Fluent Essays

Need help to read the 4 articles and follow the 3 steps below4 pagesFollow APA (6th editon) format for references and in-text citations.Plagarism freeStep 1. ImagineImagine you plan to pitch membrane bioreactor (MBR), nanofiltration (NF), or reverse osmosis (RO) technology to your local water board to reduce PPCP pollution in your community. How would you pitch your ideas to convince the water board to reduce PPCP pollution? What do you need to know about PPCP pollution in your community? What do you need to know about MBR/NF/RO technology to create the pitch? What do you need to know about your local sewage treatment center to make the pitch?Step 2. ResearchLearn more about the topics of MBR/NF/RO technology and your local sewage treatment center. Note key ideas for the topics.Start by researching the agencies responsible for sewage treatment in your area. Is sewage treatment managed by a private company, the municipal government, or a combination of the two? How does the increasingly complex relationship between private business and government influence the problem of tackling PPCP pollution?Step 3. DesignDesign a pitch for the local water board addressing a specific problem related to PPCP pollution in your community. For example, this might address antibiotic resistance in microorganisms caused by PPCP pollution.Include a lay explanation of the problem and the science of a specific MBR/NF/RO technology to tackle the PPCP pollution.Consider reasons the water board might not want to accept your ideas, and then think of counter-arguments. For example, consider the extent to which an individual can be held responsible for levels of PPCP pollution. Is it practical for people simply to wash less down the drain? chemical_test_for_caffeine.pdf an_examination_of_america_s_water.pdf antibiotic_resistance.pdf removal_of_pharmaceutical_and_personal_care_products_from_municipal_waste_water_from.pdf Unformatted Attachment Preview 1 Hong Kong Chemistry Olympiad for Secondary Schools (2013-14) Chemical Test for Caffeine Christian Alliance S C Chan Memorial College Ho Chun Lok (何晉樂) Kwok Man Kit (郭文傑) Chan Kam Tung (陳淦童) Tse Sze Ho (謝思昊) Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 2 Contents Abstract ............................................................................................. 3 Objective ............................................................................................... 4 Principle ........................................................................................... 5-7 Solvent Extraction ...................................................................................... 5 Thin Layer Chromatography ......................................................................................... 5 Iodometric Back Titration ............................................................................................ 6 Spike test……………………………………………………………………………………………….7 Apparatus and Chemicals .................................................................... 8 Experimental Methods and Procedure .......................................... 9-13 Solvent Extraction ...................................................................................... 9 Thin Layer Chromatography ...................................................................................... 11 Iodometric Back Titration ......................................................................................... 12 Spike test ………………………………………………………………….…………………………..13 Result ...........................................................................................14-18 Solvent Extraction .................................................................................... 14 Thin Layer Chromatography ...................................................................................... 16 Iodometric Back Titration ......................................................................................... 18 Spike test …………………………………………………………………………………..………….17 Discussion .........................................................................................21 Conclusion ........................................................................................22 Further Work ....................................................................................23 Reference ..........................................................................................24 Acknowledgement…………………………………………………………………………….25 Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 3 Abstract We are interested in the alkaloid --- caffeine (C8H10N4O2) which is very common substance in many drinks, such as coffee, tea, Coca-Cola etc. Adults or even students will drink a cup of coffee to temporarily restoring alertness and warding off drowsiness. However, how much caffeine in our coffee? How can we determine the amount of caffeine in coffee? The following project will investigate the chemical test for caffeine. At first, we extract caffeine from coffee. Then we need to prove that the extraction contain caffeine. Finally we try to find out the amount of caffeine in coffee. We’ll first follow the common procedure, which is the solvent extraction and the thin layer chromatography. We also do some research on other chemical test for caffeine. We come up with the test of iodometric back titration. All the tests we investigate can be done in school laboratory, and pure caffeine is bought for verifying and investigating these chemical tests. We hope that these tests can be further developed in order to become more popular, more efficient, lower the cost and less pollute to environment. Structure of Caffeine [1] Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 4 Objective First, we try to extract caffeine from coffee by a suitable method. Then, by using chemical tests to analysis the amount of caffeine in coffee and extract. Last, we want to validate the efficiency of the extraction method. Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 5 Principles Solvent extraction [2] It mainly based on the difference of solubility of caffeine in different solvent. Caffeine is sparingly soluble in water at room temperature but highly soluble in boiling water (100 °C). Thus we can extract most of caffeine in raw coffee powder to a coffee solution. Then, in order to extract crude caffeine from coffee solution, we can base on the property that caffeine is more soluble in organic solvent (here we use chloroform (CHCl3)) than that in water at room temperature. Also chloroform is much denser than water and insoluble in water, the caffeine in coffee solution are transferred to the chloroform and separated out. Caffeine solubility Water (25 °C ) Chloroform (25 °C) Water (100 °C ) 2.17 g/100 cm3 15.8 g/100 cm3 67.0 g/100 cm3 [3] Then to prove that the extraction is mainly caffeine, we can carry out two tests, which are Thin Layer Chromatography (TLC) and iodometric back titration. Thin Layer Chromatography (TLC) There are different types of chromatographic methods such as paper chromatography, thin-layer chromatography, column chromatography, gas chromatography, etc. They have the same principle : (1) Different solutes have different solubility in a solvent /different solutes have different degrees of tendency to be dissolved in the same solvent. (2) As the solution ( contains the solvent with the dissolved solutes ) moves along a stationary solid surface ( a solid surface ) , different solutes adsorbed onto the solid surface in different extent as they have different degree of adsorption characteristics ( due to the different degrees of dissolve tendency). Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 6 (3) The “less soluble” solute will be retained first, and the “more soluble” solutes will be retained afterwards. ( Note : No two substances have the same solubility and adsorption characteristics. ) (4) Different solutes will then be separated on the different positions of the solid surface. (5) Retention Factor (Rf) of each components is calculated as follow Rf = distance traveled by the component substance form the baseline distance traveled by the solvent from the baseline Pure caffeine and the extract are analyzed in the same TLC plate and compare any differences of their Rf . Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 7 Iodometric Back Titration Caffeine reacts with excess accurately known amount of iodine in acidic environment, forming insoluble precipitate. Then the insoluble precipitate is removed by filtration. Using titration by a standard sodium thiosulphate solution with starch solution as indicator, we can determine the amount of remaining iodine, and thus the amount of caffeine can be found. Here are the chemical equations [4]: C8H10N4O2 + 2 I2 + KI + H2SO4 → C8H10N4O2 .HI .I4 + KHSO4 I2 + 2 Na2S2O3 → 2NaI + Na2S4O6 Note : Where the second equation is to determine the remaining iodine (I2 is the remaining Iodine) Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 8 Spike Test By adding known amount of standard caffeine in distilled water and raw coffee solution , then carry out solvent extraction. By comparing the extraction results, we can analyze the recovery percentage of the spiked caffeine and efficiency of solvent extraction. Chemicals Caffeine (C8H10N4O2 , chemical pure grade, min 98.5\%) Solvent Extraction : Chloroform (CHCl3) TLC Ethyl Acetate (C4H8O2) Ethanoic acid Iodometric back titration Standard caffeine solution Standard Na2S2O3 solution Standardized iodine solution Starch solution Apparatus Separating funnel TLC plate ( 0.25mm silica gel ) Burette Pipette Volumetric flask Analytical balance Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 9 Experimental Methods and Procedures (A) Extraction of caffeine from raw coffee power Preparation of raw coffee solution 1. 4.58g of fine grinded raw coffee powder is weighted, add 100 cm3 of distilled water and 3.0g of sodium carbonate to increase solubility of Caffeine (alkaloid) and boil it and brew it by following the instruction on the Coffee package (one tablespoon of coffee powder in 100 cm3 of hot water, about 4.58g /100 cm3). 2. Cool down the raw coffee solution to room temperature Solvent Extraction 1. Rinse all apparatus with chloroform. 2. Transfer the raw coffee solution to separating funnel (Figure a). 3. Add 10 cm3 of chloroform and swirl vigorously, (*Don’t shake the mixture because an emulsion will form*)(Figure b). Allow the mixture to stand and separate out the bottom chloroform layer to a beaker. Repeat this step for 5 times. 