Analytical Cumulative Examination The purpose of analytical cumulative examination is to test broad knowledge of fundamental principles of analytical chemistry and  to serve the preparation for the successful graduation with the PhD degree. The examination is based on 95 questions from the list below. These questions are provided in advance of cumulative exams to give students guidance for self- or team-studying and mastering the knowledge of analytical chemistry. It is not expected that students will approach faculty for to check answers, or to have faculty provide answers. Each exam will have 5 questions randomly selected from the list. Because of the random nature of selecting questions for each exam, some questions may appear again on subsequent exams. The answer to each question will be graded on the 20% scale and the total percent will be calculated by adding the individual percents. Based on the total percent earned on the exam, points will be awarded according to the following scheme: less than 50% - 0 points; 50% to 59% -1 point; 60% to 74% - 2 points; 75% and more – 3 points. These points will go towards the total of ten (10) points required to pass Cumulative Examination. List of Questions 1A. i) Using a Bohr atom schematic, explain Kα, Lα, and Mα X-ray fluorescence. ii) Using the following version of Mosley's equation, calculate the Kα energy for Fe (Z= 26) in keV 1

, where RH = 13.6 eV. [Note, another element may be given

in place of Fe]. 2A. How does an energy dispersive X-ray detector work? How is it calibrated? 3A. What are the advantages and disadvantages of using X-ray fluorescence (XRF) for elemental analysis compared to more traditional analytical techniques such as AA or ICP-OES. 4A. i) Derive the equation for a Langmuir isotherm. ii) If a sensor only responds to bound analyte, sketch the response as a function of concentration, assuming that Kd = 10-9 M-1. Plot with both concentration (x-axis) and response (y-axis) on a linear scale; also plot with x-axis concentration on a log scale, y-axis linear. iii) Calculate the percent of bound analyte when the concentration in solution is 0.3 nM [another value may be substituted for 0.3 nM on the test] . 5A. What is ELISA? Give a typical ELISA protocol and explain why enzymes are used. 6A. In 1958, Matthew Meselson and Frank Stahl published a landmark paper on cellular replication in PNAS. Describe the experiments, analytical methods, and results.

7A. Centrifugation is important to understand because it widely used in sample preparation, and is also used as an analytical tool (analytical centrifugation). If a centrifuge is spinning with an rcf = 1000 x g, how long will it take for a 100 nm diameter polystyrene particle (density 1.05 g/cm3) to settle by 1 cm in water (density = 1.0 g/cm3; Viscosity ~ 1 mPas, )? b) Compare this to the amount of time required for a 100 nm diameter gold nanoparticle (density 19.3 g/cm3) and to a 1 µm diameter polystyrene particle. 8A. Why does the equilibrium concentration of particles in a colloid decrease with height. At what height above the bottom would the concentration of particles decrease by a factor of 1/e for 100 nm diameter polystyrene nanospheres (density 1.05) in water (density 1.00)? Assume gravity is 9.8 m/s2, the solution temperature is 25 C, and kB is 1.38x10-23 J/K? What height for 10 nm diameter polystyrene nanospheres? 9A. Compare and contrast fluorescence and Raman spectroscopy. 10A. Explain the quantitative relationship between number of independent trials averaged and relative random error of the averaged results. 11A. Sketch a Czerny-Turner spectrograph. How does decreasing the slit size affect the spectrum? 12A. What is Mossbauer spectroscopy? Sketch an apparatus and explain how one measures wavelength with a Mossbauer spectrometer. 13A. How does a photomultiplier tube (PMT) work? What are some advantages and disadvantages compared to a back-thinned CCD camera? 14A. For a CCD camera, define/explain the following terms and explain how they depend upon exposure time: a) read (readout) noise

b) dark current

c) cosmic spike

d) shot noise

15A. What type of physical and chemical information can be obtained from the optical spectrum of a star, explain. 16CH. Define absorbance (often referred to as optical density) and relate it to absorption cross section and oscillator strength. 17CH. According to Beer’s Law, the absorbance is linear with the concentration of an analyte. When performing UV-vis measurements, however, a nonlinear dependence can be observed. State factors that contribute to the nonlinear behavior and how one can account/correct for these factors in the measurements.

