Application Notes - DVS

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Application Notes
1	Validation of Relative Humidity using Saturated Salt Solutions   C. L. Levoguer, Surface Measurement Systems Ltd, UK.   Abstract Validation of humidity generation and measurement in gravimetric vapour sorption instrumentation is an important issue for the Pharmaceutical and related industries. This application note sets out a standard DVS method for calibration of relative humidity data using saturated salt solutions.
2	Moisture Sorption of EC Standard Reference Material RM 302 on a DVS-1 instrument.   C. L. Levoguer, Surface Measurement Systems Ltd, UK. J. Booth, Scientific and Medical Ltd, UK.   Abstract Microcrystalline cellulose (RM 302) is a standard EC reference material for validation of the measurement of water sorption isotherms of food materials following the COST 90 procedure.  This procedure involves the periodic weighing of samples stored over saturated salt solutions until equilibrium is established (nominally after 7 days). The moisture content RM 302 at ten specified relative humidities  has been certified in a study between ten independent labs within the EC. The DVS-1 instrument provides many potential benefits over the COST 90 procedure for isotherm measurement including much faster equilibration times, independently validated humidity generation, and fully automated weighing of samples, thus eliminating some sources of error in the measurement. This application note therefore presents data from two independent laboratories using DVS instruments to measure water sorption isotherms on RM 302 for comparison with the COST 90 procedure.
3	Polymorphism in Spray Dried Lactose   C. L. Levoguer, Surface Measurement Systems Ltd, UK. J. Booth, Scientific and Medical Products Ltd, UK.   Abstract The presence of amorphous material in spray dried powders such as lactose monohydrate is of great interest to the pharmaceutical industry, since even small amounts can lead to significant changes in the physico-chemical properties of the material. Recently DVS has been used to estimate the amorphous content of lactose powders for amorphous contents as low as 0.125% (compared to 10% detection limit for XRD). This short application note describes the use of a DVS water sorption analyser to demonstrate the physico-chemical  behaviour of a highly amorphous lactose powder by using a rapid humidity ramping method.
4	Measuring the Vapour Pressure of Solid Pharmaceutical Compounds using a Vacuum Knudsen Cell Method   C. L. Levoguer, Surface Measurement Systems Ltd, UK. J. Booth, Scientific and Medical Products Ltd, UK.   Abstract The vapour pressure of solid pharmaceutical compounds is a physical property which affects both stability and shelf-life of a wide range of pharmaceutical products. This application note describes the use of a gravimetric Knudsen cell method to measure the vapour pressure of a solid pharmaceutical compound as a function of temperature using a modified DVS-1 vapour sorption analyser.
5	Adsorption of High Concentrations of Organic Vapours on Activated Carbon   C. L. Levoguer, Surface Measurement Systems Ltd, UK. J. Booth, Scientific and Medical Ltd, UK.   Abstract The study of adsorption of organic vapours on activated carbon substrates is of importance in many areas within the chemical industry. The adsorption characteristics of activated carbons at high solvent concentrations are particularly pertinent to environmental cleaning processes such as solvent recovery. This application note therefore describes how a standard DVS gravimetric flow adsorption system may be used to study the adsorption of organic vapours at high concentrations on activated carbons and other porous solid substrates.
6	Automated Measurement of Sorption Isotherms using a Dynamic Vacuum Method   C. L. Levoguer, Surface Measurement Systems Ltd, UK.   Abstract The study of the adsorption of vapours on porous substrates is of wide ranging importance within many sectors of the chemical industry. Standard gravimetric methods for measuring sorption isotherms are usually based on static vacuum methods, where the sample chamber is initially evacuated and then isolated from the pump before vapour is introduced into the system at the required pressure. The main limitation of this technique is that for low partial pressures of vapour, outgassing of the vacuum chamber components contributes significantly to the measured pressure and hence sorption measurements in this regime tend to be inaccurate. In this application note we describe the use of a Dynamic Vacuum Sorption instrument, which overcomes this limitation, for accurately measuring isotherms of organic vapours on activated carbons.
7	Measurement of Diffusion of Liquids and Vapours Through Real Polymer Tube Packaging Devices   C. L. Levoguer, D.R.Williams, Surface Measurement Systems Ltd, UK.   Abstract The measurement of diffusion and permeation of vapours and liquids through real packaging devices is important for the development of both pharmaceutical and food packaging solutions. Typical requirements of these packaging systems are that the ingress and/or loss of moisture over long storage periods must be kept to a minimum in order to prolong the shelf life of the product.  In recent years, the use of high resolution gravimetric flowing gas or Dynamic Vapour Sorption instrumentation has been adopted for accurate measurement of the uptake and desorption of moisture and organic vapours in pharmaceutical and food products. Surface Measurement Systems have developed a novel method for rapidly measuring the diffusion of saturated vapours through real polymer packaging systems using existing Dynamic Vapour Sorption instrumentation.
8	Moisture Sorption of Coffee Granules studied using the DVS- mScope   C. L. Levoguer, Surface Measurement Systems Ltd, UK.   Abstract The moisture sorption properties of food materials are fundamental considerations for development and enhancement of food products, since they may influence the stability and performance during processing, storage and product use. This application note describes the moisture sorption properties of coffee granules, using the combined techniques of DVS and in-situ video microscopy.
9	Measuring the Moisture Sorption Kinetics of Cements using DVS   C. L. Levoguer, Surface Measurement Systems Ltd, UK.   Abstract An important factor in the long term storage stability of cements is the rate at which moisture is taken up by the cements under specific storage conditions. Traditionally this is done by storing large containers of cement under controlled conditions and periodically weighing over many months or even years. In this application note we measure the kinetics of moisture sorption of two different cements using a rapid Dynamic Vapour Sorption (DVS) methodology.
