Chemicalanalysisin the biorefinery–inorganics 4.5.2010, 8...
Transcript of Chemicalanalysisin the biorefinery–inorganics 4.5.2010, 8...
416509.0 The Forest based Biorefinery: Chemical and
Engineering Challenges and Opportunities (5 cr)
3-7.5.2010
Chemical analysis in the biorefinery – inorganics
4.5.2010, 8:30–10:45
Johan Bobacka
Laboratory of Analytical ChemistryBiskopsgatan 8, FI-20500 Åbo-Turku
Finland
e-mail: [email protected]
Objective• Instrumental methods that are widely used for analysis of
inorganic components will be presented and discussed
• The main focus will be on basic principles and uniquefeatures of the following methods:
– Atomic absorption spectroscopy (AAS)
– Atomic emission spectroscopy (AES, ICP-OES)
– Inductively couple plasma-mass spectrometry (ICP-MS)
– Ion chromatography (IC)
– Ion-selective electrodes (ISEs)
Reference: D.C. Harris, Quantitative Chemical Analysis, 7th edition, Freeman, USA, 2007.
The Analytical Process
• Formulating the question → Selecting analytical procedures →Sampling → Sample preparation → Analysis → Reporting and interpretation → Drawing conclusions
• Classical methods (gravimetry, titrimetry)– Accurate
• Instrumental methods (electrochemistry, spectroscopy, chromatography, …)– Fast
– Sensitive
Spectroscopy
• Spectrophotometry is any technique that uses light to measurechemical concentrations
• Light waves consist of perpendicular, oscillating electric and magnetic fields (electromagnetic radiation)
• Plane-polarized electromagnetic radiation of wavelength λ:
• Ordinary, unpolarized light has electric field components in all planes
Spectroscopy
• Electromagnetic radiation can be described in terms of bothwaves and particles
• Each wave has a certain wavelength, λ, and frequency, ν
νλ = c = speed of light (2.998×108 m/s in vacuum)
• Each particle (photon) carries a certain energy, E
E = hν (h = Planck’s constant = 6.626×108-34 Js)
Electromagnetic spectrum
High frequencymeans
High energy !
Low frequencymeans
Low energy !
What happens when a molecule absorbs light?
• Absorption of light increases the energy of a molecule
• Emission of light decreases the energy of a molecule
Excited singlet and triplet electronic states
• When a molecule absorbs a photon, the molecule is promoted to a more energetic excited state
• Excited state in which the spins are opposed is called a singlet state. If the spins are parallel we have a triplet state.
• In general vibrational and rotational transitions occur as well
Absorption of light
A substance/molecule absorbs light of the same
energy, which is required to excite the molecule to a
higher energy level
A substance absorbs light of CERTAIN SPECIFIC
WAVELENGTHS. The other wavelengths are not
absorbed !
Spectrophotometric analysis
• The absorbance of light is measured when a specificwavelength of light passes through the sample
• Monochromatic light = light with a specificwavelength
Irradiance, P
• P0 The irradiance of incoming light
• P The irradiance of outgoing light
• Irradiance, P, is the energy per second per unitarea of the light beam [W/m2]
• Irradiance, P, is also called intensity, I
P ≤ P0
Transmittance, T
• Transmittance is the fraction of the original light that passes through the sample
• T has the range 0 to 1
• Percent transmittance is 100×T and rangesbetween 0 and 100 %
0 0
= =P I
TP I
DIMENSIONLESS
Absorbance, A
0 0log log logP I
A TP I
= = = −
DIMENSIONLESS
I/I0 T A
1 1 (100%) 0
0.1 0.1 (10%) 1
0.01 0.01 (1%) 2
Beer-Lambert law
• Absorbance is directly proportional to concentration
– ε molar absorptivity [M-1cm-1]
– b length of the light path through sample [cm]
– C concentration [mol/l]
DIMENSIONLESSA b Cε= ⋅ ⋅
Molar absorptivity, ε
• Depends on wavelength, λ
b, C constantλ λ( )A f ε=
Example: The UV-vis spectrum of the (ferrozine)3Fe(II) complex as a functionof wavelength, λ (b and C are constant)
Atomic spectroscopy
• In atomic spectroscopy, samples are vaporized and decomposed into atoms in a flame, furnace, or plasma at very high temperature (2000–8000 K).
