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Dynamic Vapor Sorption
Dr Vladimir MartisSurface Measurement Systems, October 2015
OUTLINE
Material Characterization by Sorption Processes1. How it compares to other characterization techniques2. Types of sorption processes and what they measure
DVS Introduction1. Gravimetric Sorption2. Organics3. Video4. Raman/Other access port
Applications/Examples• Isotherm Shape/Modelling• Isotherm Hysteresis• Phase Transitions• Amorphous Content• Diffusion Experiments• Organic Vapors
States of Matter
Vapour / gas
particles move freely
Liquid
particles move close together
Solid
particles fixed close together
Characterization of SolidsEnergy as a Probe
1.Spectroscopy2.Light, x-rays, lasers, etc. 3.Analytical and structural information
Heat as a Probe1.Calorimetry2.Thermodynamic information
Molecules as a Probe1.Sorption techniques2.Thermodynamic, chemical, and structural
Information
Energy
Matter
Energy as a Probe
•Structural Information1.XRD, XRPD
•Chemical Composition1.XPS (ESCA), NMR, FTIR
•Visual Information1.Optical Light Microscopy (polarized)2.SEM3.Particle size measurements (laser diffraction)4.Particle shape
Heat as a Probe
•Thermodynamic Information1.DSC (modulated; hyper)2.TGA
•Chemical Reactions• Reaction Calorimetry
Molecules as a Probe
Molecules Absorbed
Molecules Adsorbed
sam
ple
Vapour molecules
Molecules in Molecules out
Molecules Absorbed
Molecules Adsorbed
Absorption•Bulk absorption•Absorption into lattice structure
Adsorption•Physisorption•Chemisorption
Molecules as a Probe - Interactions
Adsorption•Physisorption•Chemisorption
• Weak interactions• Probe molecules not chemically bound to surface• Reversible sorption
Associated properties measured:• Structural: surface area, pore size, surface
roughness• Chemical Interactions: surface sorption
capacity, surface energy, hydrophilicity, Lewis acidity-basicity, surface heterogeneity
• Thermodynamic: heat of sorption, free energy
• Usually strong interactions• Probe molecules are covalently bound to surface • Can be reversible or irreversible sorption
Associated properties measured:• Titrate acid-base sites• Active surface area• Catalyst Dispersion
Molecules as a Probe - Interactions
Molecules Absorbed
Molecules Adsorbed
Absorption•Bulk absorption•Absorption into lattice structure
Adsorption•Physisorption•Chemisorption
Molecules as a Probe - Interactions
Absorption•Bulk absorption•Absorption into lattice structure
• Penetrate surface• Desorption is often diffusion limited• Reversible or irreversible sorption
Associated properties measured• Structural: vapor-induced phase
changes (glass transition, crystallization, deliquescence), glass transition temperatures, crosslink density
• Chemical: total sorption capacity, solubility parameters
• Kinetic: diffusion coefficients, solid-solid phase transformation, drying kinetics
• Solvate formation• Reversible or irreversible solvate formation
Associated properties measured
• Structural: stoichiometric hydrate/solvate, channel hydrate/solvate
• Kinetic: hydrate/solvate formation/loss kinetics
Molecules as a Probe - Interactions
OUTLINE
Material Characterization by Sorption Processes1. How it compares to other characterization techniques2. Types of sorption processes and what they measure
DVS Introduction1. Gravimetric Sorption2. Organics3. Video4. Raman/Other access port
Applications/Examples• Isotherm Shape/Modelling• Isotherm Hysteresis• Phase Transitions• Amorphous Content• Diffusion Experiments• Organic Vapors
DVS IntroductionDynamic gravimetric Vapor Sorption (DVS)
1.Fully automatic sorption instrument2.Fast equilibrium: significantly improved kinetics over static sorption
systems3.SMS pioneer in vapor sorption technology
SMS UltraBalance1.Up to 0.1 µg sensitivity2.Allows use of small samples 1-10 mg3.Unrivaled long-term baseline stability
‘Real-world’ conditions• Wide range of temperatures: measurement and preheat conditions• Wide range of measurement pressures: atmospheric down to 10-6 Torr
(DVS-vacuum)• Wide range of vapors: water and organic vapors
DVS – Water Sorption
Water-solid interactions important for wide range of industries:
•Food•pharma•proteins•fuel cells
Accurately determining water sorption isotherms critical for proper development and storage of these materials
•packaging•high energy materials•personal care
Where can Vapour Sorption occur?• On the surface• In pores – micro/meso?• Between the particles (condensation?)• Sorbed into the bulk• Chemically reacted (hydrate formation)?
What can vapour sorption tell me?• The stability of materials at different vapour concentrations.•Accurately determining water sorption isotherms is critical for proper development and storage of these materials
How do Dynamic Vapour Sorption (DVS)compares to the Static Gravimetric Techniques
Jar Method (static method)
Need many of them: each one for a different relative humidity (RH) level
DVS (dynamic sorption)
Just one instrument can cope with all relative humidity levels
Jar Method (static sorption)
Needs 1 to 10 gramsof sample
DVS (dynamic sorption)
Needs 1 to 10 milligrams of sample, thanks to high sensivity microbalance (0.1 µg)
Very slow achievement of equilibrium: only brownian motion transports gases
Fast equilibrium due to optimized flow of gas + vapours (up to 200 ml/min)
Jar Method (static sorption) DVS (dynamic sorption)
Jar Method (static sorption)
Can take weeks or months for a singledata point
DVS (dynamic sorption)
Can take less than a day for the wholeexperiment
Sample is constantly weighted throughout the experiment: no contamination or loss of sample
Need to remove sample from desiccator for weighting every time: risk of contamination or sample loss
DVS Change In Mass (dry) Plot
-5
0
5
10
15
20
25
0 2000 4000 6000 8000 10000 12000 14000
Time/mins
Chang
e In Ma
ss (%
) - Dry
0
10
20
30
40
50
60
70
80
90
100
Target
RH (%
)
dm - dry Target RH
© Surface Measurement Systems Ltd UK 1996-2001DVS - The Sorption Solution
Date: 07 Dec 2001 Time: 4:14 pm File: ricestarch071201_reduced.XLS Sample: rice starch
Temp: 24.8 °C Meth: duncan.sao M(0): 40.5303Moisture Uptake of Choline Bitartrate*
0
5
10
15
20
25
30
35
40
45
50
0 50 100 150 200 250 300
Days Stored at 50% RH
Mo
istu
re P
ick
up
mg
/10
g 6000 minutes =4.2 days for full cycle300 days for a single
equilibrium data point
Jar Method (static sorption) DVS (dynamic sorption)
minutes
Usually only the sorption curve is measured, not registering the desorption curve nor any possible hysteresis involved
Can register sorption and desorption, obtaining more information in less time: eg fast kinetics or morphology changes
Relative humidity (RH)
Mas
s u
pta
ke
Mas
s u
pta
ke
Relative humidity (RH)
Jar Method (static sorption) DVS (dynamic sorption)
DVS in brief• Dynamic Flowing Gas System (200 ml/min) • Fast Equilibrium due to optimised mass transport• High sensitivity Ultra-Microbalance (0.1 µg)• Allows small sample to be used (1 to 10 mg) • Fast equilibrium – 10 point isotherm in ~ 24 hours• Electronic Mass Flow Controllers - Mix Saturated (100%RH) and Dry
(0%RH) Carrier Gas Flows.• Single Temperature Zone – Ensures Stable Humidities Throughout the
System.• Symmetrical Design – Excellent Baseline and Minimal Gas Buoyancy
Effects.• Mini RH Probe (5mm dia.) - Humidity Measured Next to Sample.• No PID Control on RH Probe – Excellent Long Term Reproducibility (Better
than 1%RH over many years)
DVS Advantage Schematic
DVS Family of Products
DVS AdvantageDVS Intrinsic
DVS Vacuum DVS Elevated Temperature
Link up to FIVEDVS-Intrinsic Analysersto ONE Computer!