10	Direct Visualisation of Moisture-Induced Tranformations using the DVS Video Microscope   Armando R. Garcia and Dan Burnett Surface Measurement Systems Ltd.      Abstract DVS is now established as a useful analytical tool in many R&D laboratories throughout the world. This application note describes the integration of DVS with a colour video microscope for the in-situ visualisation of moisture induced morphological transformations, which may be correlated with the gravimetric data
11	Moisture Stability of Powdered Milk Formulations   C. L. Levoguer, Surface Measurement Systems Ltd, UK. J. Booth, Scientific and Medical Products Ltd, UK.   Abstract The moisture stability of powdered milk formulations is a crucial factor in ensuring the safe storage life of such products, particularly in countries which experience prolonged periods of both high humidities and temperatures. It is desirable that these products do not contain or release unbound moisture during storage, which under certain conditions may encourage growth of microbiological organisms.
12	Absolute Measurement of Moisture Diffusion into Blister Packaging Systems   C. L. Levoguer, Surface Measurement Systems Ltd, UK. J. Booth, Scientific and Medical Products Ltd, UK.   Abstract Blister packaging systems are used as a primary barrier to the ingress of moisture into moisture sensitive products. These blister packaging systems often show substantial differences in barrier properties to the unformed polymer film due to localised defects/stresses in the polymer material as a result of the forming process. This application note describes a rapid methodology, using a DVS automated gravimetric sorption analyser, for the determination of the permeability of blister packing systems. This information may then be used to assess batch to batch quality variations, or may be used to predict product life under a wide range of storage conditions for example.
13	Moisture Sorption of Hydrophobic Pharmaceutical Substances   C. L. Levoguer, Surface Measurement Systems Ltd, UK.   Abstract DVS is commonly employed to measure the moisture sorption properties of hygroscopic pharmaceutical materials. The affinity of these materials for the sorption of moisture is often due to a degree of amorphous character present in the material. Highly crystalline materials such as salts of drugs for example, may have very low affinities for moisture sorption due to the low surface energy of the particles formed during the crystallisation process. This application note describes the measurement of moisture sorption properties on two batches of a relatively hydrophobic drug, which is expected to have a maximum moisture uptake of less than 0.1%, using a DVS-1 instrument.
14	Moisture Sorption of Activated Carbon   C.L.Levoguer, Surface Measurement Systems, UK.   Abstract Activated carbons are widely used throughout industry in a variety of applications from environmental air filtration to solvent and heavy metal recovery. The sorption of moisture by activated carbons is pertinent to many of these applications and has traditionally been measured volumetrically or by expensive vacuum gravimetric systems. This application note describes the measurement of moisture sorption on BPL activated carbon using DVS.
15	Faster Sorption Isotherms using Helium Carrier Gas   C. L. Levoguer, Surface Measurement Systems Ltd., UK. J. Booth, Scientific and Medical Products Ltd., UK.   Abstract Dynamic Vapour Sorption is now used in many R&D labs throughout the world to measure moisture sorption and desorption isotherms, providing researchers with a 10-100 fold increase in measurement time over traditional static methods. Although a typical measurement time using nitrogen carrier gas is 24 hours, very hygroscopic materials such as cellulose, or microporous materials such as activated carbons, often take 2 days or more if good establishment of equilibrium is required. In this application note we demonstrate the use of helium carrier gas to reduce the measurement time required for such materials and thus further increase productivity.
16	Calculation of Diffusion Constants in Thin Polymer Films using DVS   C. L. Levoguer, Surface Measurement Systems Ltd., UK. J. Booth, Scientific and Medical Products Ltd., UK.   Abstract Moisture diffusion in thin polymer films is of interest to a variety of different industrial sectors including packaging materials and membrane technologies. In this application note we describe the measurement of moisture diffusion coefficients in polymer thin films by measuring adsorption isotherms on the thin films in a DVS-1 instrument.
17	Measurement of the Surface Energies of Pharmaceutical  Powders using a Novel Vapour Adsorption Method   C. L. Levoguer, Surface Measurement Systems Ltd, UK.   Abstract The measurement of the surface properties of powders is of increasing importance to many industries, which depend upon powder processing or powder technology. If known, the surface energy of a powder may be used to predict a wide range of properties such as processing stability, adhesion, colloid stability, toughness, powder flow and product performance. In practice the measurement of the surface energy of powders is non-trivial and prone to potentially large errors or uncertainties despite a wide range of techniques being available. In this paper we present a novel method for determining the surface energy of powders by measuring the adsorption isotherm of organic vapours using an automated gravimetric vapour sorption analyser. This approach avoids the limitations inherent in many of the currently available methods.
18	Measuring BET Surface Areas Using Organic Probe Molecules   D. R. Willliams, C. L. Levoguer, Surface Measurement Systems   Abstract The adsorption method of Brunauer, Emmett and Teller (BET) is based on the physical adsorption of a vapour or gas onto the surface of a solid. Historically, this work has been typically undertaken using inert gases such as nitrogen, argon and krypton. For the samples to adsorb at least a monolayer of these inert species, the experimental temperatures must be close to their boiling point (i.e. 77K for nitrogen adsorption). There can be no doubting the universality or importance of the nitrogen BET method at low temperatures, however the rapid development of newer dynamic gravimetric methods for BET analysis offers interesting options compared with the traditional approach. A comparison of the two techniques is given.
19	Determining the Heat of Sorption on Organic and Inorganic Powders using DVS   Dan Burnett and Frank Thielmann, Surface Measurement Systems Ltd. John Booth, Scientific and Medical Products Ltd, Manchester, England   Abstract Dynamic Vapour Sorption (DVS) allows a simple and accurate determination of the heat of sorption for a wide range of solid-vapour systems. This paper describes heat of sorption measurements on an alumina and a crystalline lactose sample using water and 1-butanol.
20	Caking of Lemon Flavour Powdered Drink Using DVS Humidity Cycling   P. T. Attwool, Surface Measurement Systems Ltd., London, England.   Abstract The moisture sorption properties of foods are critical for their shelf-life stability.  This is especially true for powdered products which are vulnerable to either temperature or humidity shocks.  Products can cake, become sticky and collapse thus rendering them unsaleable.
