Analytical Methods
Analytical Methods
Detection Levels
Quick Tests
element
Flame color
Titration Setup
pipette
titrationsolution
Colorimetry
warning zone
nitrate zone
Air pollution measurement
Outdoor / indoor air pollution measurement
Outdoor measurement: Emissions – from sources
Imissions - in outdoor air
Emissions + imissions: Mass concentration.
Emissions: Mass flow
What is necessary to know:
volume, flow and gas velocity,
temperature, pressure
Emission measurement:
Emission limit: concentration (mg/m3), ppm, mass flow (kg/h)
Particulate matter measurement:
• Gravimetric analysis
• Radiometric metod
• Photometric metod
Toxic matter estimation:
• Chemical analysis
Common estimation of solid chemical elements:
• Atomic absorption spectrometry
• Neutron Activation Analysis
• Roentgen fluorescent analysis
• Mass Spectrometry
Estimation of gas‘s pollutants:
• Infrared spectrometry – SO2, CO, NO, CO2, HCl, NH3, H2O
• Ultraviolet spectrophotometry – SO2, NO, Cl2, NO2, O3
• Potentiometry – HF, HCl
• Colorimetry – H2S
• Ionisation in flame - CxHy
• Catalytic burning - CxHy
• Chemiluminisce – NO
• Paramagnetic princip – O2
• Photometric method – SO2, NO
Imission measurement:
Imission limits (mass concentration)
AIM stations (net)
Particle aerosol: Radiometry
SO2: UV – fluorescence
NOx: Chemiluminiscence
O3: UV spectrometry
Cx Hy: Gas chromatografy
CO Infrared spectrometry
TX/RX 1
TX/RX 2
Classification of analysators
1) Physical princip
• Density• Sound velocity• Heat conductivity• Viscosity• Diffusion• Absorption of radiation• Light refraction• Magnetic susceptibility• Ionisation• Elektrolytic conductivity
2) Physical – chemical princip
• Temperature measurement through chemical reaction • Current measurement at electrochemical cell • Voltage measurement between two electrode immersed into analysed
fluid
3) Chemical princip• Difference of values before and after a chemical reaction
Obr.3 Time progression of measured value andmeasuring device reading
Obr.5 Absorption/concentration dependence (Lambert-Beer law) c – concentration of absorbing matter, A – absorption of light–
dependance on λ, ε - absorption coefficient of the absorber, l - path length
I = I0 e-εcl
A = (I0-I)/ I0
Obr.6 Modification of absorption. 1 – exponencial dependence(Lambert-Beer law), 2 – if filter is wide, 3 – if solid particles are present
Obr.7 Setup of photometric analysator. 1- source ofradiation, 2-filter, 3-measuring cell, 4-detector, 5-signal
processing
Obr.9 Two beam photometric analysator with commondetector. 3- filter for λ, 7-rotating shutter, 4-measuring cell, 8-
reference cell
Obr.11 Photometric analysator with switching of thewavelength
Obr.12 Absorption for heterochromatic arrangement ofpfotometric analysator. λ1-created by interf. filter If1, dark area –
absorbance of the measured sample, A,B- low concentration of measured sample, C,D-higher concentration
Obr.14 Light dispersion on particles–nephelometry
Obr.15 Light absorption at particles–turbidimetry
Obr.16 Absorption spectra of some gases in UV region
Obr.21 Absorptionspectra of some
gases in infrared region
Obr.23 Infrared analysator Hartmann & Braun URAS21 – source of infrared radiation, 2 – reflector, 3 – rotating shutter, 4 –
measuring cell, 5 – reference cell, 6 – detector, 7 – membrane of pressure sensor, 8 – solid stable electrode, 9 – amplifier
Obr.24 Infrared analysator Brüel a Kjær1 – source of infrared radiation, 2 – detector, 3 – rotating shutter– modulator, 4 – carousel with filters, 5 – infrered transparent window, 6 – měřící kyveta, 7 – pressure sensor – micropfone, 8 – valve, 9 – measuring gas supply, 10 –
filter
Obr.50 Fluorescent analysator SO21 – Hg gas tube, pulsed supplied, 2 –lens, 3 – interferential filter, 4 –
measuring cell, 5 – pfotomultiplier, 6 – amplifier
Obr.54 Chemiluminiscent analysator Horiba1 – light detector, 2 – measuring gas supply, 3 – measuring cell, 4 –
modulation gas valve, 5 – generator of ozone, 6 – clean air supply, 7 –amplifier, 8 – gas output
Obr.56 Magnetic field effect to fifferent matters - paramagneticspenetrate to highest magnetic field. Pole, d- diamagnetics are expeled, f-
paramagnetics stronger penetrate to magnetic field
Obr.57 Magnetical analysator. 1- support for fibre, 2- pole extension, 3-nitrogen filled bulb, 4- mirror, 5- led diode, 6- photo-cell twins
Obr.60 Magnetic analysator. 1-measuring tube, 2-magnetic pole extension, 3,5-heated coils , 4-analysed gas input, 6-circlar chamber, 7-analysed
gas output, 8-second resistor branche of Wheatst. bridge, 10-power supply
ELECTROCHEMICAL ANALYZERS
1) Potentiometry
2) Amperometry: ConductivityPolarographyDepolarisation
Metals in some electrolyte are dissolved into ions. Potential is created. Polarity depends on metal.
