Boston College Chemistry Experiment Data Analysis Paper

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Internal Standards Author: Group: Contributions: Dave X: Calculations, Data and Results, Discussion Conclusion Muhammad Y: Calculations Han Z: Calculations Performed: August 31, 2014 Submitted: Sep 04, 2014 Results: Table 1. Resulting concentrations from the two instruments, the confidence interval for the results, and literature values. Table 2. Results of the t-tests for unknowns for instrument 1 Table 3. Results of the t-tests for the literature t-tests Table 4. Results of the paired t-test Analysis/Discussion: [Discuss the results that we get. Each table and figure needs to be discussed/tied together and referenced by Table/Figure #. Context for the method. What does it mean for unknowns to be the same or different? What does it mean for the paired t-test so show they are the same?Answer the post-lab questions. ] [If an equation was used to find a reported value make sure to incorporate it appropriately.] Example equation: 𝑦 = 𝑚𝑥 + 𝑏 (1), Where y is the dependent variable, m is the slope, b is the y intercept, and x is the independent variable. Example Table: Table 1 Results of the fitting reported with two standard deviations. Slope (units) Intercept (units) Value A C +/- 2 standard deviations B D [Discuss the actual meaning of the results and how they compare to your hypotheses. Do your results confirm the answers to your Pre-lab questions? Why or why not ? Include any error analysis here. Address any problems in the experiment, how they could have affected the outcome, and how they could be fixed. This section is the most important because it is where you will show your level of comprehension of the science going on in the experiment.] Conclusion: [In a way, the conclusion is a summary. Include the major findings of the experiment and explain why the results are significant. You may also want to propose an interesting future experiment that builds on the one you have just reported. This is often done in journal articles to answer a question that was raised by the results of the original experiment. Any other observation that was made should be summarized here.] This document has presented an acceptable way to present your results for a laboratory experiment, provided example of figures and tables, and provided useful questions to answer for different sections. References: If you used any sources, including the ones provided for the class, cite them here and reference them in the text. JACS formatting. General Tips: Write the report in the 3rd person passive voice i.e. “This was done” not “We did this” or in the active voice. Be consistent. - A lab report has no strict minimum or maximum length. It concisely states what needs to be said about the experiment and then it ends. Guideline: If you are over 4 pages it is probably too long. - It is very important to only draw conclusions from the results you actually obtained in the lab and not the ones you “should” have obtained. Do not assume that there are correct results and incorrect results. You are encouraged to compare your results to those of other groups or other similar experiments and reflect on what may have caused the differences but in the real world there is no “right answer” to check yours with. - The purpose of a lab report or paper is to communicate your finding to the rest of the community. As such, you will be mentioning your key results multiple times in the report. A good format for the overall report follows this basic structure: Tell them what you are going to tell them (abstract), tell them (The middle stuff), and then tell them what you told them (Conclusion). Alternate Figure examples: Fig. 2: Fluorescence spectra of pyrene using 362nm excitation. Compiled Experiments 1 Internal Standard: Standards (ISS) Learning objects By the end of this experiment students will: 1. Have calculated response factors for four monoterpenes from a standard solution. 2. Used the response factors to determine the concentration of monoterpenes in 3 different standard solutions. 3. Have evaluated the accuracy of their results. 4. Have determined the precision of their results. 5. Compared their results with their partner group. Pre-Lab Questions 1. In your own words, what is an internal standard? ⚫ An internal standard is when the standard analyte and the unknown measured in the same mixture. 1. Have you ever used an internal standard before? ⚫ SACV 2. Why do you have to run standard solutions when using an internal standard? ⚫ The standard solutions provide a reference point to the unknown analyte 3. Why do you think it is called response factor? ⚫ Response factor shows how the response depends on the instrument and analyte’s interactions. 