Presentation on theme: "MWF 11:30-12:20, Rm 108, College of Business Administration"— Presentation transcript:
1 MWF 11:30-12:20, Rm 108, College of Business Administration ANALYTICAL CHEMISTRYCHEM 421/821, Spring 2013MWF 11:30-12:20, Rm 108, College of Business AdministrationCOURSE OUTLINEInstructor: Dr. Robert PowersOffice LabsAddress: 722 HaH HaHPhone:web page:Office Hours: 10:30-11:30 am MWF or by Special Appointment.Required Items:(i) Chem 482 & 484 are prerequisites(ii) Text: “Principals of Instrument Analysis”, 6/e D. A. Skoog, J. F. Holler and S R.Crouch; Thomson, New York(iii) Calculator for exams (TI-89 style or a simpler model)
2 Course Outlined (cont.) Course Work:Exam 1: pts. (Mon., Feb. 10)Exam 2: pts. (Fri., Mar. 7)Exam 3: pts. (Mon, Apr. 14)Final: pts. (10-12, Wed., May 5)Written Report: pts. (Fri., Apr. 18)Problem Sets (8): pts. (various due dates)Total: pts.ALL PowerPoint presentations, and answer keys for the problem sets and exams will be posted on BlackBoard.Grading scale: A+=95%; A=90%; A-=85%; B+=80%; B=75%; B-=70%;C+=65%; C=60%; C-=55%; D=50%; D-=45%; F=40%
3 Course Outlined (cont.) Class ParticipationReading assignments should be completed prior to each lecture.You are expected to participate in ALL classroom discussionsExamsAll exams (except the final) will take place at 6 pm in Rm 105, College of Business Administration on the scheduled date.The length of each exam will be open-ended. You will have as much time as needed to complete the exam.Bring TI-89 style calculator or a simpler model, approved translator and text book (you will be able to use certain charts, tables and appendix)A review session will take place during the normal class time.ALWAYS SHOW ALL WORK!!!!
4 Course Outlined (cont.) Problem SetsProblem sets are worth either 15 or 20 points each and are selected from the questions/problems at the end of each chapter in the text.You may work together in groups, but everyone must submit their own set of answers to the problem set.Please feel free to visit me during office hours for assistance in answering the problem sets.You must show all work to receive full credit.Problem sets are due at the beginning of class on the due dates listed in the syllabus course schedule.Late Problem sets will incur a 5 point penalty.Problem sets will not be accepted after the next problem set due date has occurred or after the last day of class.
5 Course Outlined (cont.) Problem Sets (cont.)Students generally perform very well on the problem set, which provides a “grade cushion” to the more challenging Exams.PLEASE DO THE PROBLEM SETS!DO NOT USE THE INTERNET, ANSWER KEYS OR SOLUTION MANUALS TO COMPLETE YOUR PROBLEM SET.Failure to comply will result an automatic zero score for ALL problem sets.You will receive a zero out of the possible 150 pointsPenalty will occur for a single infraction.A single problem on a single problem set – no exceptions.
6 PAPER ON INSTRUMENTAL METHODS Paper General4-5 pages single space textAdditional pages for figures, references12 pitch fontDouble spacing between paragraphs and headingsPaper TopicInstrumental methodPrincipals behind techniqueHow the technique is usedKind of instrumentationWhat samples are usedAdvantages/disadvantages
7 PAPER ON INSTRUMENTAL METHODS Application of instrumental methodBrief review of the properties of sample of interestHow these properties are used to analyze sampleWhat types of techniques are availableAdvantages/disadvantagesSource of ideasJournals: Analytical Chemistry, Analytical Biochemistry Trends in Analytical Chemistry(TrACs), C&E News, Science, NatureGrading (50 points total)ContentClarity of PresentationComprehension of materialPaper topic needs to be approved by Monday, March 10thDue Date: 11:30 am, Friday April 18th
8 PAPER ON INSTRUMENTAL METHODS Your Paper is Not a “Cliff” Notes Summary of a Scientific Journal ArticleWrite the paper in a manner that explains the technique or application to a colleague or friendUse Specific Data and/or ComparisonsExamples:Poor – “mass spectrometry is very sensitive”Excellent – “mass spectrometry has very high femtogram limits of detection compared to the micrograms required by NMR.Use Figures within the textIt is much easier to describe a concept or results by referring to and describing the details of a figureDO NOT PLAGIRAZE!Plagiarism will result in an automatic failing grade and the incident of academic dishonesty will be reported to the Dean of Students.
