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Major topics in course are: Atomic Absorption, Atomic Fluorescence Spectrometry, Atomic Emission Spectrometry, Chromatographic Separations, Components of Optical Instruments, Electroanalytical Chemistry, Gas Chromatography, High-Performance Liquid Chromatography and Infrared Spectrometry. Key points of this lecture are: Introduction, Analytical Chemistry, Qualitative Analysis, Quantitative Analysis, Analytical Methods, Types of Instrumental Methods, Atomic Spectroscopy, Molecular Spectroscopy,
Typology: Slides
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Block diagram of an instrumental measurement
Block diagram of a fluorometer
Analytical Methodology
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.
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 indeterminate error of an analysis.
Accuracy: How close the measurement approaches the real value.
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
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)
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), Sbl = mean blank signal m = sensitivity (i.e., slope of calibration curve)
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).
The lower limit of quantitative measurements is generally taken to be equal to ten times the standard deviation of repetitive measurements on a blank or 10 Sbl. Dynamic range is the range over which detector still responds to changing concentration (at high concentrations
Calibration of Instrumental Methods
All types of analytical methods require calibration
Standard Addition Methods
Better method to use when matrix effects can be substantial
Standards are added directly to aliquots of the sample, therefore matrix components are the same.
Procedure:
