Both the USGS and Lamont Doherty seek to maintain high standards for collection of all samples and encourage sample collectors to seek training.Safety-coated 500cc glass bottles with polycone seals are recommended for the tritium sample, though high-density polyethylene bottles with polycone seals may be substituted.USGS staff collecting groundwater samples in copper tubes for 3He/4He and/or noble gases have access to training at the Field Methods for the Collection of Water Quality Samples courses at the UGGS Office of Employee Development in Denver.
The empty tubes are shipped directly to the project office .
If glass bottles are used, a headspace of several cc's should be left in the bottle to prevent breakage on warming due to expansion.
The water samples for helium and neon determinations are collected in crimped copper tubes (3/8-inch diameter, 30-inch length, containing about 40 cc of water).
Back pressure of approximately 1 atmosphere, 14 psi, is normally sufficient to prevent gas bubble formation in a ground-water sample.
However, in general, to prevent gas bubble formation, the back-pressure applied must exceed the internal pressure of the dissolved gases in the water sample.
The copper tube, which is fixed in an aluminum channel holding the stainless steel clamps, is connected to a closed path from the sample pump.