...
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% HNO3 . 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 are most often used for ICP analyses, however it is not always the case. Please speak to your scientist regarding their preference.
Wait until there are about six or more samples so you can prepare a 'batch' of six or more at a time.
Apparatus, Reagents, & Materials
...
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.
...
To start the polisher flip the 'On' switch in the back (Figure 1A). The power indicator light (Figure 1B) should illuminate. Press the timer on/off button (Figure 1C) to get continuous disc rotation. Turn the water on by flipping the 'Water' switch to the 'On' position (Figure 1D). The water flow can be adjusted by turning the knob shown in Figure 1E.
The rotation speed is controlled by the dial shown in Figure 1F. 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 1G). 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 a 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'.
Figure 2. Buehler diamond disc discs for polishing (use either one, or start with the courser grain and finish with finer grain).
Figure 3. Labeled beaker with polished rock inside.
...