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Sorption technology for pharmaceutical applications
Nachal Subramanian
Surface Measurement Systems
• Surface Measurement Systems - Introduction
• Dynamic Vapour Sorption (DVS)
• Inverse gas chromatography (iGC)
Overview
Surface Measurement Systems
Surface Measurement Systems develops and engineers techniques and instrumentation for
physico-chemical characterisation of complex solids. We are the world leaders in Dynamic Vapor
Sorption technology and Inverse Gas chromatography instrumentation, providing professional world-
class scientific and technical support for our international customers.
Our range of characterization instruments continues to help solve difficult problems in the
pharmaceuticals, biomaterials, polymers, catalysts, chemical, cosmetics, building materials and food
industries, and are used by hundreds of leading laboratories and universities throughout the world.
• Surface Measurement Systems - Introduction
• Dynamic Vapour Sorption (DVS)
• Inverse gas chromatography (iGC)
Overview
Dynamic Vapour Sorption
DVS is a gravimetric technique that measures how quickly and how
much of a solvent is absorbed by a sample.
- Sample is exposed to a series of step changes in relative humidity
and the mass change is measured as a function of time.
What is DVS?
Time
Rela
tive H
um
idit
y
Weig
ht
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 Uptake/Content? i.e. how much moisture/vapour is taken up or release
• Static system - Very slow achievement of equilibrium• Longer experiment time• Large amounts of sample required (1 to 10 g) • Risk of contamination or sample loss due to manual
weighing
Jar Method (static sorption)
Comparison to traditional jar method
• Dynamic Flowing Gas System - Faster Equilibrium
• High sensitivity Ultra-Microbalance (0.1 µg resolution)
• Allows small sample to be used (1 to 10 mg)
• No risk of contamination or sample loss
• Both sorption and desorption measured
DVS (dynamic sorption)
Typical DVS data
DVS Change In Mass (dry) Plot
-5
0
5
10
15
20
25
0 2000 4000 6000 8000 10000 12000 14000
Time/mins
Ch
an
ge In
Mass (
%)
- D
ry
0
10
20
30
40
50
60
70
80
90
100
Targ
et
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): 40.5303
Drying
Sorption SorptionDesorption Desorption
First cycle Second cycle
Phase transitions - Amorphous Lactose
DVS Data
DVS Sorption Data - LACTOSE
20.5
21
21.5
22
22.5
23
23.5
0 500 1000 1500 2000 2500
Time/mins
Ma
ss
/mg
0
10
20
30
40
50
60
70
80
90
100
Ta
rge
t %
P/P
o
Mass
Target % P/Po
© Surface Measurement Systems Ltd 2008DVS - The Sorption Solution
Amorphous State Crystalline State
60% RH
Amorphous State Crystalline State
Video
Images
Raman Data
Absorption Cycle 1
0
200
400
600
800
1000
1200
1400
1600
0 500 1000 1500 2000 2500 3000 3500 4000
Raman shifts (cm-1
)
Co
un
ts
Amorphous State
Crystalline State
0% RH
40% RH
60% RH
95% RH
Applications of DVS - Examples
Glass Transition and Crystallisation
Applications of DVS - Examples
Time /mins
Ch
an
ge I
n M
as
s (
%)
-d
ry
Ta
rge
t R
H (
%)
Tg RHSurface adsorption
Glass transition
Bulk absorption & surface adsorption
Recrystallisation
Pure Sucrose Images
❑ 0% RH ❑ 32.7% RH Glass Transition
❑ 80.9% RH Crystallized ❑ 92.6% RH Deliquesced
Properties measured by DVS
DVS is a tool for thermodynamic and kinetic studies of surface and bulk properties
• Sorption Isotherms
• BET Specific Surface Area
• Phase Transitions
• Permeability and Diffusion
• Competitive (Multicomponent) Adsorption
• Kinetics information
• Heat of Sorption
• Tg RH determination
• Amorphous content determination
• Camera and Raman capability
DVS Family of Products
DVSADVENTURE
Water vapor only
20-40 °C Small footprint
10-6 Torr to Atmospheric
20-70 °C
Water + Organic Vapors
& Gases
Competitive sorption Sample preheat to 400 °C
Water only
5-85 °C
Temp stability +/-
0.1°C
Camera and Raman
Sample preheat up to
300 °C
Water + Organic Vapors &
Gases
5–85 °C
Speed of Sound Sensor
Temp stability +/- 0.1°C
Camera and Raman
Sample preheat up to 300°C
Has 2 configurations:
Standard and Advanced
5 experiments in
parallel
DVSENDEAVOUR
DVSRESOLUTION
DVSVACUUM
DVSINTRINSIC PLUS
• Surface Measurement Systems - Introduction
• Dynamic Vapour Sorption (DVS)
• Inverse gas chromatography (iGC)
Overview
Inverse Gas Chromatography
• Gas phase sorption technique.
• Focus on physicochemical studies - kinetic information and
thermodynamic quantities from sorption equilibria.
• Earlier work on catalytic materials, e.g. activated carbon,
alumina and silica.
• Powerful physico-chemical characterization tool for
powders, fibres, films, particulates, semi-solids.
• Surface Energy is the most common measured property by
iGC.** Schultz, J., Lavielle, L., and Martin, C., The role of the interface in carbon fibre epoxy composites. J. of Adhesion, 1987. 23(1): p45-60.
IGC Principles
Animation by L. Teng, Surface Measurement Systems
iGC-SEA Introduction• Gas phase injection (like Headspace) - 12 vapor
reservoirs (50 ml)
• Carrier gas is helium/nitrogen
• 2 column position oven design: 20 to 150 °C
• Background Humidity Controller
• Flame Ionization Detector (FID)
• User Friendly Control and Analysis Software
Safety Features:Hydrogen Leak & Organic Vapor
Leak Detectors
medicalmetalimplants
Carbonfiber
cotton hair granules powder
Properties measured by IGC-SEA
The IGC-SEA provides unique access to the following physico-chemical properties of a wide range of solid
materials in a controlled humidity environment:
• Dispersive and Polar Surface Energies
• Heats and Entropies of Adsorption
• Acid/Base Interactions
• BET Specific Surface Area
• Phase Transitions
• Sorption Isotherms
• Permeability, Solubility and Diffusion
• Competitive (Multicomponent) Adsorption
• Thermodynamic Work of Cohesion and Adhesion
• Surface Energy heterogeneity mapping
• Constantly extend the applications – future applications e.g. Chemisorption
Thank you!
Head Office:
Surface Measurement Systems, Ltd.
5 Wharfside, Rosemont Road
London HA0 4PE, UK
Tel: +44 (0)20 8795 9400
Fax: +44 (0)20 8795 9401
Email: info@surfacemeasurementsystems.com
United States Office:
Surface Measurement Systems, Ltd, NA
2125 28th Street SW, Suite 1
Allentown PA, 18103
Tel: +1 610 798 8299
Fax: +1 610 798 0334
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