What factors effect unpreserved samples
- volatilization
- adsorption
- diffusion
- precipitation
- chem changes
- biodegradation
What is the purpose of preservation
To minimize effect that chemically change the sample including oxidation and photochemical reactions
What are techniques to minimize volatilization
- minimize headspace
- minimize sample agitation
- low temp
- avoid agitation
- do not vacuum filtration
What are the preservation techniques for adsorption
- 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)
What are the preservation techniques for diffusion
- 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
Precipitation preservation techniques
- add acid
- must be added immediately after sampling
- nitric acid (keeps the hydroxides that precipitate from forming)
Preservation techniques for biodegradation
- reduced temp
- extreme pH
- these kill organisms that degrade samples
How do you maintain sample integrity
-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
What does holding time mean
How long a sample can be stored after collection and preservation(but prior to prep and analysis) without significantly altering analytical results
How to preserve water for chemical/physical analysis
—clean polyethylene bottle
-refrigerator or cooler at 4c