18CH. Electronic structure of organic molecules can be described in terms of nonbonding and different types of bonding electrons. Discuss how electronic transitions of different electrons contribute to the absorption of light. Consider the absorption strength and the absorption spectral range. Please elaborate on how chemical modifications of molecules and the solvent environment affect electronic transitions. 19CH. Explain LASER principles in terms of stimulated emission, population inversion and optical resonator. 20CH. Explain the Frank-Condon principle and how it determines molecular electronic absorption and emission spectral line shapes. 21CH. Explain vibrational modes and their relevance to the structure and symmetry of molecules. 22CH. Explain principles of Raman and resonance Raman spectroscopy? What is the origin of Stokes and anti-Stokes spectral shifts during Raman scattering? 23CH. Compare Raman scattering spectroscopy and infrared absorption spectroscopy in terms of: information revealed by the techniques, vibrational selection rules, methods required for sample preparation, applicability to different types of samples. 24CH. What is surface plasmon resonance (SPR)? Describe an analytical technique that utilizes SPR for measuring molecular binding. Give a representative example. 25CH. Explain principles and applications of Surface-enhanced Raman Scattering (SERS) spectroscopy. Give a representative example. 26CH. What is dynamic light scattering (DLS) and what information can be revealed using this technique? Explain how the measurements are performed. 27CH. Explain how to determine electronic configurations of multielectronic atoms. Consider LS and Russell-Saunders coupling schemes. 28CH. Define spectroscopic term. Give a spectroscopic term symbol for a sodium atom in the ground sate. Explain in details how you have constructed it. 29CH. Describe major mechanisms contributing to the spectral line broadening in atoms. 30CH. Draw Jablonski diagram. Depict and explain ground state, first and the second excited singlet states, triplet state, internal conversion, intersystem crossing, vibrational relaxation, fluorescence, phosphorescence, Rayleigh, Raman and resonance Raman scattering, infrared absorption.

31CH. Define fluorescence and phosphorescence and explain differences between the two. Give a representative example of an analytical application of phosphorescence. 32CH. What is DNA microarray (DNA chip)? How it is made? How it is used? Give an application example. 33CH. Explain near-field microscopy and spectroscopy. 34CH. Describe optical labeling using nanoparticles for bioanalytical applications. Consider fluorescent micro- and nano-particle, fluorescent quantum dots, plasmonic nanoparticles. Give an example of each. 35CH. Please discuss the role of analytical chemistry in modern chemical analysis based on the following review article: “Is the Focus on “Molecules” Obsolete?” by George M. Whitesides, published in Annual Review of Analytical Chemistry, Vol. 6, p. 1-29, 2013. 36M. The van Deemter equation H = A + B/U + CU globally describes the roll of column hydrodynamics in chromatographic separations. Consider two model compounds, caffeine and bovine serum albumin (BSA). Explain how each term (A, B, and C) will be manifest for these two molecules. That is, in practical words, how do these terms differ in how they are seen for the two compounds in a chromatogram? What is the key physical process/constant in which these molecules differ? 37M. For many years (decades), traditional chromatographers refused to acknowledge that capillary electrophoresis (CE) was not a form of chromatography. The argument dealt with the fact that there is no partitioning taking place in CE. Indeed, partitioning does take place in micellar electrokinetic chromatography (MEKC). Draw a diagram depicting the partitioning event in MEKC and show the corresponding equilibrium equation. 38M. Lab-on-a-chip methods have been developed for a wide variety of reasons. Give 5, with single-sentence justifications. 39M. Make the philosophical arguments of both opposing views that: “chromatography is an admission of the failure of spectroscopy” and “spectroscopy is an admission of the failure of chromatography”. 40M. In liquid chromatography in packed columns, a critical attribute of the packing is the particle size. Discuss the PRACTICAL advantages and disadvantages of using very small particles to pack a separation column. 41M. In ion exchange chromatography, gradient elution usually involves adjustment of the salt concentration in the mobile phase from low to high concentration. In contrast, in

hydrophobic interaction chromatography, gradients usually proceed from high to low salt concentration. Compare and contrast these processes. 42M. Which HPLC detector would you use? One simple sentence of justification is required. a.

Determination of polymer molecular weight distribution in an SEC separation.

b.

Detection of polyaromatic hydrocarbons in a CEC separation.

c.

