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Lectures: Tuesday, Thursday 9:00-9:50 am Room 136 Teach fundamentals of instrumental analysis (3) instrument design and nature of response (4) signal processing and relationship between readoutto property measured Laboratory: Provides hands-on experience in (1) relating lecture material to practical analysis (2) design and operation of a real instrument (4) example analyses to illustrate value of technique Qualitative instrumental analysis is that measured property
indicates presence of analyte in matrix Quantitative instrumental analysis is that magnitude of measured
property is proportional to concentration of analyte in matrix Often need pretreatment - chemical extraction, distillation,separation, precipitation Qualitative - identification by color, indicators, boiling points,odors Quantitative - mass or volume (e.g. gravimetric, volumetric) Qualitative - chromatography, electrophoresis and identificationby measuring physical property (e.g. spectroscopy, electrodepotential) Quantitative - measuring property and determining relationshipto concentration (e.g. spectrophotometry, mass spectrometry) Often, same instrumental method used for qualitative andquantitative analysis Property
Example Method
Emission spectroscopy - fluorescence,phosphorescence, luminescence Absorption spectroscopy -spectrophotometry, photometry, nuclearmagnetic resonance, electron spinresonance (Often combined with chromatographic or electrophoretic methods) Instrument: spectrophotometerStimulus: monochromatic light energyAnalytical response: light absorptionTransducer: photocellData: electrical currentData processor: current meterReadout: meter scale Data Domains: way of encoding analytical response in electrical ornon-electrical signals.
Interdomain conversions transform information from one domain toanother.
Detector (general): device that indicates change in environment Transducer (specific): device that converts non-electrical toelectrical data Sensor (specific): device that converts chemical to electrical data Time - vary with time (frequency, phase, pulse width) Analog - continuously variable magnitude (current, voltage, charge) Digital - discrete values (count, serial, parallel, number*) Advantages (1) easy to store (2) not susceptible to noise Performance Characteristics: Figures of Merit How to choose an analytical method? How good is measurement? How small a difference can be measured? - Sensitivity Precision - Indeterminate or random errors
Accuracy - Determinate errors (operator, method, instrumental)
Sensitivity
(larger slope of calibration curve m, more sensitive measurement) Detection Limit
Signal must be bigger than random noise of blank From statistics k=3 or more (at 95% confidence level) Dynamic Range
At detection limit we can say confidently analyte is present butcannot perform reliable quantitation Limit of linearity (LOL): when signal is no longer proportional toconcentration Selectivity:
No analytical method is completely free from interference byconcomitants. Best method is more sensitive to analyte thaninterfering species (interferent).
k's vary between 0 (no selectivity) and large number (veryselective).
Basis of quantitative analysis is magnitude of measured property is proportional to concentration of analyte Signal ∝ [x] or Signal = m[x]+ Signal blank Calibration curves (working or analytical curves) (−2.02 × −0.188) + (−1.12 × −0.088) + (−0.02 × 0.002)+.
Absorbance=0.0883[Analyte (ppm)]+0.0596

Source: http://icole.mut-es.ac.ir/downloads/Sci_Sec/W04/01-Introduction%20to%20instrumental%20analysis.pdf