When material is the method

The rows that permit one thing

On this page11

Glass only Why glass Which is a loss you cannot detect Plastic only Why not glass Boron is the clearest case of all So the error runs both ways The protozoan rows name a specific polyethylene And dissolved oxygen names the whole vessel What a supplier should take from this References

Glass for oil and grease. Plastic for fluoride. Both are about what the wall does.

Glass only

Oil and grease: G, 28 days. Phenols: G, 28 days. Phosphorus (elemental): G, 48 hours. One letter in the container column.

Why glass

Because a polymer wall adsorbs those analytes out of the sample. The bottle quietly takes part of what you are measuring and the result reads low.

Which is a loss you cannot detect

A low oil and grease number looks like a clean sample. There is no symptom, no haze, nothing in the chain of custody to notice. That is what makes it worth a rule.

Plastic only

Fluoride: P, no preservation required, 28 days. Silica: P or Quartz, 28 days.

Why not glass

Because glass gives those analytes back to the water. A silica result from a glass bottle is partly a measurement of the bottle.

Boron is the clearest case of all

"P, FP, or Quartz", with no G. Borosilicate glass is named for its boron, and sampling for boron in a glass bottle is sampling the container.

So the error runs both ways

Polymers subtract organics; glass adds inorganics. The table is a map of which direction the container will push each result.

The protozoan rows name a specific polyethylene

Cryptosporidium and Giardia: "LDPE; field filtration", 1 to 10 degrees C, 96 hours. Not polyethylene generally, and the filtration happens in the field rather than at the bench.

And dissolved oxygen names the whole vessel

"G, Bottle and top". The closure is part of the specified container, because a dissolved oxygen sample is defined by excluding air and the top is what excludes it.

What a supplier should take from this

Material first, always, and before capacity or shape. For several rows it is the only question, and getting it wrong does not produce an error, it produces a plausible wrong number.

References

40 CFR 136.3, Table II, selected rows. Oil and grease: G, cool to 6 degrees C or below and acidify to pH below 2, 28 days. Phenols: G, 28 days. Phosphorus (elemental): G, 48 hours. Fluoride: P, no preservation required, 28 days. Silica: P or Quartz, 28 days. Boron: P, FP, or Quartz, nitric acid to pH below 2, 6 months. Cryptosporidium and Giardia: LDPE with field filtration, 1 to 10 degrees C, 96 hours. Dissolved oxygen by probe: G, bottle and top, analyze within 15 minutes. Chlorine, total residual: P, G, analyze within 15 minutes. pH: P, FP, G, analyze within 15 minutes. Coliform and E. coli: PA, G, 8 hours. Hardness: P, FP, G, 6 months. Nitrate: P, FP, G, 48 hours. ecfr.gov

40 CFR 136.3, Table II, "Required Containers, Preservation Techniques, and Holding Times", footnote 1: "'P' is for polyethylene; 'FP' is fluoropolymer (polytetrafluoroethylene [PTFE]; Teflon(R)), or other fluoropolymer, unless stated otherwise in this Table II; 'G' is glass; 'PA' is any plastic that is made of a sterilizable material (polypropylene or other autoclavable plastic); 'LDPE' is low density polyethylene." Footnote 2: "Except where noted in this Table II and the method for the parameter, preserve each grab sample within 15 minutes of collection." ecfr.gov

Written from 40 CFR 136.3 Table II and from the catalog as it stood on 19 October 2026. Part 136 governs Clean Water Act compliance monitoring; it is used here for everything else as the best available statement of what a container does to a water sample, not as a rule that binds a student with a creek. Nothing on this shelf is sold precleaned or certified for regulated sampling, and no preservation chemistry is given, because that belongs to the laboratory running the analysis.