21	Moisture Sorption on Tobacco of Various Origins   D. Fetsch, P. T. Attwool, D. R. Williams, Surface Measurement Systems Ltd., London, England.   Abstract The moisture sorption properties of tobacco are critical for characterisation of their drying and shelf life stability.  Tobacco is vulnerable to both temperature and humidity shocks which can occur during transport.  Once tobacco becomes wet, it can lose taste, any added flavour or even its combustibility.  Problems can also occur with very dry tobacco, which can become too fragile to be used in manufacture.
22	A Simple Shelf Life Prediction of Crackers   D. Fetsch, D. R. Williams, Surface Measurement Systems Ltd., London, England.   Abstract The moisture sorption properties of foods are critical for their shelf-life stability. This is especially true for materials like biscuits or crackers which are vulnerable to either temperature or humidity shocks. These products can take up a high amount of water, melt and collapse thus rendering them unsaleable. The aim of this work was to investigate the water sorption behaviour of cracker materials and calculate the shelf-life stability.
23	The Water Sorption Properties of Ramyun Noodles   P. T. Attwool, Surface Measurement Systems Limited, England   Abstract The measurement of water uptake in oriental noodles is vital for determining their stability and eating quality.  In many cases, excess water uptake will lead to poor texture, dissolution or even mould growth.  The Dynamic Vapour Sorption (DVS) machine permits real time measurement of the kinetics of water sorption on food materials over a wide range of relative humidities (from 0%RH to 98%RH) and temperatures (from 5°C to 50°C).  This information can be used to help in the rational design of food products.
24	Moisture Sorption on Commercial Humic Acids   D. Fetsch, P. T. Attwool, D. R. Williams, Surface Measurement Systems Ltd., London, England.   Abstract The sorption properties of Humic Acids (HA) are nowadays important, intensively studied and well established in the literature. This is especially true for some examples we are reporting here: the association of triorganotin with dissolved HA; the sorption characteristics of 241Am(III) and Eu(III) bound by Humic Substances (HS) chemically immobilised on silica gel; the phenanthrene binding and sorption to dissolved and to mineral-associated HA; the sorption of non-ionic organ solutes to HA-mineral complexes and the sorption of heavy metals by mineral-HA substances. Furthermore, HA present also play an important role in the sorption of different compounds in soils, organo-clays, kaolinite, montmorillonite and even to silica. Finally, HA are themselves sorbed onto inorganic/mineral surfaces which allow the studies of the mitigation of facilitated pollutant transport processes and of their role in contaminant binding. Nevertheless, HA sorption properties still need to be intensively studied. Surprisingly, nobody in the literature is yet studying the moisture uptake of HA or their salt forms, humate. In this work using a Dynamic Vapour Sorption (DVS) device, we studied the water sorption by HA to better understand the possible complexation of water by HA. The differences between batches and the effect of humidity perturbations were also studied and the need to use any alkali solution for dissolving HA will be discussed.
25	Moisture Sorption on Bohemian Brown Coal Humic Acids   D. Fetsch, P. T. Attwool, D. R. Williams, Surface Measurement Systems Ltd., London, England.   Abstract The water sorption properties of Humic Acids (HA) were recently studied for commercial samples. In this work using a Dynamic Vapour Sorption (DVS) device we studied the water sorption by HA of Bohemian brown coal origin to follow the possible complexation of water by HA. The effect of humidity modulations was also studied. These results will be discussed in regard to previous work.
26	Isotherm Types and Adsorption Mechanisms of Solvents on Pharmaceutical Excipients   Frank Thielmann and Daniel Burnett Surface Measurement Systems Ltd., London, England.   Abstract The interaction of organic solvents and water with pharmaceutical powders is highly important for the understanding of solvent-based processes, e.g. wet-granulation, crystallization, drying or prediction of product stability and shelf life. For these reasons information about the adsorption mechanism of these solvents on powder surfaces is required. This information can often be obtained from the shape of the vapour sorption isotherm.
27	Hygroscopicity of Japanese Green Tea Powder   P. T. Attwool, Surface Measurement Systems Ltd., England   Abstract The water uptake in food products is key to determining their stability.  In many cases, excess water uptake will lead to caking, dissolution or even mould growth.  The Dynamic Vapour Sorption (DVS) machine enables real time measurements to be undertaken of the kinetics of water sorption on food materials over a wide range of relative humidities (from 0%RH to 98%RH) and temperatures (from 5°C to 50°C).
28	Water pickup in Monosodium Glutamate   P. T. Attwool, Surface Measurement Systems, England   Abstract The water uptake in flavour delivery systems is key to their performance.  Monosodium glutamate (MSG) is widely used in hot, humid Asian countries where flavour enhancers can become extremely unstable.  The Dynamic Vapour Sorption (DVS) machine is designed to undertake real time measurements on the kinetics of water sorption of food products.  The operating relative humidity is from 0% to 98%RH and the machine can be run at any temperature between 5°C and 50°C.  This easily encompasses the standard heat and humidity conditions found in Asia and will give directions to product developers in their search for greater product stability.
29	Moisture Desorption of Creams and Calculation of Diffusion Constants   S. Reutenauer, Surface Measurement Systems Ltd, UK.   Abstract Cream formulations are widely used in a variety of applications, from cosmetics such as hand cream and suntan cream to medical uses such as antiseptic cream. The moisture content of creams and the rate of moisture loss under different conditions are important for determining factors such as the texture, the feeling on the skin and the efficacy of the cream. In this application note, we describe the measurement of moisture (and organic vapour) loss in creams using DVS and apply it to the calculation of diffusion coefficients.
30	Calculation of Diffusion Constants in a Pharmaceutical Powder using DVS   D. Burnett and F. Thielmann, Surface Measurement Systems Ltd. T. Sokoloski and R. Wilson, Glaxo Smith Kline   Abstract Water sorption experiments were performed over a range of relative humidities to elucidate bulk vapour diffusion coefficients for an amorphous pharmaceutical powder.  The activation energy of diffusion was measured by performing experiments over a series of temperatures at a constant water vapour concentration.
