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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

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

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

• 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 Absorbed

Molecules Adsorbed

• 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

OUTLINE

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

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

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

0 2000 4000 6000 8000 10000 12000 14000

Time/mins

e In Ma

) - Dry

Target

dm - dry Target RH

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 50 100 150 200 250 300

Days Stored at 50% RH

g 6000 minutes =4.2 days for full cycle300 days for a single

equilibrium data point

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)

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 50 100 150 200 250

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

Carbon Fibers – 0% RH

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

0 500 1000 1500 2000 2500 3000Time/mins

Mass Target % P/Po

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

0102030405060708090100

0 500 1000 1500 2000 2500

ity (%

Time (min)

Mass Change of Amorphous Lactose at 25 deg C

dm (%) - refRaman Spectrum at StepTarget PP (Water)

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 Analysis Suite

Isotherm Suite

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

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)

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.

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

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

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

DVS – Kinetics of Moisture Sorption of Rice Starch

0 2000 4000 6000 8000 10000 12000 14000

Time/mins

dm - dry Target RH

Temp: 24.8 °C Meth: duncan.sao M(0): 40.5303

DryingSorption SorptionDesorption Desorption

First cycle Second cycle

DVS- Rice Starch IsothermsDVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100Target RH (%)

Cycle 1 Sorp Cycle 1 Desorp

Desorption

Sorption

Back to 0 reversible

Hysteresis

Point: from

last 3-5

datapoints of

humidity step

Isotherm types (BDDT classification)

Alkanes

Sorption Mechanisms

Monolayer Mechanism(typical type II/IV)Hads >> Hcond

Cluster Mechanism(typical type III/V)

Hads Hcond

Sorption Mechanisms

Change of isotherm shape from III to IILactose Isotherms

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0

RH (%)

WaterMethanolEthanolPropanolButanol

Less polar isotherm approaches type II

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

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

experiment fit

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

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 10 20 30 40 50 60 70 80 90 100

Target % P/Po

DVS Isotherm Plot

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 10 20 30 40 50 60 70 80 90 100Target RH (%)

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

experiment Mono

experiment Multi

experimentAbsorbed fit Mono

fit Multi

fit Absorbed

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

Alumina Isotherm – Mesopore HysteresisCan be described by Kelvin Equation

Capillary CondensationDVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100Target PP (%)

Cycle 1 Sorp Cycle 1 Desorp Cycle 2 Sorp Cycle 2 Desorp

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

0 200 400 600 800 1000 1200 1400

Time/mins

dm - dry Target RH

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

Reversible Hydrate - Hysteresis

DVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

Cycle 1 Sorp Cycle 1 Desorp Cycle 2 Sorp

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

Irreversible Hydrate - Hysteresis

DVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

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

DVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

Cycle 1 Sorp Cycle 1 Desorp Cycle 2 Sorp

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

Channel Hydrate - Hysteresis

0 500 1000 1500 2000 2500 3000 3500 4000

Time/mins

dm - dry Target RH

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

Channel Hydrate - Hysteresis

DVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

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

Channel Hydrate

• Water sorption on Channel Hydrate• 0.2% RH steps: 0 to 10% RH

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

DVS Isotherm Plot

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 2 4 6 8 10 12 14 16 18 20

Target RH (%)

DVS Isotherm Plot

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

Channel Hydrate

• Dubinin-Radushkevich Analysis for total pore volume: 0.0353 cm3/g; R-value: 0.989; analysis between 0.3 and 20% RH

0 2 4 6 8

(Log10(po/p))^2

DR Volume Plot

linear fit

experiment

0 200 400 600 800 1000 1200

Time/mins

dm - dry Target PP

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

-Lactose Anhydrous- Hysteresis

DVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100

Sample PP (%)

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!

-Lactose Anhydrous- Hysteresis

Overview

Conclusions

Glass Transition and Crystallisation

-100 100 300 500 700 900 1100 1300 1500Time/mins

% Change in Mass Target RH

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

0.00 2.00 4.00 6.00 8.00 10.00 12.00

Ramping Rate (%RH/hour)

Glass Transition (%RH)

Linear (Glass Transition (%RH))

Critical Tg RH = 30% +/- 1% RH at 25 °C

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

Freeze-Dried Sucrose with Various BSA Loadings

0 10 20 30 40 50 60 70 80 90

Target RH

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

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

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.

