ANALYTICAL CHEMISTRYCHEM 421-821, Spring 2013MWF .ppt

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1、ANALYTICAL CHEMISTRY CHEM 421/821, Spring 2013 MWF 11:30-12:20, Rm 130 Hamilton HallCOURSE OUTLINEInstructor: Dr. Robert PowersOffice LabsAddress: 722 HaH 721 HaHPhone: 472-3039 472-5316e-mail:rpowers3unl.eduweb page: http:/bionmr-c1.unl.edu/Office Hours: 10:30-11:30 am MWF or by Special Appointment

2、.Required Items: (i) Chem 482 Thomson, New York,Course Outlined (cont.),Course Work:Exam 1: 100 pts. (Mon., Feb. 4)Exam 2: 100 pts. (Fri., Mar. 1)Exam 3: 100 pts. (Mon, Apr. 8)Final: 200 pts. (10-12, Wed., May 1)Written Report: 50 pts. (Fri., Apr. 13)Problem Sets (8): 150 pts. (various due dates)Tot

3、al: 700 pts.,Answer keys for the problem sets and exams will be posted on BlackBoard, on the bulletin board next to Room 722 Hamilton Hall and on the web (http:/bionmr-c1.unl.edu/). If removed for photocopying, these keys must be returned to the bulletin board immediately after use.,Grading scale: A

4、+=95%; A=90%; A-=85%; B+=80%; B=75%; B-=70%; C+=65%; C=60%; C-=55%; D=50%; D-=45%; F=40%,Class Participation Reading 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 Hamilton

5、 Hall Rm. 130 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

6、 will take place during the normal class time. ALWAYS SHOW ALL WORK!,Course Outlined (cont.),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

7、 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

8、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.,Course Outlined (cont.),Problem Sets (cont.)Students generally perform very well on the problem set, which provides a “grade cu

9、shion” 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

10、 for a single infraction. A single problem on a single problem set no exceptions.,PAPER ON INSTRUMENTAL METHODS,Paper General 4-5 pages single space text Additional pages for figures, references 12 pitch font Double spacing between paragraphs and headingsPaper Topic Instrumental method Principals be

11、hind technique How the technique is used Kind of instrumentation What samples are used Advantages/disadvantages,PAPER ON INSTRUMENTAL METHODS,Application of instrumental method Brief review of the properties of sample of interest How these properties are used to analyze sample What types of techniqu

12、es are available Advantages/disadvantagesSource of ideas Journals: Analytical Chemistry, Analytical Biochemistry Trends in Analytical Chemistry(TrACs), C&E News, Science, NatureGrading (50 points total) Content Clarity of Presentation Comprehension of material Paper topic needs to be approved by Mon

13、day, March 4th Due Date: 11:30 am, Friday April 12th,PAPER ON INSTRUMENTAL METHODS,Your Paper is Not a “Cliff” Notes Summary of a Scientific Journal Article Write the paper in a manner that explains the technique or application to a colleague or friend Use Specific Data and/or Comparisons Examples:

14、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 text It is much easier to describe a concept or results by referring to and describing the details of a figureDO NOT

15、PLAGIRAZE! Plagiarism will result in an automatic failing grade and the incident of academic dishonesty will be reported to the Dean of Students.,Lecture TopicsDate Chapter Topic I. Introduction to Analytical ChemistryJan 7 Chap 1 IntroductionII. Spectroscopic MethodsJan 9 Chap 6 Introduction to Spe

16、ctroscopy Jan 11 Chap 6 Jan 14 Chap 7 Instrumentation for Spectroscopy Jan 16 Chap 7 Jan 18 Problem Set #1 due Jan 23 Chap 13-14 UV/Visible Molecular Absorption SpectroscopyJan 25 Chap 13-14 Jan 28 Chap 13-14 Jan 30 Chap 15 Molecular Luminescence Spectroscopy Feb 1 Problem Set #2 due Feb 4 EXAM 1Feb