Exact molecular weight of an isolated protein.

d.

Determination of transition metal ion identity in an IEC separation.

e.

Detect any solute eluting from an HPLC column.

f.

Determine whether an anionic eluent is carbonate or carboxylate.

43M. It is easy to envision that a molecule that is in an unobstructed flow will experience zone (longitudinal) broadening as a function of time. If we add a stationary phase, the more retained species show more broadening. But does this make sense, since by definition, more retained species are simply spending more time on the stationary phase where longitudinal broadening should not occur? Argue your way out of this box . . . 44M. The ultimate limiting factor in a chromatographic separation is the temporal integrity of the sample injection. Draw the evolved elution profile, no specific chromatography, for the case of the following injection profiles.

a)

b)

c)

d)

45M. In principle, a mass spectrum can provide the highest information density of any instrumental technique. What types of information can be derived from a single mass spectrum of a small organic molecule (caffeine, nicotine, etc.)? 46M. Mass spectrometer analyzers operate in various levels of vacuum (10-3 to 10-9 Torr). Generally, the higher the employed ion optic voltages, the lower the operating pressure, why? On the other hand, ion cyclotron resonance (ICR) analyzers employ single-volt potentials, but also operate at very low pressures (10-9 Torr), why? 47M. What is outgassing and why is it relevant in mass spectrometry? Explain how this process is relevant in terms of the choice of materials for insulating high voltage

conductors/feedthroughs. How are outgassing and electric arcing relevant in terms of the cleaning and reassembly of spectrometer components? 48M. A key part of the theoretical derivation and implementation of JJ Thomson’s classic “e/m” experiment dealt with effects of the earth’s magnetic field. Magnetic fields are the basis of separation in sector-field and ion cyclotron resonance (ICR) mass analyzers. Explain on a first-principle basis the role of the earth’s magnetic field in the typical time-of-flight (ToF) analyzers used in MALDI-MS of proteins. (words and equations may help) 49M. MALDI and electrospray ionization have been revolutionary for the use of mass spectrometry in the analysis of biological molecules. Why would you use one of these techniques over the other? The more examples the better. Think about the potential applications, sample introduction methods, etc. 50M. In many implementations of ion mobility spectrometry, the IMS is used as a “separation” stage. Presumably, this separation would be based on aerodynamic size and charge state. In fact, IMS used to be called “plasma chromatography”. What analogies can be made between IMS and gel electrophoresis for the separation of proteins? There are many points of comparison, provide 3 different points of view. Simple sentences will suffice. 51M. What ionization source would be best applied in the given application? One simple sentence of justification is required. a.

elemental analysis of a liquid sample

b.

mixture of small hydrocarbons introduced by GC

c.

high molecular weight proteins and peptides

d.

molecular weight determination of a polar compound such as nicotine

e.

residual pesticides on the surface of an orange

f.

active (small molecule) components of a plant extract, separated by RP-HPLC

52M. MALDI is probably the most widely employed ionization method for polymer analyses. How would you go about choosing a matrix for the analysis of an unknown polymer. What are the pertinent considerations? A narrative and flow chart might be an efficient way to approach the problem.

53M. The inductively-coupled plasma (ICP) is a great atomization/excitation/ ionization source. What about using an ICP as an atomizer for atomic fluorescence spectroscopy? Why, in general, does atomic fluorescence hold the potential to be more sensitive and selective than atomic emission spectroscopy? There are no commercially-available ICP-AFS instruments today, though one was sold by Baird Corporation in the 1980’s. Suggest in practical terms why it failed for laboratories wanting to do simultaneous, multi-element analysis? 54M. What is laser-induced breakdown spectroscopy (LIBS) and what is the role of the laser? Describe the process of dielectric breakdown of a gaseous medium. How is a solid sample vaporized? Why is it important to “gate” the optical emission signal to get good analytical performance? 55M. For each of the following prominent analytical scientists, give their present place of employment, and state their principle area of research in a simple sentence. Note: only four (4) names will be given on a particular exam. a.

Paul Bohn

b.

Purnendu Dasgupta

c.

Norman Dovichi

d.

Attila Felinger

e.

Catherine Fenselau

f.

Detlef Gunther

g.

William Hancock

h.

Amy Herr

i.