• Elements in the vaporized sample absorb or emit lightat certain specific wavelengts
• Absorbed or emitted light is used to determine the concentration of the elements in the sample.
An important difference betweenatomic and molecular spectroscopy
• Absorption and emission bands of gaseous atomsare very narrow (~0.001 nm) in comparison to solidand liquid samples (~100 nm).
• Usually little overlap between spectra of differentelements in the sample
• Some instruments can measure more than 70 elements simultaneously
Atomic spectroscopy
• Principal tool of analytical chemistry
• High sensitivity
• Complex samples can be analysed
• Low concentrations can be measured– from ppm (µg/g) to ppt (pg/g) levels
• Multielement analysis possible
• Automated methods of analysis
Atomic spectroscopy
• Atomic spectroscopy divided into:
– Atomic absorption spectroscopy (AAS)
– Atomic emission spectroscopy (AES)
– Atomic fluorescence spectroscopy (AFS)
Atomic spectroscopy
Atomic absorption spectroscopy (AAS)
2000–3000 KLight path
Emits light of the λ that is absorbed by the analyte
0
log logP
A TP
= − = −
Atomic emission spectroscopy
Atomic emission spectroscopy (AES)
• Collisions in the very hot plasma promote someatoms to excited electronic states from which theycan emit photons to return to lower energy states. Emission intensity is proportional to concentration.
• No lamp is needed
• Today AES is the dominant form of atomicspectroscopy
Atomization of the sample
• Decomposes the sample into atoms, whichcan be analyzed with different techniques
• Different methods of atomization:– Flame
– Electrically heated furnace
– Plasma
Flame atomization
• Premix burner
– Fuel, oxidant and
sample are mixed beforegoing into the flame
– The sample is transportedto the nebulizer through a thin capillary
Flame atomization
• Nebulizer– Creates an aerosol
from the liquidsample
Flame atomization
• Glass bead– Splits the aerosol to even
smaller particles
• Baffles– Mix the aerosol
– Drops of the same sizepasses to the flame (largerdrops are trapped by the baffles)
– ∼5% of the aerosol reachesthe flame
Flame atomization
• Drop size distribution– The drop size distribution should be even in order to
obtain a stable signal with small relative standarddeviation
Flame atomization
• Combinations of fuel and oxidant– A mixture of acetylene and air is commonly used
Flame atomization
• The flame– Aerosol (sample) entering the preheating region is
heated in the primary reaction cone (blue cone)
– Combustion is completed in the outer cone
Furnaces
• An electrically heatedgraphite furnace– More sensitive than a
flame (the atomizedsample stays longer in the optical path in the furnace)
– Requires less sample(1 – 100 µl)
– Maximum recommendedtemperature: 2550 oC
Electrically heated graphite furnace
• L´vov platform– Gives more uniform
heating of the sample
– Solid samples can be analysed withoutsample preparation
Inductively coupled plasma (ICP)
• The temperature is twice as hot as a combustionflame
Inductively coupled plasma (ICP)
• T = 6000–10000 K
• Plasma: partially ionized electrically conductinggas (the fourth aggregation state)
• The high temperature, stability and relatively inertAr environment in the plasma eliminate much of the interference encountered with flames.
Inductively coupled plasma (ICP)
• Two induction coils (27 MHz or 41 MHz) around the quarz tube
• High-purity Ar is used as plasma gas
• A spark generated by the Tesla coilresults in ionization of the argon gas
• Free electrons are accelerated by the radio-frequency field and collidewith atoms:
⇒ transfers energy to the Ar gas⇒ keeps the temp. at 6000-10000 K
• Argon coolant gas protects the torchfrom overheating.
The Boltzmann distribution
• The degree of atomization of the sample is determined bythe temperature and shows how much of the sample is in the ground and excited state.