4. Add calcium sulphate to the separated chloroform to remove water. Shake well and stop until fluffy, cloudy effect. 5. Weight the beaker which is going to hold the filtrate. 6. Filter out the excess calcium sulphate. (Figure c) 7. Put the beaker with filtrate into hot water bath to evaporate chloroform (Boiling Point : 61.2 oC) (Figure d) 8. Weigh the powder and calculate the amount of powder extracted. Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 10 Figure a Figure b Figure c Figure d Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 11 (B) Qualitative analysis of caffeine by Thin Layer Chromatography (TLC) 1. Dissolve the extract and pure caffeine into distilled water separately. 2. Prepare the TLC plate ( silica gel coating, and cut it to 3 cm x 10 cm ). 3. Use a pencil to draw a horizontal line 0.5 cm above the bottom of the TLC plate. 4. Spot the extracted caffeine and pure caffeine by 10µ L micro-capillary tubes separately on the pencil line of the TLC plate. 5. Immerse the TLC plate into the solvent ( a mixture of 20:1 of ethyl acetate : ethanoic acid ). 6. Let the plate stand and develop the chromatogram. 7. Visualize the result with a UV lamp, use a pencil to circle the spot seen under UV light. Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 12 (C) Quantitative analysis of caffeine by iodometric back titration 1. Transfer 15.00 cm3 of standard caffeine solution / the solution prepared by the extract to a conical flask and add 10 cm3 sulfuric acid . 2. Add 25.00 cm3 of standardized iodine solution to the mixture and swirl gently, brown-red precipitate will form. 3. Filter the solution. 4. Take down the initial reading of burette. 5. Titrate the filtrate against a standard sodium thiosulphate solution (Na2S2O3). 6. Add a few drops of starch solution when the titrand becomes pale brown. 7. Slowly run Na2S2O3 until titrand become colorless from dark blue. 8. Take final reading of burette. 9. Repeat the above steps until two to three consistent results are obtained. Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 13 Results (A) Solvent Extraction For the first time of the solvent extraction, we use the 3 in 1 instant coffee and lots of emulsion formed and we failed. Then we use fine grinded raw coffee powder in the later analysis. We also use Coca cola for extraction, nearly no caffeine can be extracted but after evaporation of boiling water bath, the beaker holding “the extraction” has strong, sweet, coca cola’s smell. During extraction, the chloroform become pale brown. (Refer to Picture 1). Picture 1 After Solvent Extraction, we obtain powder of pale yellow (In the left bottle in Picture 2) with irritating, choking, distinct, strong smell like soot of cigarette and coffee. Comparing with pure caffeine (In the right bottle in Picture 2) and by observation, it’s obvious that the extraction does contain impurities (where pure caffeine is white powder). Picture 2 Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 14 (B) Mass of extract obtained from raw coffee solution Volume of raw coffee solution used in each extraction = 100 cm3 Concentration of raw coffee powder in raw coffee solution = 4.58 mg/ 100 cm3 Mass of Beaker (g) Mass of Beaker with extracted Crude Caffeine (g) Mass of Extract (mg) Extraction 1 48.5210 Extraction 2 48.5176 Extraction 3 48.8572 48.5822 48.5773 48.9097 61.2 59.7 52.5 Average mass of extract in 100 cm3 of raw coffee solution : = (61.2+59.7+52.5)/3 = 57.8 mg We extracted average of 57.8 mg of solid from 100 cm3 of raw coffee solution ( with 4.58 mg dry coffee powder dissolved in 100 cm3 hot water which is the normal concentration in brewing drinkable coffee). There is caffeine loss during the extraction process. Thus we carry out spike test to find out the percentage recovery of caffeine in raw coffee solution and distilled water after the solvent extraction process. Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 15 (C) Thin Layer Chromatography (TLC) We carry out TLC to prove the existence of caffeine in the extracts. By the results of comparing Retention Factor (Rf) of the developed spots on chromatograms, we find out that there are caffeine in the extract and no obvious impurities are observed under UV light. Also, we have tried different solvents and solvent’s combination and we found out that 5\% ethanoic acid in ethyl acetate is the better solvent. Here is the chromatograms : Standard Caffeine solution , (red) Extract from coffee solution , Raw coffee solution (blue) (brown) Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 16 (D1) Spike test--- Raw Coffee Solution For each of the following trials, an accurate known amount of standard caffeine solution was added into the raw coffee solution, then extracted it by the above extraction process and analyze by the iodometric back titration. *Concentration of standard caffeine solution used : 4.8308 mg/cm3 *100 cm3 of raw coffee solution was used in each extraction sample * Refer to Result in Part (B), we assumed that each 100 cm3 of raw coffee solution can obtained 57.8 mg of extract Volume of standard Mass of