Separation, Electroanalytical, and Spectrochemical Techniques

SEPARATION, ELECTROANALYTICAL, AND SPECTROCHEMICAL TECHNIQUES Copy write This document is published under the conditions of the Creative Commons http://en.wikipedia.org/wiki/Creative_Commons I have received kind permission to reproduce diagrams and text from Dr Scott Van Bramer for Mass Spectrometry DR William Reusch for Molecular Spectroscopy of Michigan State University from his Organic Chemistry Course These are gratefully acknowledged, other sources are acknowledged where quoted C.C Some Rights Reserved 1.1 Table of Contents 1.1 Table of Contents INTRODUCTION .6 PREREQUISITE KNOWLEDGE .6 TIME MATERIALS .7 MODULE RATIONALE OVERVIEW .7 2.1 Resume .7 2.2 Outline .8 2.3 Graphic Organiser 10 2.4 General Objective 11 2.5 Specific Objectives 11 PRE ASSESSMENT 14 2.6 Answer Key .19 KEY CONCEPTS .21 LEARNING TIPS 26 COMPULSORY READING 27 3.1 Reference 1: 27 3.2 Reference 2: 27 3.3 Reference 3: 27 USEFUL LINKS .28 MULTI MEDIA RESOURCES 36 UNIT I SEPARATION AND CHROMATOGRAPHIC TECHNIQUES .38 4.1 Summary of the Learning Activity 38 4.2 Required Readings 38 4.3 Separation Techniques 39 4.4 Distillation 40 4.5 Chromatography .44 4.6 Types of Chromatographic Techniques 50 4.7 Thin Layer Chromatography 51 4.8 Liquid Chromatography 53 4.9 Gas Chromatography 57 UNIT II ELECTROANALYTICAL TECHNIQUES .62 4.10 Summary of the Learning Activity 62 4.11 List of Required Readings .62 4.12 Potentiometry 63 4.13 Voltammetry 65 4.14 Pulse Polarography .69 UNIT III SPECTROSCOPY AND ATOMIC SPECTROSCOPIC TECHNIQUES .75 4.15 Summary of the Learning Activity 75 4.16 List of Required Readings .75 4.17 List of Relevant Useful Links 75 4.18 List of Relevant Multimedia Resources 76 4.19 Electromagnetic Radiation 76 4.20 Beer’s Law 82 4.21 Atomic Spectroscopic Techniques 85 4.22 Atomic Absorption 87 UNIT IV MOLECULAR SPECTROCOPY 1: UV-VISIBLE AND IR 90 4.23 Summary of the Learning Activity 90 4.24 List of Required Readings .90 4.25 List of Relevant Useful Links 90 4.26 List of Relevant Multimedia Resources 91 4.27 Ultraviolet- Visible Spectroscopy 91 4.28 Instrumentation for UV Visible Spectrometry 94 4.29 Infrared Spectroscopy 96 4.30 Identifying Functional Groups by Infrared Spectroscopy 97 UNIT V MOLECULAR SPECTROSCOPY 2: NUCLEAR MAGNETIC RESONANCE 104 5.2 Nuclear Magnetic Resonance Spectroscopy 105 5.3 Proton NMR 106 5.4 Carbon Nmr Spectroscopy 111 UNIT IX MASS SPECTROMETRY 116 5.5 List Of Relevant Useful Links 116 5.6 Mass Spectrometry .116 5.7 Fragmentation Patterns 118 MODULE SYNTHESIS 123 SUMMATIVE EVALUATION 125 FILE STRUCTURE 129 INTRODUCTION PREREQUISITE KNOWLEDGE • Atomic structure and the concept of energy levels • RedOx introduction • Balancing RedOx equations • Standard reduction potentials • Nernst equation • Concepts of Sampling • Errors and statistics • Theories of bonding • Electrochemistry TIME • Separation Techniques and Chromatographic 25 hours • Electrochemical Techniques 15 hours • Spectroscopy and Atomic Spectroscopic Techniques 20 hours • Molecular Spectroscopy 1(UV and IR) 30 hours • Molecular Spectroscopy (NMR) 15 hours • Mass Spectrometry 15 hours MATERIALS You will require the following tools and resources for completing this module • Computer, CD-ROMs, and e-library • To access this module, exams, and other relevant materials on a computer • Internet Connection to access the module and other suggested reference materials • For interactive discussions/chat sessions • Recommended textbooks and reference materials to assist learning and further understanding of the topics in the module • Macromedia flash player MODULE RATIONALE Separation, Electro analytical and Spectroscopic Techniques are the basis of instrumental analysis widely applied in industry, chemistry, biochemistry, environment and school science These techniques are based on principles of chemistry taught at school level Therefore in this module we shall study the principles on which these techniques are based and acquire the basic skills necessary to use the techniques Studying this area deepens the understanding of the underlying chemistry principles making the learner better able to teach them at school level OVERVIEW 2.1 Resume This module consists of three interrelated subject areas; Separation Techniques and Chromatographic Techniques, Electro analytical Techniques and Spectroscopic Methods The module will be taught in six learning units reflecting common concepts and approaches Separation Techniques and Chromatographic Techniques unit will review elementary separation techniques that are usually taught in the school system, followed by a discussion of Chromatography Techniques these are covered by introducing the general chromatographic theory, followed by its application in different techniques of plane and column chromatographic techniques Electro Analytical Techniques will introduce principles on which potentiometry is based, elaborate