31	Measurement of Moisture Ingress in Microelectronics Device Packaging C. L. Levoguer, Surface Measurement Systems Ltd., UK. Abstract Moisture issues have created the need for accelerated testing of microelectronic packaging systems to prevent significant problems during manufacture or during service of the device. One of the most commonly used conditions is 85% RH and 85°C originally adopted from US military standards but now widely accepted within the industry. However nearly all the existing test protocols are semi-empirical in basis, measuring the functionality of the device as the pass or fail criteria. A deeper understanding of the fundamental moisture interaction with the packing materials is clearly needed, in order to develop a better understanding of the effect of moisture over the entire lifecycle of a microelectronic device. In this study a detailed investigation of these issues has been conducted by DVS.
32	Accelerated Moisture Sorption Measurements  by DVS Microsample Analysis J. Booth, Scientific and Medical Products Ltd. S. Reutenauer, C. L. Levoguer, Surface Measurement Systems Ltd.   Abstract A key requirement in the development of new pharmaceutical products is the screening of large numbers of candidate substances for potentially undesirable physical properties such as moisture sorption/stability. Dynamic Vapour Sorption (DVS) automated moisture sorption analysers are now widely used throughout the industry to do this, thus reducing the typical analysis times from weeks/months with static sorption methods to hours/days. Modern pharmaceutical development is driven by the need to discover new active substances and bring them to the market as quickly as possible. Therefore there is an increasing demand for even faster methods of screening the large number of candidate substances generated by the latest pharmaceutical discovery processes. This application note describes one such approach to reduce analysis times further by up to ten times by utilising the very high sensitivity of the ultra-microbalance employed in the DVS-1 instrument.
33	Impact of Protein Concentration on the Moisture-Induced Phase Transitions of Protein-Sugar Formulations   D. Burnett, F. Thielmann,Surface Measurement Systems Ltd. K. Ward, A. Ingham, Biopharma Technologies Ltd.   Abstract In the development of solid-state dosage forms of biopharmaceuticals the effect of moisture on the stability and structure have become increasingly important. This paper investigates the affects of bovine serum albumin (BSA) loading on the moisture sorption behaviour with co-lyophilised sugars.  For maltose and sucrose, increasing BSA content increased the moisture-induced crystallization humidity.  For mannitol, the water sorption results indicate a higher mannitol amorphous content is possible with higher BSA loadings.
34	A New Gravimetric Method to Calculate Low Levels of Amorphous Content   D. Burnett and F. Thielmann, Surface Measurement Systems Ltd.   Abstract A new method to quantify low amorphous contents using DVS was developed using organic vapours. The difference in sorption capacity between crystalline and amorphous phases was used to determine amorphous contents below 1%. This new method is compared with four established methods for measuring amorphous contents using gravimetric vapour sorption techniques.
35	Determining the Moisture-Induced Glass Transition in an Amorphous Pharmaceutical Material   Dan Burnett and Frank Thielmann, Surface Measurement Systems Ltd.   Abstract A new method to determine the onset relative humidity for a glass transition in an amorphous material was developed using the DVS. Water vapour can act as a plasticising agent in amorphous materials, causing a recrystallisation event below the glass transition temperature. This method calculates the threshold relative humidity for this moisture-induced glass transition at a particular temperature.
36	Investigation of Hydrate Formation and Loss Using the DVS   Dan Burnett and Frank Thielmann, Surface Measurement Systems Ltd.   Abstract Dynamic Vapour Sorption (DVS) allows the fast and accurate determination of hydrate/solvate stoichiometry for a wide range of solid-vapour systems. This paper describes hydrate loss and formation on naloxone HCl and nedocromil sodium samples
37	Hysterisis Effects in Vapour Sorption   Frank Thielmann, Surface Measurement Systems Ltd.   Abstract Hysteresis effects in vapour sorption on solid materials can have different causes. Four different mechanisms responsible for fundamental hysteresis effects are described and discussed in this paper. Although hysteresis can occur through a combination of different causes, misinterpretation occurs quite regularly in literature. For this reason it is important to analyse the hysteresis shape carefully.
38	Mesopore Size Distribution by Organic Vapour Sorption   Frank Thielmann and Daniel Burnett, Surface Measurement Systems Ltd.   Abstract Alumina samples have been investigated by organic vapour sorption. Mesoporous structures were studied and pore size distributions have been calculated based on octane adsorption experiments at ambient conditions. The results were in good agreement with standard low temperature nitrogen adsorption measurements.
39	Fuel Cell Membranes using DVS   Dan Burnett, Armando R. Garcia, and Frank Thielmann, Surface Measurement Systems Ltd.   Abstract Dynamic Vapour Sorption (DVS) allows the fast and accurate determination of water sorption isotherms and diffusion kinetics over a wide temperature and humidity range. This paper describes the water sorption behaviour on three Nafion® based fuel cell membranes.
40	Water Sorption Properties of Multi-Component Systems   Dan Burnett, Armando R. Garcia, and Frank Thielmann, Surface Measurement Systems Ltd.   Abstract Dynamic Vapour Sorption (DVS) was used to measure the water sorption isotherms of two pharmaceutical formulations and were compared to the moisture isotherms of the individual components. The first formulation was granules consisting of microcrystalline cellulose, hydroxypropylcellulose (HPC), and Lovastatin. The second mixture consisted of co-lyophilised bovine serum albumin (BSA) and mannitol.
41	Investigation of Solvate Formation and Loss Using the   Dan Burnett and Frank Thielmann, Surface Measurement Systems Ltd.    Abstract Pharmaceutical solids can often form solvated species which can affect the material’s physical and chemical stability. Dynamic Vapour Sorption (DVS) allows the fast and accurate determination of solvate stoichiometry for a range of solid-vapour systems. This paper describes acetone solvate formation of anhydrous carbamazepine and ethanol solvation of erythromycin. A 1:1 carbamazepine-acetone solvate and a 1:3 erythromycin-ethanol solvate were observed in this study.