4. What does a response factor of 1.5 tell you about the relative sensitivity of the instrument to the internal standard and analyte? ⚫ A 1.5 response factor tells us the relative sensitivity of the instrument in comparison to the internal standard and analyte is standard is 1.5 times that of the analyte’s peak. 5. You have a response factor of 1.5 and concentration of internal standard of 2mg/mL and areas of 300 and 800 for the standard and the analyte respectively. What is the analytes concentration? ⚫ Ax = 800, As = 300, F = 1.5, S =2 mg/mL 1.5*(300/2mg/mL) X = 800*2 mg/mL/ (300*1.5) = 3.5 mg/mL 6. Do you think response factor for each analyte will be the same or different? ⚫ I think the response factor for each analyte will change for each analyte 7. In the procedure look for key words like record, calibrate, make, or prepare in order to identify what information you will be using later. Add in relevant empty data tables to the procedure, label columns and rows appropriately so you can be prepared to record this information. 8. Does anything need to be added to or removed from the Materials and Safety for Part 1? Update if necessary. 9. What is the goal for today? What is the basic idea for the technique to be used today? ⚫ To identify the composition of the unknown compounds using internal standards and the instruments GC-MS and the GC. Researchers signature: 9/26/16 12:35 PM Instructor Signature: 9/26/16 12:35 PM Compiled Experiments 2 Researchers signature: 9/26/16 12:35 PM Instructor Signature: 9/26/16 12:35 PM Compiled Experiments 3 Materials: Chemicals Volume/Mass D-limonene [2 mg/mL] gamma terpinene [2 mg/mL] beta pinene [2 mg/mL] alpha pinene [2 mg/mL] ethylisovalerate 100mg per unknown = 200 mg total methylene chloride [2 mg/mL] 70 mL per unknown = 140 mL Equipment Number/Size GC-MS 1 GC 1 vacuum extraction apparatus 1 small beakers or vials 2 25mL volumetric flask 1 two GC vials Per standard 125mL Erlenmeyer flask 1 graduated cylinder 1 filter cake 1 Mass balance 1 GC vials 16 Compound/structure Hazards Classification Handling (Summary of section 2 of SDS, less than 15 words) D-limonene Disposal (Summary of section 7 of SDS less than 15 words) Flammable liquid Lab coat, goggles, EH&S and vapour. Causes gloves skin irritation. Causes serious eye irritation. May cause respiratory irritation Researchers signature: 9/26/16 12:35 PM Instructor Signature: 9/26/16 12:35 PM Compiled Experiments 4 gamma terpinene Flammable liquid Lab coat, goggles, EH&S and vapour. Causes gloves skin irritation. Causes serious eye irritation. May cause respiratory irritation beta pinene Flammable liquid Lab coat, goggles, EH&S and vapour. Causes gloves skin irritation. Causes serious eye irritation. May cause respiratory irritation alpha pinene Flammable liquid Lab coat, goggles, EH&S and vapour. Causes gloves skin irritation. Causes serious eye irritation. May cause respiratory irritation ethylisovalerate Flammable liquid Lab coat, goggles, EH&S and vapor. Causes gloves skin irritation methylene chloride Toxic if swallowed. Lab coat, goggles, EH&S Causes severe skin gloves, venilation burns and eye damage. Suspected of causing cancer. Introduction A known amount of a known compound that is not your analyte is considered an internal standard. This internal standard gives you a reference point to compare the amounts of analyte present. This method is valuable to use if instrument has slightly varying responses each run or sample quantity varies from run to run or sample is lost during preparation. The instrument though will have a consistent relative response to both the analyte (x) and the internal standard (S). For instance, using a chromatogram of sample eluting will have an area the analyte’s peak (Ax) and the internal standards peak (As). These are then related to each other through equation 1. 