N*: number of atoms in the excited stateN0: number of atoms in the ground stateg*: number of excited statesg0: number of ground statesT: temperature (K)k: Boltzmann’s constant (1.381×10-23 J/K)
*/ k
0
*TEg
eN
N g
−∆= ⋅0
Inductively coupled plasma opticalemission spectroscopy (ICP-OES)
• Also called: inductively coupled plasma atomicemission spectroscopy (ICP-AES)
• ICP-OES allows multielement analysis and giveslower detection limits than flame-AAS.
• Sensitivity is improved further by detecting ions witha mass spectrometer (ICP-MS)
Inductively coupled plasma–massspectrometry (ICP-MS)
• Solid samples can be analysed by using laser ablation (LA-ICP-MS)
Detection limits of atomic spectroscopy(ng/g = ppb ”parts per billion”)
Chromatography
• Chromatography follows the same principle as extraction, but one phase is held in place (stationary phase) and the other phase moves (mobile phase) past it.
• If solute A has agreater affinity than solute B to the stationary phase, then A moves more slowly:
Two types of columns:- Packed
- Open tubular
Adsorption chromatography- separates molecules by adsorption on a solid phase
• Stationary phase
– Solid
• Mobile phase
– Liquid or gas
Partition chromatography- separates molecules by partitioning into a liquid phase
• Stationary phase
– Liquid bonded to a solid surface(SiO2)
• Mobile phase
– Gas
Ion-exchange chromatography- separates ions by electrostatic interactions
• Stationary phase
– Anions such as –SO3-
or cations, such as –N(CH3)3
+ are covalently attachedto a solid phase(resin)
• Mobile phase
– Liquid
Molecular exclusion chromatography-separates molecules by size
• Also called: gel filtration or gel permeation chromatography
• Stationary phase
– Porous gel
• Mobile phase
– Liquid or gas
Affinity chromatography- separates molecules by selective molecular interactions
• Stationary phase
– Selective moleculesare covalentlyattached(immobilized) to the stationary phase
• Mobile phase
– Liquid
The chromatogram
• Retention time: tr
• Adjusted retention time: tr´ = tr – tm
– where tm is the minimum retention time (unretained mobile phase)
• Relative retention (for components 1 and 2): α = tr´2 / tr´1
– where tr´2 > tr´1 (α >1)
The chromatogram• For each peak in the chromatogram the capacity factor, k´,
is defined as:k´ = (tr – tm)/tm = tr´ / tm
– The longer a component is retained by the column, the greater is the capacity factor
• The capacitay factor is related to the partition coefficient, K, (known from solvent extraction), where Vs is the volumeof the stationary phase and Vm is the volume of the mobile phase:
k´ = K×(Vs/Vm)
• Relative retention (for components 1 and 2) can also be expressed as:
α = tr´2 / tr´1 = k´2 / k´1 = K 2 / K 1
Efficiency of separation
• Two factors contribute to how well twocomponents are separated by chromatography:– Difference in elution times between peaks: ∆tr
– The average width of the two peaks: wav
Efficiency of separation
• Resolution = ∆tr / wav
Column efficiency
• Plate height: H = σ2 / x– where σ is the standard deviation of the Gaussian band
and x is the distance travelled
• Plate height, H, is the constant of proportionalitybetween the variance, σ2, of the band and the distance it has travelled, x.
• The smaller the plate height, the narrower the bandwidth.
High-Performance Liquid Chromatography(HPLC)
• HPLC uses high pressure to force solvent through closedcolumns containing very fine particles that give high-resolution separations.