Gain Throughput – using IntrinsiLink™
• DVS technique recognised standardfor characterising water-solid sorptioninteractions under Chapter 1241 of theAmerican USP and the EuropeanPharmacopoeia (Ph. Eur. Draft)
• DVS technique soon to be ‘JapaneseStandard’ for characterising water-solidinteractions
Regulatory Requirement:
DVS Advantage Plus - Organics
0
10
20
30
40
50
60
70
80
90
100
0 50 100 150 200 250
% P
artia
l Pre
ssur
e
Time/mins
DVS Octane Partial Pressure PlotTarget % P/Po Actual % P/Po
DVS Advantage Plus - Video
•Microscope mounted below sample area allows for in-situ monitoring of sample•Up to 200x magnification•Polarized light option•Fully digital•Annotated images•Adjustable focal point
DVS Camera Assembly
DVS Advantage Plus - Video
Carbon Fibers – 0% RH
DVS Advantage Plus - Video
Maltodextrin – 0% RH Maltodextrin – 95% RH,0 minutes
Maltodextrin – 95% RH,30 minutes
Maltodextrin – 95% RH,50 minutes
DVS Advantage Plus - Raman
•Two independent ports for additional in-situ measurements of sample•Integrated safety locks•Trigger from DVS control software•Raman Spectroscopy•NIR Spectroscopy•UV light source•Other probes Ports for
additional measurements
DVS Mass Plot
20.5
21
21.5
22
22.5
23
23.5
0 500 1000 1500 2000 2500 3000Time/mins
Mas
s/m
g
0
10
20
30
40
50
60
70
80
90
100
Targ
et %
P/P
o
Mass Target % P/Po
© Surface Measurement Systems Ltd UK 1996-2007DVS - The Sorption Solution
Date: 21 Nov 2007 Time: 5:57 pm File: amorphous lactose 21st Nov 2007.xls Sample:
Temp: 24.9 °C Meth: anhydrate.SAO MRef: 20.6428
Crystallization
DVS Advantage Plus - Raman
0102030405060708090100
0,0
2,0
4,0
6,0
8,0
10,0
12,0
0 500 1000 1500 2000 2500
Rel
ativ
e H
umid
ity (%
)
Time (min)
Sam
ple
Mas
s C
hang
e (%
)
Time (min)
Mass Change of Amorphous Lactose at 25 deg C
dm (%) - refRaman Spectrum at StepTarget PP (Water)
0
1
2
3
4
Rel
ativ
e In
tens
ity
Raman Shifts (cm^-1)
Baseline-Corrected Raman Spectraof Amorphous Lactose at 25 deg C
End of 95%RH Step
End of 60%RH Step
End of 40%RH Step
End of 0%RH Step
DVS Advantage Plus - Raman
DVS Analysis Suite
Isotherm Suite
BET
Guggenheim Anderson DeBoer
Double Freundlich
Dubinin Radushkevich
Micropore distribution
Mesopore distribution
Reference
Langmuir
Alternative
Young & Nelson
Advanced
Spreading pressure
BET isotherm
Heat of sorption
Diffusion
Activation energy of diffusion
Knudsen vapor pressure
Iso activity plot
Amorphous content
Permeability
Database
Standard
Plot Manager
Isotherm
Baseline Correction
Vapor Content Offset
Salt validation calibration
Partial pressure check
Drift noise check
Method report
Configurations
The widest range of isotherm models available in a single suite.
Automatic best fit selection.
Chart and plot options.
Automatic report summary generation.
OUTLINE
Material Characterization by Sorption Processes1. How it compares to other characterization techniques2. Types of sorption processes and what they measure
DVS Introduction1. Gravimetric Sorption2. Organics3. Video4. Raman/Other access port
Applications/Examples• Isotherm Shape/Modelling• Isotherm Hysteresis• Phase Transitions• Amorphous Content• Diffusion Experiments• Organic Vapors
DVS Applications Pharmaceutical
Important areas of interest include:
– Preformulation - Stability Testing of Active Salt
Complexes.
– Formulation - Excipients / Formulations.
– Characteriztation of Amorphous Content in
Pharmaceutical Powders.
– Moisture Induced Morphology Changes.
Applications/Examples
DVS Applications Personal Care
Important areas of interest include:
– Hair: moisture retention with different
treatments (i.e. shampoo, conditioner)
– Skin: moisture retention/drying with
different treatments
– Contact Lens: drying of films
– Super Absorbent Polymers (i.e. diapers)
Applications/Examples
DVS Applications Foods
• Moisture induced morphology changes in food ingredients and products.
• Stability of Food Ingredients – e.g. Unstable amorphous moisture behavior.
• Rapid Isotherms for Food Ingredients – e.g. Starches, Celluloses, Sugars
• Moisture Adsorption/absorption/expulsion.• Diffusion in Food Packaging Materials.
Applications/Examples
DVS Applications Packaging
Materials applications for packaging films and materials:
– Pill Capsules and Blister Packs
– Electronics Components
– Packaging of Foodstuffs
Type of measurements:
– Permeability of Real Packages
– Calculation of Diffusion Constants
Applications/Examples
DVS Applications - Other
Other applications include:
– Fuel Cells: water content critical to PEM fuel cell performance
– Fabrics/Fibers: moisture management important for many advanced
fabrics
– Building Materials: cements, wood, insulation materials
– Agriculture: seeds, fertilizer release
Applications/Examples
What can the DVS do for me?1.How does my material interact with moisture or solvents and temperature in the vapour
phase?
2.Stability, Performance and Processing issues: Reversible and Irreversible effects of moisture
3.Create Moisture Isotherms – i.e. Equilibrium moisture content as a function of %RH
4.Heterogeneity? – Identify the Heterogeneity of a sample batch
5.Homogeneity? – Identify variance within one sample
6.Kinetics – Moisture transport properties, how fast or slow?
7.Energy – How strongly is the moisture bound to the material, surface or bulk?
