INSTRUMENTAL ANALYSISVT 2013 C HKD 2013 CLASSICAL ANALYTICAL METHODS Wet-chemical methods Separation of component of interest analyte from the sample by precipitation, extraction, or
Trang 1INSTRUMENTAL ANALYSIS
VT 2013
(C) HKD 2013
CLASSICAL ANALYTICAL METHODS
Wet-chemical methods
Separation of component of interest (analyte) from the sample by
precipitation, extraction, or distillation.
Followed by gravimetric or titrimetric measurement for quantitative analysis
Trang 2INSTRUMENTAL ANALYSIS
(C) HKD 2013
INSTRUMENTAL ANALYSIS
Instrument converts information stored in the physical or chemical characteristics of the analyte into useful information
Require a source of energy to stimulate measurable response from analyte
Data domains
9 Methods of encoding information electrically
Trang 3INSTRUMENTAL ANALYSIS
Detector
9 Device that indicates a change in one variable in its environment (eg., pressure, temp, particles)
9 Can be mechanical, electrical, or chemical
Sensor
9 Analytical device capable of monitoring specific chemical species continuously and reversibly
Transducer
9 Devices that convert information in nonelectrical domains to electrical domains and the converse
(C) HKD 2013
METHOD SELECTION
Whataccuracyis required
How much sample is available
What is theconcentration rangeof the analyte
What components of the sample will causeinterference.
What are the physical and chemical properties of thesample matrix
How many samples are to be analyzed
Trang 4ACCURACY vs PRECISION
Accuracy
9 Describes the correctness of an experimental result
9 Absolute error
9 Relative error
Precision
9 Describes the reproducibility of results
9 Standard deviation
9 Variance
9 Coefficient of variation
9 Relative standard deviation
(C) HKD 2013
ACCURACY vs PRECISION
Trang 5 Sensitivity of aninstrument or method is its ability to discriminate between small differences in analyte concentration
S = mc + Sbl
S = measured signal; c= analyte concentration;
Sbl= blank signal; m = sensitivity (Slope of line)
Analytical sensitivity (J)
J = m/ss
m = slope of the calibration curve
ss= standard deviation of the measurement
2 factors limit sensitivity
9 Slope of calibration curve
9 Precision of measuring device
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CALIBRATION CURVE
Trang 6CALIBRATION CURVE
Least-square regression line
Y = b 0 + b 1 X
(C) HKD 2013
CALIBRATION CURVE
External Standard Method
Trang 7CALIBRATION CURVE
Internal Standard Method
(C) HKD 2013
CALIBRATION CURVE
Standard Addition Method
Trang 8DETECTION LIMIT
Detection limit: the minimum concentration or mass of analyte that can be detected 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
(C) HKD 2013
LINEARITY
Linear range: extends from the lowest concentration at which quantitative measurements can be made (LOQ), to the concentration at which the calibration curve departs from linearity (LOL)
Trang 9INSTRUMENTAL METHODS
Chromatographic methods
9 Gas chromatography
9 Liquid chromatography
Spectrophotometric methods
9 Absorption: Atomic absorption, Molecular absorption (UV-Vis, IR)
9 Inductively coupled plasma
Spectroscopic methods
9 Mass-spectrometry
9 Nuclear Magnetic Resonance spectrometry
(C) HKD 2013
APPLICATIONS
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
Trang 10 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)
Sample preparation: depends on analytical techniques
Analytical measurement
Data Analysis: Whether the data make sense or not.
(C) HKD 2013