High-Performance Liquid Chromatography(HPLC)
• The column– Length: 5–30 cm
– Inner diameter: 1–5 mm
• The guard column– Replaceable
– Collects irreversiblyadsorbed impurities
High-Performance Liquid Chromatography(HPLC)
• The stationary phase
High-Performance Liquid Chromatography(HPLC)
• The stationary phase– Commonly microporous particles of silica
High-Performance Liquid Chromatography(HPLC)
• The stationary phase– Commonly: R = octadecyl (C18)
– ODS = octadecylsilane
High-Performance Liquid Chromatography(HPLC)
• In adsorption chromatography, solvent moleculescompete with solute molecules for sites on the stationary phase
• The eluent strength, εo, is a measure of the solventadsorption energy– εo for pentane is defined as 0 for adsorption on bare
silica
High-Performance Liquid Chromatography(HPLC)
High-Performance Liquid Chromatography(HPLC)
• Normal-phase chromatography– Polar stationary phase
– More polar solvent has higher eluent strength
• Reversed-phase chromatography– Nonpolar stationary phase
– Less polar solvent has higher eluent strength
High-Performance Liquid Chromatography(HPLC)
• Isocratic elution– Elution is performed with a single solvent (or constant
solvent mixture)
• Gradient elution– Increasing amounts of solvent B are added to solvent A
to create a continuous gradient
– Used to obtain sufficiently rapid elution of allcomponents
Injection and detection in HPLC
• Injection valve
Injection and detection in HPLC
• Detector– Sensitive to low concentrations of every analyte
– Provides linear response
– Does not broaden the eluted peaks
– Insensitive to changes in temperature and solvent composition
Ion Chromatography (IC)
• Ion chromatography (IC) is a high-performanceversion of ion-exchange chromatography that is used for separation and determination of ions
• Ion chromatography (IC) has many commonfeatures with HPLC
Ion Chromatography (IC)
• Suppressed-ion anion chromatography– A mixture of anions is separated by ion-exchange and
detected by electrical conductivity
• Suppressed-ion cation chromatography– A mixture of cations is separated by ion-exchange and
detected by electrical conductivity
• Suppression = removal of unwanted electrolyteprior to conductivity measurement
Suppressed-ion anion chromatography
K+ + OH- H2O+H+
- K+
Suppressor:
Suppressed-ion cation chromatography
H+ + Cl- H2O+OH-
- Cl-
Suppressor:
Ion chromatography of pond water
valuesin µg/ml(ppm)
Ion-selective electrodes (ISEs)Potentiometric ion sensors
• ISEs for 60 analytes (Na+, K+, Cl-, Ca2+, H+, ….)
• ISEs respond to ion activity
• Compact, portable, low-cost instruments
• Billions of measurements / year
Reviews:
E. Bakker, P. Bühlmann, E. Pretsch, Chem. Rev. 97 (1997) 3083.
P. Bühlmann, E. Pretsch, E. Bakker, Chem. Rev. 98 (1998) 1593.
J. Bobacka, A. Ivaska, A. Lewenstam, Chem. Rev. 108 (2008) 329.
ISEs are electrochemical sensors
Ion-selective electrodes
O2-sensor (Lambda)
Glucose sensorpH-electrode
- environmental analysis
- clinical analys
• In clinical analysis, ISEs are used all over the world for the
determination of pH, Na+, K+, Li+, Ca2+, Mg2+, Cl- and
CO32- at well-defined concentrations in biological fluids
– Standardized ISEs fulfill a global demand !
• In process analysis, each industry has a different ”wish list”
in terms of species to be monitored and the concentration
range of interest
– ISEs should be developed and tested for each case !
Two different applications of ISEs
E. Bakker, D. Diamond, A. Lewenstam, E. Pretsch, Anal. Chim. Acta, 393 (1999) 11.
mV
K - selective electrode Reference electrode
Sample solution
Ion-selective membrane
Ag/AgCl Ag/AgCl
KCl(3 M)
Potentiometry
ION-SELECTIVE ELECTRODE
K +
e- e-
Liquid junction
K +
Cl -
Ag + Cl = AgCl + e- -
Ag + Cl = AgCl + e- -
+
Potentiometric response (cationic)
log a
EWhen ni = +1Slope = +59.16 mV / log ai
When ni = +2Slope = +29.58 mV / log ai
2.303logo
i
i
RTE E a
n F
×= +
detection limit
Potentiometric response (anionic)
log a
E
2.303logo
i
i
RTE E a
n F
×= +
detection limit
When ni = -1Slope = -59.16 mV / log ai
When ni = -2Slope = -29.58 mV / log ai
Selectivity of ion-selective electrodes
• The potential of an ion-selective electrode is determinedprimarily by the activity of the main ion (primary ion = i) but also other ions (interfering ions = j) may contribute to the potential.