42	Using the DVS to Investigate Moisture-Induced Crystallization   Dan Burnett and Frank Thielmann, Surface Measurement Systems Ltd. Jeff Brum and Theodore Sokoloski, GlaxoSmithKline   Abstract Numerous low molecular weight amorphous materials will revert to their more thermodynamically stable, crystalline forms if exposed to conditions above the glass transition. Crystallization rates can be affected by temperature, relative humidity, and other neighbouring materials. In particular, water vapour can have a dramatic effect on amorphous materials. Amorphous solids often absorb relatively large amounts of water vapour compared to their corresponding crystalline phases. Sorbed water can act as a plasticizing agent, thus significantly lowering the glass transition temperature below the storage temperature and cause phase transitions and lyophile collapse. Additionally, moisture sorption can lead to particle agglomeration and powder caking. Spray-dried lactose is commonly used in solid formulations and is likely to be the most commonly used (partially) amorphous material in the pharmaceutical industry. Additionally, there is an abundance of information regarding its crystallization and polymorphic forms. The degree of lactose crystallinity can affect tabletting properties, storage of micronised powders, texture, and flow properties. Therefore, understanding the crystallization behaviour of amorphous lactose is vital for the successful development, processing, and storage of formulations containing amorphous lactose. This application note investigates the crystallization kinetics and mechanism over a range of temperatures and humidities. This aim of this paper is to understand the moisture-induced crystallization of lactose on a fundamental, mechanistic basis without assuming any previously derived crystallization models.
43	Determination of Surface Energetics of Mineral Aggregates by Dynamic Vapour Sorption   Frank Thielmann, Majid Naderi and Dan Burnett Surface Measurement Systems Ltd.     Abstract The quality of asphalt depends strongly on the affinity of the mineral aggregates to the bitumen binder. This affinity is directly related to the surface energetics of the individual components. Dynamic gravimetric vapour sorption is an accurate and reliable method for the characterisation of solid powders. In the current study dispersive and specific (acid-base) contributions to the surface energy have been measured for six different mineral aggregates.
44	Determining Amorphous Contents without a Standard: Hydrate/Solvate Stoichiometry   Dan Burnett and Frank Thielmann, Surface Measurement Systems Ltd.     Abstract A method to quantify low amorphous contents using DVS was developed based on the formation of a stoichiometric hydrate or solvate. If only the amorphous phase hydrates/solvates upon exposure to the appropriate vapour, then the amorphous content of a partially amorphous material can be determined. This method does not require any amorphous standards. Theophylline hydrate formation and carbamazepine-acetone solvate formation were used as examples.
45	Investigation of Desolvation Kinetics Using the DVS   Dan Burnett and Frank Thielmann, Surface Measurement Systems Ltd. Dr. Ted Sokoloski, emeritus status The Ohio State University   Abstract The rate of salvation/desolvation for pharmaceutical solids can often affect the material’s physical and chemical stability. Dynamic Vapour Sorption (DVS) allows the fast and accurate determination of solvation/desolvation kinetics for a range of solid-vapour systems. This paper describes acetone desolvation behaviour for a 1:1 carbamazepine:aceteone solvate.
46	Combining Raman Spectroscopy with Gravimetric Vapour Sorption Analysis for Pharmaceutical Materials   Daniel J. Burnett, Duncan Pearse and Nishil Malde, Surface Measurement Systems Ltd.   Abstract Raman spectroscopy is a widely used physical characterization technique used in the pharmaceutical industry.  The combination of Raman spectroscopy and Dynamic Vapour Sorption (DVS) allows for a more complete understanding of vapour-solid interactions for pharmaceutical materials as it relates to structural properties.  This paper overviews the DVS-Raman capabilities and gives several examples.
47	Determination of True Density by Dynamic Vapour Sorption    Majid Naderi, Manaswini Acharya, Armando Garcia and Dan Burnett Surface Measurement Systems Ltd.   Abstract The versatility and impact of Dynamic Vapour Sorption (DVS) for the true density measurements of solid powder materials have been investigated. True density measurements on different amounts of Lactose and Avicel (microcrystalline cellulose) samples were successfully determined using DVS and a gas Pycnometer for comparison.
48	Vapour Pressure Measurement of Pesticides using the DVS Knudsen method   Peng Miao and Majid Naderi, Surface Measurement System Ltd   Abstract The vapour pressure of solid materials can be useful in predicting thermodynamic stability.  The DVS-vacuum instrument allows for reliable determination of solid vapour pressures and enthalpies of vaporisation.  This note describes this technique and uses two pesticides (bifenthrin and quinclorac) as examples.  DVS-vacuum results are compared to literature values.
49	Measuring Water Vapor Flux Across Model Proton Exchange Membranes     Daniel J. Burnett and Armando R. Garcia, Surface Measurement Systems Ltd.   Abstract Water content and flux are important properties for proton exchange membrane fuel cell performance. This application note describes the use of a novel cell to measure vapour flux or permeation rates across polymer films. Nafion® membranes were used as model membranes. Water vapour flux measurements were performed at three temperatures for three Nafion® membranes.
50	The Use of Flow or Vacuum Methods for Gravimetric Water Sorption Characterisation of Pharmaceutical Materials   Daryl R. Williams, Surface Measurment Systems Ltd., UK.   Abstract A common question asked by many potential users of gravimetric instrument systems is whether they should use an ambient flowing gas method or a traditional vacuum method.
51	Gas Capture and Vapour Separation by Microporous Materials   Peng Miao, Majid Naderi, Dan Burnett, Manaswini Acharya and Jiyi Khoo Surface Measurement Systems Ltd.   Abstract Metal Organic Frameworks (MOFS) as well as inorganic solids are of great importance due to their high adsorption capacity and surface reactivity and are used for various applications. Dynamic vapour sorption (DVS) methods have been a very useful tool for the characterization of these properties using water and organic vapours at process relevant temperatures.
