Research by homechemist Open source environmental science research at Public Lab Homemade Raman spectrometer homechemist Wed, 16 Aug 2017 20:32:13 +0000 <p>Raman spectroscopy is a very powerful analytical technique that can be used for the <strong>identification of almost any sample</strong> .Unfortunately , commercial raman spectrometers are quite expensive so i have decided to make a "<strong>cheap</strong>" and <strong>fully functional</strong> <strong>raman spectrometer</strong></p> <p>**<br/> **</p> <p>**All the details are in the following video: ****<a href=""></a> ****<br/> **</p> <p>**<br/> **</p> <p><strong>Enjoy it !<img src="" title="ramanmini2.jpg" alt="image description" /></strong><img src="" title="raman_spectrometer.jpg" alt="image description" /><img src="" title="Toluene_1.jpg" alt="image description" /></p> <p>Image shows the raman spectrum of toluene</p> The importance of infrared radiation:INFRARED SPECTROSCOPY homechemist Fri, 12 Jun 2015 18:19:50 +0000 <h4>What I want to do</h4> <p>As we Know ,Spectroscopy is a very powerful technique for analytical chemistry, it help us to understand how light interacts with a certain compound or element allowing us to identify it, there are several types of spectroscopy, the most common one is visible spectroscopy which allows us to analyze in the visible range, (from 400-700 nm) this is good specially for colorimetric analysis and determination of the amount of analyte in solution, for element detection or specific compounds which emits/absorbs in visible light.., but one of the most important types of spectroscopy is infrared spectroscopy which works in the infrared region, infrared light is associated with vibrations, that’s why we usually associated infrared light with heat(thermal motion) , so let's go farther and lets imagine a molecule as a spring, this molecule is able to vibrate among the different bonds between atoms, some bonds are able to rotate , while others cannot depending on the electronic overlapping of the atoms that are bond to form the molecule, so let´s consider a vibration of atoms with respect to a certain bond, if a pulse of infrared radiation reaches the compound this vibration can be absorbed producing great variations on the infrared spectrum of the compound so we can conclude that infrared light is as a consequence the most cheap and non destructive analytical method that we can use to detect functional groups, and consequently to detect the presence of organic molecules among other analytes.The problem is that infrared spectroscopy instruments are extremely expensive , so the aim of this note would be to develop a powerfull but cheap spectroscope in order to be able to detect more infrared radiation than what we can detect with nowaday´s spectroscopes.</p> <h3>My attempt and results</h3> <p>As an example I want to show you two different solutions shown bellow, they are complete different from the chemical composition point of view, as you can see both interacts with the light in the same way in the visible range(both are blue). That´s meaning that they interact with photons in the visible range exactly in the same way, and as a consequence at our eyes they seem to be almost the same solution, so with visible spectroscopy we cannot notice any difference at all.</p> <p><a href=""><img src="" alt="testcolor.JPG" /></a></p> <p>Let´s see now, the same solutions but with a near infrared camera which is able to see from 700-1000nm , a range that our eyes cannot see</p> <p><a href=""><img src="" alt="testbn.jpg" /></a></p> <p>As we can notice, one of the solution is black under the infrared , while the other is colorless, that´s indicating us that one solution is absorbing all the infrared light that is coming to the test tube and additional vibrations are produced, however the other solution cannot absorb the infrared radiation at this range so all of the photons between 700-1000 nm can pass trough it without been absorbed , remember that a photon is absorbed if its energy coincides with the difference in energy between two energetic levels involved in the electronic transition. In fact, the solution on the right is simply an aqueous solution of an organic dye, while the solution in the left is also an aqueous solution but in this case of an inorganic slat, cooper sulfate penta hydrated, when cooper sulfate is dissolved in water , it dissociates into Cu 2 + ions as well as sulfate ions, then the cation gets solvated and it´s surrounded by water molecules , this is what makes the solution blue, however cooper is a metal , and metallic solutions tend to block infrared light , that´s why it seem black under the infrared cam, while the other solution is colorless.</p> <p>From a more technical point of view, the spectrum obtained for the transmitted light that passed through the solution is the following.</p> <p><a href=""><img src="" alt="comparacion_sulfato_de_cobre_azul_de_metileno.jpg" /></a></p> <p>Blue plot represents the transmitted light of the solution that contains a blue dye</p> <p>Red plot represents s the transmitted light of the solution that contains the copper sulfate aqueous solution.