1. UV-Vis Spectroscopy 1.1 Introduction Objective Review basic analytical chemistry skills, including solution making, transferring and linear diluting. Understand the error involved and error propagation. Materials: Methylene Blue C16H18ClN3S, MW 319.85.Also called Swiss blue. One gram dissolves in about 1000 ml of water. Peak absorption at 369 nm 1.2 Create Calibration Curve from standard solutions Procedures: 1. 2. 3. 4. 5. Weigh 500mg dye on electric balance Dissolving all the solid dye in beaker Transfer all the solution into a 500ml volumetric flask Fill up the volumetric flask to the tick mark Prepare standard solutions of 500, 200, 100, 50 and 20 ppm from 1000 ppm stock solution Table 1-1 Preparation of standard solutions STD PPM Stock DI water Total Volume 20 0.2 9.8 10ml 50 0.5 9.5 10ml 100 1 9 10ml 200 2 8 10ml 500 5 5 10ml 6. Vortex vial to complete mix 7. Transfer Standard solutions to cuvette 8. Measure the transmissivity at a peak measure three times and make a note of your results in your lab notebook 9. Create calibration curves from data. Table 1-2 Absorbance of standard solutions PPM Wavelength 1 Absorbance 2 Average 20 50 100 200 500 UV/VIS Absorbance 1 0.8 0.6 0.4 0.2 0 0 50 100 150 200 250 300 Concentration (ppm) 350 400 450 500 Figure 1-1 Calibration curve from standard solutions 5.3 Two steps of a serial dilution and measure the concentrations of unknown samples 1. Pour about 11 ml unknown concentration of methylene blue solution from the bottle to your vial 2. Dilute the dye solution 10 fold by using pipettes : Pipette 1 ml above sample solution to your vial 3. Fill the solution to 10 ml 4. Transfer Standard solutions to cuvette 5. Measure absorbance of each 2 Figure 1-2 Serial Dilution of unknown samples Table 1-3 Absorbance of unknown samples Absorbance Serial Dilution 1 1/10 Sample 1 Sample 2 Sample 3 1/100 Wavelength Instrument Use 1. Power on instrument (switch is on left side). 2. Turn on monitor and double-click ‘Cary win UV’ 3. Instrument will run through a start-up check for about 1 minutes. 4. In the toolbar frame, select the ‘Concentration’ icon. 5. In dialog box, enter wavelength 369 nm. a. Choose Abs (absorbance). b. Replicate is 2 6. Click on ‘Standard’. a. unit : mg/L b. number of standard and concentration of standard solution 7. Click on ‘Sample’ and enter sample number 8. Click ‘OK’ 9. Click on Zero icon after insert Blank cuvette into UV slot. 10. Fill cuvette ¾ with standard samples and cleaning cuvette surface with chem wipes. 11. Place cuvette in the slot. 12. Click ‘Start’ 13. Record Abs(absorbance) 14. Drawing standard graph 15. Fill cuvette ¾ with unknown samples and cleaning cuvette surface with chem wipes. 16. Place cuvette in the slot. 17. Click ‘Start’ 18. Record concentrations 3 Lab report requirement o Calculate solution concentration by ppm for all solutions o Discuss source of data errors o How do you improve your skill to get better accuracy and precision of solution making o Describe the key steps of the experiment o Attach all the original data and spectrum 4 Lab Report Guidelines You should consider the last section of each lab experiment as well as 1.5 Report Preparation part when writing a lab report. The Materials and Methods and results section should be written in the past tense, since your experiments are completed at the time you are writing your paper. Your lab report should include the following sections: Cover Page (0.5 pt) Include the title of the experiment, name, group number, and the date on which the experiment was performed Introduction(1 pt) Purpose of experiment Background Information Materials and Methods(2 pt) Equipment Used Schematic diagram of main equipment used (if required ) Test procedure generally contains information on the physical nature of the experiment, such as the type of instrumentation used, the variables controlled and those that are not controlled, and any unusual conditions. Here is an example of a section of that type. The experiment was carried out with a Nicolet Fourier transform infrared (FTIR) spectrometer. The resolution of the spectrometer was set at 1 cm-1 for all spectra. The experiment involved the accumulation of a background spectrum which were subtracted from the spectrum of the sample to provide the response of the sample. The detector was a nitrogen-cooled cadmium-telluride detector. Each experiment resulted from the average 64 transient responses coadded, with the background spectrum being the accumulation of 64 spectra without the sample present. The data were analyzed by Fourier transformation using the software of the instrument. The data were saved to disk, and were subsequently analyzed with a spreadsheet program, in this case, Microsoft EXCEL. Theoretical values of the parameters were predicted by computation with the program GAUSSIAN. The section need not be long, but it should include everything about the experimental setup that the author thinks is important. retrieved from"https://www1.udel.edu/pchem/C446/example.pdf" Results(4 pt) Present your data using text AND figures/tables. Describes your major findings in the data presented in the figures and tables. Don’t interpret the data. It could be done in the Discussion section of the lab report. All figures and tables are properly formatted with numbers, titles and legends that are easy to the reader to follow. DO NOT ATTACH YOUR LAB DATA SHEET to show your results. Discussion(2 pt) Summarize what you found. Explain and interpret your results. It may involve comparison of the test results with existing empirical relationship Source of errors if any Other details not included in the report References(0.5 pt) Sufficient and appropriate sources cited. All references are formatted appropriately 1 Results Table PP 1 wavelegen Absorbance of standerd solalian Absorbance no 3,69 cogcia ooool 820 ooool 3.69 0.9459 e 0,0459 0.0459 sotto 3,69 hitle 0,1724 1724 o, 1726 نی همه Ingi'o 0,2843 3.69 3.69 0.2892 2009 bill 0.6114 0.6H2 1 2 3 Si 1, 1 yol 3 1.374 52136 o, loqu 53 09729 1.1385 o.1073 o o.1073 of 2 97 24 81tb'o hs oplossloolas 6 olo 57 1.9251 1.4251 1.4240 SS
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