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Inductively Coupled Plasma Optical Emission Spectroscopy, ICP-OES, 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-OES 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% HNO_{3 .} This is further diluted and the resulting solution is processed by the ICP-OES machine.
The complete process (from sample table to ICP-OES 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. Note that ignited powders is most often used for ICP analyses, however it is not always the case. Please speak to your scientist regarding their preference.

Apparatus, Reagents, & Materials

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• Compensated Dual Analytical Balance System 
• Drying ovens at 110°C and 60°C
• Muffle furnace
• Sonicating bath

Rock Grinding

• Splitting room saw
• Buehler grinder/polisher with 70 µm grit diamond grinding wheel
• Sonicator (with small water bath)
• X-Press crusher 
• Spex Shatterbox with tungsten carbide (WC) grinding vessel 
• Spex Mixer Mill Mill with tungsten carbide or alumina canisters 

LOI/Bead-Making

• Fisher Ashing Furnace 
• Sample Bead Maker 

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• Wrist-action shaker 
• Acid baths 

Reagents

• 0.0172 172 mM LiBr wetting agent (0.15 mg ultrapure LiBr in 10 mL DI water)
• 400mg of drew sighed lithium metabolite flux (weighed on shore)
• 10% nitric acid (143 mL concentrated nitric acid/L of solution). Caution! always add acid to water.
• Isopropyl alcohol, laboratory grade
• Methanol, laboratory grade
• Acetone, laboratory grade
• DI water (18.2 M¿ laboratory water)

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• Beakers
• Glass cleaner
• Tweezers
• Teflon spatula
• X-Press aluminum die
• Core liner pieces and clear endcaps
• Delrin plugs
• Acid-washed 1-oz glass bottles
• Weighing paper, 6 x 6
• Kimwipes

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• Quartz crucibles
• Tongs
• Vials containing 400 mg lithium metaborate flux (preweighed on shore)
• Milligram calibration weighing set
• Weighing paper, 2 x 2
• Acid-washed vials Vials for excess ignited powder
• Agate mortar and pestle
• Pt-Ag crucibles

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Each sample will correspond to one beaker; collect as many as needed. Beakers need to be cleaned (DI water and isopropyl alcohol) and labeled ( ex. 1, A, or sample label).
Next start the grinding process using the Buehler grinder located in the Xray prep area of the thin section lab (Figure 1).
Note: Make sure that the correct diamond disc is attached to the wheel. The diamond disc is attached to a magnetic disc which is then placed on the wheel plate. Attach the diamond disc using either the adhesive on the back or an aluminum ring. 

Figure 1: Buehler Grinder Polisher. A. On/Off switch B. Power Indicator light C. Timer On/Off button D. Water On/Off switch E. Water flow control knob F. Disc speed control. G. Stop/Start. H. Emergency Stop

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To start the polisher flip the 'On' switch in the back (Figure 1A). The power indicator light (Figure 1A1B) should illuminate. Press the timer on/off button (Figure 1B1C) to get continuous disc rotation. Turn the water on by flipping the 'Water' switch to the 'On' position (Figure 1C1D). The water flow can be adjusted by turning the knob shown in Figure 1D1E.
The rotation speed is controlled by the dial shown in Figure 1E1F. The range is 0 rpm to 500 rpm. 150 rpm is a good starting position. Adjust the speed if needed: faster for hard rocks and slower for softer rocks.
With the water on and the RPM adjusted press the 'Run' button (Figure 1F1G). Move the sample back and forth across the disc to prevent making a groove. If there is an emergency press the 'Emergency Stop' button (Figure 1H) to stop rotation and cut off the water. To enable the wheel again twist the knob until it pops back out.
Polish the rocks with the Breuler diamond disc (Figure 2) until they're completely smooth and round on all edges. The purpose of grinding on a diamond disc is to remove any possible contaminates caused by the drilling mud (or drill bit) along with the rock saws in the splitting room. There should no pits or jagged corners. Put the rock into a labeled beaker (Figure 3) and polish the next sample. Do this for all samples and then move on to 'Cleaning Samples'.

Image Added

Figure 2. Buehler diamond disc for polishing.

Figure 23. Labeled beaker with polished rock inside 

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inside. 

Cleaning Samples

To remove contamination (oil, skin, and residue from the diamond wheel) wash the polished samples in 70% isopropyl alcohol and DI water. From this point onward, wear gloves when handling samples to avoid reintroduction of contaminants.

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Pour either DI water or isopropyl alcohol (70%) into the beaker to cover the sample. Check with the scientists for their preference in solution. There should be enough liquid to keep the sample from floating in the sonic bath (Figure 3).

Figure 34. Sonic Bath 

Fill the sonic bath (Figure 4) with a little bit of water and place beakers inside. Sonicate for 15 minutes. You should notice the water becoming cloudy from residue being shaken off the samples. Then follow the wash sequence below:

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