𝐴𝑥 [𝑥] 𝐴 = 𝐹 [𝑆]𝑠 (1) Where F is the response factor. The response factor takes into account differences in how the sample has transported through the system and how effectively the instrument responds to your compound of interest. Researchers signature: 9/26/16 12:35 PM Instructor Signature: 9/26/16 12:35 PM Compiled Experiments 5 In an analysis, start with a solution where you know the concentration of your internal standard and your analyte. Using this information, you can determine the response factor. This response factor for an analyte will not change during your analysis. Make sure that the internal standard is added at or near the beginning of sample preparation in case any sample is lost in the process the internal standard undergoes similar losses. This keeps the relationship between internal standard and analyte consistent throughout the entire process. The instrument we are using is a gas chromatograph (GC) that may be coupled to a mass spectrometer (GC-MS). This instrument first separates components based mainly on their boiling points (GC) and then generates a mass to charge spectrum of the components as they enter the mass spectrometer. This enables you to identify a component not just by their retention time, but also their fragmentation pattern. The sum of all mass to charge components at a given point in time is related to the concentration of the material coming off of the GC. You will be studying solutions of monoterpenes with an internal standard of ethylisovalerate. Procedure You will be provided with two unknowns for determination. Sample preparation: Standards preparation 1. Prepare a single solution that contains 2 mg/mL of each of the monoterpenes (D-limonene, gamma terpinene, beta pinene, and alpha pinene) and ethylisovalerate in a 25mL volumetric flask with methylene chloride as your solvent. This is called your standards solution. Transfer a portion into two GC vials. 2. In a 25 mL volumetric flask, prepare a solution that contains only the internal standard in methylene chloride (conc. 2 mg/mL). 3. Repeat step 2 for each monoterpene. They do not contain internal standard. 4. Start running these samples on the instruments while you prepare the unknowns. ethylisovaler ate alpha pinene Beta pinene D-limonene gamma terpinene Purity error in balance (mg) Unknowns preparation 1. 2. 3. 4. 5. Put together a vacuum extraction apparatus as shown by an instructor. Obtain two unknown samples in small beakers or vials. Record the mass of each sample. Weigh 100mg of ethylisovalerate directly into each sample. Add ~50 mL of methylene chloride to the sample and stir for 30 s. Transfer the slurry to the vacuum apparatus and filter the extract. Turn the vacuum off when the filtering is finished. 6. Rinse the beaker with an additional 20 mL of methylene chloride and wash the filter cake. Repeat again. (Due to evaporation, there will be less then 50 mL of filtrate in the flask.) Researchers signature: 9/26/16 12:35 PM Instructor Signature: 9/26/16 12:35 PM Compiled Experiments 6 7. Transfer the solution to a graduated cylinder and dilute up to 50mL 8. Store the filtrate in a stoppered 125mL Erlenmeyer flask. 9. Repeat steps 6 through 11 for the other sample. 10. Obtain GC sample vials, label and fill vials ½ full with solution. Prepare two vials for each solution. Standar ds solution s Preparat ethyliso ion of valerate the (mg) standard s solution alpha pinene Beta pinene Dlimonen e gamma terpinen e Final volume (mL) balance toleranc e (mg) flask toleranc e (mL) standard s (all terpenes ) alpha pinene Beta pinene Dlimonen e gamma terpinen e unknowns mass of ethylisovaler substrate (g) ate (mg) final solution error in final balance volume (mL) volume (mL) tolerance (mg) Unknown 1 Unknown 2 Unknown 3 Data collection 1. Collect a chromatogram or total ion chromatogram (TIC) for the individual monoterpenes. Researchers signature: 9/26/16 12:35 PM Instructor Signature: 9/26/16 12:35 PM Compiled Experiments 7 2. Record elution order. Is the elution order as expected? 3. Take three measurements each for the standard mix and the three unknown samples. GC-MS ethylisovaler alpha pinene Beta pinene D-limonene gamma ate elution elution time elution time elution time terpinene time (min) (min) (min) (min) elution time (min) standards (all terpenes) alpha pinene Beta pinene D-limonene gamma terpinene GC ethylisovaler alpha pinene Beta pinene D-limonene gamma ate elution elution time elution time elution time terpinene time (min) (min) (min) (min) elution time (min) standards (all terpenes) alpha pinene Beta pinene D-limonene gamma terpinene Researchers signature: 9/26/16 12:35 PM Instructor Signature: 9/26/16 12:35 PM Compiled Experiments 8 4. Analyze them on the Shimadzu GC-MS or the GC. GC-MS settings Method name: To be provided Sample volume: 1μL Temperature ramp: Tinit at 80 ºC; 70-150 at 20 ºC per minute; 150-300 at 80 ºC per minute and hold for 1 minute Column: Shimadzu SHRXI-5MS (30m x 0.32mm x 0.25μm). The stationary phase for this type of column is 5% phenyl methyl siloxane. Mobile phase: He(g). Ion source temp: 200°C Solvent cut time: 1.2 min Start data at 1.5 min stop data at 4.0 min m/z range of: 