1. ANALYTICAL CHEMISTRY
deals with methods for determining the chemical composition of samples.
Dr Seemal Jelani ENVR-303
6/16/2018

2. Qualitative Analysis (identification) provides information about the identity of species or functional groups in the sample (an analyte can be identified).
Quantitative Analysis provides numerical information of analyte (quantitate the exact amount or concentration).
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6/16/2018

3. Analytical Methods Classical Methods:
Wet chemical methods such as precipitation, extraction, distillation, boiling or melting points, gravimetric and titrimetric measurements.
Instrumental Methods
Analytical measurements (conductivity, electrode potential, light absorption or emission, mass-to-charge ratio, fluorescence etc.) are made using instrumentation.
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4. Types of Instrumental Methods
1. Spectroscopic methods:
Atomic spectroscopy
Molecular spectroscopy
2. Chromatographic methods (separations):
3. Electrochemistry:
Dr Seemal Jelani ENVR-303
6/16/2018

5. Block diagram of an instrumental measurement
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6. Applications of Instrumental Methods
Bioanalytical: biological molecules and/or biological matrices (e.g., proteins, amino acids, blood, urine)
Environmental: pesticides, pollution, air, water, soil
Material science: polymers, characterization of new materials
Forensic science (application of science to the law): body fluids, DNA, gun shot residue, hair, fibers, elemental analysis, drugs, alcohols, poisoning, fingerprints, etc.
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7. Analytical Methodology
Plan: Qualitative or quantitative or both; what kind of information have; which technique is suitable etc.
Sampling: Accuracy depends on proper sampling, characteristic of sample is very important, required good representative sample (from top, middle and bottom and mix up and take average sample).
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8. 5 Analytical measurement:
4 Sample preparation: depends on analytical techniques.
5 Analytical measurement:
6 Data Analysis: Whether the data make sense or not.
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9. Selecting an Analytical Method
In order to select an analytical method intelligently, it is essential to define clearly the nature of the analytical problem
In general, the following points should be considered when choosing an instrument for any measurement.
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10. Accuracy and precision required Available sample amount
Concentration range of the analyte
Interference in sample
Physical and chemical properties of the sample surrounding substance
Number of sample to be analyzed
Speed, ease, skill and cost of analysis
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11. Aims Logic Design Collection
Analysis of data to solve environmental management issues
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12. Figures of Merit Precision Bias Sensitivity Detection limit
Concentration range (Dynamic range)
Selectivity
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13. Precision
How close the same measurements are to one another
The degree of mutual agreement among data that have been obtained in the same way
Precision provides a measure of the random or undetermined error of an analysis.
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14. Accuracy How close the measurement approaches the real value
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15. Bias
Bias provides a measure of the systematic, or determinate error of an analytical method.
bias =  - xt, where,  is the population mean and xt is the true value
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17. Absolute standard deviation
In statistics the absolute deviation is a measure of how much a particular sample deviates from the average sample.
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18. Relative standard deviation
In probability theory and statistics, the relative standard deviation (RSD or %RSD) is the absolute value of the coefficient of variation
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19. Sensitivity
Sensitivity of an instrument is a measure of its ability to distinguish between small differences in analyte concentration
The change in signal per unit change in analyte concentration
The slope of the calibration curve at the concentration of interest is known as calibration sensitivity.
S = mc + Sbl
S = measured signal; c= analyte concentration;
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20. Sbl = blank signal; m = sensitivity (Slope of line)
Analytical sensitivity ()
 = m/ss
m = slope of the calibration curve
ss = standard deviation of the measurement
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21. Detection Limit (Limit of detection, LOD)
The minimum concentration of analyte that can be detected with a specific method at a known confidence level.
LOD is determined by S/N, where, S/N = Signal-to-noise ratio = (magnitude of the signal)/(magnitude of the noise)
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22. Noise
Unwanted baseline fluctuations in the absence of analyte signal (standard deviation of the background)
The detection limit is given by,
Cm = (Sm – Sbl)/m, where,
Cm = minimum concentration i.e., LOD,
Sm = minimum distinguishable analytical signal (i.e., S/N = 2 or S/N = 3),
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23. m = sensitivity (i.e., slope of calibration curve)
Sbl = mean blank signal
m = sensitivity (i.e., slope of calibration curve)
The amount of analyte necessary to yield a net signal equal to 2 or 3x the standard deviation of the background.
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24. Dynamic Range
The lowest concentration at which quantitative measurements can be made (limit of quantitation, or LOQ) to the concentration at which the calibration curve departs from linearity (limit of linearity, or LOL).
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25. Selectivity
Selectivity of an analytical method refers to the degree to which the method is free from interference by other species contained in the sample matrix
No analytical method is totally free from interference from other species, and steps need to be taken to minimize the effects of these interferences.
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6/16/2018

26. Selectivity coefficient gives the relative response of the method to interfering species as compared with analyte
Selectivity coefficient can range from zero (no interference) to values greater than unity.
A coefficient is negative when the interference caused a reduction in the intensity of the output signal of the analyte.
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27. Spectroscopic methods
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28. Spectroscopic methods
Spectroscopy measures the interaction of the molecules with Electromagnetic radiation
Spectroscopy consists of many different applications such as
Atomic absorption spectroscopy,
Atomic emission spectroscopy
Ultraviolet visible spectroscopy
X-Ray fluorescence spectroscopy
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29. Infrared spectroscopy Nuclear magnetic resonance spectroscopy
Photoemission spectroscopy
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30. Extremely expensive and complex as compared to optical spectroscopy
In type of spectroscopy , the main division is between optical and mass spectrometry
Mass spectrometry generally gives significantly better analytical performance, but is also significantly more complex.
Extremely expensive and complex as compared to optical spectroscopy
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6/16/2018

31. Atomic absorption spectrometers are one of the most commonly sold and used analytical devices.
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32. Atomic spectroscopy
Determination of elemental composition by its Electromagnetic or Mass spectrum
It is related to other forms of spectroscopy
Can be divided by:
Atomization source
Type of spectroscopy used
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33. Optical spectroscopy Electrons exist in energy levels within an atom
These levels have well defined energies and electrons moving between them must absorb or emit an energy equal to the difference between them
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34. In optical spectroscopy, the energy absorbed to move an electron to a more energetic level and/or the energy emitted as the electron moves to a lower energy level is in the form of a Photon (a particle of light).
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6/16/2018

35. The wavelength of light can be related to its energy.
Because this energy is well- defined, an atom's identity can be found by the energy of this transition
The wavelength of light can be related to its energy.
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6/16/2018

36. It is usually easier to measure the wavelength of light than to directly measure its energy.
Optical spectroscopy can be further divided into absorption, emission, and fluorescence
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6/16/2018