Webinar: Determination of Specific Surface Area and Surface Energy analysis using iGC

Good morning and good afternoon to all our participants and welcome to today's webinar which is on the surface area determination and surface energy calculations using inverse gas chromatography. I'm Dr. Saby Ahmed, an application scientist here at Surface Measurement Systems and this webinar will present the theory and calculation process of the BET specific surface area and surface energy analysis using inverse gas chromatography and comparison with other techniques. Inverse gas chromatography can be used to measure both finite and infinite dilution experiments depending on the requirement and application. The BET specific surface area analysis is a finite dilution experiment which requires saturation to monolayer coverage of the surface with the vapor phase probe molecules and where solute to solute interactions occur. Today's presenter is Dr. Annette Condor who is the IGCSE Project Manager and product Specialist at Surface measurement systems. Since 2004, Annette has been working on gas chromatographic, GC and IGC techniques. She studied chemical engineering at the University of Nonia in Hungary where she received her MSc in Chemical Engineering accredited by British Institution of Chemical engineers and her PhD in chemistry and Environmental Science. She's published several research work in peer reviewed journals and collaborated with research groups around the world. So we'd like before we begin just like to request all our participants that during the presentation you just mute your microphones and after the presentation we'll have to take any questions. So you can either use your mic or the chat box at this time. And now I'm going to hand over to Annette.