8.Identify & Characterise Phase Transition/Changes, e.g. polymorphs, amorphous stoichiometry
9.Hydration and Solvate Formation
10.Drying Analysis
11.Diffusion and Activation Energy
12.Heat of Sorption
13.Moisture Content? – how much moisture/vapour is taken up or released
Applications/Examples
DVS – Kinetics of Moisture Sorption of Rice Starch
DVS Change In Mass (dry) Plot
-5
0
5
10
15
20
25
0 2000 4000 6000 8000 10000 12000 14000
Time/mins
Cha
nge
In M
ass
(%) -
Dry
0
10
20
30
40
50
60
70
80
90
100
Targ
et R
H (%
)
dm - dry Target RH
© Surface Measurement Systems Ltd UK 1996-2001DVS - The Sorption Solution
Date: 07 Dec 2001 Time: 4:14 pm File: ricestarch071201_reduced.XLS Sample: rice starch
Temp: 24.8 °C Meth: duncan.sao M(0): 40.5303
DryingSorption SorptionDesorption Desorption
First cycle Second cycle
Applications/Examples
DVS- Rice Starch IsothermsDVS Isotherm Plot
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90 100Target RH (%)
Cha
nge
In M
ass
(%) -
Dry
Cycle 1 Sorp Cycle 1 Desorp
© Surface Measurement Systems Ltd UK 1996-2001DVS - The Sorption Solution
Date: 07 Dec 2001 Time: 4:14 pm File: ricestarch071201_reduced.XLS Sample: rice starch
Temp: 24.8 °C Meth: duncan.sao M(0): 40.5303
Desorption
Sorption
Back to 0 reversible
Hysteresis
Point: from
last 3-5
datapoints of
each
humidity step
Applications/Examples
Isotherm types (BDDT classification)
Alkanes
Water
Applications/Examples
Sorption Mechanisms
Monolayer Mechanism(typical type II/IV)Hads >> Hcond
Cluster Mechanism(typical type III/V)
Hads Hcond
Applications/Examples
Sorption Mechanisms
Applications/Examples
Sorption Mechanisms
Change of isotherm shape from III to IILactose Isotherms
0.00
0.00
0.00
0.01
0.01
0.01
0.01
0.01
0.02
0.02
0.02
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0
RH (%)
Cha
nge
in m
ass
(%)
WaterMethanolEthanolPropanolButanol
Less polar isotherm approaches type II
Applications/Examples
Sorption Mechanisms
– Kuhn model gives best fit for water isotherm (top)
– Assumption that different surface sites have different adsorption potentials – cluster formation on each site as P/P0 increases
– Good model for type III sorption behaviour
Kuhn Plot
0.00E+00
2.00E-05
4.00E-05
6.00E-05
8.00E-05
1.00E-04
1.20E-04
1.40E-04
0 0.2 0.4 0.6 0.8 1
p/p0
n [M
ol/g
]
experiment fit
Kuhn Plot
0.00E+00
5.00E-07
1.00E-06
1.50E-06
2.00E-06
2.50E-06
0 0.2 0.4 0.6 0.8 1
p/p0
n [M
ol/g
]
experiment fit
Applications/Examples
Isotherm Shape/Modelling
Fits are useful for:
Adsorption mechanism
Full description of isotherm
Drying and moisture content
Prediction of transition points and stability
Prediction of formulation sorption behaviour
Applications/Examples
Overview
Part I – Isotherm Shape/Modelling
Part II – Isotherm Hysteresis
Part III – Phase Transitions
Part IV – Amorphous Content
Part V – Diffusion Experiments
Part VI – Organic Vapors
Conclusions
RH Control at Low, Middle, and High RH Steps
• Water sorption on microcrystalline cellulose (MCC)• 0.2% RH steps: 0 to 5% RH; 50 to 55% RH; and 90 to 95% RH
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60 70 80 90 100
Cha
nge
In M
ass
(%) -
Ref
Target % P/Po
DVS Isotherm Plot
Cycle 1 Sorp Cycle 1 Desorp
© Surface Measurement Systems Ltd UK 1996-2010DVS - The Sorption Solution
Date: 11 Mar 2011Time: 5:10 pmFile: Avicel 0.2 steps - Fri 11 Mar 2011 17-10-29.xlsSample: Avicel 0.2 steps
Temp: 25.1 CMeth: Avicel 0.2 stepsB.saoMRef: 12.192
II – Isotherm hysteresis
Rice Starch Isotherm - Bulk Hysteresis
DVS Isotherm Plot
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90 100Target RH (%)
Cha
nge
In M
ass
(%) -
Dry
Cycle 1 Sorp Cycle 1 Desorp
© Surface Measurement Systems Ltd UK 1996-2001DVS - The Sorption Solution
Date: 07 Dec 2001 Time: 4:14 pm File: ricestarch071201_reduced.XLS Sample: rice starch
Temp: 24.8 °C Meth: duncan.sao M(0): 40.5303
II – Isotherm hysteresis
Bulk Absorption Models
Young & Nelson AnalysisAllows for a separation in different contributions to water sorption on rice starch: monolayer formation, condensation and bulk absorption
Adsorption constants A=0.0029 Mol/g, B=0.0026Mol/g and E=0.072.
Young & Nelson Component Plot
00.0010.0020.0030.0040.0050.0060.0070.008
0 0.2 0.4 0.6 0.8 1
p/p0
n [
Mo
l/g
]
experiment Mono
experiment Multi
experimentAbsorbed fit Mono
fit Multi
fit Absorbed
II – Isotherm hysteresis
Bulk Absorption Models
Flory-Huggins interaction parameter χ is a property of the solid and vapor (solvent). Further parameters can be derived, e.g.
p/po = Φ1exp[(1-(1/x))Φ2+χΦ22]
Solubility parameters: solvation and dissolution behavior; drug delivery; ingredient compatability
II – Isotherm hysteresis
Alumina Isotherm – Mesopore HysteresisCan be described by Kelvin Equation
Capillary CondensationDVS Isotherm Plot
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100Target PP (%)
Cha
nge
In M
ass
(%) -
Dry
Cycle 1 Sorp Cycle 1 Desorp Cycle 2 Sorp Cycle 2 Desorp
© Surface Measurement Systems Ltd UK 1996-2004DVS - The Sorption Solution
Date: 27 Mar 2002 Time: 4:14 pm File: 03-27-02-AlumunaCagg.XLS Sample: Alumina-C agglomerated
Temp: 25.0 °C Meth: Alumina-Cagg-octane.SAO M(0): 6.4214
II – Isotherm hysteresis
DVS Change In Mass (dry) Plot
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 200 400 600 800 1000 1200 1400
Time/mins
Cha
nge
In M
ass
(%) -
Dry
0
10
20
30
40
50
60
70
80
90
100
Targ
et R
H (%
)
dm - dry Target RH
© Surface Measurement Systems Ltd UK 1996-2002DVS - The Sorption Solution
Date: 07 Jul 2004 Time: 10:51 am File: 07-07-04-MOX02.xls Sample: Labindia, MOX-2
Temp: 25.1 °C Meth: Labindia01.SAO M(0): 19.854
Reversible Hydrate - Hysteresis
“Transformation” step
II – Isotherm hysteresis
Reversible Hydrate - Hysteresis
DVS Isotherm Plot
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 10 20 30 40 50 60 70 80 90 100
Target RH (%)
Cha
nge
In M
ass
(%) -
Dry
Cycle 1 Sorp Cycle 1 Desorp Cycle 2 Sorp
© Surface Measurement Systems Ltd UK 1996-2002DVS - The Sorption Solution
Date: 07 Jul 2004 Time: 10:51 am File: 07-07-04-MOX02.xls Sample: Labindia, MOX-2
Temp: 25.1 °C Meth: Labindia01.SAO M(0): 19.854
“Transformation” step
II – Isotherm hysteresis
Irreversible Hydrate - Hysteresis
DVS Isotherm Plot
-2
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60 70 80 90 100
Target RH (%)
Cha
nge
In M