Amorphous Fraction versus Time at 25 C

0 100 200 300 400 500 600 700 800 900 1000

Time/mins

60% RH 57% RH 55% RH 53% RH 51% RH 50% RH

Time to Recrystallization versus Temperature at 51% RH

294 296 298 300 302 304 306

Temperature (K)

Time to Recrystallization (hr)

Dehydration Kinetics

DVS Mass Plot

0 200 400 600 800 1000 1200 1400 1600 1800Time/mins

Mass Target % P/Po

Temp: 19.9 °C

Hydrate Loss

Hydrate Formation

Dehydration Kinetics

Fraction Dehydrated

0 100 200 300 400 500 600 700 800 900 1000Time/mins

30 °C 27.5 °C 25 °C 22.5 °C 20 °C 17.5 °C 15 °C

Phase Transition – Isoactivity Analysis

Figure 1a:Phenol Isoactivity 10C 50C 0RH 1C step

0 100 200 300 400 500 600 700 800

Time/mins

) - re

dm (%) - ref Target Temp/°C

Crystallization point at 40°C

Shelf-Life and “Caking”

0 200 400 600 800 1000 1200 1400Time in minutes

Change

In Mas

s (%) - D

Target

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)

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

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”

RH Cycling – Powdered Flavor

0 500 1000 1500 2000 2500 3000 3500 4000

Time in minutes

Water pickup during relative humidity cycling, 20-60 % RH at 20% RH/hour.

0 10 20 30 40 50 60 70 80 90 100

Sample relative humidity

Free-flowing

Multiple hysteresis phenomenon for Kool Aid powder.

RH Cycling – Irreversible Sorption

Hydrophobic Drug - 2 Batches

0 100 200 300 400 500 600 700 800

Time/mins

Batch Variation(Particle Size?)

Polymorphic Drug

0 100 200 300 400 500 600 700 800 900

Time/mins

• Polymorph A• (Reversible Hydrate)

• Polymorph B• (Hydrophobic)

0 50 100 150 200 250

Time/mins

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

Heat of Sorption - -Lactose monohydrate

DVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

25 C 35 C 45 C

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

Overview

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

Spray Dried Lactose - Kinetics

0 500 1000 1500 2000 2500 3000

Time/mins

ity (%

Collapse of Amorphous Lactose

Component

Amorphous Lactose Isotherm

0 10 20 30 40 50 60 70 80 90

Relative Humidity (% )

libriu

Sorption - 1st Cycle

Desorption

Sorption - 2nd Cycle

– 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

Isotherm Plot

0 5 10 15 20 25 30

Sample RH (%)

100% Crystalline Lactose 100% Amorphous Lactose 10% Amorphous Lactose

Temp: 25.0 °C

Method 1

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

– 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

0 20 40 60 80 100

Relative Humidity (%)

Amorphouscompound XCrystallinecompound X

Moisture Sorption profiles for amorphous and crystalline compound X.

Method 2

– 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

0 20 40 60 80 100

Target pp Acetone (%)

Cycle 1 Sorp

Acetone sorption profile for amorphous compound X

Method 2

0 200 400 600 800 1000 1200Time/mins

mass Target relative pressure

Change in mass profiles for a sample of X with a 4.8% amorphous content

Method 2

0 200 400 600 800 1000 1200Time/mins

mass Target relative pressure

AmorphousContent

DVS change in mass profiles for a sample of X with a 4.8% amorphous content

Method 2

– Acetone method gave an excellent linearity.

– Accounts for surface vapor uptake of crystalline material

– Does not require a high level of sample mixing homogeneity as required

by XRPD since the entire sample is analyzed.

– Requires vapor that causes crystallization of amorphous phase

Pros and ConsMethod 2

– 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

– 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

Method 3

DVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100

Target % P/Po

Crystalline Theophilline Sorption Crystalline Theophilline Desorption Amorphous Theophilline Sorption Amorphous Theophilline Desorption

Method 3DVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90

Sample RH (%)

0% Amorphous

1.1% Amorphous

10.1% Amorphous

63.6% Amorphous

100% Amorphous

Temp: 25.1 °C

Monohydrate Formation

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.

– Must form a stoichiometric hydrate/solvate during exposure to vapor

Pros and Cons

Octane adsorption on amorphous lactose and -lactose monohydrate

Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100

Target P/Po (%)

100% Crystalline Lactose 100% Amorphous

Temp: 25.0 °C

Method 4

DVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100

Target p/po (%)

100% Crystalline Lactose 2.1700% Amorphous 6.017% Amorphous 24.801% Amorphous 100% Amorphous

Temp: 25.0 °C

Octane adsorption on mixtures of amorphous lactose and -lactose monohydrate

Method 4

Effects of milling time (Ball Mill) on the

amorphous content for Lactose using Method 4

Method 4

– Octane method gave an excellent linearity.