40-250 split 500:1 GC settings Method name: to be provided Sample volume: 1μL Temperature ramp: Tinit at 80 ºC; 70-150 at 20 ºC per minute;150-300 at 80 ºC per minute and hold for 1 minute Column: Agilent HP-5 (30m x 0.32mm x 0.25μm). The stationary phase for this type of column is 5% phenyl methyl siloxane. Method name: Start data at 1.3 min stop data at 4.0 min. Mobile phase: He(g). file types: .txt, .csv, .xls pressure 9.5 PSI split 100:1 Researchers signature: 9/26/16 12:35 PM Instructor Signature: 9/26/16 12:35 PM Compiled Experiments 9 Data Analysis 1. Find the peak area for each analyte and the internal standard 2. Find the average response factors for each standard with error. 1. Using the response factors determine the concentration of unknown in the solutions in mg of monoterpene/g of vermiculite. 2. Propagate the error to determine the confidence intervals for your unknowns. 3. Once you have calculated the unknown concentration, show an instructor your results in person or via email in order to receive the samples’ actual concentration. 4. Compare your unknowns using a two sample t-test 5. Compare the results from your two instruments using a paired t-test 6. Compare your results to the actual concentrations using a literature t-test Lab Report 1. Results: Complete the 4 tables provided in the informal report. Modify or duplicate if necessary. 2. Results: Include table of response factors with error. 3. Discussion: Basic theory behind the analytical technique used in this experiment. 4. Discussion: Evaluate the results of your t-tests and other tables. Since there are a number and all of the results are listed in the tables, do not go through every single one. Instead, summarize what the tables are telling us. Each table’s implications should be addressed briefly. Make sure to address accuracy, precision, and differences between instruments. 5. Discussion: What could you do to improve your ability to determine an accurate unknown concentration? What is your data telling you about where you had technical challenges Where do you know had problems? The instruments can have some error, but they are generally not the primary source. Conclusion: 1. 2. 3. 4. 5. What did the group like about the instructors' facilitation? What did the group do well in regards to the process skill of the experiment? How can the group improve in regards to the process skill of the experiment? What are three things you learned today? What do you still have questions about? References 1. Harris, D.C. Quantitative Chemical Analysis, 7th ed.; W.H. Freeman & Co.: NewYork, 2007; pp 90-92, 474-484 and 528-546. Researchers signature: 9/26/16 12:35 PM Instructor Signature: 9/26/16 12:35 PM Lab Report 1. Results: Complete the 4 tables provided in the informal report. Modify or duplicate if necessary 2. Results: Include table of response factors with error. 3. Discussion: Basic theory behind the analytical technique used in this experiment. 4. Discussion: Evaluate the results of your t-tests and other tables. Since there are a number and all of the results are listed in the tables, do not go through every single one. Instead, summarize what the tables are telling us. Each table’s implications should be addressed briefly. Make sure to address accuracy, precision, and differences between instruments. 5. Discussion: What could you do to improve your ability to determine an accurate unknown concentration? What is your data telling you about where you had technical challenges Where do you know had problems? The instruments can have some error, but they are generally not the primary source.
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CHEMISTRY

1

Internal Standards
Student Name
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CHEMISTRY
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Internal standards
Introduction
In quantitative analysis, there are cases where samples are unknown. The
concentration samples could be easily distinguished if their response factors are known. (Fan
et al., 2017) The purpose of this analysis is to determine whether response factors do change
depending on the solution and to know whether the measurements yielded by the two
instruments do vary using t-test. The concentrations of the actual solutions are also being
compared.
Results
From the experiment done, values were recorded and various tests done on the results
obtained. The results of the tests are tabulated below.
Table 1. Resulting concentrations from the two instruments, the confidence interval for
the r...


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