ass
(%) -
Dry
Cycle 1 Sorp Cycle 1 Desorp Cycle 2 Sorp Cycle 2 Desorp
© Surface Measurement Systems Ltd UK 1996-2004DVS - The Sorption Solution
Date: 09 Jul 2004 Time: 10:52 am File: 07-09-04-GAT.xls Sample: GAT
Temp: 25.1 °C Meth: Indialab01.SAO M(0): 8.3452
II – Isotherm hysteresis
DVS Isotherm Plot
-2
0
2
4
6
8
10
12
0 10 20 30 40 50 60 70 80 90 100
Target RH (%)
Cha
nge
In M
ass
(%) -
Dry
Cycle 1 Sorp Cycle 1 Desorp Cycle 2 Sorp
© Surface Measurement Systems Ltd UK 1996-2003DVS - The Sorption Solution
Date: 16 Jul 2004 Time: 3:55 pm File: 07-16-04-IndialabOMG.xls Sample: IndiaLab OMG
Temp: 25.1 °C Meth: Indialab02.SAO M(0): 5.3393
Non-Stoichiometric Hydrate - Hysteresis
II – Isotherm hysteresis
Channel Hydrate - Hysteresis
DVS Change In Mass (dry) Plot
-1
0
1
2
3
4
5
0 500 1000 1500 2000 2500 3000 3500 4000
Time/mins
Cha
nge
In M
ass
(%) -
Dry
0
10
20
30
40
50
60
70
80
90
100
Targ
et R
H (%
)
dm - dry Target RH
© Surface Measurement Systems Ltd UK 1996-2005DVS - The Sorption Solution
Date: 13 Jul 2005 Time: 11:23 am File: 07-13-05-Ricerca-FormII.xls Sample: Ricerca MRE 0470 Form II
Temp: 24.9 °C Meth: Ricerca-0-95-H2OI.SAO M(0): 5.7068
II – Isotherm hysteresis
Channel Hydrate - Hysteresis
DVS Isotherm Plot
-1
0
1
2
3
4
5
0 10 20 30 40 50 60 70 80 90 100
Target RH (%)
Cha
nge
In M
ass
(%) -
Dry
Cycle 1 Sorp Cycle 1 Desorp Cycle 2 Sorp Cycle 2 Desorp
© Surface Measurement Systems Ltd UK 1996-2005DVS - The Sorption Solution
Date: 13 Jul 2005 Time: 11:23 am File: 07-13-05-Ricerca-FormII.xls Sample: Ricerca MRE 0470 Form II
Temp: 24.9 °C Meth: Ricerca-0-95-H2OI.SAO M(0): 5.7068
II – Isotherm hysteresis
Channel Hydrate
• Water sorption on Channel Hydrate• 0.2% RH steps: 0 to 10% RH
0
0.5
1
1.5
2
2.5
3
3.5
4
0 10 20 30 40 50 60 70 80 90 100
Cha
nge
In M
ass
(%)
-Ref
Target RH (%)
DVS Isotherm Plot
Cycle 1 Sorp Cycle 1 Desorp
© Surface Measurement Systems Ltd UK 1996-2007DVS - The Sorption Solution
Date: 15 Dec 2011Time: 16-13File: Channel Hydrate -
Thu 15 Dec 2011 16-13-33.xlsSample: Channel Hydrate
Temp: 25.0 °CMeth: Channel Hydrate small steps 2.sao
MRef: 13.4291
0
0.5
1
1.5
2
2.5
0 2 4 6 8 10 12 14 16 18 20
Cha
nge
In M
ass
(%)
-Ref
Target RH (%)
DVS Isotherm Plot
Cycle 1 Sorp Cycle 1 Desorp
© Surface Measurement Systems Ltd UK 1996-2007DVS - The Sorption Solution
Date: 15 Dec 2011Time: 16-13File: Channel Hydrate -
Thu 15 Dec 2011 16-13-33.xlsSample: Channel Hydrate
Temp: 25.0 °CMeth: Channel Hydrate small steps 2.sao
MRef: 13.4291
II – Isotherm hysteresis
Channel Hydrate
• Dubinin-Radushkevich Analysis for total pore volume: 0.0353 cm3/g; R-value: 0.989; analysis between 0.3 and 20% RH
-3
-2.8
-2.6
-2.4
-2.2
-2
-1.8
-1.6
0 2 4 6 8
Log1
0(V
a)
(Log10(po/p))^2
DR Volume Plot
linear fit
experiment
II – Isotherm hysteresis
DVS Change In Mass (dry) Plot
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
0 200 400 600 800 1000 1200
Time/mins
Cha
nge
In M
ass
(%) -
Dry
0
10
20
30
40
50
60
70
80
90
100
Targ
et P
P (%
)
dm - dry Target PP
© Surface Measurement Systems Ltd UK 1996-2004DVS - The Sorption Solution
Date: 31 Aug 2005 Time: 2:14 pm File: B lactose - Wed 31 Aug 2005 14-14-44temp2.xls Sample: B lactose
Temp: 25.1 °C Meth: B Lactose.sao M(0): 55.7266
II – Isotherm hysteresis
-Lactose Anhydrous- Hysteresis
DVS Isotherm Plot
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 10 20 30 40 50 60 70 80 90 100
Sample PP (%)
Cha
nge
In M
ass
(%) -
Dry
Cycle 1 Sorp Cycle 1 Desorp
© Surface Measurement Systems Ltd UK 1996-2004DVS - The Sorption Solution
Date: 15 Sep 2005 Time: 2:10 pm File: Lactose Boculo - Thu 15 Sep 2005 14-10-50.xls Sample: Lactose Boculo
Temp: 25.1 °C Meth: lough3.sao M(0): 45.4484
No dehydration of alpha lactose monohydrate!
II – Isotherm hysteresis
-Lactose Anhydrous- Hysteresis
Overview
Part I – Isotherm Shape/Modelling
Part II – Isotherm Hysteresis
Part III – Phase Transitions
Part IV – Amorphous Content
Part V – Diffusion Experiments
Part VI – Organic Vapors
Conclusions
Glass Transition and Crystallisation
DVS Change In Mass (dry) Plot
0
2
4
6
8
10
12
14
-100 100 300 500 700 900 1100 1300 1500Time/mins
Cha
nge
In M
ass
(%) -
Dry
0
10
20
30
40
50
60
70
80
90
100
Targ
et R
H (%
)
% Change in Mass Target RH
© Surface Measurement Systems Ltd UK 1996-2001DVS - The Sorption Solution
Date: 05 Dec 2002
Time: 11:58 am
File: 12-05-02-lactoseramp900.XLS
Sample: amorphous lactose
Temp: 25.1 °C
Meth: lactoseramp0-90-900min.SAO
M(0): 93.2048
Glass Transition
Surface Adsorption
Bulk Absorption and
Surface Adsorption
Recrystallization
III – Phase transitions
Tg RH versus Ramping Rate
Glass Transition Humidity (Tg RH) versus Humidity Ramping Rate
y = 1.155x + 29.822R2 = 0.979
28.00
30.00
32.00
34.00
36.00
38.00
40.00
42.00
44.00
0.00 2.00 4.00 6.00 8.00 10.00 12.00
Ramping Rate (%RH/hour)
Hum
idity
at G
lass
Tra
nsiti
on (%
RH
)
Glass Transition (%RH)
Linear (Glass Transition (%RH))
Critical Tg RH = 30% +/- 1% RH at 25 °C
III – Phase transitions
Phase Transitions - Mixtures
Lyophilized Protein-Sugar Formulations Bovine Serum Albumin (BSA) as a model proteinSucrose, Maltose, and Mannitol as model sugarsBSA loadings of 0, 11, 20, and 33 wt%DVS sample size between 2 and 4mg
Freeze-Dry Conditions-50 C freeze temp; 20 C secondary drying temp
III – Phase transitions
Freeze-Dried Sucrose with Various BSA Loadings
0
5
10
15
20
25
30
35
40
45
50
0 10 20 30 40 50 60 70 80 90
Target RH
Cha
nge
In M
ass
(%) -
Dry
100% Sucrose FD1 11% BSA FD1 20% BSA FD1 33% BSA FD1 100% BSA FD1
Temp: 25.1 °C
Sucrose Crystallization
Sucrose Glass Transition
Sucrose Deliquescence
III – Phase transitions
Phase Transitions - Mixtures
Three distinct phase transitions Glass Transition not greatly affected by
BSACrystallization humidity increases with
increasing BSA content – components interact strongly, thus stabilizing mixture
Sucrose deliquesces above 87% RH for all samples
III – Phase transitions
Phase Transitions - Mixtures
Crystallization Kinetics
• Glass transition for spray-dried lactose at 25 OC can be
found at 30 % RH.
• Crystallisation for spray-dried lactose at 25 OC can be
found at 58 % RH.
• If temperature and humidity is kept constant (between 30% and 58% RH at 25
OC) crystallisation is kinetically
controlled and can be followed by loss of weight due to water desorption.