52	Vapour Permeability of Porous Materials using Payne Diffusion Cell   Jiyi Khoo1, Armando R. Garcia1, Dan Burnett1, Haydar Abdalghafor2, Majella E. Lane2, Sandra Van Vlierberghe3, Ana dos Santos3, Veerle Boterberg3 and Peter Dubruel3   Surface Measurement Systems Ltd. Department of Pharmaceutics, The School of Pharmacy, University of London, Brunswick Square, London WC1N 1AX, UK. Polymer Chemistry & Biomaterials Group, Department of Organic Chemistry, Ghent University, Krijgslaan 281, S-4, B-9000 Ghent, Belgium.   Abstract Vapour permeability in porous materials is of interest to a variety of different industrial sectors including packaging materials, membrane technologies, tissue engineering scaffolds etc. This application note describes the measurement of moisture vapour transmission rates (MVTR) through porous materials (i.e. silicone membranes/human skin and electrospun polymer fibre mats), using a Payne type diffusion cell and DVS instrument.
53	Moisture Sorption and Pore Collapse of Coals   Armando R. Garcia and Dan Burnett Surface Measurement Systems Ltd.   Abstract   Porosity is a common characteristic of many natural and man-made systems.  The pores in these systems can have significant impact on the way materials behave and react to conditions in the environment.  Coals are known to be porous in nature.  This application note investigates the moisture sorption properties and pore collapse of different coal samples.
54	Detecting and Modelling Porosity in Natural and Engineered Materials   Armando R. Garcia and Dan Burnett Surface Measurement Systems Ltd.     Abstract   Porosity is a common characteristic of many natural and man-made systems.  The pores in these systems can have a significant impact on the way materials behave and react to conditions in the environment.  Dynamic Vapour Sorption (DVS) can be a valuable technique in detecting and characterizing porosity in these systems.
55	Measurement of Moisture Uptake Capacity in Human Hair Using Dynamic Vapour Sorption Technique   Majid Naderi, Jiyi Khoo, Manaswini Acharya, Armando Garcia and Dan Burnett Surface Measurement Systems Ltd.   Abstract Dynamic Vapour sorption(DVS) was used to investigate the water sorption performance of three types of human hair classified as; Asian(Undamaged), Caucasian (undamaged), and bleached Caucasian damaged hair.
56	Measuring TEWL or Moisture Flux Across Artificial Skin   Armando R. Garcia, Jiyi Khoo and Dan Burnett Surface Measurement Systems Ltd.   Abstract The measurement of water flux through human skin is important in the cosmetics and pharmaceutical industries. It plays an important role in the evaluation of treatments for skin injuries and diseases. In this note we demonstrate how to measure this quantity using the DVS line of instruments and a Payne type diffusion cell.
57	Characterisation of Wheat Straw for Bio-fuel Application   Peng Miao, Majid Naderi, Manaswini Acharya, Dan Burnett and Daryl Williams Surface Measurement Systems Ltd. Thian Hong Ng and Jim Song School of Engineering, Brunel University   Abstract Biomass, such as wheat straw is an abundant and inexpensive natural biopolymer rich in cellulose and hemicellulose [1] which can be converted into bio-fuel. The bio-fuel has been attracting attention due to the future potential shortages of fossil fuel [2,3]. One of the crucial steps of producing bio-ethanol from wheat straw is its pre-treatment which should facilitate the economic feasibility and yield efficient conversion into biofuel. This pre-treatment is expected to increase the accessible chemical sites of the straw to increase convertibility in subsequent hydrolysis and fermentation steps. Dynamic Vapour Sorption (DVS) [4] and UV were used to assess the wheat straw pre-treatment and sugar yield, respectively.
101	The Characterisation of Pharmaceutical Materials by Dynamic Vapour   Carl L. Levoguer and Daryl R. Williams, Surface Measurement Systems Ltd.   Abstract The water vapour or moisture sorption properties of pharmaceutical materials such as excipients, drug formulations and packaging films are recognised as critical factors in determining their storage, stability, processing and application performance.
102	Moisture Sorption Properties of Food Products and Packaging Materials Studied by   Carl L. Levoguer and Daryl R. Williams, Surface Measurement Systems Ltd.   Abstract The moisture sorption properties of food products are recognised as critical factors in determining their storage, stability, processing and application performance.
103	Organic Solvent Sorption using a Dynamic Vapour Sorption Instrument-an   Dan Burnett and Frank Thielmann, Surface Measurement Systems Ltd.   Abstract Dynamic Vapour Sorption (DVS) has long been used for investigating the interaction of water vapour with solid materials. However, the versatility and impact of DVS can be greatly expanded by also studying organic vapour sorption phenomena. This overview application note summarises several examples of using organic vapours with the DVS: solvate formation, amorphous contents, BET surface areas, porosity, and surface energies.
104	Vapour Pressure Measurement of Pesticides using the DVS Knudsen method   Peng Miao and Majid Naderi, Surface Measurement System Ltd   Abstract The vapour pressure solid materials can be useful in predicting thermodynamic stability.  The DVS-vacuum instrument allows for reliable determination of solid vapour pressures and enthalpies of vaporisation.  This note describes this technique and uses two pesticides (bifenthrin and quinclorac) as examples.  DVS-vacuum results are compared to literature values.
Case Studies
602	Investigation of the acid-base properties of an MCM-supported Ruthenium oxide catalyst by Inverse Gas Chromatography and Dynamic Gravimetric Vapour Sorption   Frank Thielmann, Majid Naderi, Dan Burnett, Helen Jervis, Surface Measurement Systems Ltd.   Abstract Thermodynamic parameters of catalysts are highly relevant for practical applications. In particular, surface energies and acid-base properties of catalysts are of high interest since they reflect properties of active sites involved in the catalytic process and the initial adsorption step. Dynamic vapour phase techniques are interesting tools for the determination of these properties. When compared to standard wettability experiments, they provide two main benefits. They can easily and reproducibly be applied to powders and a wide variety of probe molecules can be selected. In the current study dynamic gravimetric vapour sorption (DVS) and inverse gas chromatography (IGC) have been used to characterise the energetic and acid-base properties of a calcined ruthenium oxide / MCM41 catalyst as well as the corresponding MCM41 support.