9 Lecture Topics Date Chapter Topic I. Introduction to Analytical ChemistryJan 13 Chap 1 IntroductionII. Spectroscopic MethodsJan 15 Chap 6 Introduction to SpectroscopyJan 17 Chap 6Jan 22 Chap 7 Instrumentation for SpectroscopyJan 24 Chap 7Jan 27 Problem Set #1 dueJan 29 Chap UV/Visible Molecular Absorption SpectroscopyJan 31 Chap 13-14Feb 3 Chap 13-14Feb 5 Chap Molecular Luminescence SpectroscopyFeb 7 Problem Set #2 dueFeb 10 EXAM 1Feb 12 Chap Infrared SpectroscopyFeb 14 Chap 16-17Feb 17 Chap Raman SpectroscopyFeb 19 Problem Set #3 dueFeb 21 Chap Atomic SpectroscopyFeb 24 Problem Set #4 dueFeb 26 Chap Introduction to ChromatographyIII. Separation MethodsFeb 28 Chap Gas ChromatographyMar 3 Chap 27Mar 5 Problem Set #5 dueMar 7 EXAM 2
10 Lecture Topics Date Chapter Topic Mar 10 Chap Liquid Chromatography/Paper Topic ApprovalsMar 12 Chap 28Mar 14 Chap Other Separation MethodsMar 17 Problem Set #6 dueIV. Electrochemical MethodsMar 19 Chap Introduction to ElectrochemistryMar Chap 22March Spring BreakMar 31 Chap 22Apr 2 Chap PotentiometryApr 4 Chap 23Apr 7 Chap CoulometryApr 9 Chap VoltammetryApr 11 Problem Set #7 dueApr 14 EXAM 3V. Other TechniquesApr 16 Chap NMRApr 18 Chap 19 Instrumental Methods Paper DueApr 21 Chap 19Apr 23 Chap 19Apr 25 Chap 11,20 Mass SpectrometryApr 28 Chap 11,20Apr 30 Problem Set #8 dueMay Review SessionMay 5 FINAL EXAM
11 Introduction to Analytical Chemistry BackgroundA.) ANALYTICAL CHEMISTRY: The Science of Chemical Measurements.B.) ANALYTE: The compound or chemical species to be measured, separated or studiedC.) TYPES of ANALYTICAL METHODS:1.) Classical Methods (Earliest Techniques)a.) Separations: precipitation, extraction, distillationb.) Qualitative: boiling points, melting points, refractive index, color,odor, solubilitiesc.) Quantitative: titrations, gravimetric analysis2.) Instrumental Methods (~post-1930’s)a.) separations: chromatography, electrophoresis, etc.b.) Qualitative or Quantitative: spectroscopy, electrochemical methods,mass spectrometry, NMR,radiochemical methods, etc.
12 How Do We Answer or Address These Questions? CHOOSING AN ANALYTICAL METHODWhat Factors to Consider:What type of information does the method provide?What are the advantages or disadvantages of the technique versus other methods?How reproducible and accurate is the technique?How much or how little sample is required?How much or how little analyte can be detected?What types of samples can the method be used with?Will other components of the sample cause interference?Other factors: speed, convenience, cost, availability, skill required.How Do We Answer or Address These Questions?