III – Phase transitions
Amorphous Fraction versus Time at 25 C
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
0 100 200 300 400 500 600 700 800 900 1000
Time/mins
Am
orph
ous
Frac
tion
(The
ta)
60% RH 57% RH 55% RH 53% RH 51% RH 50% RH
© Surface Measurement Systems Ltd UK 1996-2003DVS - The Sorption Solution
Crystallization Kinetics
III – Phase transitions
Time to Recrystallization versus Temperature at 51% RH
0
5
10
15
20
25
30
294 296 298 300 302 304 306
Temperature (K)
Tim
e to
Rec
ryst
alliz
atio
n (h
r)
Time to Recrystallization (hr)
Crystallization Kinetics
III – Phase transitions
Dehydration Kinetics
DVS Mass Plot
1.4
1.45
1.5
1.55
1.6
1.65
1.7
1.75
1.8
1.85
1.9
0 200 400 600 800 1000 1200 1400 1600 1800Time/mins
Mas
s/m
g
0
10
20
30
40
50
60
70
80
90
100
Targ
et %
RH
Mass Target % P/Po
© Surface Measurement Systems Ltd UK 1996-2005DVS - The Sorption Solution
Temp: 19.9 °C
Hydrate Loss
Hydrate Formation
III – Phase transitions
Dehydration Kinetics
Fraction Dehydrated
0
0.2
0.4
0.6
0.8
1
1.2
0 100 200 300 400 500 600 700 800 900 1000Time/mins
Frac
tion
Deh
ydra
ted
30 °C 27.5 °C 25 °C 22.5 °C 20 °C 17.5 °C 15 °C
© Surface Measurement Systems Ltd UK 1996-2005DVS - The Sorption Solution
III – Phase transitions
Phase Transition – Isoactivity Analysis
III – Phase transitions
Figure 1a:Phenol Isoactivity 10C 50C 0RH 1C step
0
200
400
600
800
1000
1200
1400
0 100 200 300 400 500 600 700 800
Time/mins
dm (%
) - re
f
0
10
20
30
40
50
60
Targ
et T
emp/
°C
dm (%) - ref Target Temp/°C
Crystallization point at 40°C
Shelf-Life and “Caking”
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 200 400 600 800 1000 1200 1400Time in minutes
Change
In Mas
s (%) - D
ry
0
10
20
30
40
50
60
70
80
Target
RH (%
)
Effect of relative humidity spike on lemon flavour Kool Aid powder at varying temperature.
Blue = 25 deg. C.Red = 35 deg. C.
Kool Aid Powder (Lemon Flavor)
III – Phase transitions
0
1
2
3
4
5
6
7
0 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0T im e in m in u te s
Ch
ang
e In
Mas
s (%
) -
Dry
Kool Aid Powder (Lemon Flavor)
Blue = 5 min.
Green – 30 min.
Pink = 60 min.
Aqua = 180 min.
Water pickup by lemon flavor Kool Aid at 25C exposed to different length 70% RH pulses.
Shelf-Life and “Caking”
III – Phase transitions
RH Cycling – Powdered Flavor
0
0.5
1
1.5
2
2.5
3
3.5
4
0 500 1000 1500 2000 2500 3000 3500 4000
Time in minutes
Chan
ge In
Mas
s (%
) - D
ry
0
10
20
30
40
50
60
70
80
Targ
et R
H (%
)
Water pickup during relative humidity cycling, 20-60 % RH at 20% RH/hour.
III – Phase transitions
Kool Aid Powder (Lemon Flavor)
100
101
102
103
104
0 10 20 30 40 50 60 70 80 90 100
Sample relative humidity
Perc
enta
ge c
hang
e in
mas
s
Free-flowing
Caked
Multiple hysteresis phenomenon for Kool Aid powder.
RH Cycling – Irreversible Sorption
III – Phase transitions
Hydrophobic Drug - 2 Batches
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0 100 200 300 400 500 600 700 800
Time/mins
Cha
nge
In M
ass
(%) -
dry
0
20
40
60
80
100
Targ
et R
H (%
)
Batch Variation(Particle Size?)
III – Phase transitions
Polymorphic Drug
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 100 200 300 400 500 600 700 800 900
Time/mins
Cha
nge
in M
ass
(%)
0
10
20
30
40
50
60
70
80
90
100
Targ
et R
H (%
)
• Polymorph A• (Reversible Hydrate)
• Polymorph B• (Hydrophobic)
-0.05
0
0.05
0.1
0.15
0.2
0.25
0 50 100 150 200 250
Time/mins
Cha
nge
in M
ass
(%)
0
10
20
30
40
50
60
70
80
90
100
Targ
et R
H (%
)
III – Phase transitions
DVS – Heat of Sorption
– Clausius-Clapeyron Equation– Isotherm at two temperatures T1, T2
– dlnp/dT ~ H/RT2
– For fixed surface coverage can calculate p1, p2
– Equivalent chemical potentials at equilibrium
– Can use to estimate H sorp over the range T1- T2
– Assumes gas ideality
III – Phase transitions
Heat of Sorption - -Lactose monohydrate
DVS Isotherm Plot
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0 10 20 30 40 50 60 70 80 90 100
Target RH (%)
Chan
ge In
Mas
s (%
) - D
ry
25 C 35 C 45 C
© Surface Measurement Systems Ltd UK 1996-2001DVS - The Sorption Solution
III – Phase transitions
Change in mass (%) Heat of sorption (kJ/mol)
(25 and 35 °C)
Heat of sorption (kJ/mol)
(35 and 45 °C)
0.06 -46.1 -43.3
0.07 -47.3 -44.2
0.08 -47.9 -44.5
0.09 -47.4 -45.2
Hads for Water Hcond for Water
Heat of Sorption - -Lactose monohydrate
III – Phase transitions
Overview
Part I – Isotherm Shape/Modelling
Part II – Isotherm Hysteresis
Part III – Phase Transitions
Part IV – Amorphous Content
Part V – Diffusion Experiments
Part VI – Organic Vapors
Conclusions
Amorphous Content
Amorphous
Crystalline
Partially Amorphous
IV – Amorphous content
Amorphous Content
Lactose in Aqueous Solution
Crystallisation Fully amorphous Partially amorphous
-Lactose (anhydrous)
-Lactose (monohydrate)
-Lactose anhydrous (unstable)
-Lactose anhydrous (stable)
(amorphous phase created by defect sites/impurities/mechanical activation/spray/freeze drying, etc)
-Lactose and -Lactose differ only in the
anomeric form of the glucopyranose ring
that forms lactose
IV – Amorphous content
Spray Dried Lactose - Kinetics
0
2
4
6
8
10
12
14
0 500 1000 1500 2000 2500 3000
Time/mins
Chan
ge in
Mas
s (%
)
0
10
20
30
40
50
60
70
80
90
100
Relat
ive H
umid
ity (%
)
Collapse of Amorphous Lactose
Component
IV – Amorphous content
Amorphous Lactose Isotherm
0
2
4
6
8
10
12
14
0 10 20 30 40 50 60 70 80 90
Relative Humidity (% )
Equi
libriu
m M
oist
ure
Cont
ent (
%)
Sorption - 1st Cycle
Desorption
Sorption - 2nd Cycle
IV – Amorphous content
– Based on relative uptakes of amorphous and crystalline phases
– Uptake measured at humidity BELOW any moisture-induced transformations occur
– Calibration curve of known amorphous contents is required
Method 1
IV – Amorphous content
Isotherm Plot
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 5 10 15 20 25 30
Sample RH (%)
Cha
nge
In M
ass
(%) -
Dry
100% Crystalline Lactose 100% Amorphous Lactose 10% Amorphous Lactose
Temp: 25.0 °C
Method 1
IV – Amorphous content
Pros and Cons
– Lower detection limit of 0.25% amorphous content reported.