• The influence of interfering ions is given by the selectivitycoefficient (Ki,j) included in the Nicolsky-Eisenman-equation:
• This equation has some limitations in those cases when the primary (i) and interfering (j) ions have different charge.
/
,ln( )i jn no
i i j j
ji
RTE E a K a
n F= + +∑
Classification of ion-selective electrodesbased on the type of membrane used
• Glass membranes– for H+ (pH) and certain monovalent cations
• Solid-state membranes based on inorganic saltcrystals
– LaF3, AgCl, AgBr, AgI, Ag2S, CuS, CdS
• Polymeric membranes– hydrophobic polymer membranes containing neutral
or charged carriers (ionophores)
pH-electrodewith glassmembrane
The referenceelectrode is builtinto the same electrode bodyas the indicatorelectrode(combination electrode).
Glass membranes
SiO2 Na2O Li2O CaO Al2O3
72 % 22 % 6 % H+
80 % 10 % 10 % H+
71 % 11 % 18 % Na+
69 % 27 % 4 % NH4+
Cross-section of a pH-sensitive glassmembrane
Calibration curve (pH-electrode)
Solid-state membranes based on inorganic salt crystals
Polymeric membranes
• Plasticized polymer membranes– PVC (33 %)
– Plasticizer (65.5 %)
– Ionophore (1 %)
– Lipophilic ions (0.5 %)
• Plasticizer-free polymer membranes– methacrylic–acrylic copolymers
– covalently bound ionophore / ions
B
CF3
CF3
CF3CF3
CF3
CF3
CF3 CF3
-
Cl
( )n
Poly(vinyl chloride)(PVC)
33 %
Potassium tetrakis[3,5-bis-(trifluoro-methyl)phenyl]-borate (KTFPB)
0.5 %
K +
OO
O O
CH3
CH3
CH3
CH3
Bis(2-ethylhexyl)sebacate(DOS)
65 %
Valinomycin
1 %
H
H
H
H
H
HN OO
NN
O O
N N
O ON
O
OO
O
O
O
OO
O
O
O
O
+K ISE
Typical composition
of a K+-selective
membrane :
Pb2+-selective electrode withvery low detection limit
Applications of ion-selectiveelectrodes range from conventionalpH measurements to automatedanalysis on the planet Mars.
pH of rainwater (year 2001)
pH-sensitive fieldeffect transistor
Solid-contact ISEs and CHEMFETs can be miniaturized
The ”Chem 7” test
Na+, K+, Cl-, total CO2glucose, urea, creatinine
constitutes up to 70 %
of the tests performed
in the hospital lab.
•Mg2+
•NH4
+
•ClO4
-
•NO3
-
•Silver/Sulfide
•Cadmium
•Pb/Cu/Zn/Fe - via ASV
•Cyclic Voltammetry
•ORP (redox potential)
•Temperature
•Conductivity
•pH (3 sensors)
•Li Reference (3 sensors)
•Dissolved O2
•Dissolved CO2
•Cl- (2 sensors)
•Br-
•I-
•Na+
•K+
•Ca2+
2007 Phoenix Mars Scout mission
Copyright © 2004 The Kounaves Research Group, Department of Chemistry,Tufts University, Medford, Massachusetts 02155 USA
Automatic analysis on the planet Mars !
mV
K - selective electrode Reference electrode
Sample solution
Ion-selective membrane
Ag/AgCl Ag/AgCl
KCl(3 M)
Potentiometry
ION-SELECTIVE ELECTRODE
K +
e- e-
Liquid junction
K +
Cl -
Ag + Cl = AgCl + e- -
Ag + Cl = AgCl + e- -
+
Conventional ISE(liquid-contact ISE)
Solid-contact ISEs are more robust
e- e-
Inner reference electrode& inner solution
Conductingpolymer
- First article published in 1992- Innovation Prize in 2001- Commercial products emerging
https://www.abo.fi/student/analytisk_kemi
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S+ .
