Module 5

Question 1

What factors effect unpreserved samples

Answer 1

• volatilization
• adsorption
• diffusion
• precipitation
• chem changes
• biodegradation

Question 2

What is the purpose of preservation

Answer 2

To minimize effect that chemically change the sample including oxidation and photochemical reactions

Question 3

What are techniques to minimize volatilization

Answer 3

• minimize headspace
• minimize sample agitation
• low temp
• avoid agitation
• do not vacuum filtration

Question 4

What are the preservation techniques for adsorption

Answer 4

• correct sample bottles
• add acid if necessary
• do field tests
• preserve quickly

Metal analysis

• plastic bottles
• acidity to less then 2

Organics
-glass bottles (rinsed with organic solvent to remove oil at the lab)

Question 5

What are the preservation techniques for diffusion

Answer 5

• proper container
• minimize headspace
• Glass bottles lined with Teflon-lined caps and liners are best choice because of their inertness
• analytes can easily diffuse from liquid to gas

Question 6

Precipitation preservation techniques

Answer 6

• add acid
• must be added immediately after sampling
• nitric acid (keeps the hydroxides that precipitate from forming)

Question 7

Preservation techniques for biodegradation

Answer 7

• reduced temp
• extreme pH
• these kill organisms that degrade samples

Question 8

How do you maintain sample integrity

Answer 8

-type of sample container:
-> glass for organics
•pre-cleaned with Teflon-lined caps
•amber glass (for photosensitive analytes)
-> plastic for organics
-pH of sample
-protection from light
-absence of headspace
-chemical addition
-temp control

Question 9

What does holding time mean

Answer 9

How long a sample can be stored after collection and preservation(but prior to prep and analysis) without significantly altering analytical results

Question 10

How to preserve water for chemical/physical analysis

Answer 10

—clean polyethylene bottle

-refrigerator or cooler at 4c