chromatography: gas and paper gas and paper ... two forms of chromatography will be used in this...
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Chem 100 Section _______ Experiment 3
Name ____________________________ Partners Name ___________________________
Chromatography: Gas and Paper INTRODUCTION This experiment is being constructed to acquaint you, the student, with two powerful techniques used in science to identify substances; viz., gas chromatography and paper chromatography. The reason for introducing these concepts and procedures is to answer the basic questions posed in the very realistic story given below.
The Case of the Corroding Cans
Adapted from a laboratory experiment developed by J. Steehler et al at Roanoke College and Steven M. Wright at the University of Wisconsin Stevens Point
A law-suit is brewing, and weve been asked to help. An unsuspecting buyer has purchased some land on the Chain of Lakes near Eagle River, Wisconsin for a family cottage. While walking the property, the buyer discovered several large, partially full, corroding cans. Not knowing the contents of the cans and fearing environmental contamination, the buyer did what any red-blooded American would do go straight to an attorney! The buyer is suing the seller for the cost of removing all the barrels and testing the soil for contamination; a total of $75,000. You have been hired by the County Court as a legal consultant to determine the contents of the barrels and to give your opinion concerning their hazard. Your results will determine the sellers liability. Several of the cans contain a deeply colored liquid. With some investigation of land-transaction records at the Court House, youve learned that the seller (who was the previous owner of the property) manufactured and sold inks many years ago to three different pen-manufacturing companies Papermate, Pinpoint, and Vis--Vis. Ink is a reasonable first guess for these cans contents. The previous owner denies any knowledge of the cans, so you will need to find some way to compare the inks found in Papermate, Pinpoint, and Vis--Vis pens to the colored liquids found in the corroding cans. This will help determine whether the cans contents were inks possibly used by these companies. Several other cans contain clear, colorless liquids. Although the cans are corroded, you can make out the letters HOL on one can. Perhaps this is the end of the word alcohol. Unfortunately, there are many types of alcohol, some considered toxic, some not as toxic. Methanol, ethanol, and 2-propanol (also known as methyl alcohol, ethyl alcohol, and isopropyl alcohol) are the most commonly used alcohols. These alcohols may have been used in the preparation of inks. You will compare the colorless liquids in the cans to liquid samples of common alcohols in order to identify the cans contents.
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EXPERIMENTAL PROCEDURE To identify both these liquids, you will use chromatography, a technique that is often used to perform both qualitative and quantitative analysis on unknown samples.
Qualitative Analysis is any method used to determine the identity and/or presence of a particular substance in a mixture.
Quantitative Analysis is a method which gives information on how much of the substance is present in a sample.
Two forms of chromatography will be used in this experiment gas and paper. The World Wide Web is full of sites explaining the details and intricacies of both methods. Please familiarize yourself with these methods by visiting the following sites (last accessed 02/01/05) prior to your laboratory session. Your laboratory instructor will discuss these methods with you. Gas chromatography:
http://www.yesmag.bc.ca/projects/paper_chroma.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Chromatography_paper.html http://chemlearn.chem.indiana.edu/demos/PaperChr.htm
After collecting your chromatographic data, you are to write a report for the County Court. Your report must be in the following format: Purpose, brief Procedure, Data and Observations, and Conclusion. Look in the previous paragraphs for hints on the purpose of the lab exercise. Briefly outline the procedures you used - first paper chromatography, then gas chromatography. Carefully organize and present your data so that the County Court will be convinced of your first conclusion; viz., the identity of the two liquids. Be sure to attach your chromatograms to your report. Your conclusion must also include your recommendation concerning the property and how you came to that recommendation; i.e., Is the seller liable for the clean-up? Consider some of the following questions when making your recommendation1. Are the colored liquids found on the property the inks sold to the pen-manufacturers? Are the colored liquids hazardous, making the property unsafe? Does the buyer assume all responsibility, once the property is sold? To help you with these questions, find a list of LD50s and PELs for the inks and some other common substances on page 3-3. Use the common substances as reference points to determine the relative hazard of the inks. Further you will find definitions for some terms at the bottom of the page. Please note: The values for the inks have simply been made up.. You will also be provided with Material Safety Data Sheets for these alcohols. Use the MSDSs to determine the potential hazards of the alcohols and make your recommendation based on that information. You may see abbreviations like UEL, LEL, flash point, and/or autoignition temperature on the MSDSs. These terms are also defined page 3 - 3. Be sure to consider the hazards associated with the alcohols. Does the presence of the alcohols make the property unacceptably risky? Who should be responsible for the clean up? Lastly, remember that you are the courts expert witness. Speculation and innuendo should not be a part of your report. Base your recommendations only on data and observations.
1 These questions are meant to help you discuss your recommendation. While some may be appropriate to include in your conclusion, you do not have to address each question individually.
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Table of Toxicity Data
Substance LD502 PEL3
Sodium chloride (table salt) 3.75 g/kg (rats) 15 mg/m3 (nuisance particulate) Sucrose (table sugar) 29.7 g/kg (rats) 15 mg/m3 (nuisance particulate) Caffeine (in coffee) 0.13 g/kg (mice) N/A
Sodium cyanide (nasty poison) 6 mg/kg (rats) 5 mg/m3 Strychnine (nastier poison) 0.5 mg/kg 0.15 mg/m3
Papermate Ink4 4.75 g/kg (mice) 12 mg/m3 Pinpoint Ink4 80 mg/kg (rats) 9 mg/m3 Vis--Vis Ink4 2 mg/kg (rats) 0.10 mg/m3
2 LD50 is the lethal dose for half (50%) of a large population of animals. These values were taken from several sources and MSDSs.
3 PEL is the Permissible Exposure Level for a substance. These are often given as 8-
hour, time weighted averages (TWA). These values have been taken from MSDSs. 4 Remember, these are just made up the numbers for these inks.
Some Useful Definitions for Reading MSDSs
Flash Point Lowest temperature at which a flammable liquid gives off sufficient vapor to form an ignitable mixture with air near its surface.
Autoignition Temperature Minimum temperature at which a substance ignites without application of a flame or spark.
LEL Lower Explosive Limit The lowest concentration of a material in air (% by volume in air) that produces an explosion when it contacts an ignition source.
UEL Upper Explosive Limit The highest concentration of a material in air (% by volume in air) that produces an explosion when it contacts an ignition source.
ATTACHMENTS Please find MSDS for methyl alcohol, ethyl alcohol and isopropyl alcohol attached. These
sheets are from Flinn Scientific Inc., of Batavia, Illinois.