Table of Contents

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

LOI/Sample Bead

• Quartz or alumina ceramic crucibles
• Tongs
• Vials containing 400 mg lithium metaborate flux (preweighed on shore)
• Milligram calibration weighing set
• Weighing paper, 4 x 4
• Vials for excess ignited powder
• Agate mortar and pestle
• Pt-Ag crucibles

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Rock samples are prepared for ICP analysis using the following procedures on each sample:

1. Cut to size (see Cutting Samples to Size below)
2. Polish (see Polishing Samples on Diamond Wheel below)
3. Clean (see Cleaning Samples below)
4. Dry (see Drying Samples below)
5. Crush (see Crushing Samples in the X-Press in XRD Sample Preparation Hard Rock )
6. Grind (see Grinding Samples in the Shatterbox in XRD Sample Preparation Hard Rock)

Cutting Samples to Size

To cut samples for the X-Press, use the splitting room rock saws (located in the Core Deck) following these guidelines:

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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 of solution. There should be enough liquid in the beaker to keep the sample from floating in the sonic bath (Sonic Bath without basket Figure 4).

Figure 4. Sonic Bath Bath (without basket).

Fill the sonic bath with 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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Shipboard sample preparation and LOI determination procedures described in Murray (2000) and updated in recent IODP Proceedingsvolumes (e.g., Reagan et al. [2015] for Expedition 352) are appropriate for a range of sediment and rock compositions, but some care must be taken with unusual sample matrixes. As an example, attempting sample ignitions on carbonate-rich materials can lead to spurious results and issues with contamination if quartz crucibles are used for sample ignitions because carbonates will react with quartz upon heating to both devitrify and decompose the crucible. Alumina ceramic crucibles may be better for carbonates but risk contamination for Al and potentially other elements due to spallation over time. Putting carbonate rich samples or sediment in quartz crucibles ruins the crucibles and the LOI (consulted with Jeff Ryan on this Exp 393). Consult with the scientists to be determine what crucible will be needed.

Maximum ignition temperatures of 1000°C and higher are appropriate for ultramafic and some mafic igneous materials but may result in sample sintering and/or sticking to some Si- or Ca-rich materials. Ignition temperatures of <850°C are inadequate to decompose carbonate minerals in sediment samples, even if samples are held at temperature for several hours. In general, igniting samples to at least 900°C as a maximum temperature is advisable to decompose all volatile-bearing phases and obtain reliable measures of LOI.

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Post-ignition measurements should be taken soon (within an hour) after removing crucibles from the furnace. Failure to do so will disrupt the LOI values. Reweigh the crucible plus the ignited sample to determine how much weight was gained or lost. Follow the same weighing procedure as in Pre-ignition Weighing.

1. Record the final weight in the excel spreadsheet under 'CRUCIBLE + IGN SAMPLE WT'. The spreadsheet will populate the columns 'Post Ignition Loss' and '%LOI'.
2. The formula used to calculate LOI is:

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Copy and paste your spreadsheet into that uploader. Click the 'Edit' button and 'Validate Sheet'. This checks and highlights any errors that need to be fixed. When the spreadsheet comes up clean, click 'Lims' and 'Upload'. The sheet will turn green when the measurements are successfully uploaded. The data is now in LIMS under Chemistry > ICP-AES Solids >Expanded LOI.

Cleaning the Quartz or Alumina Ceramic Crucibles

1. Wash the crucibles with DI water and a small piece of a scouring pad (no soap).
2. Rinse several times with DI water.
3. Place crucibles in a 10% HNO₃ bath for 12 hr. If in urgent need, the quartz crucibles can be soaked a minimum of 2 hours, but extra flux blanks will need to be made and added to batches that use these crucibles.
4. Rinse 3 times with DI water after the acid bath.
5. Dry the quartz crucibles in the oven at a maximum temperature of 60°C. Heat the alumina ceramic crucibles to 800°C in the muffle furnace for 2 hours and allow to cool to room temperature before removing

Some crucibles will develop a thin white or red cloudy film, become spotted, or start flaking. If any of these things happen thrash discard the crucible in the sharps container. When the crucible undergoes one of those changes the quartz has started to react at high temperatures, and could start contaminating the samplesamples. 

Making the Sample Bead

• In a vial, mix 400 mg lithium metaborate flux (pre-weighed onshore) with either ignited or non-ignited powdered sample, check with the science party to determine which sample type should be used. Typically we use unignited powder as that is how our standard beads are prepared and what correlate to the certified values.  This step is typically completed by the chemistry technicians.
• Fuse both sample powder and flux into a glass bead (Figure 43). Dissolve the bead in nitric acid. This solution will be further diluted and analyzed by the ICP.

Figure 43. Fused glass bead. 

• An analytical procedural blank of Flux is prepared identically to the samples. The 0.4 g of flux (the pre-weighed flux) is fused with 10µL 0.172 mM of LiBr and dissolved. An additional 0.1 g of flux is NOT added to mimic the TDS of the 0.5 g mix of sample + flux because this would provide an inaccurate quantitation of the impurities introduced by the amount of flux used in preparation of the unknowns.

Weighing the Sample

Note: This process is typically done by the chemistry technicians.
Weighing the sample is a critical step. The sample weight should be as close to 100 mg as possible. Inaccuracies in the weight will show up in the analytical results. Print small labels for each sample and place on your small, clear capped vial. On the lid label a sticker with the core, section, and interval. Confirm with scientists what powder you will be using Fresh or Ignited.

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1. Rinse crucibles with DI water.
2. If beads are stuck to the bottom, sonicate with DI water for 30 min or more.
3. Place crucibles in HNO3 10% bath for 12 hr. If you notice any signs of residue, leave in the acid bath for longer. If the crucibles are in urgent need, a minimum cleaning time in the HNO3 10% acid bath is 2 hrs, however, extra flux blanks should be made with these crucibles for analysis to ensure there isn't leftover contamination.
4. Clean a Tupperware container with isopropyl alcohol. Lay down sheets of paper towel and large Kimwipes.
5. Take crucibles out of the acid bath and rinse with DI water 3 times. Place crucible in the container. If the crucibles require polishing, see Polishing the Platinum Crucibles.
6. Cover all crucibles with a large Kimwipe and place in the drying oven in the Chemistry Laboratory. Leave overnight.
7. When dry remove crucibles and bring into the XRD laboratory. Wrap each crucible in a small Kimwipe and and place back in the safe. Lock the safe after all crucibles have been put back.

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