the common applications of potentiometry, this will be followed by voltammetry, starting with polarographic techniques ending with cyclic and anodic stripping voltammetry The unit on Spectroscopy and Atomic Spectroscopic Techniques will review concept of energy matter interaction, concepts of energy levels in atoms and molecules, and the unit will end with a discussion of atomic spectroscopic techniques Molecular Spectroscopy will start with a discussion of the theory of UV-Visible spectroscopy, how it arises and how it is used in qualitative and quantitative analysis, instrumentation of the modern UV-visible spectrophotometer The unit will end with a discussion of infrared spectroscopy starting with how the spectra arises, the different peaks exhibited by specific functional groups and how to apply IR in identification of functional groups and compounds Molecular Spectroscopy will introduce nuclear magnetic resonance phenomenon, followed by a discussion of proton NMR, the relationship of chemical shift with the molecular chemical environment and how proton NMR used in identification of functional groups The unit ends with a discussion of the carbon NMR and how it compliments proton NMR in analysis of compounds The last learning unit will be Mass Spectrometry starting with how mass spectra arises, how it is used in identification of organic compounds ending with the Instrumentation for mass spectrometry 2.2 Outline UNITI I SEPARATION AND CHROMATOGRAPHIC TECHNIQUES- 25 hours • Separation Techniques o Solvent Extraction o Distillation • Chromatography o Theory of Chromatography o The Development Process • Types of Chromatographic Techniques o Plane Chromatography o Plane Chromatography o Liquid Chromatography o Gas Chromatography UNIT II ELECTROANALYTICAL TECHNIQUES- 15 Hours • Potentiometry o Ion Selective Electrodes o pH Glass Electrodes o Potentiometric Titrations • Voltammetry o Polarography o Pulse Polarography o Cyclic Voltammetry o Anodic Stripping Voltammetry UNIT III SPECTROSCOPY AND ATOMIC SPECTROSCOPIC TECHNIQUES- 20 hours • Spectroscopy: o Electromagnetic Radiation o The Atom and Atomic Spectroscopy o Beers law • Atomic Spectroscopic Techniques UNIT IV MOLECULAR SPECTROCOPY 1: UV-VISIBLE AND IR- 30 hours • Ultraviolet- Visible Spectroscopy o Electronic transitions o Identification of functional groups Using UV o Instrumentation for UV Visible Spectrometry • Infrared Spectroscopy o Molecular Vibration and IR Spectroscopy o Relative energies of IR Absorptions o Identifying Functional Groups by Infrared Spectroscopy UNIT V MOLECULAR SPECTROSCOPY 2: NUCLEAR MAGNETIC RESONANCE 15 hours • Nuclear Magnetic Resonance Spectroscopy o Proton NMR o Chemical Shift o Correlation of HNMR With Structure • Carbon NMR Spectroscopy UNIT IX MASS SPECTROMETRY- 15 hours • Mass Spectrometry o Fragmentation Patterns o Finger Print Spectrum 2.3 Graphic Organiser SEPARATION, ELECTROANALYTICAL, AND SPECTROCHEMICAL TECHNIQUES SEPARATION SEPARATION TECHNIQUES TECHNIQUESAND AND CHROMATOGRAPHIC CHROMATOGRAPHIC TECHNIQUES TECHNIQUES ELECTROANALYTICAL ELECTROANALYTICAL TECHNIQUES TECHNIQUES MOLECULAR MOLECULAR SPECTROSCOPY SPECTROSCOPY11 INTRODUCTION TO INTRODUCTION TO SPECTROSCOPY AND SPECTROSCOPY AND ATOMIC ATOMICSPECTROSCOPY SPECTROSCOPY MOLECULAR MOLECULAR SPECTROSCOPY SPECTROSCOPY22 MASS MASSSPECTROMETRY SPECTROMETRY 10 come from alpha-cleavages Further examples of functional group influence on fragmentation are provided by a selection of compounds that may be examined by clicking the left button below 5.7.3 Finger Print Spectrum The complexity of fragmentation patterns has led to mass spectra being used as "fingerprints" for identifying compounds Environmental pollutants, pesticide residues on food, and controlled substance identification are but a few examples of this application Extremely small samples of an unknown substance (a microgram or less) are sufficient for such analysis The following mass spectrum of cocaine demonstrates how a forensic laboratory might determine the nature of an unknown street drug Even though extensive fragmentation has occurred, many of the more abundant ions (identified by magenta numbers) can be rationalized by the three mechanisms shown above 120 Figure 37: A Finger print Mass Spectrum of Cocain Odd-electron fragment ions are often formed by characteristic rearrangements in which stable neutral fragments are lost Mechanisms for some of these rearrangements have been identified by following the course of isotopically labeled molecular ions 5.7.4 Formative Assessment 1) An organic compound (A) is composed of carbon, hydrogen and nitrogen, with carbon constituting over 60% of the mass It shows a molecular ion at m/z=112 amu in the mass spectrum Answer the following questions by entering numbers in the answer boxes a Write a plausible Molecular Formula for compound A: C H N 121 b How many Rings + Double Bonds must be present in compound