temporarily pause the operation press the 'Pause/Stop' button once (Figure 28E).To stop the machine press 'Pause/Stop' twice.
Normal Sounds: The shatterbox is extremely loud. The foam and strap surrounding the shatterbox helps keep it in place and minimize some of the noise.
Abnormal Sounds. If there are any metal on metal sounds shut off the shatterbox immediately. Something inside the shatterbox has probably come loose and will damage the inside of the container.
When the shatterbox cycle is done open the lid and remove the vessels, placing them on the counter. Open the grinding vessel and with clean tweezers take a bit of the powder and feel it against the inside of your wrist. The sample should feel like baby powder, if it does not, repeat the shatterbox cycle.
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