</p> <p>As we can see form the picture both solutions interact with electromagnetic radiation in the same way in the visible range that´s why at our eyes they seem exactly the same solution, However above 700 nm more or less the cooper sulfate solution absorbs almost all the light in the infrared region , while the other solution transmitted almost all the radiation coming out from the bulb. That´s why infrared is so important for detection of functional groups.</p> <p>The work range of this very simple device that I have designed is okay, but is not large enough to detect most of the functional groups present , the idea is to start a project to try to go farther and be able to look at lower frequencies, so we would be able to detect in the infrared range much more contaminants and chemicals in solution , than what we can do nowadays, It would be a nice idea a collaboration in between the spectroscopy and the infrared cam projects to try to achieve a camera able to detect more infrared light than what at the moment our cams are able to see.</p> <p>As another example which for me is more interesting is the result that I have obtained when comparing chloroform and water, both are completely colorless, and in fact they behave almost equal at any wavelength, but I could notice a small difference in the infrared region.</p> <p><a href=""><img src="" alt="comparacion_agua_cloroformo.jpg" /></a></p> <p>If we magnify the infrared region we can even appreciate it better</p> <p><a href=""><img src="" alt="ampli_1.jpg" /></a></p> <p>This small difference would be enough to detect the presence of dangerous solvents in solution or other organic solvents , which would be very hard to identify with any other conventional technique</p> <h3>Questions and next steps</h3> <p>As future projects related with this one I would like to contribute with this research looking for more variations on the near infrared spectrum, of several compounds that I have available such as ketones , alcohols, esters and aldehydes and then compare it with the reference ( water) to try to stay if there is a significance difference in the spectrum or not in order to be able to detect a certain functional group in our problem solution.</p> <p>It would be very nice as I have said a collaboration between the infrared cam project and the spectroscopy one to contribute to the design of a more sensitive instrument able to detect wider region of the infrared spectrum.</p> <p>If you have any suggestion , comment or question please send me a comment or get in contact with me</p> Homemade Colorimeter (determine the concentration of a sample) homechemist Mon, 04 Aug 2014 17:44:32 +0000 <h2>What i want to do?</h2> <p>The aim of this project is to develop a simple but accurate gadget for the determination of a sample´s concentration. This instrument uses the optical interaction of the molecules with a source of light for determine the concentration of a sample. Design and how does it work? So , the construction and design is very simple, as I show in the following picture:</p> <p><a href=""><img src="" alt="fotometro.jpg" /></a></p> <p>It consists in the following parts: Firstly, a light source , which consists in 3 primary LED diode (green, yellow and blue)and an additional one which is a multirange LED, which means that generates all the colors in a sequence , starting by red and finishing by blue , so this is use for scanning the full visible spectra. The leds are connected to a 3 v battery, this is no shown in the picture. Then , there is a small hole which is used as a support for holding the test tube that contents our sample. And finally immediately next to the test tube there is a photoelectric cell which turns light in to electric current , this cell is also connected to a small voltmeter which allows us to measure the voltage generated by the cell as a consequence of the non absorbed light.</p> <h2>So,how does it work?</h2> <p>Firstly the leds generate a continuous source of light of a determine wavelength range ,this light travels trough the chamber and gets the test tube, there the electromagnetic radiation interacts with the molecules of our sample , after that the molecules have absorbed part of the light emitted by the LED, the rest of the light leaves the test tube and impacts against the photoelectric cell, when that photons impact against the surface of the cell some electrons are released from the surface generating an electric current , which travels by the wires and finally, they get the multimeter(voltmeter), this apparatus has a small cooper coil designed for electric measurements called(galvanometer cell) when the electrons flow pass trough this small piece an electromagnetic force is generated, this is shown in the screen of the voltmeter as a measurement in volts. Is very important to choose the right light source color , which has to be the opposite of the sample´s color , for example if we want to determine the concentration of a cooper sulfate hydrate solution we have to use a red light source ,as the solution has an intense blue color, this means that the sample stuff absorb most of the visible light except the blue one. The right light color for a sample is shown in the next picture:</p> <p><a href=""><img src="" alt="rueda.jpg" /></a></p> <p>So , the idea is that the voltage