– Accounts for surface vapor uptake of crystalline material

– Does not require solvent-induced crystallization

– Lower vapor uptakes require higher masses (100 to 150 mg)

Pros and Cons

• 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

Overview

Conclusions

Diffusion – Skin Creams

0 50 100 150 200

Time/mins

One Sided Diffusion

Experiment

V – Diffusion experiments

0 10000 20000 30000 40000 50000 60000

Sqrt(t)/d

20% RH

20% RH (fitted)

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

Polyimide films

Two Sided Diffusion

Experiment

Diffusion constant increases slightly with increasing vapour concentration

Diffusion – Thin Films

0 200 400 600 800 1000 1200 1400Time / min

20% RH 40% RH

60% RH 80% RH

Zeolite Tablet

(Moisture Getter)

Blister

Diffusion May be Dominated by Defects in the Blister Caused During Forming Process

Diffusion – Blister Pack

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

DVS Change In Mass (ref) Plot

0 100 200 300 400 500 600 700 800

Time/mins

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

Sorption/desorption cycle for a polymer film cell showing water sorption kinetics with and without zeolite in the Payne diffusion cell.

Diffusion Cell

Diffusion - Powders

y = -2.919E-03x2 + 9.067E-02x + 3.061E-02

0 2 4 6 8 10 12 14 16 18Tadj^0.5

Mt/Minf2nd order fit

2.0for 6

Pharmaceutical Powder

Activation Energy of Diffusion

Activation Energy Plot

-11.75

-11.65

-11.55

-11.45

-11.40.0031 0.0032 0.0032 0.0033 0.0033 0.0034

1/T (1/K)

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

Moisture Sorption on Membrane Films

N117 Isotherm Comparison Plot

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

Sorp 30C Desorp 30C Sorp 50C Desorp 50C Sorp 70C Desorp 70C

DVS Isotherm Comparison Plot at 30 °C

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

N117 Sorp N117 Desorp N112 Sorp N112 Desorp NR112 Sorp NR112 Desrop

Temp: 29.9 °C

DVS Isotherm Comparison Plot at 70 °C

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

N117 Sorp N117 Desorp N112 Sorp N112 Desorp NR112 Sorp NR112 Desrop

Temp: 70.0 °C

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

Moisture Sorption on Human Hair

DVS Change In Mass (ref) Plot

0 1000 2000 3000 4000 5000 6000 7000

Time/mins

The superimposed moisture sorption and desorption kinetic results for undamaged Asian(red), bleached Caucasian (blue) and undamaged Caucasian (green) hair samples at

• 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

HUMID STORAGE

SOLDERING HEAT

Electronic Devices

Coal-Based Activated Carbon

10 100Partial Pressure Methanol / %

Building Materials

Moisture sorption kinetics for two dry cement powders at 40.0 °C.

0 500 1000 1500 2000 2500Tim e/m ins

(%) Cement 1

Cement 2

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?

Adhesion is the fundamental force that drives interaction at interfaces (the effect of one component sticking to another).

“Sticking”

Wetting

Why measure surface thermodynamics?

Building Materials

Dispersive and specific surface energies of the different aggregate samples.

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

Building Materials – Natural WoodWater sorption (red) and desorption (blue) isotherms at 25 °Cmeasured on sawdust (a.) and a solid wood sample (b.)

0 10 20 30 40 50 60 70 80 90 100

Sample RH (%)

DVS Isotherm Plot

Temp: 25.0 C

0 10 20 30 40 50 60 70 80 90

Target % P/Po

DVS Isotherm Plot

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).

• 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.

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

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

Time: 14-41 File: 3 - Millbarh Timber - Sample: Millbarh Timber

Temp: 25.0 °C Meth: MRef: 28.73769

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).

Overview

Conclusions

Acetone Solvate of Carbamazepine

Acetone Vapour Sorption Kinetics for Carbamazepine

0 200 400 600 800 1000 1200 1400

Time/mins

dm - dry Target PP

VI – Organic vapours

DVS Isotherm Plot

0 10 20 30 40 50 60 70 80 90 100Acetone % P/Po

Acetone Solvate Loss

Acetone Solvate Formation

Acetone Solvate of Carbamazepine

BET - Model

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

DVS BET – Low Surface Area

DVS BET Plot

0 5 10 15 20 25 30 35

RH (%)

BET Data Line Fit

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 %

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

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 10 20 30 40 50 60 70 80 90

Target RH (%)

Cycle 1 Sorp

Analysis Results

Vm: 6.476 cm³/g

c: 6.666

Specific surface area: 208813 cm²/g

R-squared of line fit: 99.751 %

– 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

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)

Fractal Dimension

R2 = 0.9952

-1.43.9 4 4.1 4.2 4.3 4.4

ln (x-sectional area)

– 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

DVS – Spreading Pressure

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

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

DVS Instrument Training

QUESTIONS?

ADDITIONAL DISCUSSION?

Acknowledgements

Colleagues at Surface Measurement Systems

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