603	Correlating Drug-Binder Adhesive Strengths Measured using Inverse Gas Chromatography with Tablet Performance   Frank Thielmann1, Daniel Burnett2, Kate Lusvardi3, and Thomas Durig3 1Surface Measurement Systems Ltd, UK 2Surface Measurement Systems, Ltd, USA 3Aqualon Division, Hercules Incorporated, USA   Abstract Drug-binder interactions have a significant impact on wet-granulation behaviour and product performance. Such interaction can be described by the work of adhesion between drug and binder. In this study, the work of adhesion is calculated from surface energy measurements carried out on the individual components by Inverse Gas Chromatography. The drugs Acetaminophen and Ibuprofen have been studied as well as the binders HPC, HPMC and PVP. HPC showed the strongest adhesion, followed by HPMC and PVP. This correlated well with the trends in tablet hardness and friability. The higher the work of adhesion the higher the tablet strength and the lower the friability.
604	Determination of Carbon Fibre-Polymer Interactions by Inverse Gas Chromatography   Frank Thielmann1, Daniel Burnett2, Alexander Bismark3 1Surface Measurement Systems Ltd, UK 2Surface Measurement Systems, Ltd, USA 3Department of Chemical Engineering, Imperial College, UK   Abstract The interaction between carbon fibres with different surface treatments and thermoplastic polymer matrices were investigated through thermodynamic, work of adhesion calculations and mechanical, practical adhesion measurements. The work of adhesion between the various carbon fibres and polymers were determined by measuring the dispersive and specific surface energetics of the individual components using Inverse Gas Chromatography (IGC). The mechanical adhesion measurements were performed by measuring the interfacial shear stress of the carbon fibre embedded in the polymer through single fibre pull-out testing. Oxidation of the PAN-based carbon fibres investigated caused an increase in the dispersive surface energy and a decrease in basicity. Work of adhesion values calculated from the surface energetics correlated well with the interfacial shear strength values of the composites. For all types of polymers used in this study there was an increase in both the work of adhesion and shear strength values on oxidation of the carbon fibre. Sizing does not significantly increase the shear strength despite a higher work of adhesion value, which may be caused by incompatibility of the polymers and epoxy-based sizing agent.
605	The effect of primary particle surface energy on agglomeration rate in fluidised bed wet   F. Thielmann1, M. Naderi1, M. Acharya1, M. Ansari2, F. Stepanek2 1Surface Measurement Systems, Ltd., London 2Department of Chemical Engineering, Imperial College London UK   Abstract The effect of primary particle surface wettability by a binder solution on the rate of agglomeration in a fluid-bed top-spray granulation process was investigated. A model system consisting of hydrophilic and hydrophobic spherical primary particles with a narrow size distribution, and an aqueous solution of hydroxy propyl-cellulose (HPC) as binder, was used. The surface energy of the primary particles was measured by inverse gas chromatography (IGC) and their wettability was characterised by contact angle experiments. Granulation was carried out in a desktop fluid-bed granulator and the resulting granule size distribution and granule microstructure were analysed. The hydrophobic particles gave a wider granule size distribution (larger maximum granule size) than hydrophilic ones under otherwise identical conditions, and the granules were notably rounder and more compact. SEM analysis of granule microstructure revealed that the hydrophilic particles were coated by the binder solution while all of the binder was found to form solid bridges for the hydrophobic primary particles. This behaviour suggests that the surface energy of the starting materials affects the outcome of the granulation significantly.
606	Correlating Surface Energies to Adhesion Data for Thermoplastic Polyolefins via Inverse Gas Chromatography   Daniel Burnett1), Frank Thielmann2), Rose A. Ryntz3) 1) Surface Measurement Systems, 2222 South 12th Street, Suite D, Allentown, PA 18103, USA 2) Surface Measurement Systems UK, 5 Wharfside, Rosemount Road, London HA0 4PE, UK 3) Visteon Corporation, 401 Southfield, Dearborn, MI 48120, USA   Abstract Polyolefins are used over a wide range of industries due to their low cost and adaptable mechanical properties. However, their low surface energy makes fabricating composites and applying coatings challenging. Therefore, various surface treatments have been utilized to enhance their adhesion properties. In this paper, the surface energies of various thermoplastic polyolefins (TPO) have been measured via Inverse Gas Chromatography (IGC). These surface energy values were correlated to mechanical adhesion testing of the painted polyolefins. The adhesive integrity of the painted TPO was determined by applying a comprehensive-shear load to the material. Higher surface energies measured by IGC lead to increased adhesion with the paint. The surface energies also correlate with TPO crystallinity, as determined by microhardness testing of the unpainted TPO.
607	Surface Energy and Water Sorption Characterization of Fuel Cell Components at Different Relative Humidity Conditions   Daniel Burnett1, Frank Thielmann1, David Wood2, Yu Seung Kim2 1 Surface Measurement Systems 2 Los Alamos National Laboratory, Los Alamos, NM   Abstract The research of fuel cells as alternative power generators is growing significantly. The humidity of the feed stream is vital to the performance of proton exchange membrane fuel cells. Also, the surface energies of fuel cell components is related to electro-osmotic drag, back diffusion of water, and water retention. In this paper, the surface energies of different fuel cell components have been measured via Inverse Gas Chromatography (IGC) over a range of relative humidities. Additionally, the water sorption isotherms have been determined using Dynamic Vapour Sorption (DVS).
608	Characterizing Disorder in Pharmaceutical Materials by Vapor Sorption Techniques   Daniel J. Burnett, Majid Naderi, Manaswini Acharya, and Armando R. Garcia; Surface Measurement Systems   Abstract The thermodynamic stability of pharmaceutical materials affects all levels of formulation, process development and storage.  Thermodynamic instability can range from highly ordered crystals with different polymorphs or solvates to completely amorphous materials.  Vapor sorption techniques like Dynamic Vapor Sorption and Inverse Gas Chromatography are powerful tools in the identification and characterization of these materials.