A? 2) Another compound, B, composed only of carbon, hydrogen and oxygen, also shows a molecular ion at m/z=112 amu a Write a plausible Molecular Formula for compound B, assuming it has three double bonds and no rings C H O 3) Compound C is composed only of carbon, hydrogen and oxygen, and shows a molecular ion at m/z=180 amu Carbon accounts for 60% of the molecular mass a) Write a plausible Molecular Formula for compound C C H O c) How many Rings + Double Bonds must be present in compound C? 122 MODULE SYNTHESIS In Unit I separation methods taught in school were revisited these were solvent extraction and distillation for each of the technique definitions were made, the conditions under which each separation method is appropriately applied were discussed and the equipment for carrying out the techniques were also presented Later in the unit chromatography techniques were introduced starting with the general theory, including different types of development Principal types of chromatography were introduced, including paper, thin layer, and equipment for their implementation discussed This was followed by column chromatography in which was introduced, instrumentation discussed including different types of columns, and detectors In the last part of the module liquid chromatography was introduced and HPLC discussed in detail this included scales of application of HPLC, Instrumentation and the major modes of separation of HPLC In Unit II the major Electrochemical Techniques were introduced, the discussion of potentiometry included theory of potentiometry and the application of potentiometry to pH measurement using the glass electrode, ion selective electrodes or Red Ox electrodes were discussed and their application to automatic titration stations highlighted The second part of unit discussed different techniques of voltammetry starting with a general discussion of the of the theory of voltammetry, followed by polarographic techniques based on the dropping mercury electrode The unit ended with a discussion of two voltammetric techniques cyclic and anodic stripping voltammetry Spectroscopy and Atomic Spectrometric Techniques, Spectroscopy was introduced by recalling different components of the electromagnetic spectrum, their relative energies common spectroscopic terms and measurement units The interaction of radiation and matter was discussed in depth and how this can be used for qualitative and quantitative analysis in both molecular and atomic spectroscopy The last part of the unit discussed atomic spectroscopy defining the three major modes of atomic spectroscopy, the phenomena leading to their existence, how they are used in qualitative and quantitative analysis The unit ended by discussing instrumentation used in atomic spectroscopy Molecular spectroscopy discussed UV-Visible spectroscopy and Infrared spectroscopy starting with how each of the two phenomena arises 123 The transitions that give rise to UV-visible spectra were discussed their correlation to specific functional groups was offered The factors that affect absorption of functional groups were elaborated Examples of how UV is used in structural determination were presented This discussion was concluded by application of UV-visible spectroscopy in quantitative analysis and UV-Visible Instrumentation The last part of the unit presented IR spectroscopy, in this explanation of IR spectroscopy arises was given This was followed by discussion of typical absorption peaks of major functional groups and correlation of IR spectrum with structure Molecular Spectroscopy discussed nuclear magnetic resonance spectroscopy, this started by description of the NMR phenomena, the requirement for a nucleus to exhibit NMR phenomena and the influences of the structural environment The discussion included correlation of hydrogen NMR with specific functional elements in the molecule, spin-spin interactions, correlation of magnitude of peaks with number of hydrogen atoms and peak position with molecular environment and functional groups The unit was concluded by discussion carbon13 NMR this discussion highlighted the C-13 NMR, technical limitation of information provided by C-13 NMR, how it is used to complement Hydrogen NMR in structural determination Mass spectrometry started with how mass spectrometry is effected, and the arising spectrum This was followed by rules of fragmentation, how the presence of the isotopes affects fragmentation and correlation of structure with mass spectrum 124 SUMMATIVE EVALUATION Calculate the energy of the photons in radiation of wavelength: (a) 635 nm (in the visible) (b) 18.7 nm (in the ultraviolet) (c) 58.6 µm (in the infrared) The carbon-13 NMR spectrum of one of the butyl acetate isomers (C4H9OCOCH3) showed signals at δc22, 28, 80 and170 What is its structure? Why is the intensity of the peak at δ 28 much more intense than that at δ 22 (by factor of approximately eight)? How would the multiplicity and signal intensity in the proton NMR spectrum of this compound confirm your deductions? 