Laboratory Experiment for Atoms, Molecules & ReactionsWinter Quarter 2006Instrument Exploration # 1: Atomic Absorption (AA)Written by Rebecca Sunderman, Ph.D.Responsibilities:- Instrument theory and introduction lecture/workshops are scheduled for week 2.- Solution preparation is scheduled for week 2: Tuesday at 1:00 for groups B, C & D. and then Thursday at 1:00 group A (and any other who absolutely could not make Tuesdays time.)- Solution dilution before your laboratory time week 3.- Running experiment week 3- Optional lab notebook photocopies due 9:00 AM on 2-2-06 (week 4)- Final draft of lab report due 9:00 AM on 2-8-06 (week 5)Introduction:Atomic Absorption is a common analytical technique used for both qualitative and quantitative detection of single elements, usually metals, within a given sample. The material to be studied isdissolved into solution, often with strong acids, and sprayed over a flame. Light, of a particular wavelength appropriate for the element being examined, is passed through the sample. The amount of light absorbed by the sample is proportional to the elemental concentration within the sample. Multiple light sources are used to study each element in question.This technique is frequently used to study archaeological artifacts, especially pottery and glass materials. The sample preparation method is destructive, but sample sizes are often so small that the needed material can be removed from the artifact easily. The Experiment:In addition to becoming familiar with the AA instrument, clay samples will be analyzed for two metals. You will be measuring potassium and sodium content in four different types of clay (E.P.K, Ball Clay, Hawthorn Fire Clay, Barnard) and in an unknown. Standardization curves prepared from data on your standards will be used to determine potassium and sodium content, quantitatively, in each of the four clay samples. A quality control, prepared by Jenna, will be usedto verify the qualitative detection of potassium and sodium. Blanks will be used to maintain consistency and reduce error. From these data you should be able to identify the unknown.Each element will require a separate lamp. An example of an experimental run for one of the elements is provided below. This procedural order would be repeated for each element to be studied. We will be repeating it twice. Keep in mind that this may be altered if needed.Example Experimental Run for One Element: BlankStandard Solution lowest concentrationBlankStandard Solution middle concentrationBlankStandard Solution highest concentrationBlankQuality ControlBlankClay Sample 1BlankClay Sample 2BlankClay Sample 3BlankClay Sample 4BlankUnknown sampleBlankBe sure you are ready to start the experimental runs at the beginning of your lab time during week 3. You will have two hours to complete the experiment.Solution Preparation:Prepare a mixed standard solution of KCl and NaCl. The glassware needed for this solution will have already been acid washed. When making standard solutions for using with AA it is essential that the sample matrix match that of the standard. Anhydrous lithium metaborate and nitric acid were added to the clay samples to get them into solution. Both anhydrous lithium metaborate and nitric acid will need to be added to your standard solution. A cesium ionizing buffer solution will also be added to prevent ionization of the potassium and sodium atoms. After completing the calculations necessary to make your standard solution, make your solution. Next calculate the amounts needed to complete the dilutions for next week: These numbers must be checked before you leave. Remember these dilutions must be made the day of your experiment and before your laboratory start time. When working with metal solutions it is essential that all glassware is acid washed. Gather the glassware (volumetric pipettes, flasks, polypropelene containers, etc) needed to make yourdilutions next week and place them in the acid bath. The procedure for acid bath removal will be discussed during the solution prep time. Do not leave before you are informed.References and/or Suggested Readings:Bower, N.W; Bromund, R.H.; Smith, R.H.: “Atomic Absorption for the Archaeologist: An Application to Pottery from Pella of the Decapolis” J. Field Archaeology (1975) 2, 389-398Henderson, J: The Science and Archaeology of Materials (2000)Hughes, M.J.; Cowell, M.R; Craddock, P.T.: “Atomic absorption techniques in Archaeology” Archaeometry (1976) 18, 19-37Orna, M.V.: Archaeological Chemistry (1995)Rice, P.M.: Pottery Analysis: a sourcebook (1987)Skoog; Holler; Nieman: Principles of Instrumental Analysis