– Does not require a high level of sample mixing homogeneity as
required by XRPD since the entire sample is analyzed.
– Requires amorphous standards
– Does not account of surface uptake of crystalline phase
– Requires no humidity-induced phase transformations
Method 1
IV – Amorphous content
– Measure vapor uptake BEFORE and AFTER vapor-induced
crystallization
– Must use a vapor that induces crystallization.
– Calibration curve with known amorphous contents is
required
Method 2
IV – Amorphous content
0
5
10
15
20
25
0 20 40 60 80 100
Relative Humidity (%)
Chan
ge in
Mas
s (%
w/w
-dry
)
Amorphouscompound XCrystallinecompound X
Moisture Sorption profiles for amorphous and crystalline compound X.
Method 2
IV – Amorphous content
– Water did not cause the amorphous phase to crystallize.
– Acetone vapor caused the amorphous materials to crystallize at a
partial pressure of 0.6 P/Po
– Expose samples to 0.3 P/Po (amorphous + crystalline); exposure to
0.85 P/Po (crystallize amorphous phase), then a further exposure to
0.3 P/Po (fully crystalline)
– This methods allows for the adsorption of acetone onto the powder
surface to be properly accounted for.
Method 2
IV – Amorphous content
0
2
4
6
8
10
12
0 20 40 60 80 100
Target pp Acetone (%)
Cha
nge
In M
ass
(%) -
Dry
Cycle 1 Sorp
Acetone sorption profile for amorphous compound X
Method 2
IV – Amorphous content
0
0.2
0.4
0.6
0.8
1
1.2
0 200 400 600 800 1000 1200Time/mins
Cha
nge
In M
ass
(%)-D
ry
0
10
20
30
40
50
60
70
80
90
Rel
ativ
e pr
essu
re
Ace
tone
(%)
mass Target relative pressure
Change in mass profiles for a sample of X with a 4.8% amorphous content
Method 2
IV – Amorphous content
0
0.2
0.4
0.6
0.8
1
1.2
0 200 400 600 800 1000 1200Time/mins
Cha
nge
In M
ass
(%)-D
ry
0
10
20
30
40
50
60
70
80
90
Rel
ativ
e pr
essu
re
Ace
tone
(%)
mass Target relative pressure
AmorphousContent
DVS change in mass profiles for a sample of X with a 4.8% amorphous content
Method 2
IV – Amorphous content
– Acetone method gave an excellent linearity.
– Accounts for surface vapor uptake of crystalline material
– Lower detection limit of 0.2% amorphous content reported.
– Does not require a high level of sample mixing homogeneity as required
by XRPD since the entire sample is analyzed.
– Requires amorphous standards
– Requires vapor that causes crystallization of amorphous phase
Pros and ConsMethod 2
IV – Amorphous content
– Measurement based on formation of a stoichiometric
hydrate/solvate
– Amorphous phase will form a hydrate/solvate, while crystalline
phase will not
– No calibration curve is necessary
Method 3
IV – Amorphous content
– Theophylline used as a case study
• Amorphous phase will form a monohydrate when exposed to
80% RH at 25 C; resulting in a 10.0% weight change (WC)
• Weight Change at 80% RH should scale with amorphous content
in partially amorphous sample
Method 3
%0.10%100*/1.180
/01.18
netheophylliamu
wateramuWC
IV – Amorphous content
Method 3
DVS Isotherm Plot
-2
0
2
4
6
8
10
12
0 10 20 30 40 50 60 70 80 90 100
Target % P/Po
Cha
nge
In M
ass
(%) -
Dry
Crystalline Theophilline Sorption Crystalline Theophilline Desorption Amorphous Theophilline Sorption Amorphous Theophilline Desorption
© Surface Measurement Systems Ltd UK 1996-2005DVS - The Sorption Solution
IV – Amorphous content
Method 3DVS Isotherm Plot
0
1
2
3
4
5
6
7
8
9
10
0 10 20 30 40 50 60 70 80 90
Sample RH (%)
Cha
nge
In M
ass
(%) -
Dry
0% Amorphous
1.1% Amorphous
10.1% Amorphous
63.6% Amorphous
100% Amorphous
Temp: 25.1 °C
Monohydrate Formation
IV – Amorphous content
Method 3
– Theoretical values correlated very well with experimental values.
– No amorphous standards are necessary
– Lower detection limit of 0.5% amorphous content reported for
theophylline.
– Does not require a high level of sample mixing homogeneity as required
by XRPD since the entire sample is analyzed.
– Must form a stoichiometric hydrate/solvate during exposure to vapor
Pros and Cons
IV – Amorphous content
Octane adsorption on amorphous lactose and -lactose monohydrate
Isotherm Plot
0
0.05
0.1
0.15
0.2
0.25
0 10 20 30 40 50 60 70 80 90 100
Target P/Po (%)
Net
Cha
nge
In M
ass
(%)
100% Crystalline Lactose 100% Amorphous
Temp: 25.0 °C
Method 4
IV – Amorphous content
Method 4
DVS Isotherm Plot
0
0.05
0.1
0.15
0.2
0.25
0 10 20 30 40 50 60 70 80 90 100
Target p/po (%)
Cha
nge
In M
ass
(%) -
Dry
100% Crystalline Lactose 2.1700% Amorphous 6.017% Amorphous 24.801% Amorphous 100% Amorphous
© Surface Measurement Systems Ltd UK 1996-2000DVS - The Sorption Solution
Temp: 25.0 °C
Octane adsorption on mixtures of amorphous lactose and -lactose monohydrate
IV – Amorphous content
Method 4
Effects of milling time (Ball Mill) on the
amorphous content for Lactose using Method 4
IV – Amorphous content
Method 4
– Octane method gave an excellent linearity.
– Accounts for surface vapor uptake of crystalline material
– Lower detection limit of 0.3% amorphous content reported.
– Does not require a high level of sample mixing homogeneity as required
by XRPD since the entire sample is analyzed.
– Does not require solvent-induced crystallization
– Requires amorphous standards
– Lower vapor uptakes require higher masses (100 to 150 mg)
Pros and Cons
IV – Amorphous content
• Dynamic gravimetric vapor sorption techniques can be used to determine amorphous contents below 1%
• Selection of method depends on system under investigation
• Methods 1, 2, and 4 based on relative uptakes of amorphous and crystalline phases; requires amorphous standards
• Method 3 based on solvate/hydrate formation requires NO amorphous standards
Amorphous Content Summary
IV – Amorphous content
Overview
Part I – Isotherm Shape/Modelling
Part II – Isotherm Hysteresis
Part III – Phase Transitions
Part IV – Amorphous Content
Part V – Diffusion Experiments
Part VI – Organic Vapors
Conclusions
Diffusion – Skin Creams
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 50 100 150 200
Time/mins
Cha
nge
In M
ass
(%)
0
10
20
30
40
50
60
Targ
et R
H (%
)
One Sided Diffusion
Experiment
V – Diffusion experiments
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10000 20000 30000 40000 50000 60000
Sqrt(t)/d
Mt/M
infi
nity
20% RH
20% RH (fitted)
Previous
RH (%) Target
RH (%)
Diffusion
Coeff. (cm²/s)
R-sq. (%)
0.0 20.0 7.63E-10 99.55
20.0 0.0 4.38E-10 99.58
0.0 40.0 9.04E-10 99.52
40.0 0.0 6.05E-10 99.59
0.0 60.0 9.30E-10 99.54
60.0 0.0 6.55E-10 99.57
Dt
dM
Mt 4
Polyimide films
Two Sided Diffusion
Experiment
Diffusion constant increases slightly with increasing vapour concentration
Diffusion – Thin Films
V – Diffusion experiments
0
0.5
1
1.5
2
2.5
0 200 400 600 800 1000 1200 1400Time / min
Cha
nge
in M
ass
/ mg
20% RH 40% RH
60% RH 80% RH
O%RH
Zeolite Tablet
(Moisture Getter)
x%RH
Blister
Diffusion May be Dominated by Defects in the Blister Caused During Forming Process
Diffusion – Blister Pack
V – Diffusion experiments
Experimental set-up for moisture vapour transmission rate measurement.