+
S
S
S
S
S
S
S
S
+
A-
A-
e-
e-
ELECTROACTIVE MATERIAL
(polythiophene)MEMBRANE /
SOLUTION
(ionic conductor)
METAL
or otherelectronicconductor
polaron
bipolaron
Electrochemical oxidation (p-doping)
Electrochemical oxidation (p-doping)
e-
Conjugatedpolymer Electrolyte
Electronicconductor
Oxidized (p-doped) conjugated polymer
Conjugatedpolymer
Electronicconductor
Electrolyte
Potentiometric response of
conducting polymers
[ ][ ]Red
Oxln'
FRTconstE +=
[ ]−−= XconstEF
RT ln''
[ ]++= MconstEF
RT ln'''
SubstrateConductingpolymer Solution
A. Lewenstam, J. Bobacka, A. Ivaska, J. Electroanal. Chem. 368 (1994) 23.
J. Bobacka, Z. Gao, A. Ivaska, A. Lewenstam, J. Electroanal. Chem. 368 (1994) 33.
Solid-contact ISE
SubstrateConductingpolymer Solution
Ion-selectivemembrane
A. Cadogan, Z. Gao, A. Lewenstam, A. Ivaska, D. Diamond, Anal. Chem. 64 (1992) 2496.
Poly(3,4-ethylenedioxythiophene)
(PEDOT)
Stable conducting polymer !
G. Heywang, F. Jonas, Adv. Mater. 1992, 4, 116 .
S
O O
( )n
Solution-casting of
PEDOT and ISM
Gold
Insulating layer
Alumina
Alumina
Gold
Insulating layer PEDOT(PSS)
(Baytron P)
Ion-selective membrane
(a)
(b)
(c)
Screen-printed
substrates
M. Vázquez, P. Danielsson, J. Bobacka,A. Lewenstam, A. Ivaska,Sens. Actuators B, 2004, 97, 182.
Radial
flow cell
M. Vázquez, J. Bobacka, A. Ivaska, A. Lewenstam, Talanta, 2004, 62, 57.
Ion-selective microelectrodes
Electrode substrate
Conducting polymer
Capillary glass
Polyethylene
Mercury
Epoxy glue
Electrode substrate
Conducting polymer
Capillary glass
Polyethylene
Mercury
Epoxy glue
Electrode substrate
Conducting polymer
Capillary glass
Polyethylene
Mercury
Epoxy glue
Mikael Södergård
PSS-K+
K+
e-
Solution
K+H
H
H
H
H
HN OO
NN
O O
N N
O ON
O
OO
O
O
O
OO
O
O
O
O
OO
O O
CH3
CH3
CH3
CH3
Cl
( )n
B Cl
Cl
Cl
Cl
-
e-
e-
K+
K+
e-Ag / AgCl
PlasticizedPVC
Solution
K+H
H
H
H
H
HN OO
NN
O O
N N
O ON
O
OO
O
O
O
OO
O
O
O
O
OO
O O
CH3
CH3
CH3
CH3
Cl
( )n
B Cl
Cl
Cl
Cl
-
e-
Ion
e-
Solution
Ion
e-
e-
PlasticizedPVC
Cl-
Ag + Cl = AgCl + e- -
Inner solution
Pt, Au, C
Cond.polymer
Ag+
Pt, Au, C
Funct.cond.polymer
+n
n)(
S
OO
S
OO
S
O O
S
O O
+
.
Conventional ISE Solid-contact ISE
Functionalized
conducting polymer
”Three generations” of ISEs
Many conducting polymers
have been applied as
ion-to-electron transducers
and/or
sensing membranes
in
solid-state ISEsNH2
N
H
S
CH3
N
H3C CH3
N
CH3
S
O O
S
N
NH2 OH
NH2
NH2
OCH3
OH
O
NH
OH
N N
NH2
HO OH
N
H
N
HNH2
BOH
OH
(1) (2) (3)
(4) (5) (6)
(7) (8) (9) (10)
(11)
(12) (13)
(14) (15)
Review:J. Bobacka, Electroanalysis
2006, 18, 7.
