1. Nature of Samples Flashcards
1. List of the main environmental components and their inter-dependency 2. Physical & chemical composition of matrices 3. Types of interference presented in samples 4.Relate the concept of a representative sample to sample matrices 5. measure physical and chemical properties of soil and water samples
what are three cycles come together to form a sample matrix
Air cycle
Water cycle
Soil cycles
the general interaction of gasses and living being in the Air cycles
CO2 - Plants - O2 - Human - CO2 - Plants - etc
how the water cycles work?
as a purifier, sun heats and vaporizes surface water. water vapor condenses to form clouds and precipitate to earth
soil formations depends on which factors
parent materials
climate
topography
organisms present
What are five soil horizons?
- Litter box
- A - Highly weather, abundance of mineral, OM, Decaying vegetation
- B - Partially weather material from A, clays, OM, Fe, Al
- C - Partially weather bedrock
- D - unmodified bedrock
Factors that affect water sample
- Depth, flow
- proximity to source
- recharge rate
- soil composition
- topography
- Natural of contaminant
Factors that affect soil sample
Depth, proximity to source topography, nature of contaminant
3 categories that Air samples can be divided into
- Volatiles -> 0.1 kpa
- Semi-volatiles 0.1 - 10^-8 kpa
- Nonvolatiles <10^-8 kpa
What is an interference
a chemical or physical property of a sample that causes errors in the measurement process
Sources of interferences
- sample collection
- sample transport and storage
- sample preservation
- sample analysis - equipment errors
Types of interferences
- Addictive interference
- Subtractive interference
- Multiplicative interference
- Additive interference
caused by sample constituents that generate a signal that add to the analyte signal, change the intercept not slope.
- Subtractive interference
an interference reacts with chemical reagents to prevent them from reacting with the analyte -> lower test results
- Multiplicative interference
caused by sample constituents that either increase or decrease the analyte signal without generating a signal of their own –> change the slope not intercept
the differences btw False positive and False negative
False positive: shows A high/higher [ ] of analyte than actually present in the sample is reported
False negative: shows a lower [ ] of analyte
