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Use the Bruker Tracer 5 pXRF Safety Presentation PowerPoint found on the desktop of pXRF laptop and the pXRF Safety Information guide on the pXRF Laboratory Manuals page to inform the operating scientists of all safety measures and procedures for the device. Also provide a demonstration of the operation of the device. Make sure to provide the pXRF Safety Information guide and the Bruker Tracer 5 pXRF Quick Start guide for their reference
Sample
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Shielded Holder for section halves - the Tracer must be picked up and moved, do not slide the nose of the device along the core surface!
Desktop Stand
Benchtop Chamber
Sample Preparation
Preparing section halves
If measurements are taken on a section half, of sediment or hard rock, some steps must be taken to protect the device measurement window from puncture or sediment contamination. The beam coverage is about 8 mm2 and the ideal thickness of a sample should be ~1 cm or more.
For sediment cores, the surface of the core must be covered with a thin plastic film (Fig Next, Ultralene, 0.16 mil/4 µ thick, Glad wrap GLAD® wrap is too thick and will interfere with measurements). Cover the area of measurement and about 4-5 cm on each side, so a 10 cm piece of Ultralene would be appropriate. This is to protect the device nose from becoming dirty from the core. If making several measurements in an area, the entire area can be covered. If the entire core section will be measured ('high' resolution measurements), cover the entire core section. Important! Do not measure on sediment core sections without covering with film, however, do not waste Ultralene Ultralene® to cover areas that will not be measured .
Figure Next. Ultralene polypropylene plastic covering the sediment surface.
For hard rock cores, place a layer of Ultralene over the nose of the device. This can be taped in place on each side of the device nose and adding an extra layer over the measurement window.
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(it costs about $1 USD/meter). Tape the film on the sides of the liner and use a Kimwipe on the film to remove any trapped air bubbles under the film in the area of measurement. Cover the rest of the section in GLAD® Plastic Wrap so the instrument and holder does not get dirty. Make sure the top of the plastic is clean, dry, air-free and mud-free, especially the Ultralene®-covered locations. Important! Even a small amount of sediment on top of the thin film from a measurement will affect the next measurement of the core section half.
Figure Next. Ultralene® polypropylene plastic covering the sediment surface.
For hard rock cores, following the procedure at the onshore XRF laboratory in College Station (Texas), no film is put on hard rock sections. The surface is cleaned with DI and Kimwipe. When dried, the core surface is brushed to remove any remaining dust/contaminating particles. The pXRF device is then placed on top of the hard rock core section for measurement.
Preparing powdered samples
Discrete samples are dried, ground to powder, and loaded into a XRF sample cup. Powdered samples allow the analysis of a specific interval or feature on a section half. This process is more involved, time-consuming, and invasive (destructive) compared to the section half measurement. However, powdered samples can be run along with powdered standard reference materials and the data can therefore be reduced for quantitative elemental data. Powdering a sample also creates a homogeneous sample. If the powder is fully homogeneous and the sample cup is loaded to sufficient thickness (~1cm) and uniform powder density, quantitative error should be low.
Drying Samples
It is important to dry discrete samples prior to grinding them. Freeze-dry samples for 12 hours. For details on how to operate the Freeze Dryer refer to the X-Ray Diffraction (XRD) sample preparation
Grinding Samples
Once dry, samples are ground into a talc-like powder. Grinding is accomplished by three methods: agate mortar and pestle, SPEX Mixer/Mill®, or SPEX Shatterbox®. The specific grinding method used is dependent on sample hardness. For more details on grinding methods refer to the X-Ray Diffraction (XRD) Sample Preparation and ICP Hard Rock Prep User Guide.
Loading Samples into an XRF Sample Cup
To create a powdered XRF sample, assemble the following components shown in Figure Aloha:
- Powdered & dried sample
- Scoopula
- XRF sample cups (32 mm Double Open Ended)
- SPEX Ultralene® thin film (0.16 mil; 4 µm thick) OR Polypropylene pre-cut circles (0.16 mil; 4 µm thick)
- Whatman Filter Paper Circles (32mm) or Parafilm M® film
- Foam plug
- Scalpel for trimming foam plug
Figure Aloha. Mortar and pestle along with scoopula. XRF Sample Cup components denoted with red arrows A. Open-end Ring B. Cup C. Cap D. Ultralene® film box E. Whatman Filter Paper F. Foam plug inserts
1. A XRF Sample cup has three components: cup, ring, and cap. Take a piece of Ultralene® film or polypropylene pre-cut circle and stretch it over one end of the cup. Place the open ring over the film and cup and snap it firmly onto the cup. This will create a tight window on one end of the sample cup (Fig. 16, step 1). Ultralene® is very thin and prone to ripping. Check for rips before and after sample powder is added.