GC / SWCNT / KClaq
G.A. Crespo, S. Macho, J. Bobacka, F.X. Rius, Anal. Chem. 81 (2009) 676.
Rs = solution resistanceCd = bulk capacitanceZD = finite-length Warburg diffusion
ISEs using conjugated polymers as
solid contact
• Good long-term stability
– Gyurcsányi & Lindner et al., Talanta, 63 (2004) 89.
– Hall et al, Anal. Chem. 76 (2004) 2031.
• Low detection limit (< 10-9 M)
– Bakker & Pretsch et al., Anal. Chim. Acta 523 (2004) 53.
– Maj-Zurawska & Lewenstam et al., Anal. Chem. 76 (2004)6410.
• Single-use sensors
– Michalska & Maksymiuk, Anal. Chim. Acta, 523 (2004)97.
• Polyaniline-based pH nano-electrode
– Ogorevc & Wang et al., Anal. Chim. Acta, 452 (2002) 1.
• Polypyrrole-based NO3- sensor
– Bendikov & Harmon, J. Chem. Edu. 82 (2005) 439.
• Conjugated polymer-based Ag+ sensors
– Vázquez & Bobacka et al., J. Solid State Electrochem. 9(2005) 312.
• Conjugerade polymers doped with complexingligands
– Migdalski & Lewenstam et al., Polish J. Chem. 78 (2004)1543.
ISEs using conjugated polymers as
selective membrane
0 10 20 30 40 50
-50
0
50
100
150
200
250
300
350
precipitation
starts
E / m
V
Vtartaric acid
/ ml
S
N
N
CH3
H3C
CH3COOH
HC OH
CH
COOH
HO
S
N
N
CH3
H3C
CH3
2
COOH
HC OH
CH
COOH
HO2 +
Titration of trimeprazine base with tartaric acid in
isopropanol using GC/PANI as indicator electrode
The ”new wave” of ISEs
• Low detection limit
• Solid-contact ISEs
• Solid-state reference electrodes
• Plasticizer-free membranes
• Covalently bound ionophores
• Advanced non-equilibrium models
J. Bobacka, A. Ivaska, A. Lewenstam, Chem. Rev. 108 (2008) 329.
Solid-state ion sensors and
solid-state reference electrode
2. Ion-to-electron transducer
3. Ion-selective membrane
1. Electronic conductor
All-solid-state ISE
2. Ion-to-electron transducer
3. Equitransferent membrane
1. Electronic conductor
All-solid-state
reference electrode
E / mV
E / mV
Signal interpretation
Low detection limit
Miniaturization
Sensor materials
SC-ISEs & SC-RE
pH-ISE
Pb2+-ISE
Referenceelectrode
Au / PEDOT / PVC-based membrane *
* pH-ISE: PVC + oNPOE + H II + KTpClPB
Pb2+-ISE: PVC + DOS + Pb IV + NaTFPB
Reference electrode: PVC + oNPOE + TBATBB
Electrode body designed by:J. Migdalski and B. Bas,
AGH University of Science and Technology, Cracow, Poland
Solid-contact pH-ISE vs. SC-RE
-150
-100
-50
0
50
100
150
200
250
300
350
0 1 2 3 4 5 6 7 8 9 10 11 12 13
pH
E / m
V Slope = 58 mV/dec
Solid-contact Pb2+-ISE vs. SC-RE
-225
-200
-175
-150
-125
-100
-75
-13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1
log aPb2+
E / m
V
Slope = 29.6 mV/dec
LOD = 10-7.3
Simultaneous measurement of Pb2+ and pH
in environmental water samples
pH-ISEs
Pb2+-ISEs
Referenceelectrode
S. Anastasova-Ivanova, U. Mattinen, A. Radu, J. Bobacka, A. Lewenstam, J. Migdalski, M. Danielewski, D. Diamond, Sens. Actuators B, 146 (2010) 199–205.
� Speciation of lead
� pH measurements
Detection limit = ca. 2 ppb
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• J. Bobacka, Electroanalysis, 18 (2006) 7.
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