generated by the cell is related with the amount of light non absorbed by the solution (trasmitance) so, as we increase the concentration of our sample , less voltage should be generated. This idea is very simple and it is actually one of the principal techniques used for determine the concentration of a sample, the modern instruments that are used for this propose are called colorimeters and are similar to the one I have designed but instead of a photoelectric cell they used a photoresistence and a diffraction grating as the way to choose their wavelength. The physical fundaments of this apparatus are two: The Einstein Photoelectric effect and The Beer-Lambert ´s law, I am not going to talk about them more because they are related with quantum physics and ,for me, it is quite difficult to explain them in a foreign language.</p> <h2>Calibration , sample preparation and analytical treatment</h2> <p>This is probably the most important part of the project Calibration: is important to know that each compound has an specific calibration, so for example if we want to determine the concentration of a solution of a compound A we have to calibrate the apparatus for this compound , if the sample is of a compound B we have to calibrate again the apparatus even both solution has the same color, as different compounds behave different with the light even we could think that they are quite similar. The calibration is very simple ,firstly you select the “color” you are going to use, for example the blue light, then you fill the test tube with your solvent(I use water) and you measure the voltage of the solvent (this is called a blank) , after that ,you prepare several solutions with different concentration of the compound ( I recommend to do around 20 different solutions) and finally you measure the values for each solution. Once you have done this , the next step is to do an analytical treatment of the data, you can use a software like excel for data treatment, you only have to find a function(mathematical formula) which establishs a relation between the volts and the concentration(I found that cubic functions works perfectly) once you have done this you have successfully calibrated the apparatus .And now you can determine with a lot of accuracy the concentration of a sample.</p> <h3>My attempt and results</h3> <p>Results I have test the apparatus with cooper sulfate pentahydrate ,which as you can see in the following picture ,absorbs significant amounts of red light, so I used as a light source the red light (which emits light of around 590-650 nm)</p> <p><a href=""><img src="" alt="graf.jpg" /></a></p> <p>For the calibration I prepared around 20 solutions (5 ml each) which allows me to calibrate the apparatus with a lot of accuracy Here I show you the data I obtained after the calibration:</p> <p><a href=""><img src="" alt="tabla.jpg" /></a></p> <p>The results, were treated with Excel software , after the treatment I obtained the following relation between concentration and voltage:</p> <p><a href=""><img src="" alt="excel.jpg" /></a></p> <p>I found that cubic function is just perfect for my apparatus (this depends on the photoelectric cell and its efficiency),as you can see the relation is very good and the error made by the apparatus is very small, which means it is very accurate.</p> <h3>Why I'm interested</h3> <p>Well , firstly I have to said that I decided to work in the developing of this apparatus because is more accurate and sensitive than the optic based one (using a spectrometer).And it has several uses, for example it can determine the concentration of proteins in a solution (using the biuret reaction) , we will also be able to determine the amount of free chlorine (a toxic chemical) on water by adding to the samples a reagent called Orthotolidine , or even determine the quantity of metals in solutions or contaminants by developing color-based detection techniques, so this could help us in the detection of some oil contamination or toxic chemicals in water or ground.</p> <h2>Interesting aplications</h2> <p>As i have said before , color-based detecting method is very important, so i have decided to show you some examples of detection techniques which allows us to determine its concentration:</p> <p>Test for Chlorine: Free chlorine is a quite toxic compound which is present in low level in tap water and in swimming pool water.Chlorine gas has a greenish colour , but when is it solved in water , the colour almost disappear, so we can´t detect it , but if we add a reagent called Orthotolidine it turns orange.</p> <p><a href=""><img src="" alt="cloro.jpg" /></a></p> <p>As you can see in the picture, the first test tube is colorless even it contents high levels of free chlorine, the right one has the same amount of chlorine , but we add a drop of the reagent, so with this procedure we are able to measure chlorine level in water or some others.</p> <p>Test for iron ions(Fe 2+):</p> <p>iron (2+) solutions commonly have a light yellow-greenish color, but when is in very low concentrations it is almost transparent , however if we add a drop of a reagent called Potassium ferrocyanide a chemical reaction takes place , giving a complex called prussian blue, which has an intense blue color.