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Application Notes |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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10 |
Direct Visualisation of Moisture Induced Morphological Transformations using the DVS - mScope
C. L. Levoguer, Surface Measurement Systems Ltd, UK.
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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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). |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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 |
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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. |
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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. |
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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. P> |
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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.
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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. |
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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.
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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Case Studies |
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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. |
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Technical Notes |
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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. |
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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. |
VGI
