Analysing water for organic compounds Flashcards
How can organic compounds enter the water?
Soluble organic compounds can dissolve directly in the water. Insoluble organic compounds may adhere to soil particles, which are then swept away by rain.
Why are some herbicides designed to be water soluble?
Enable their uptake through the leaves or roots of plants. If rain is expected within 24 hours; rain would wash the herbicide away before it had penetrated the plant.
How could you distinguish which substance had the lowest concentration from a chromatogram?
The substance that had the lowest peak.
How to distinguish which substance is most attracted to the mobile phase?
The component most strongly attracted to the mobile phase will be first to exit the column.
How to distinguish which substance is most attracted to the stationary phase?
The component most strongly attracted to the stationary phase will be last to exit the column.
What is a chemical contaminant?
Presence of unwanted substances that make air, water, soil, or food unfit for consumption or use.
What are some sources of chemical contaminants?
Dioxins, insecticides, pesticides, oil spills faulty pipes.
What are three pieces of information that can be observed from a chromatogram?
- how much compound is present - by the height of the peak (higher = more).
- the number of compounds in the mixture - by the number of peaks.
- the retention time: indicated by the position of the peak.
How to distinguish which compound is most attracted to the stationary phase?
The compound will have the highest retention rate (takes the longest to leave the column) so it will be the peak last peak on the graph.
How to distinguish which compound is most attracted to the mobile phase?
The compound will have the lowest retention rate (quickest to leave the column) so it will be the first peak on the graph.
Which of the following changes is least likely to change the retention time?
- replacing solvent with another
- increasing temp of column
- decreasing rate of flow of mobile phase
- diluting the sample being analysed
- diluting the sample being analysed.
This will not affect the retention time as the substance will still have the same attraction to the mobile/ stationary phase.
In chromatography, particles adsorb…?
Particles adsorb onto the stationary phase and desorb into the mobile phase.