SMS Payne style diffusion cell design.
% Relative Humidity Diffusion rate[mg/min]
Water vapour flux[g/(hr.m2)]
90 1.39 x 10-4 0.5569
Water vapour flux through the polymer film sample at 90% RH.
Diffusion Cell
V – Diffusion experiments
DVS Change In Mass (ref) Plot
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
0 100 200 300 400 500 600 700 800
Time/mins
Cha
nge
In M
ass
(%) -
Ref
0
10
20
30
40
50
60
70
80
90
100
Targ
et %
P/P
o
Sample 3 w ith Zeolite beads diffusion - Tue 07 Feb 2012 12-13-24 dm - dry Sample 3 diffusion - Thu 02 Feb 2012 14-42-40 dm - dry
Sample 3 w ith Zeolite beads diffusion - Tue 07 Feb 2012 12-13-24 Target % P/Po Sample 3 diffusion - Thu 02 Feb 2012 14-42-40 Target % P/Po
© Surface Measurement Systems Ltd UK 1996-2010DVS - The Sorption Solution
Sorption/desorption cycle for a polymer film cell showing water sorption kinetics with and without zeolite in the Payne diffusion cell.
Diffusion Cell
V – Diffusion experiments
Diffusion - Powders
y = -2.919E-03x2 + 9.067E-02x + 3.061E-02
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 2 4 6 8 10 12 14 16 18Tadj^0.5
Mt/M
inf
Mt/Minf2nd order fit
2.0for 6
inf
5.0
inf
M
MDt
rM
M t
p
t
Pharmaceutical Powder
V – Diffusion experiments
Activation Energy of Diffusion
Activation Energy Plot
-11.8
-11.75
-11.7
-11.65
-11.6
-11.55
-11.5
-11.45
-11.40.0031 0.0032 0.0032 0.0033 0.0033 0.0034
1/T (1/K)
ln D
p (c
m²/s
ec)
EthanolActivation Energy fit
Activation Energy of Diffusionfor an amorphous drug (30 oC)
EA=14.46 kJ/Mol
(measured between 30 and 45oC)Low activation energy would suggests
a low barrier to vapour sorption
ln Dp = Ed / RT + constant
V – Diffusion experiments
Moisture Sorption on Membrane Films
N117 Isotherm Comparison Plot
0
2
4
6
8
10
12
14
16
18
0 10 20 30 40 50 60 70 80 90 100
Target RH (%)
Cha
nge
In M
ass
(%) -
Dry
Sorp 30C Desorp 30C Sorp 50C Desorp 50C Sorp 70C Desorp 70C
© Surface Measurement Systems Ltd UK 1996-2004DVS - The Sorption Solution
V – Diffusion experiments
DVS Isotherm Comparison Plot at 30 °C
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60 70 80 90 100
Target RH (%)
Cha
nge
In M
ass
(%) -
Dry
N117 Sorp N117 Desorp N112 Sorp N112 Desorp NR112 Sorp NR112 Desrop
© Surface Measurement Systems Ltd UK 1996-2004DVS - The Sorption Solution
Temp: 29.9 °C
Moisture Sorption on Membrane Films
V – Diffusion experiments
DVS Isotherm Comparison Plot at 70 °C
0
2
4
6
8
10
12
14
16
18
20
0 10 20 30 40 50 60 70 80 90 100
Target RH (%)
Cha
nge
In M
ass
(%) -
Dry
N117 Sorp N117 Desorp N112 Sorp N112 Desorp NR112 Sorp NR112 Desrop
© Surface Measurement Systems Ltd UK 1996-2004DVS - The Sorption Solution
Temp: 70.0 °C
Moisture Sorption on Membrane Films
V – Diffusion experiments
Moisture Sorption on Membrane Films
V – Diffusion experiments
Measuring Vapour Flux Across Films
• The experiments over a range of temperatures show an increase in flux with increasing temperature.
• Thicker sample shows lower flux values than the thinner sample.• Wider range of temperatures to be studied.
25 °C 40 °C 60 °C
N117 Thick) 0.000183 1.89E-03 2.54E-03 5.39E-03
N112 (Thin) 0.000051 3.81E-03 7.56E-03 1.77E-02
NR112 0.000051 3.70E-03 7.00E-03 1.75E-02
Sample Thickness (m)Flux (mol/m
2s)
V – Diffusion experiments
Moisture Sorption on Human Hair
DVS Change In Mass (ref) Plot
-5
0
5
10
15
20
25
30
35
0 1000 2000 3000 4000 5000 6000 7000
Time/mins
Ch
ang
e In
Mas
s (%
) - R
ef
0
10
20
30
40
50
60
70
80
90
100
Tar
get
% P
/Po
© Surface Measurement Systems Ltd UK 1996-2010DVS - The Sorption Solution
The superimposed moisture sorption and desorption kinetic results for undamaged Asian(red), bleached Caucasian (blue) and undamaged Caucasian (green) hair samples at
25C.
V – Diffusion experiments
• Polymer resin encapsulation is used in electronic devices.
• Epoxy resins absorb moisture and lead to ‘popcorning’ effect during soldering.
• Standard testing conditions include 85% RH and 85C within the industry.
• Small weight changes over a long time.
Electronic Devices Packaging
H2O
H2O
H2O
H2O
HUMID STORAGE
SOLDERING HEAT
V – Diffusion experiments
Electronic Devices
V – Diffusion experiments
Coal-Based Activated Carbon
0
5
10
15
20
25
30
10 100Partial Pressure Methanol / %
Am
ount
of m
etha
nol s
orbe
d / %
V – Diffusion experiments
Building Materials
Moisture sorption kinetics for two dry cement powders at 40.0 °C.
0
2
4
6
8
10
12
14
16
0 500 1000 1500 2000 2500Tim e/m ins
Cha
nge
in M
ass
(%) Cement 1
Cement 2
V – Diffusion experiments
Techniques available: • AFM
• Difficult to perform
• Low reproducibility
• Wettability (Contact Angle)• Poor reproducibility on powders
• Limited sensitivity
• Vapour Sorption• IGC
• Gravimetric Vapour Sorption (DVS)
How to measure surface energetics?
V – Diffusion experiments
Adhesion is the fundamental force that drives interaction at interfaces (the effect of one component sticking to another).
“Sticking”
Wetting
Why measure surface thermodynamics?
V – Diffusion experiments
Building Materials
Dispersive and specific surface energies of the different aggregate samples.
0.00
50.00
100.00
150.00
200.00
250.00
SE[mJ/m2]
Augite Basalt Calcite Feldspars Granite Quarz
Surface Energy (della Volpe)
Spec. Surf. EnergyDisp. Surf. Energy
V – Diffusion experiments
Building Materials – Natural WoodWater sorption (red) and desorption (blue) isotherms at 25 °Cmeasured on sawdust (a.) and a solid wood sample (b.)
0
2
4
6
8
10
12
14
16
18
20
0 10 20 30 40 50 60 70 80 90 100
Cha
nge
In M
ass
(%) -
Ref
Sample RH (%)
DVS Isotherm Plot
Cycle 1 Sorp Cycle 1 Desorp
© Surface Measurement Systems Ltd UK 1996-2005DVS - The Sorption Solution
Temp: 25.0 C
0
2
4
6
8
10
12
0 10 20 30 40 50 60 70 80 90
Cha
nge
In M
ass
(%)
-Ref
Target % P/Po
DVS Isotherm Plot
Cycle 1 Sorp Cycle 1 Desorp
© Surface Measurement Systems Ltd UK 1996-2005DVS - The Sorption Solution
Temp: 25.0 C
(a.) (b.)