Thank you Sabia. I hope everyone can hear me. Welcome for everyone. Good morning, good afternoon and good evening. I saw there's some attendees from Japan. Probably it's a bit late over there. Today's webinar is about determination of specific surface area and surface energy using inverse gas chromatography. So first I will just introduce the technique and I will talk about then the BT surface area analysis using IGC with an example on natural fibers and then I will go through the determination of surface energy using IGC technique and I hope we'll have time to show you an example on this as well. On a fiber IDC technique was developed in the 60s. It's mainly used to measure surface energetics of solid materials. Nevertheless, it's suitable to determine other physicochemical properties of solid materials such as adsorptionizer termination, absorption, solubility parameter and so on. IGE is specially suited to fibrose and powdery substrates, but it can be also used to other type of morphology samples like granules or some other materials like films or membranes. We also used to measure some sponge with IGC. IGC was developed in the 60s and at the beginning everyone just used analytical GC by converting it to IGC measurement. SMS is the first company and so far the only one who's producing commercial IGC system. And we call our IGC instrument Sea Surface Energy Analyzer igc. The principle of IGC is actually the reverse of the analytical gc. In case of analytical gc, the solid phase is known. And what we inject the mixture and the compounds is what we investigate actually. And during this analysis we can get quality and quantity information about the injected compounds. So this technique is a kind of separation technique. And IGC is a characterization technique technique. It's used to characterize the solid phase which is in the column. So in this case, what we investigate is the solid phase. And what we inject through this column is a known pure organic solvent. And we inject the single organic vapors through the column, which is packed with our sample. And we measure the retention time, the different organic vapors. And from this retention time, the different physical chemical properties can be determined because this retention time will indicate the interaction strength between the solid surface and the injected probe. On this slide you can see the schematic of the IGC system. Of our IGC system, the carrier gas, helium or nitrogen. The oven has two column positions and it has a special design. It's really designed for thermodynamic measurements. And the standard oven has a 2250 degrees C operating range. And our instrument is an automated injection system based on the gas phase injection, like a headspace injection. And we have a very unique and user friendly control and analyzer software with the instrument. So everything is automated and it's very to. It's very easy to operate and also to analyze the data. The instrument has features like humidity option or film cell device to measure films or plate surface properties. The humidity option, I think is one of the most unique and one of the most important benefits of our instrument. Because the impact of the relative humidity on the surface properties can be measured with this option. And it's very important to know how the humidity, how the humid environment can affect the surface energy or the surface area is there's humidity everywhere during production, during storage, or during the application of the solids. And how this humidity could affect the surface properties is important to know. Our IGCSE system has glass columns with different inner diameters, as you can see on the picture. And these are straight Stalinized glass cubes, all of them 30 centimeter long. These are non reusable columns and once you pack the column with a sample, you can use for the different type of analysis because measurement is non destructive analysis. On our YouTube channel you can watch some videos about column packing and sample preparation. If you are interested in how to pack a column with fiber or with the powder sample. With IGC technique you can determine different physical chemical properties of the solid materials and not just be specific surface area and surface energy. You can also measure the acid base interactions on the surface, the solubility parameters or the diffusion coefficients of different gases and so on. We constantly implement new applications or new features to our analysis software. So currently we are working on a chemist option application and hopefully we'll have some nice application notes on that. So first the BET specific surface area analysis of solids. I guess adsorption. To apply the BET method you have to measure gas adsorption isotherm. The gas the adsorptive can be any gas which physically absorb on the solid surface, which means a weak bond when there was forces. And also it means that at the same temperature it can desorbed from the surface. Nitrogen soption measurement carried out at 77 Kelvin. It's the boiling point of nitrogen. And nitrogen is the most suitable absorptive. But it's not standard for every industry is just the most commonly used adsorptive. There's other adsorptives which is in the ISO standard listed in the ISO standard what I referred. And you can see that organic vapors can also use to measure gas adsorption for BT method like heptane, octane or benzene and also water. The benefit of this probes that you can measure the adsorption isotherm at room temperature. Ambient condition, you don't need a liquid nitrogen condition 77 kelvin which is quite an extreme condition. Especially for organic samples or inorganic materials which are more rigid and they are not sensitive or different conditions. Probably nitrogen condition is suitable, but for organic materials ambient condition it's more recommended is at very very low temperature, some structural changes can happen in the sample. To apply the bet method there's two types of isotherm. The type 2 and 4 based on the IUPAC classification which is suitable for the BET method. And during the BET specific surface area measurements only the surface which is accessible for the probes is measured. And during the analysis at least 4 points within the relative pressure range for BET equation is required. So the BET relative pressure range is from 0.05 to 0.3 or 35. And within this relative pressure range you need minimum four points to get to fit the BET equation and to get the specific surface area. There's different techniques that you can use to measure adsorption isotorm like the volumetric technique, Volumetric nitrogen sorption technique and the dynamic vapor sorption technique also can be used to measure adsorption isothermic based on a gravimetric method. And also carrier gas method is a technique you can use to measure adsorption isotherms like igc. The benefits using IGC that the degassing is in situ and you can measure the adsorption isotherm at ambient condition and you can use organic