caffeine Trial caffeine solution spiked (cm3) spiked (mg) 1 10 48.3080 95.63 37.83 78.31\% 2 20 96.6160 105.87 48.07 49.75\% Mass of the extract obtained (mg) Mass of spiked Recovery caffeine percentage recovered (mg) (D2) Spike Test--- Distilled Water *Concentration of standard caffeine solution used : 4.8308 mg/cm3 *100 cm3 of hot distilled water was used in each extraction sample. Trial Volume of Mass of standard caffeine caffeine spiked solution spiked (mg) 3 (cm ) Mass of spiked caffeine recovered (mg) Recovery percentage 1 10 48.3080 29.46 60.99 \% 2 20 96.6160 60.95 63.08 \% Averaged Recovery Percentage is about 62\% Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 17 Recovery Percentage of Standard Caffeine in Recovery Percentage (\%) distilled water and raw coffee solution 100 80 60 40 Coffee 20 Water 0 10 20 Volume of Standard Caffeine Solution added (cm3) (E) Iodometric Back Titration (1) To find the accuracy of the back titration method. *Concentration of standard caffeine solution used : *Concentration of the standard Na2S2O3 solution : *Concentration of the standard iodine solution : 0.421 mg/cm3 0.00595 M 0.0028 M Volume of standard caffeine solution used in each titration: 15.00 cm3 3 Initial Reading (cm ) Final Reading (cm3) Volume of Na2S2O3 added (cm3) Trial 1 0.90 3.00 2.10 Run 1 3.00 5.30 2.30 Run 2 5.30 7.60 2.30 Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 18 Averaged amount of Na2S2O3 added = (2.30 + 2.30)/2 = 2.30 cm3 Number of mole of I2 originally added = (25/1000)*0.0028 = 7*10-5 mol Number of mole of Na2S2O3 added = (2.3/1000)*0.00595 = 1.3685*10-5 mol By the following equation, I2 + 2 Na2S2O3 → 2NaI + Na2S4O6 Number of mole of I2 reacted with Na2S2O3 (remaining I2) = (1.3685*10-5)/2 = 6.8425*10-6 mol Number of mole of I2 reacted with caffeine = 7*10-5 - 6.8425*10-6 = 6.31575*10-5 mol By the following equation, C8H10N4O2 + 2 I2 + KI + H2SO4 → C8H10N4O2 .HI .I4 + KHSO4 Number of mole of Caffeine = (6.31575*10-5)/2 = 3.157875*10-5 mol Mass of caffeine found in the 15.00 cm3 of standard solution = 3.157875*10-5 - 194.19 = 6.1323*10-3 g = 6.1263 mg Original mass of caffeine contained in 15.00 cm3 standard solution = 6.315 mg Accuracy of Iodometric Back Titration: (6.126/6.315) * 100\% = 97\% Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 19 (2) To find the amount of caffeine in the extract ( from raw coffee solution ) *0.251 g of extract was made up to 250.00cm3 *Concentration of standardized iodine solution : *Concentration of the standard Na2S2O3 solution : 0.0321 M 0.00308 M Volume of extracted caffeine solution used in each titration: 25.00 cm3 3 Initial Reading (cm ) Final Reading (cm3) Volume of Na2S2O3 added (cm3) Run 1 15.80 25.40 9.60 Run 2 1.60 11.30 9.70 Run 3 11.30 21.10 9.80 Average amount of Na2S2O3 added = 9.70 cm3 Number of mole of Na2S2O3 added = (9.70/1000)*0.003088 = 2.9876*10-5 mol Number of mole of I2 originally added = (5/1000)*0.0321 = 1.6054*10-4 mol By the following equation, I2 + 2 Na2S2O3 → 2NaI + Na2S4O6 Number of mole of I2 reacted with Na2S2O3 (remaining I2) = (2.9876*10-5)/2 = 1.4938*10-5 mol Number of mole of I2 reacted with caffeine = 7*10-5 - 6.8425*10-6 = 6.31575*10-5 mol No. of mole of I2 reacted with caffeine : = 1.6054*10-4 – 1.4938*10-5 = 1.4361*10-4 mol Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 20 By the following equation, C8H10N4O2 + 2 I2 + KI + H2SO4 → C8H10N4O2 .HI .I4 + KHSO4 Number of mole of Caffeine = (1.4361*10-4)/2 = 7.8035*10-5 mol Mass of caffeine in 25.00 cm3 extracted caffeine solution =1.4361*10-4 ( 194.19) = 14.14 mg Mass of caffeine in the 0.251g of extracted = 14.14 ( 250/25) = 141.4mg ∵100 cm3 of coffee solution has 57.8 mg of extracted by referring to the result Part (B), ∴ Mass of caffeine in 100 cm3 of coffee solution = (57.8/251) * 141.4 = 32.56 mg ∴ 32.56 mg of caffeine contained in the extract of 100 cm3 raw coffee solution. Christian Alliance S C Chan Memorial College/2013-14 Chemistry Olympiad/Caffeine 21 Discussion For the TLC test, the possible reason that we can’t see other impurities maybe impurities can’t be visualize under UV light or they dissolved in the solvent used to develop the plate. The detail constituent compounds and elements can be known by some advance instrument, e.g. HPLC etc. For iodometric back titration, because Iodine solution is volatile, some Iodine may loss during experiment process especially filtration. Thus it contributes the error of the titration. The “standard iodine solution” should be standardized by a standard sodium thiosulphate solution from time to time to acquire its concentration. Conclusion After the above tests, we confirmed that the about solvent extraction method is a practical experimental procedure for extracting caffeine in school laboratory. Due to the nature of the partition coefficients of solvent-solvent extraction, the amount of loss of caffeine could be reduced by increasing the number of portion of chloroform used in the process. ( Refer to the step 3 of the section of Solvent Extraction). However, chloroform is a CFCs and a carcinogenic substance, it is not recommended to use. Christian Alliance S C Chan Memorial College/2 ... Purchase answer to see full attachment