3a For a typical chromatographic separation giving just-resolved peaks (Rs = 1.5), assume that N = 3600, k' = 2, and α = 1.15 Sketch the effects of changing these parameters one at a time to (a) N = 1600, (b) k' = 0.8, and (c) a = 1.10 b To decrease the plate height and yet increase the resolution, what courses of action are available? What penalties may accrue for each approach? 4a) Why are atomic spectra different from molecular spectra? b Why are the atomic spectra of Ca° and Ca+ different? c What is the difference between atomic emission spectroscopy and atomic absorption spectroscopy? A pleasant sweet smelling liquid BP 1010C bas the following IR spectra and MS spectra shown 125 For each of the compounds A through F indicate the number of structurally-distinct groups of carbon atoms, and also the number of distinct groups of equivalent hydrogens Enter a number from to in each answer box A Number of distinct carbon atoms: Number of distinct hydrogen groups: B Number of distinct carbon atoms: Number of distinct hydrogen groups: C Number of distinct carbon atoms: Number of distinct hydrogen groups: D Number of distinct carbon atoms: Number of distinct hydrogen groups: E Number of distinct carbon atoms: Number of distinct hydrogen groups: F Number of distinct carbon atoms: Number of distinct hydrogen groups: 126 Determine the structure f the compound 127 MAIN AUTHOR OF THE MODULE Vincent Makokha was educated at Makerere University Kampala earning his BSc (Ind Chemistry 1991) and MSc (Analytical Chemistry 2000) He subsequently worked in Industry worked in industry and research organizations in various capacities as analytical chemistry specialist He later joined Kyambogo University were he teaches Chemistry Education and Chemistry Technology courses Vincent is married to Florence and they have two children Collette and Vivienne TEACHING TIPS This module aims at presenting the most common instrumental analytical techniques to the learners With three principal aims of providing • Knowledge of principles of the analytical techniques • Skills for interpreting analytical data generated by instrument s, • Practice for the skills and knowledge delivered For undergraduate level students there is the delicate task of managing the level of complexity of information and skills delivered For this module there are lots of resources many of them intended for the practicing professional and advanced graduate student and therefore unsuitable for our purposes The material was therefore selected and presented in a simple form to provide a working knowledge of the subject matter, leaving room for the more enthusiastic student to pursue the matter further, without confusing the average student The basic teaching aid is the material presented in the module which forms the back borne of the course The recommended texts and online materials are required to add depth to the understanding of the module by providing detail and extra practice for the learner The major task of the e learning teacher is to encourage the learner and pace him through each learning unit Each learning unit should be covered and mastered before advancing to the next unit The material presented should be preferably covered in the order presented in the module 128 REFERENCES Crow D.R : Principles and applications of Electrochemistry Chapman and Hall, nd Edition 1996 Galen Wood Ewing Instrumental methods of chemical analysis Publisher: MacgrawHill 1986 Braun D Robert Introduction to chemical Analysis Publisher: McGrawHill st Edition 1982 Heslop R.B, Wild Gillian M S I Units in chemistry Applied Science Publishers, 1971 Hobarth Willard, Lynne Merritt, John Dean, and Frank Settle, Instrumental Methods of Analysis Wadsworth Publishing Company; Sub edition (February 1988) FILE STRUCTURE Microsoft Word File Separation, Electroanalytical, and Spectrochemical Techniques Final Version.doc PDF File Separation, Electroanalytical, and Spectrochemical Techniques Final Version.pdf AAS Atomic Absorption Instrument Cyclic Voltammetry Distillation Electromagnetic Spectrum Energy Levels Gas Chromatography HPLC 129 Infra Red Spectroscopy Ion Selective Electrodes Mass Spectrometry Potentiometry Separation and Chromatography 130 ... Graphic Organiser SEPARATION, ELECTROANALYTICAL, AND SPECTROCHEMICAL TECHNIQUES SEPARATION SEPARATION TECHNIQUES TECHNIQUESAND AND CHROMATOGRAPHIC CHROMATOGRAPHIC TECHNIQUES TECHNIQUES ELECTROANALYTICAL... Separation Techniques and Chromatographic Techniques, Electro analytical Techniques and Spectroscopic Methods The module will be taught in six learning units reflecting common concepts and approaches... Separation Techniques and Chromatographic 25 hours • Electrochemical Techniques 15 hours • Spectroscopy and Atomic Spectroscopic Techniques 20 hours • Molecular Spectroscopy 1(UV and IR) 30 hours