reapers. The BET surface area can mean a very wide range. And normally nitrogen solption technique is used to measure the bed specific surface area. It's very accurate, especially at the high surface area. You see the relative standard deviation is about one or less than one, around 1,000 meter square per gram surface area. IGC can't measure that high surface area due to the pulse injection, but it's really accurate and applicable in a low surface area range. Whereas other techniques struggle a little bit and the accuracy is not that good. DBS also can be used in a quite wide range of surface area. And because during the measurements the organic vapor concentration is constant in the carrier flow. So it's very different type of measurements compared with igc. In the table you can see the measurement parameters and which kind of disruptive gas you can use and also the pressures. So to measure adsorption isotherm with IGC technique you have to inject a solvent at different concentration. And once you injected the selected adsorptive for example the octane a different concentration. You can determine the partial pressure and retention volume from the different from the series of injection and then from that plot easily. With integration, the adsorptionizer term can be determined and this adsorptionizer term can be used to determine the BT specific surface area or the sorption capacity or a Henry adsorption constant as well. We perform the validation of our IGC instrument using standard reference materials like this alpha luminar sample170, which is a reported BT surface area value 1.05 meters square per gram. During the measurements we used 500 milligram sample. The octane isotherm was determined at 30 Celsius. Before the adsorption isotherm measurements. In situ conditioning was applied at 100 degrees C for six hours. The surface area, what we determined using this Octane isotherm was 1.01, which is really close to the Reported value and the validation of the instrument contained other reference materials as well. What you can find in the application 225 if you are interested in the validation of the technique. We also performed a reproducibility study for BET specific surface area. The reliability of the instrument on surface area. During this study we used paracetamol, commercially available paracetamol from Sigma Aldrich and we packed 22 columns. Each column contained 250 milligram samples. And on the first 10 column we repeated the experiment 10 times and determined the experiment to experiment reproducibility as you can see on this slide and it was less than one or maximum two. The reproducibility the surface area of the paracetamol is very low, is less than 0.3 meter square per gram. As you can see with IGC technique we could determine very accurately this surface area. Whereas other techniques struggle to measure accurately the surface area. So IGC as you can see is very applicable at low surface area. And now I'd like to share with you some advices, some practical advices. I can set up a method in our software. So in our control software when you create a method there's two different injection options. If you have the advanced software so you can inject in surface coverage or in moles, I usually select the surface coverage injection. It's much easier to work with. And if you select also the surface coverage, then when you create the sample id, the the bet, the initial bet is to be overestimated. So like in case of this sample just created an example. So if it's a lactose monohydrate, usually lactose has around 1 meter square per gram surface area. And in case of this low surface area samples around 500mg sample or less than 500mg sample is enough. And as you see the the bet, the initial bet, what I entered is two because I definitely want to reach the the layer coverage. So I want to over saturate the surface with the probe. So that's just a practical advice. If you use the surface coverage injection, that's what you have to do to trick the system. But of course if you use the moles injection you don't need to. And then once you created the sample ID and selected the type of injection, you can create the method a series of as I mentioned, the series of injection from a probe in this case octane or you can use also heptane is to be inserted. And I usually start with the highest achievable average injection. And then I Reduce the concentration, you see. So going down to the smallest concentration and there's only just a practical reason why I choose the highest achievable surface coverage is the BET specific surface area can be determined in a specific relative pressure range. So the BET relative pressure range is from 0.05 to 0.35. So once the first injection performed in IGCSEA we can analyze it while the experiment is running. So if the first injection is in the in the highest relative pressure range of the BET relative pressure range, I leave the experiment to complete to finish is the rest of the injections will be under that point. So I will have enough data points in the in the BET pressure range to analyze the the BET specific surface area. But for example, if the first injected if the first injection is in a lower relative pressure range, so for example around 0.1 or less than 0.05, that means that probably I will not have enough data points in the BET pressure range to analyze accurately the BET specific surface area. In this case I just stopped the experiment and changed the sample ID because probably I underestimated the BET specific surface area of my sample. So using a higher BET surface area then rerun the method. Hopefully we'll get higher relative pressure points. We have a BET troubleshooting guide and it's available also in Chinese as well. So if you can contact the dance or probably have this guide help you to perform the BET experiment most accurately. And it's available also on our website. So I recommend you if you just start bet analysis with igc. This also contains a nice summary of the BET analysis. So just quickly like to show you a case study on the BT surface area analysis of some natural fibers. During this study we analyzed three different fibers. One was a cell loss fiber which you can see on the first picture on the left side it's a biomed fiber. And you can see the surface of this cellulose fiber is quite uniform. There's no defects on the surface. Also we measured another two fibers, a kina and a flex fiber. The surface of these two natural fibers wasn't that smooth and you can see there's some defects. And especially in case of the flex fiber, there's a lot of irregularities, surface irregularities. So we packed the fibers into our formulae columns and we performed the experiment three times in order to determine the relative standard deviation experiment. And you can see in case of those fibers which had a uniform smooth surface, the relative standard deviation is not that high. It's excellent. Smaller than the 1 percentage in case of the flex Fiber which was the most IRregular. We measured 