13 Two types of error: random or systematic CHARACTERISTICS OF AN ANALYTICAL METHODSAccuracy: The degree to which an experimental result approaches the true or accepted answer.Ways to Describe Accuracy:Error: An experimental measure of accuracy. The difference between the result obtained by a method and the true or accepted value.Absolute Error = (X – m)Relative Error (%) = 100(X – m)/mwhere: X = The experimental resultm = The true resultAll Methods, except counting, contain errors – don’t know “true” valueTwo types of error: random or systematic
14 CHARACTERISTICS OF AN ANALYTICAL METHODS Random Error: results in a scatter of results centered on the true value for repeated measurements on a single sample.Systematic Error: results in all measurements exhibiting a definite difference from the true valueRandom ErrorSystematic Errorplot of the number of occurrences or population of eachmeasurement (Gaussian curve)
15 CHARACTERISTICS OF AN ANALYTICAL METHODS Precision: The reproducibility of results. The degree to which an experimental result varies from one determination to the next.Precision is related to random error and Accuracy is related to systematic error.Illustrating the difference between “accuracy” and “precision”Low accuracy, high precisionLow accuracy, low precisionHigh accuracy, low precisionHigh accuracy, high precision
16 CHARACTERISTICS OF AN ANALYTICAL METHODS Ways to Describe Precision:Range: the high to low values measured in a repeat series of experiments.Standard Deviation: describes the distribution of the measured results about the mean or average value.Absolute Standard Deviation (SD):Relative Standard Deviation (RSD) orCoefficient of Variation (CV):where: n = total number of measurementsXi = measurement made for the ith trial= mean result for the data sample
17 CHARACTERISTICS OF AN ANALYTICAL METHODS Response: The way in which the result or signal of a method varies with the amount of compound or property being measured.Ways to Describe Response:Calibration Curve: A plot of the result or signal vs. the known amount of a known compound or property (standard) being measured.
18 CHARACTERISTICS OF AN ANALYTICAL METHODS Parameters used to Describe a Calibration Curve: S = mc + SblS – measured signalc – analyte concentrationSbl – instrument signal for blankSensitivity: calibration sensitivity = slope (m) of calibration curve.analytical sensitivity (g) = slope (m)/standard deviation (Ss)ability to discriminate between smalldifferences in analyte concentration.Slope and reproducibility of thecalibration curve.Method AMethod B
19 No method is totally free from interference from other species. Selectivity: degree to which the method is free from interference by otherspecies in the sampleNo method is totally free frominterference from other species.Selectivity coefficient (k):kB,A = mB/mARelative slopes of calibration curves indicate selectivity:S = mA(cA + kB,Acb) + SblSpecies ASpecies BInterested in detecting species A, but signal will be a combination of signalfrom the presence of species A and species B.
20 Signal-to-noise Ratio (S/N): Limits of Detection (cm ): (minimum analyte signal (Sm) - mean blank signal( ))/slope(m)minimum/maximum concentration or mass of analyte that can be detected at a known confidence level.Signal-to-noise Ratio (S/N):Noise: random variation in signal or backgroundSignal: net response recorded by a method for a sample(Note: a value of S/N = 2 or better is considered to be the minimum ratio needed for the reliable detection of a true signal from a sample.)Estimate S/N:Multiple determination of blank samples.Estimation of best-fit to calibration curvessignalnoise
21 Dynamic Range: linear region of calibration curve where the lower limit is ten times the standard deviation of the blank.LOQ - limit of quantitationLOL - limit of linearityConcentration (mM)
22 Glucose Concentration, mM Example 1: The data in the table below were obtained during a colorimetric determination of glucose in blood serum.A serum sample gave an absorbance of Find the glucose concentration and its standard deviation, calibration sensitivity, detection limit and dynamic range.Glucose Concentration, mMAbsorbance, A0.00.0022.00.1504.00.2946.00.4348.00.57010.00.704