US Geological Survey
The Reston Groundwater Dating Laboratory
Dissolved Gases N2 / Ar, Frequently Asked Questions
- What gas analyses are available?
Dissolved N2,
Ar, CH4, O2, CO2
- What are the reporting levels for the analysis
- Why
collect samples for N2, Ar, CH4, O2,
and CO2?
- Why do I need
to collect dissolved gases in duplicate?
All dissolved gas samples are normally analyzed in duplicate.
This provides the user with some QA/QC information.
- Do I have to
pay for duplicate samples?
No.
- Can I pre-pay
for analyses?
Yes.
- How
do I collect samples for dissolved gases?
-
What Standards are used to analyze samples for dissolved gases?
- How long can
I keep the bottles before shipping?
Samples can be stored at your location in a refrigerator or on ice until the end of your project and shipped together.
- How should the
samples be stored before shipping?
Store under refrigeration (approximately 4 ºC; Caution:
Do not freeze the sample) or on ice until shipping.
This will minimize expansion of the water on warming which
could cause the stopper to come out of the bottle. This will
also minimize microbial activity that can affect dissolved
oxygen, carbon dioxide, and even nitrogen and methane in the
sample.
- Can I put labels
on the sample bottle?
No. The bottles have been weighed in the lab before shipping
to you. The label would change the weight of the bottle.
You can put the label on the sleeve that holds the bottle.
- Can I change
stoppers used on the bottle?
No. The stopper has been weighed in the lab and belongs with
the bottle it came with.
- What do I do
if there is a bubble in the bottle?
If the bubble was introduced during collection, empty the
sample and repeat the collection.
- What if a bubble
forms in the bottle during shipping or storage?
This is normal and not a problem.
- I’m having trouble
getting the stopper to go into the bottle. How far do I have
to get it in the bottle?
At least half
way. Do not add any lubricant to the stopper.