3.5 roughage standard deviation. The surface roughness, as you can see, can affect the reproducibility of the result, but it still has an excellent reproducibility. Using igc then we also perform the batch to batch variability measurement. So we packed several columns and we determined the surface area of the different fibers. In case of the cellulose fiber, commercial cellulose fiber, you can see that the reproducibility is quite good. But in case of the natural fibers, the deviation is much bigger. And also again, the flex fiber showed the biggest deviation. Natural fibers contains some irregularities on the surface and they have heterogeneous properties. And it depends on a lot of different things, harvesting the growing condition and so on. So that's basically what we expected. But still the reproducibility was quite good. If you are interested more in this case study, I recommend you the publication what we wrote about this. And during this study we also investigated the adsorptive fact on the surface area. Also the flow rate effect and the sample preparation. We also chopped the fiber once and we packed the column with the chopped fibers. But normally we used a very long fiber. So I strongly recommend this publication. If you are interested interested in WT surface area, as I mentioned, yet the humidity option is quite a huge advantage of our instrument. Because we can determine the impact of the relative humidity on the surface properties. Like on the surface area, you can see that the reference material, this alpha aluminum sample surface area with the dry carrier gas. If there's no humidity, it's 2.95 which is the reported surface area area of this sample. If we apply 50% relative humidity in the carrier, you can see that the surface area now is a little bit smaller. Using 90% relative humidity, the surface area of half of the original the dry conditioned surface area. You can see that how this relative humidity affects the available surface. Because if there's humidity, water vapors will absorb on the surface by the can and will block the available site by reducing the surface area. The available surface area. Here's an example. For example, in case of cotton, how the humidity affects the surface area. And in this case you can see that the surface area is increasing because water absorbs into the cotton the filaments and increase the distance between the filaments. So there's the effect of the humidity is always depends of the sample. It's not always. There's not always a decreasing trend or an increasing trend. It depends really of the sample how it will behave under humid condition. So the next Part of my presentation is determination of surface energy using IGC technique. Surface energy is the most common measured property by in this case chromatography. And it's analogous to the surface tension of liquids. The definition also says that surface energy indicates the maximum surface tension of a liquid which read the solid under Idaho condition. And the surface energy is also used to quantify the ability of the surface to react compared with the bulk. In the bulk, atoms surrounded with other atoms and they interact with each other. But surface on the surface atoms only interact towards to the center. So some surface electrons can react with the surroundings atoms or molecules. And the willingness of these electrons to react with the surroundings shows the ability of the surface to react. Surface energy can use to determine also the work of adhesion. The thermodynamic work of adhesion and surface energy has different components. Fox was the first to express the surface energy with different components dispersive and different specific parts. So the surface energy symbol is the gamma, like the surface tension, but there is an S which indicates that it's related to solid. So the total surface energy has different components dispersive. And specifically it's also called Lewis acid base component. And this contains the chemical short range interactions. The dispersive part contains the London van der Waals forces. And the unit is the same with the surface tension. It's joule per meter square or millijoule per meter square. Surface energy and its components between two interacting surfaces are critically important in a number of industrial applications including adhesion, coating operations, printing, lubrications and so important in daily life biology as well. The knowledge of the surface and aerotics is important in formulation design of multi component systems and the prediction of processing performance. And then in case of IGC analysis we use an extended approach, the folks theory. So where is the specific part of the surface energy provided for acid and the base parameter? During the analysis we determine the dispersive part, an acid and a base component of surface energy. And from the acid and the base components we determine the specific part. So how we determine from the retention parameters the surface energy. So what we measure is the retention time of the probes. And also we use an inert gas, methane to determine the time of the system. So from the retention time and some other measurement parameters like flow rate, temperature and simpleness and the column pressure drop, we determine the retention the specific retention volume. And this specific retention volume is used to determine the Gibbs free energy. And this Gibbs free energy is the Y axis. On the plot of surface energy calculation, there's two different Methods to determine the dispersive surface energy component, both based on a series of injections of alkane normal alkanes and in case of both methods, the Gibbs free energy of the alkanes used on the Y axis and the x axis. Depending of the method, it's the carbon number or the cross sectional area and the liquid surface tension. I recommend to use the Dorset Gray, especially at elevated temperature higher than room temperature use. In this case, the surface tension of the methylene group is corrected with the measuring temperature. While in case of Schulz method, the cross sectional area and the liquid surface tension of the injected probes are measured at room temperature. So these values comes from the literature, these are literature values and these are measured at room conditions. So that's why this method is a little bit limited at room condition or ambient condition. So if you'd like to determine the dispersive surface energy, you need to inject normal alkanes. If you inject the the alkanes you can get the alkane line and from the slope of this line the dispersive surface energy can be determined. If you inject the alkanes in a series at different concentrations, you can determine the surface energy at different averages and this can be used to determine the surface energy distribution. The the energy heterogeneity of surface uniformity surface energetic valley. Once you have the alkane line and if you inject the different polar probes, the specific Gibbs free energy of polar solids can be