609	Comparing Surface Energy/Thermodynamic Adhesion Values with Mechanical Performance in Nanocomposites   Daniel J. Burnett and Armando R. Garcia; Surface Measurement Systems Aline Granier, Bastien Pellegrin and Tinh Nguyen; National Institute of Standards and Technology   Abstract Ultimate composite strength is highly dependent on interfacial interactions between the filler material and matrix.  Nanomaterials are getting continued interest as reinforcement materials in composite systems.  The surface energy values for several nanomaterials were measured by Inverse Gas Chromatography (IGC).  In this study, the surface energy values were used to determine the thermodynamic works of adhesion and compared with the mechanical performance of the different nanofiller-polyurethane composites.
610	Correlating Mixing Properties of Model Excipient-API Blends to Spreading Coefficients Determined via Inverse Gas Chromatography   Daniel J. Burnett, Majid Naderi and Manaswini Acharya; Surface Measurement Systems Nathanial Catron and Connie Skoug; Abbott Laboratories   Abstract Blend stability of dry powder mixtures is important for optimizing pharmaceutical processing and formulation.  The spreading coefficient is a term used to predict blend quality based on individual component surface energy values.  In this study, Inverse Gas Chromatography (IGC) was used to measure surface energy values for model drugs and excipients.  The surface energy values were then used to determine the drug-excipient spreading coefficients.  Finally, the spreading coefficients were compared to physical mixing performance.
611	Use of surface energy distributions to relate the effect of surface modification to powder flow properties   Jiyi Khoo1, Majid Naderi1, Dan Burnett2, Tim Freeman3 and Brian Armstrong3 1Surface Measurement Systems Ltd., Alperton, Middlesex HA0 4PE, UK 2Surface Measurement Systems Ltd., Allentown PA 18103, USA 3Freeman Technology, Tewkesbury, Gloucestershire GL20 8DN, UK   Abstract Surface energy is a useful parameter describing the energetic properties of the surface of a solid sample. It can be determined in a fast and accurate way by iGC SEA. This paper describes measurement of surface energy heterogeneity of D-mannitol, relating surface chemical modification to flow properties of bulk particles.
612	Correlating Surface Energy Heterogeneity Measured by Inverse Gas Chromatography to Surface Cleaning Processes   Jiyi Khoo, Majid Naderi and Dan Burnett Surface Measurement Systems, Ltd.   Abstract Physical and chemical properties of a solid surface are known to influence the extent of microbial adhesion. However, the specific surface properties governing microbial contamination have yet to be fully understood. It is of great importance to identify the changes in surface energy and surface chemistry of a solid material if any surface cleaning methods are to be made more effective. This study investigates the effects of chemical cleaning processes on surface energy heterogeneity of metallic and polymeric surfaces, using a uniquely designed SEA Film Cell accessory.
613	Surface Energy Distributions and the Dissolution Rate of Aspirin   Daniel J. Burnett1, Armando R. Garcia1, Jiyi Khoo1, George D. Wang2, Jerry Y.Y. Heng2 1 Surface Measurement Systems Ltd. 2 Department of Chemical Engineering, Imperial College London.   Abstract Surface properties of crystalline solids have been shown to be anisotropic. Milling of crystals may lead to formation of amorphous state and/or exposure of new crystalline planes, resulting in particles with different surface energetics. This study uses Inverse Gas Chromatography (IGC) to relate the dissolution rates of milled and unmilled aspirin crystals as a function of surface energetics.
614	Effect of Processing Route on the Physical Properties of Amorphous Indomethacin   Jiyi Khoo1, Daniel J. Burnett1, Majid Naderi1, George D. Wang2 and Jerry Y.Y. Heng2   1 Surface Measurement Systems Ltd. 2 Department of Chemical Engineering, Imperial College London.   Abstract The aim of this case study was to investigate the effect of processing routes on material surface properties as a function of surface energetics. Inverse Gas Chromatography (IGC) was employed for determination of surface energy distributions and surface acid-base properties of crystalline, milled and amorphous Indomethacin samples.
615	In-situ Monitoring of a Moisture-Induced Polymorphic Transition using Raman Spectroscopy and Gravimetric Vapor Sorption   Majid Naderi, Jiyi Khoo, Manaswini Acharya and Dan Burnett Surface Measurement Systems Ltd.     Abstract   Raman-vapor sorption experiments have previously been reported, but in this study a unique combination of a fiber optic Raman probe with Dynamic gravimetric Vapor Sorption (DVS) has been used to monitor the real-time transformation of δ D-mannitol (delta form) to b D-mannitol (beta form).
616	Determination of Surface Properties of Human Hair by Inverse Gas Chromatography and Dynamic Vapour Sorption   Majid Naderi, Jiyi Khoo, Manaswini Acharya and Dan Burnett Surface Measurement Systems Ltd.   Abstract This paper describes the application of Inverse Gas Chromatography Surface Energy Analyzer (iGC SEA) to determine the surface energetic heterogeneity of three human hair samples; caucasian virgin (undamaged), thermally damaged (70°C) and chemically damaged (bleaching) hairs. Dynamic Vapour Sorption (DVS) was used to investigate the water sorption performance of the hair samples.
Technical Notes
701	Measuring water evaporation rates as a function of relative humidity and total flow   S. Reutenauer, Surface Measurement Systems Ltd.   Abstract In this technical note, the evaporation rate of pure water under different relative humidity and different total flow conditions has been determined. The aim is to demonstrate the performance and accuracy of the DVS, to show the effectiveness of the dynamic feature of the DVS in the fast sample drying rates and to bring some answers to competitive sorption/desorption processes.
702	Preventing and Eliminating Static Electricity During DVS Experiments   Armando R. Garcia, Surface Measurement Systems Ltd.   Abstract Static build-up in research samples is a common problem when performing DVS experiments. This technical note addresses this issue and techniques for recognizing and avoiding the same. Some examples of static build-up are shown so that users may be better able to recognize it when it is present in their system.
703	The Effect of Solvent Level on RH Generation in Dynamic Vapour Sorption    Armando R. Garcia, Surface Measurement Systems Ltd.   Abstract The question of RH generation accuracy versus solvent level for a typical DVS instrument is investigated. Experimental data is shown which indicates that the effect of solvent level is within the humidity generation specifications of the instrument at 25 oC and 40 oC, in the range of 50ml to 200ml for a 250ml solvent reservoir.

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