USGS Open-File Report 02-371, Geochemical Sediment Analysis Procedures, Drying Samples

Geochemical Sediment Analysis Procedures, Open-File Report 02-371

OVEN DRYING SAMPLES
Materials Required: Oven Sample to be dried
Several ovens are available for use: THELCO in XRay Lab for "clean" samples THELCO in Filter Room for desiccant and chemically treated samples Imperial III with N2 in Geochem Lab for samples and some small equipment (might change to air pump) Check contents of oven with other users before placing new items in it to avoid cross-contamination to open vessels. Remove top from sample container.
Place samples in oven at 60 degrees F for at least 24 hours or until cracks appear in sediment. Check oven door to make sure it latches.
Place samples in desiccator when removed from oven to cool and to avoid getting moisture from the air in your samples. Weigh samples on a balance to get the dry weight. Record dry weights on a log sheet, in a data log book, or a personal log book.

FREEZE DRYING PREPARATION

Materials Required:

Small Kimwipe
Rubberbands
Plastic Glove
Sample

Freeze Dry preparation for Planar; link to larger image

After core cutting, samples are frozen and put into storage.

When ready to analyze, locate samples in storage and wipe sides of sample container with a Kimwipe so there is no frost.

Wipe frost off container; link to larger image

Place container lid in a plastic glove so there is no contamination of sediment on the lid.

Rip a Kimwipe in half along fold so 1 layer fits on mouth of sample container.

Place Kimwipe on sample and secure with a rubber band.

*Make sure that both lid and sample container are labeled before removing lid!
*Prior to freeze drying, check to see that wet weights have been recorded on the sample.

Cover sample with Kimwipe; link to larger image

FREEZE DRYING SAMPLES

Materials Required:

Samples
Freeze Dryer
Instrument Notebook
Sharpie
Basin
Paper Towels
Vacuum Pump Oil 19 (VWR Scientific Inc.)

Freeze Drying preparation; link to larger image

Weigh the samples without lids to determine which one is the heaviest. Record the wet weights in the freeze dryer notebook. Mark the heaviest sample with a Sharpie on the Kimwipe. This sample is used as a standard to compare the drying progress of the other samples.

Place a stack of containers in the freeze dryer using the racks provided.

If the heaviest sample is completely freeze dried, then the others will be.

Remove exterior attachable jars, or, if necessary, place additional samples in the jars.

If using the exterior jars, make sure the vacuum seal is good.

Turn the white knob to 'vent' if there is no jar attached.

Turn the white knob to 'vac' if there is a jar attached.

Turn to vent or vacuum; link to larger image

Check the vacuum pump oil level and oil quality.

Oil level should be at the midline or just above - check to ensure the oil is clear and free of sediment, bubbles, and water. Check the instrument notebook for a record of the last oil change. Oil should be changed once a month during periods of frequent use.

Start the machine by pushing the Refrigeration button ON to Man. Vac. (Manual Vacuum). Once the temperature reaches -40 degrees C (this takes about 20 min), turn the vacuum on by pushing the Vacuum button up to the ON position.

You will see the word "HI" for high vacuum displayed in the window. Once numbers start appearing, you should check it periodically to make sure the numbers are decreasing. The system is functioning properly when the number drops to 200 millibars or below.

Record the pressure and temperature in the notebook and watch periodically for 3 days until all samples are dried.

To determine if samples are dry, release the vacuum slowly by venting from the black ports. Turn off the vacuum pump, open the chamber, weigh the sample, place it back in the freeze dryer, and restart the system.
Return after 2 hours - if the weight has changed, continue the drying process.

Remove samples from machine and remove the kimwipe and rubberband - remove cap from glove and replace cap over sample so you can weigh the sample immediately.

To shut down after use:
- shut down the refrigerator and vacuum
- open the lid to the condensing chamber
- turn on the DEFROST to speed the process
- position the basin beneath the drain hose
- remove the drain hose plug and place in a secure location
- leave machine to defrost
- once defrosted, dry off chamber with paper towels, replace plug in the drain hose, and close the lid.

FREEZE DRYING PREPARATION
Materials Required: Small Kimwipe Rubberbands Plastic Glove Sample
After core cutting, samples are frozen and put into storage. When ready to analyze, locate samples in storage and wipe sides of sample container with a Kimwipe so there is no frost.
Place container lid in a plastic glove so there is no contamination of sediment on the lid. Rip a Kimwipe in half along fold so 1 layer fits on mouth of sample container. Place Kimwipe on sample and secure with a rubber band. Make sure that both lid and sample container are labeled before* removing lid! *Prior to freeze drying, check to see that wet weights have been recorded on the sample.
FREEZE DRYING SAMPLES
Materials Required: Samples Freeze Dryer Instrument Notebook Sharpie Basin Paper Towels Vacuum Pump Oil 19 (VWR Scientific Inc.)
Weigh the samples without lids to determine which one is the heaviest. Record the wet weights in the freeze dryer notebook. Mark the heaviest sample with a Sharpie on the Kimwipe. This sample is used as a standard to compare the drying progress of the other samples. Place a stack of containers in the freeze dryer using the racks provided. If the heaviest sample is completely freeze dried, then the others will be.
Remove exterior attachable jars, or, if necessary, place additional samples in the jars. If using the exterior jars, make sure the vacuum seal is good.
Turn the white knob to 'vent' if there is no jar attached. Turn the white knob to 'vac' if there is a jar attached.
Check the vacuum pump oil level and oil quality. Oil level should be at the midline or just above - check to ensure the oil is clear and free of sediment, bubbles, and water. Check the instrument notebook for a record of the last oil change. Oil should be changed once a month during periods of frequent use. Start the machine by pushing the Refrigeration button ON to Man. Vac. (Manual Vacuum). Once the temperature reaches -40 degrees C (this takes about 20 min), turn the vacuum on by pushing the Vacuum button up to the ON position. You will see the word "HI" for high vacuum displayed in the window. Once numbers start appearing, you should check it periodically to make sure the numbers are decreasing. The system is functioning properly when the number drops to 200 millibars or below. Record the pressure and temperature in the notebook and watch periodically for 3 days until all samples are dried. To determine if samples are dry, release the vacuum slowly by venting from the black ports. Turn off the vacuum pump, open the chamber, weigh the sample, place it back in the freeze dryer, and restart the system. Return after 2 hours - if the weight has changed, continue the drying process. Remove samples from machine and remove the kimwipe and rubberband - remove cap from glove and replace cap over sample so you can weigh the sample immediately.

Geochemical Sediment Analysis Procedures, Open-File Report 02-371

DRYING SAMPLES - Oven or Freeze Dry (preparation)