determined which is the vertical difference between the measured polar point and the projected points on the reference line. For the specific surface energy calculation, we determine the acid and the base parameter. The extended fog story and then this incident based parameter can be used to calculate the specific part surface energy. So we determine the Gibbs the specific Gibbs free energy of dichlormatin and Delta Tate and then we can determine the specific surface energies. So two monopolar probes are needed to determine the specific surface energy. With this method, once we have all the different components of surface energy, so the lispers is acid and the base, the work of cohesion and adhesion can be calculated. These two, cohesive and adhesive energy are important in formulation design. So it's used to determine the blending performance, the uniformity of the blend. The surface energy can be measured with other techniques as well, like contact angle or atomic force microscope. In this table you can see a short summary and comparison between these techniques. If you are interested in a more detailed comparison, you can visit our website just to highlight a few differences. Between these techniques, with IGC you can measure the surface heterogeneity. With contact anchor, you actually measure just a single point, the surface where the drop is placed. Of course, if you perform that drop in the different parts of the surface, you can get a bigger picture about the surface. In case of afm, it's kind of three dimension measurements and XY and the Z is predicted. And during AFM measurement, the humidity or the temperature is not that controllable. Like in case of IGC can change temperature or the relative humidity. Reproducibility is also much better in case of IGC than contact angle or afm. And in case of IGC you can perform the experiment on the same sample. While in case of contact angle, it's really hard to perform the measurements on the same surface where you already measured the surface, the contact angle, especially if it's a powder or a sample which can absorb water. In case of powders, you use contact angle. You have to create a flat surface. So you have to compress the surface and then you put this drop on the surface, measure the angle, you see that over the time this drop will penetrate into the bond or swell into the sample. So there can be dissolution. And these are the disadvantages of this technique. So it's not really applicable on powders or rose materials. There's also several publications which highlight that for heterogeneous high energy surfaces characterized by IGC at infinite dilution solute will preferentially probe the high energy sites. And the technique will lead to surface scenario value higher than those obtained by contact angle measurement. So, which means that the surface energy measured by contact angle is lower than by igc because with IGC you can probe the high energy site and you can measure the the highest energy size. It also means that contact angle measures the surface energy at a different coverage. And of course surface energy is changing with the coverage. So for example, the dispersive surface energy value determined for conducting polymers via GC were found to be always higher than those estimated by wettability. So there's a lot of publications which already highlight that it's not easy to compare the surface energy values measured with two different techniques straight away. And it can be also different the surface energy measured with different techniques because they measure the surface energy in a different dilution, different coverage. There's other publications as well which discuss the differences between contact and gold and igc. And it was found that IGT is more accurate on rose materials and powders. Then cut rectangle during the surface energy measurements. It's really Important that you have to be in an infinite dilution as you inject the probes in infinite dilution, whereas only solute and solid material interaction occurs compared with the bet. Whereas you have to really saturate the surface by with the disruptive. So you have to above a monolayer coverage, the surface is really saturated with the with the probe the solute molecules. In case of surface energy, you don't need to. You need to be in the infinite dilution, the theoretical infinite dilution surface energy. The Gamma zero, Gamma infinite is always an extrapolated value to zero concentration. From the intercept on the plot of surface energy versus injected amount and probing with the smallest concentration of solute and getting the most data points in this infinite dilution range, whereas only solute solid interactions occur, yields a superior data fit and extrapolation to zero concentration when compared with other techniques where you can't really measure a series of concentrations. Also, real surfaces are often heterogeneous energetically. And the series of concentration in the very low solute concentration range, which reflect only the solute solid interaction, will allow to determine the degree of heterogeneity of the surface the surface energy distribution. Because real materials display structural, surface, structural and chemical heterogeneity, which in turn gives rise in their surface energetic heterogeneity. For example, structure heterogeneity can be crystal imperfections, some surface irregularities or surface pores, some chemical heterogeneities like surface contaminants, some chemical degradance on the surface and so on. So real materials often has an energetically heterogeneous surface. So with IGC technique you can determine the surface energy heterogeneity if you probe a very, very small concentration infinite dilution. So starting with the very, very small concentration, or you can go below 0.5 percentage coverage. But if you inject series of concentration from all the solvents from the different alkanes and the two monopolar probes, you can determine the surface energy. And during the analysis, what you have to always check is the regression coefficients of the alkane line and also that the polar probes should be above zero. In this case, you can see dichloromethane is around zero. It's because the retention time of the dichloromatin is very, very small. But if all the coverages are good, in this case, because dichloromatin had zero free energy, we used the chloroform to determine the surface energy distribution of this paper. And you can see the distribution graph. What you can get Directly from our software. Just one more thing I would like to mention that surface energy can also change with relative humidity. So if there's a humid environment, surface energy can change, it can decrease or sometimes also it will not change or it will increase. This example is on a cement paste. Surface energy is significantly decreased if there's around 20% or 30% relative humidity. But after that it didn't change much. So thank you for your attention and I'm happy to answer your question. Questions.