Different geometries can be used i.e. wood samples as sawdust, chunks, films, fibres, or slabs can be used to determine moisture sorption kinetics, diffusion coefficients and the equilibrium isotherm values (see SMS Application Notes 7, 12, 16, and 30).
V – Diffusion experiments
• Moisture control and measurement are critical parameters for wood and wood composites.
• moisture plays a key role in the fungal degradation and weathering of wood-plastic composites.
• Drying kinetics i.e. moisture sorption behaviour and diffusion processes.
• The hysteresis between sorption and desorption isotherms provides information related to wood stability i.e. the narrower the hysteresis, the more stable the wood sample is to fluctuating humidities.
• water vapour diffusion coefficients are related to wood species, wood grain direction, wood age, and tree ring location.
V – Diffusion experiments
Building Materials – Natural Wood and Composites
Selection of Compatible Repair Materials for Historic Buildings
Water vapour sorption isotherms for Timber materials used in the structure of Abbey Mill - an 18th century,grade II listed building. The effect of using materials with different sorption characteristics on the same structures may be investigated by using isotherm modelling software.
DVS Isotherm Plot
-5
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90 100
Target RH (%)
Cha
nge
In M
ass
(%) -
Ref
Cycle 1 Sorp Cycle 1 Desorp
© Surface Measurement Systems Ltd UK 1996-2010DVS - The Sorption Solution
Time: 14-41 File: 3 - Millbarh Timber - Sample: Millbarh Timber
Temp: 25.0 °C Meth: MRef: 28.73769
V – Diffusion experiments
Moisture Sorption of Archaeological Woodfrom the Swedish Warship Vasa
(a) Sorption isotherms for different wood materials
(b) Magnification at lower % EMC in (a)
Sorption Isotherms for Recent Oak, VAsa Oak, Extracted Vasa Oak, PEG 1500 and Vasa PEG extracted from Vasa ( J. Ljungdahl and L. Berglund, Holzforschung, Vol. 61, pp. 279-284, 2007).
V – Diffusion experiments
Overview
Part I – Isotherm Shape/Modelling
Part II – Isotherm Hysteresis
Part III – Phase Transitions
Part IV – Amorphous Content
Part V – Diffusion Experiments
Part VI – Organic Vapors
Conclusions
Acetone Solvate of Carbamazepine
Acetone Vapour Sorption Kinetics for Carbamazepine
0
5
10
15
20
25
0 200 400 600 800 1000 1200 1400
Time/mins
Cha
nge
In M
ass
(%) -
Dry
0
10
20
30
40
50
60
70
80
90
100
Targ
et P
P (%
)
dm - dry Target PP
© Surface Measurement Systems Ltd UK 1996-2006DVS - The Sorption Solution
VI – Organic vapours
DVS Isotherm Plot
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90 100Acetone % P/Po
Cha
nge
In M
ass
(%) -
Dry
Cycle 1 Sorp Cycle 1 Desorp
© Surface Measurement Systems Ltd UK 1996-2006DVS - The Sorption Solution
Acetone Solvate Loss
Acetone Solvate Formation
Acetone Solvate of Carbamazepine
VI – Organic vapours
BET - Model
VI – Organic vapours
DVS - BET Analysis
– Standard Method Using Nitrogen as Adsorbate
– Established simple model for surface physisorption.
– Adsorbed monolayer + ‘liquid’ multilayers.
– Lactose - Pharmaceutical Grade – Low Surface Area– Nitrogen BET – 0.26 – 0.43 m2/g * Ticehurst et. al.– DVS Octane – 0.25 m2/g
mm cVx
cV
c
x
x
V
11
1
1
VI – Organic vapours
DVS BET – Low Surface Area
DVS BET Plot
0
5
10
15
20
25
0 5 10 15 20 25 30 35
RH (%)
RH
/ [(
1 - R
H )
* M]
BET Data Line Fit
© Surface Measurement Systems Ltd UK 1996-2000DVS - The Sorption Solution
Date: 28 Jun 1997 Time: 12:49 pm File: BETtest02.XLS Sample: Lactose with Octane at 25C
Temp: 25.6 °C Meth: cafipa6.sao M(0): 163.4769Experimental Parameters
Molecular weight: 114.23 g/mol
Effective molecular area: 62.8 A²
Adsorbate: Octane
Temperature read from file
Calculation Options
RH lower limit range: 0.05
RH higher limit range: 0.30
RH type: Target
Half cycle: Desorption
Isotherm cycle 1
Analysis Results
Vm: 0.01526 cm³/g
c: 15.30
Specific surface area: 2576 cm²/g
R-squared of line fit: 99.964 %
VI – Organic vapours
BET- a Lactose Monohydrate
Benefits of using DVS
– Non-polar and polar probe molecules– Measurement speed– Adsorbate ‘Size’ Effects - Surface Topography– Surface Adsorption and Bulk Absorption– Flexibility in measurement temperature– Ambient pressure (flow system)– Small amount of sample
VI – Organic vapours
DVS – BET Moisture
– Non-Porous Silica– Nitrogen BET – 130 m2/g– Moisture BET – 21 m2/g
– Type II/III Isotherm– H20 - H20 Interaction– Not a good model! 0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 10 20 30 40 50 60 70 80 90
Target RH (%)
Ch
an
ge
In
Mas
s (
%)
- D
ry
Cycle 1 Sorp
© Sur f ace M easur ement Systems Ltd UK 1 996-2000DVS - T he Sor pt i on Sol ut i on
Analysis Results
Vm: 6.476 cm³/g
c: 6.666
Specific surface area: 208813 cm²/g
R-squared of line fit: 99.751 %
VI – Organic vapours
– Fractal Dimension (D): values between 2 (ideal smooth) and 3 (ideal
rough)
– Measure the monolayer coverage (Vm) for vapors with different cross
sectional areas ()
– Plot ln (Vm) versus ln () and slope = -D/2
mm cVx
cV
c
x
x
V
11
1
1
2/D
mV
VI – Organic vapours
DVS – Surface Roughness
DVS – Surface Roughness
Fractal Dimension
R2 = 0.993
-2.4-2.2
-2-1.8-1.6-1.4-1.2
-13.9 4 4.1 4.2 4.3 4.4
ln (x-sectional area)
ln (V
mon
olay
er)
Fractal Dimension
R2 = 0.9952
-2.4
-2.2
-2
-1.8
-1.6
-1.43.9 4 4.1 4.2 4.3 4.4
ln (x-sectional area)
ln (V
mon
olay
er)
– Unmilled (left) and Milled (right) alumina samples– Isotherms collected for series of n-alkanes– Calculated fractal dimensions of 2.10 (unmilled) and 2.86 (milled)– Milling substantially increases surface roughness on a level
measured by vapor probes
VI – Organic vapours
DVS – Spreading Pressure
0
0.0001
0.0002
0.0003
0.0004
0.0005
0.0006
0.0007
0.0008
0.0009
-5 -4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0
Log Vapour Partial Pressure
Cha
nge
in M
ass
(frac
tion)
Specific surface area: 0.8051 m²/gMolecular weight of vapour: 114.23 g/molSurface tension of vapour: 21.7 mN/m
Calculated pe: 7.936 mN/mWork of adhesion (WS-L): 51.34 mN/m
VI – Organic vapours
DVS Instrument Training
QUESTIONS?
ADDITIONAL DISCUSSION?
Acknowledgements
Colleagues at Surface Measurement Systems