</p> <p><a href=""><img src="" alt="fe.jpg" /></a></p> <p>Test for Proteins:</p> <p>A lot of proteins are colorless , but there is a reaction called "the biuret reaction" that allows us to detect the presence of proteins, firstly we add to the sample several drops of sodium hydroxide , after that we add a drop of cooper sulfate solution, then if there are proteins in the sample a violet color appears in the test tube</p> <p><a href=""><img src="" alt="proteina.jpg" /></a></p> <p>Test for Starch(Almidon): Starch is a white powder , almost insoluble in cold water , but quite soluble in boiling water, Starch solutions have a cloudy-transparent color , but it is not enough for the colorimeter , however if we add a reagent called "lugol", starch and iodine form a complex which has an intense blue color as shown in the image</p> <p><a href=""><img src="" alt="starch.jpg" /></a></p> <p>Miguel Gallegos</p> HOMEMADE SPECTROMETER FOR SAMPLE ABSORPTION ANALYSIS AND A TYPE OF RAMMAN SPECTROSCOPY homechemist Fri, 30 Aug 2013 10:09:22 +0000 <p>Inspired by the Public Lab great ideas and by one of the techniques that my chemistry teacher used to use for lights and color experiments, I have developed a new spectrometer design that in my opinion offers much more stability and high quality and reliable results.</p> <p>This is my prototype:</p> <p><img src="" alt="PROTOTIPO.jpg" /></p> <p>So , the idea is that 20 white led bulb and two HeNe lasers of 532 nm and 655 nm emit energy in form of light, these light passes thought a Parchment paper that blurs it, Then the light passes thought the test tube that contents our sample .(At this point the molecules of the sample absorb some of the light emitted by the whites led) , then the modified light enters by a little slit in a completely dark chamber, just before impact against a dvd piece that spreads out the light in several colors according to the wavelength. The spread light travel thought the chamber and get the VGA sensor that records the spectrum and transmit it by USB to a laptop .The difference between these new spectrometer design is that is much more reliable an sure measurement than other designs because the sample , the sensor, and the light bulb keep their positions in each measurements so the spectrum which can be modify by several factors will be much more reliable as all of these factors are controlled. Another great thing of these spectrometer is that the lasers emit a well-known wavelength so the calibration is much more accurate than the fluorescent lamp one. And the calibration should be done just one a month or something like that, so, you guarantee the spectrum is well calibrated. Another real interesting thing of these spectrometer is that just between the sample and the parchment paper there is a little chamber where you can set a color filter that restrings the wavelength of the light , so the conventional spectrometer offers you the possibility of uses as a Raman spectrometer that is use for irradiating a sample with an specific wavelength that excited the molecules which electrons absorbs energy going to upper energy levels and as they return with the standard energy levels they emit an specific wavelength , that sometimes give us a fluorescent effect, these is the mode of analysis of the Raman spectrometer.</p> <p>I HAVE TO RECOGNIZE THAT THE RAMAN SPECTROSCOPY IS JUST A FUTURE PROJECT AND I HAVE TO TEST IT, HOWEVER FOR DETERMINE THE CONCENTRATION OF A SAMPLE THE FILTERS WILL BE GREAT AS YOU CHOOSE THE WAVELEGHNT THAT YOUR SAMPLE ABSORBS</p> <p>Here I show you the laser calibration <img src="" alt="LASERS.jpg" /></p> <p>High concentrated chlorophyll spectrum diluited in non polar solvent (extracted from spinach)</p> <p><img src="" alt="CLOROFILE.jpg" /></p> <p>And now what?..Okay so , at the moment I am trying to get soil and oil samples to contribute to the open database and, as I have access to a lot of chemicals I will upload a lots of spectrums ,and I hope in a few time The great people that works In Public Lab will be able to create a fingerprint app for the analysis software that allow us to determine what chemical do we have in our sample.</p> <p>As a future project I promise I will continue investigating in this prototype of Raman Spectrometer and in the determination of the concentration of a sample with wavelength filters. I am also interesting in the isolation of photosynthetic and natural pigments which have a lot of interesting behaviors and proprieties</p> <p>If you want to get in touch with my please do it :) at this mail: <a href=""></a></p> <p>And if you want to see more of my recent work you can enter in the database and search "homechemist" the spectrum toke by this spectrometer are the ones that sais: calibration cloned from lasers</p> <p>Finally I am really interesting in capturing the spectrum of colorful changing chemical reaction like the Ph. ones so you can determine how the protonation and the DE protonation affects at the indicators molecules( the simplest indicator is the Lombard which contents anthocyanin , a natural Ph. indicator)</p> <p>The spectometer:</p> <p><img src="" alt="DSC_2842.jpg" /></p> <p>The chlorophyll:</p> <p><img src="" alt="cl.jpg" /></p> <p>Miguel Gallegos</p>