Thank you Annette for your presentation. So yeah, I would like to ask everybody if they have any questions. You can write them in the chat box or unmute your microphone. So I have one question. So what is the minimum limitation for IGC to determine VT service area? And is it possible to determine some metal powders which would be difficult to get some reproducible results with nitrogen absorption method?

Certainly yes. We did few studies on metal powders and we got a very nice result. So we can determine surface area as low as 0.05 meters square per gram. So we can go really down in the surface area range due to the pulse injection. Our instrument has a higher limit in surface area, but in lower end there's no limit. So far we haven't experienced lower limit.

Okay, thank you Annette. I have another question. So thank you for the case study for the humidity effect on surface area. And does the humidity have an impact on surface energy as well?

It does, yeah. As I showed on the last slide, surface energy can affect humidity can affect the surface energy as well. So in case of this sample cement based, you can see a decreasing trend with the relative humidity. But sometimes there's another trend. Sometimes there's just a slight difference along the relative humidity here. So you can see the the surface energy dropped significantly at a very, very small relative humidity.

Just got a comment, just saying for bet, we must be very careful to choose the appropriate amount of injected octane. So I guess how would you choose the amount of injected octane for BET foundations?

I always just start with the highest achievable coverage. I usually use the coverage injection. In that case, of course the achievable coverage range depends of the BET surface area, what you entered into the sample id. So once I enter the initial bt, just estimation that where I expect bt based on that the software will calculate the achievable range and then I start with the highest and then go down to the lowest to get the whole adsorption ice term. Sometimes yeah, if you underestimate or overestimate DBT just trying to find it so as you see here, so I start with the highest GB band and go down to make sure that we'll have enough data points in the BET range. And of course you have small relative pressure points, but then you just have to adjust the settings, the method settings, and then we rerun it. If you start with the highest available concentration after the first injection, you can modify your method. You can stop or edit the method based on that first injection. That's why I just start with the highest, so I can modify after the first injection. Yeah, sorry.

Thank you. We have one more question, so thank you for the very informative session. And for polymeric fibers which absorb alkanes, what is the best way to measure the dispersive part of surface energy?

In case of our instrument, we designed the injection that we have a target concentration what we inject. And at the end of the experiment there's an actual coverage, so we can see that is the sample really absorbed the injected probe molecules, is there chemisorption happened. So that's why we have this target and this actual coverage. Just to double check that is there any consumption or absorption of the probes into the sample. And of course if you see a significant difference between target and the axial, that can mean that maybe there's chemisorption or absorption. But you can try to increase the temperature, maybe because just temperature is not enough high, or you have to put more energy into the system to dissolve the probes. So you can try first to apply higher temperature, maybe because just the distortion is much slower, so it requires more energy. So higher temperature can help. But if high temperature will not help, then probably it's really chemical. So you have to choose another probe for the analysis, maybe to measure dispersive surface energy. There's some not very well established, but some new methods which are based on aromatic hydrocarbons instead of normal alkanes. I recommend to you to have a look at the literature, but also I can help you to find some solution to measure dispersive surface energy of this kind of samples.

Just to follow on from the question, will humidity help?

I don't think so, because with humidity you measure another effect. So I wouldn't use humidity at the beginning and just first I would like, I would try to find the best parameters to absorb and dissolve the probes and then move on to humidity. Okay, thanks.

Annette. Another question. So if I get very bad noisy peaks for ethyl acetate and I use chloroform to determine the surface energies and what are the alternative monofunctional solvents that I can use.

I mean if dietyl acetate is very noisy, I recommend to use to Lane, that might help. And yeah, you can use chloroform. That's for the other part, that's for the base part of the specific surface energy. And also dichloromatin is an alternative in case of our software. You also have opportunity to change this. So for example, if you measure the acetone surface tension parameters, the acid and the base and you wish to use acetone in the analyzer software, you can change the acetone or ethanol or any other polar probes surface tension values on screen and then you can select those probes for the surface energy calculation. So it's not limited for our recommendation. These are just the probes that we use and it's based on the literature. But of course now science improved and there's other ways to measure surface tension parameters of liquid. So if you have new values for other polar solvents, you can use them. You can enter into the analyzer software if you wish, I can contact directly with me, I can show you how you can do that and how you can use any other polar or specific service energy.

Okay, in that case I would just like to thank everybody for joining. And if you wish to know more about the DBS or IGCSEA systems or its applications, please do visit our website or attentively you can email us@scienceurfacemeasurementsystems.com thank you.