2. Flip this unit upside down (film side down) and begin to load the sample into the cup. Remember that the powdered sample will be back loaded. An ideal depth of sample is ~1.5 cm or more, if possible, with the goal being ~1 cm of pressed material. The sample layer cannot be too thin, or X-ray penetration (and the results) will be inconsistent. Make sure the powder is evenly dispersed, maintaining a relatively flat, even surface.
3. Next place a barrier layer on top of the powder, either Whatman Filter Paper or Parafilm®. This creates a seal that prevents contamination and keeps powder secured in place. Take a piece of Whatman filter paper and put it on the powder or cut a square of parafilm, wrap it over the end of the foam plug and push it down inside the cup. Press down evenly until it is firmly on the powder.
4. Insert the foam plug (if not already inserted). Take care not to insert it too quickly and cause air displacement that might disturb the powder. Depending on how much sample has been loaded into the sample cup; a couple centimeters of the foam may need to be chopped off.
5. Once you have filled the unit properly, place another piece of Ultralene® film or a polypropylene pre-cut circle across the back of the sample cup and snap the closed cap on the cup. If you have over-filled the sample cup, this is the point where the film will break, so examine both sides of the cup after you snap the lid on. Tip: place the cap on most of the way as in step 5, but then flip the sample cup over and, holding only the edges, push the sample cup down into the cap until it snaps firmly in place. Holding the sample cup toward the edges allows the film covered surface of the sediment to bulge out as seen in step 6.
6. It is important to create some outward "bulging" of the film so that the powder stays well-packed and stationary. Cracks, gaps, tears in the film or inconsistent filling of the powder will create inconsistent results. Be careful, however, not to pack too tightly or the Ultralene® film will break and you will have to start over.
Your finished product should look like the cup in Figure 16, step 6.
7. Put a sample label onto the cup. Remove excess Ultralene® to help the label stick. The powdered sample is now ready for analysis.
Figure 16: Sample preparation steps for powdered pXRF sample. Note the slight bulge of the sample when correctly filled.
Do not forget to remove the sample from the pXRF sample cup after analysis. A 3D-printed tools exist to help disassemble the sample cup. Put powder back into it's original container or put it in a labeled jar (shipboard residue). Wash and clean the pXRF sample cup components before reusing.
Sample Measurement Set Up
Shielded Holder for section halves - the Tracer must be picked up and moved, do not slide the nose of the device along the core surface!
Desktop Stand
Benchtop Chamber
Instrument Set Up
Begin by installing a fully charged battery or powering the device using an AC power adaptor. Note: The batteries cannot be 'hot swapped'. If a battery is running low, either shut off the Tracer, switch batteries and power it back on again, or plug the AC power in, change the battery, and then unplug the device again. No loss of data will occur when the device is powered off.
If the Tracer has not been used in a while, check that the date and time are correct by going to 
, then 
, and select Date/Time.
The Tracer 5 can be operated alone or connected to a laptop. Using Bruker RemoteCTRL 
, the device screen is mirrored on the laptop. This will be necessary if using the benchtop chamber or the desktop stand.
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To clear the internal memory of the device, from the main display screen select 
, then 
. Select the 'Delete' option along the top (Fig. 11, Green Box). To keep the run numbers consecutive through the expedition, deselect the 'Reset Assay filename counter' option (Fig. 11, Purple Box). If it is the end of the expedition, leave this option selected and the run number (the same as the file number), will revert back to '1'. Then select 
.
Figure 11. Backup Data screen. Green box, the Delete option. Purple box, option to select/deselect if you want to reset the run number back to 1.
Additionally, it is important to keep the number of files in the Data folder of the USB low as well. This should also be done each time the internal memory is cleared.
With the device connected to the laptop, open Bruker Instrument Tools and connect to the Tracer.
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Figure XX. The date and time setup screen.
Disconnecting and Closing Programs
Appendix
Application Calibration Information
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