atomselectrons
Zn
Negative charge on Zn (ignoble) electrode
electrolyte
Potentials of different electrodes against refence electrodeNernst equation
Obr.65 Princip of pH measurement (potentiometry), 1 – sensingglass electrode, 2 – reference (standard) usually silver chloride electrode or calomelelectrode, 3,4 – inner electrodes, 5 – pH sensitive membrane (Si glass), 6 – solution
of determinate Ph value, 7 –solution of KCl, 8 – diafragma (nonmetalic, iont connection of electrode to analysed electrolyt).
pH is a measure of the acidity or alkalinity of asolution
Fig.66 Amperometry, dependence I=f(U,c)ME – sensing electrode, SE – reference electrode
Obr.64a Electrochemical analyser with solid state electrolyte, thin Pt electrode (potentiometry), p1 – partial pressure (concentration) of oxygen at one electrode, p2 – – partial pressure of oxygen at the other electrode.
ZrO2
Oxyxen penetrates to the negative electrode through a small hole. O2 isionisated because of high temperature room (350 °C) and goes to positive
electrode to leave there their negative charge. Flowing current isproportional to oxygen concentration.
heating hole
ZrO2
Oxygen sensor
Catalytic convertersThe catalytic converter is a device, placed in the exhaust pipe, which converts various emissions into less harmful ones using, generally, a combination of platinum, palladium and rhodium as catalysts. They make for a significant, and easily applied, method for reducing tailpipe emissions.
The lead emissions were highly damaging to human health, and its virtual elimination has been one of the most successful reductions in air pollution.
λ probe catalysator
λ probe Catalytic covertor
cover of catalysator
Principle of engine with catalytic convertorPrinciple of engine with catalytic convertor
Carburatorcontrol
petrolmotor
gaswaste
convertor
λ proberegulator
petrol
Fig. 64d - Fig. 64eAir offer ratio λ – Waste gases behaviour
λ>1 (light mixture):It is necessary to increasepetrol input.
λ<1It is necessary to decreasepetrol input.
V – real air volumeVs – stechiometric required air volume
λ window
Analyser with ionisation by mean of flame1 –thermocouple, 2 – collecting electrode, 3 – flame jet– second electrode, 4 –
ignition electrode, 6 – output of gas, 7 – amplifier, 8 – voltage wiring, 9 – air input, 10 – hydrogene input, 11 – measured gas input
Rarefactive probes1 – oddělovací filtr, 2 – filtr ze skleněné vlny, 3 – skleněná dýza s nadkritickým
průtokem, 4 – ejektor, 6 – přívod kalibračního plynu, 7 – přívod čistého tlakovéhovzduchu, 8 – výstup směsi k analyzátorům
Principle of gas chromatography1 – measured gas input, 2 – carrying gas input – mobile phase, 3 – sampling unit,
4 – chromatographic cell (stationary phase eg. charcoal), 5 – thermostat, 6 –detector, 7 – plotter
Measured gas and carrying gas move at different rates because of relativeattraction to stationary phase. The separation is based on physical principles like
dissolution, adsorption and ions exchange
Succession of the different parts of measured gasmixture through cell
Chromatograph output
Mass Spectrometry1 – source of ionts, 2 – input of measured substance, 3 – electron source (glowing fiber), 4 – positive ionts, 5 – accelerating electrode, 6 –input slot, 7 – magnetic field, 8 –output slot, 9 – heavy ionts10 – light ionts, 11 – measured ionts, 12 –collector, 13 – collector electrode, 14 – current amplifier, 15 – signal processing.
An ionized vapour is passed betweenmagnets which separate the ions by charge to mass ratio. The patternproduced is characteristic of theparticular substance, which can beidentified by comparison withcomputerized „libraries“ of massspectra. For environmental analyses, where several substances occure atonce, mass spectrometry is usuallyused in tandem with anothertechnique – eg. chromatography.
Tab. 27: Meze postřehu pro některé prvky přiatomové absorpční spektrofotometrii
Záznam diferenční pulsní polarografie
Mezepostřehuněkterýchprvků při
neutronovéaktivačníanalýze
Analýza směsi pesticidů plynovým chromatografem
Monitoring oxidantů v ovzduší
Monitoring ozónu