17、 6 Chap 16-17 Infrared Spectroscopy Feb 8 Chap 16-17 Feb 11 Chap 18-19 Raman Spectroscopy Feb 13 Problem Set #3 dueFeb 15 Chap 8-10 Atomic Spectroscopy Feb 18 Problem Set #4 dueFeb 20 Chap 26 Introduction to ChromatographyIII. Separation MethodsFeb 22 Chap 27 Gas ChromatographyFeb 25 Chap 27 Feb 27

18、Problem Set #5 dueMar 1 EXAM 2,Lecture TopicsDate Chapter Topic Mar 4 Chap 28 Liquid Chromatography/Paper Topic ApprovalsMar 6 Chap 28Mar 8 Chap 29-30 Other Separation MethodsMar 11 Problem Set #6 dueIV. Electrochemical MethodsMar 13 Chap 22 Introduction to Electrochemistry Mar 15 Chap 22March 17-24

19、 Spring Break Mar 25 Chap 22 Mar 27 Chap 23 Potentiometry Mar 29 Chap 23 Apr 1 Chap 24 Coulometry Apr 3 Chap 25 VoltammetryApr 5 Problem Set #7 dueApr 8 EXAM 3V. Other TechniquesApr 10 Chap 19 NMRApr 12 Chap 19 Instrumental Methods Paper DueApr 15 Chap 19Apr 17 Chap 19Apr 19 Chap 11,20 Mass Spectrom

20、etryApr 22 Chap 11,20Apr 24 Problem Set #8 dueApr 26 Review SessionMay 1 FINAL EXAM,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

21、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-1930s)a.) separation

22、s: chromatography, electrophoresis, etc.b.) Qualitative or Quantitative: spectroscopy, electrochemical methods, mass spectrometry, NMR, radiochemical methods, etc.,CHOOSING AN ANALYTICAL METHOD,What Factors to Consider:What type of information does the method provide?What are the advantages or disad

23、vantages 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 factor

24、s: speed, convenience, cost, availability, skill required.How Do We Answer or Address These Questions?,CHARACTERISTICS OF AN ANALYTICAL METHODS,Accuracy: The degree to which an experimental result approaches the true or accepted answer.Ways to Describe Accuracy:Error: An experimental measure of accu

25、racy. 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 dont know “true” value Two types of error: random or syst

26、ematic,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 value,Random Error,Systematic Error,plot

27、of the number of occurrences or population of each measurement (Gaussian curve),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

28、is related to systematic error.,Low accuracy, low precision,Low accuracy, high precision,High accuracy, low precision,High accuracy, high precision,Illustrating the difference between “accuracy” and “precision”,CHARACTERISTICS OF AN ANALYTICAL METHODS,Ways to Describe Precision:Range: the high to lo

29、w 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) or Coefficient of Variation (CV):where: n = total number of measurementsXi = m

30、easurement made for the ith trial= mean result for the data sample,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

31、signal vs. the known amount of a known compound or property (standard) being measured.,CHARACTERISTICS OF AN ANALYTICAL METHODS,Parameters used to Describe a Calibration Curve: S = mc + Sbl S measured signal c analyte concentration Sbl instrument signal for blankSensitivity: calibration sensitivity

32、= slope (m) of calibration curve.analytical sensitivity (g) = slope (m)/standard deviation (Ss)ability to discriminate between small differences in analyte concentration. Slope and reproducibility of the calibration curve.,Method A,Method B,Selectivity: degree to which the method is free from interf

33、erence by other species in the sample,Species A,Species B,No method is totally free from interference from other species.Selectivity coefficient (k):kB,A = mB/mARelative slopes of calibration curves indicate selectivity:S = mA(cA + kB,Acb) + Sbl,Interested in detecting species A, but signal will be

34、a combination of signal from the presence of species A and species B.,noise,signal,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):Noi

35、se: 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. Estimat

36、ion of best-fit to calibration curves,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 linearity,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 0.350. Find the glucose concentration and its standard deviation, calibration sensitivity, detection limit and dynamic range.,