Environmental Chemistry – Kolev

What are the main sources of anthropogenic contaminants?
Agriculture, industry and households
Natural Contaminant sources
Animals, Plants, Minerals
By-products of imcomplete burning in boilers
Fly ash, bottom ash, boiler slag
Five main conditions for formation of photochemical smog
Heavy traffic, sunlight, high temp, ozone, quiet weather
Natural sources of aerosols
Deserts, oceans, forests, fires, volcanoes
What is an interferent?
Chemical species which affects the outcome of a measurement.
How do you eliminate interferences?
Separating analyte from sample matrix. Part of sample pretreatment step.
Seven steps of quantitative analysis
Method selection, Sampling, Solution Preparation, sample pretreatment, analytical measurement, calculating result, statistical evaluation
When is a sample representative of the bulk of a material?
If its composition is identical to the average composition of the bulk material
Steps in sampling?
Collection of a gross sampleReduction of gross sample to homogeneous laboratory sample
Three methods for calculating the analytical result
Calibration curve method, internal standards method, standard addition method
What is the calibration equation?
C = (Z-a)/b
Describe the standard addition method.
Known amounts of analyte are added to the sample with unknown analyte conc.

The analytical signal is measured before starting the additions, and after each addition.

Equation for multipoint standard addition of varying volumes
C = a/b
When should varying volume multipoint addition be used?
When there could be changes to the sample matrix
Equation for determining concentrating using multipoint constant volume
C = -[v(flask)*C/V(x)]
When is the internal standards method used?
Instrument response varies slightly in time; Sample loss can occur during pretreatment
Equation for the internal standards method
C = [(1/F)*(C(internal)/Z(internal)] * Z(analyte)
What are the three main types of experimental error?
Systematic, random, gross
How do you correct instrumental errors?
What is a gross error, and how do we determine a gross error?
Large outlier. Identified using statistical evaluation.
Can we identify and quantify the source of random error?
No, as the error introduced is usually very small.
How do we characterize precision and accuracy?
Precision – variance, standard deviation, RSDAccuracy – Absolute or relative error
What are the two main types of columns used in chromatography?
Packed columns and open tubular columns
Three types of GC detectors
Flame-ionisation (hydrocarbons), Thermal conductivity, Electron capture detector (halogens)
Diagram of GC
Gas tank – Pressure regulator – Sample port – Oven – Detector
What are the requirements of the partition coefficient such that there is separation and preconcentration of the analyte?
K >> 1 ; [Sample] >> [Extractant]
What is column resolution?
Quantitative measure of its ability to separate 2 analytes. R = 2[(tb – ta)/(Wa + Wb)]
Define “titration error”
The difference between the titrant volume to equivalence, and the actual titrant volume used.Error = V(equiv.

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Diagram of AAS
Light source – Premix Burner (Sample, fuel, air) – Monochromator – Detector
What are releasing agents and protective agents?
Releasing agents react preferentially. Protective agents form stable, non-volatile compound with the analyte.
Why is the analysis of phosphoric compounds important?
Orthophosphate supports eutrophication, which leads to anoxic conditions.
What are the main sources of ammonium salts as water comtaminants?
Decomposition of proteins, Atmospheric nitrogen, agriculture, cleaning products
What are the main sources of anions as water comtaminants?
Erosion, sedimentary release, agriculture, soaps, sewage treatment
What are the main organic derivatives as water comtaminants?
Organic decay, algae, oils, pesticides, detergents
List aerosol control devices in order of increasing particulate size.
Electrostatic precipitators, Fabric filter separator, Scrubber, Cyclone, Settling chamber
What are the effects of water hardness?
Interfering with cleaning tasks, Formation of mineral deposits in pipes, Flocculation of colloidal particles in soil.
What are the parameters of water hardness?
< 60 mg/L - soft >270 mg/L – hard
Formula for the student t-test
mean – true > ts/sqrt(n) : no difference
Formula for f-test
F =variance 1/variance 2 : compared with critical f value