Gary Hieftje

j.

Pavel Jandera

k.

Milton Lee

l.

Susan Lunte

m.

Mathias Mann

n.

Andreas Manz

o.

Alan Marshall

p.

Jeanne Pemberton

q.

Frantisek Svec

r.

Sarah Trimpin

s.

Joseph Wang

t.

Nicholas Winograd

u.

Richard (Dick) Smith

v.

J. Michael Ramsey

w.

Janus Pawliszyn

x.

R. Graham Cooks

y.

James Jorgenson

z.

Peter Schoenmakers

aa.

John Yates

bb.

George Whitseides

cc.

Pat Sandra

dd.

Jonathan Sweedler

ee.

Robert Kennedy

ff.

Rudolf Aebersold

56C. Explain the operation of a glass membrane pH electrode. Be sure to discuss the cell configuration, what is measured, and what chemical / physical phenomenon gives rise to the signal. List one limitation on the use of glass membrane pH electrodes for analysis in solutions of extreme pH. 57C. Explain the operation of an electrochemical blood glucose meter. Be sure to discuss the cell configuration, what is measured, and what chemical / physical phenomenon gives rise to the signal. Discuss some limitations on the use of electrochemical blood glucose meters for measuring glucose levels in blood. 58C. Blood glucose meters have recently been used to measure other bioanalytically important analytes besides glucose. Discuss how such a measurement might work.

59C. Amperometric electrochemical measurements are based upon measurement of currents at electrodes, usually with a specific potential being applied to the electrode, relative to a reference electrode. Discuss at least three possible factors that could affect the magnitude of the current at such an electrode. 60C. Electro-osmotic flow (EOF) is one example of a general class of phenomena called electrokinetic effects. Describe what EOF is and how it may be observed, and discuss one example of how EOF is used in a modern analytical chemistry application. 61C. Currents measured at ultramicroelectrodes (UMEs, generally taken to be electrodes with at least one dimension smaller than 50 micrometers) are usually very different from currents at larger electrodes. Explain how and why electro-analysis using UMEs differs from electro-analysis are larger electrodes. Describe an electro-analytical problem for which the use of UMEs provides significant advantages compared with analysis using larger electrodes. 62C. Enzyme electrodes frequently utilize redox mediators to allow for electrochemical analysis of enzyme substrates or inhibitors. What is a redox mediator? What properties are desired in redox mediator? What kinds of enzymers are good candidates for use with redox mediators? Discuss the electrode mechanism of an analytical measurement that would utilize a redox mediator. 63C. Double-layer phenomena are an essential part of almost any electrochemical system. What is an electrical double layer? Why do electrical double-layers form? Describe two important properties of electrical double layers, and discuss a specific example of an analytical measurement or technique in which electrical double layers are important. 64C. Electrogenerated chemiluminescence (ECL) is an electrochemical phenomena that may be used to accomplish very sensitive electrochemical analysis. What is ECL? What experiment could be performed to make ECL occur? Describe an analytical application of ECL, being sure to make clear what the analyte is, and how the measured signal gives rise to analytical information. 65C. The simultaneous application of electrochemical and spectroscopic analytical methods to samples can provide information that may not be obtained from use of either approach alone. Describe an example of an analytical experiment where the use of electrochemical and spectroscopic methods together, provides information about a sample that could not be obtained in any other way. Be as specific as possible. 66C. Electrochemical methods may be applied to detect reversible binding of analytes to biological receptor molecules. Describe a method for doing this, being as specific as possible regarding what analyte is detected, and what quantity is measured.

67C. Electrochemical measurements are inherently linked to the control and measurement of electrical properties. Please provide definitions and give the units of measurement for each of the electrical quantities listed below: Charge, Current, Potential difference, Resistance, Capacitance, Impedance, Inductance 68C. The electroanalytical technique of stripping analysis is commonly used for trace analysis of redox-active analytes. Describe how a stripping analysis experiment is performed, and discuss why stripping analysis can achieve limits of detection that are so much lower than those that can be achieved by other methods. 69C. X-ray photoelectron spectroscopy (XPS) is a powerful analytical technique. Describe the operation of this technique, being sure to address what is measured, what is done to obtain the measurement, and what physical / chemical process gives rise to the analytically important information. Be sure to discuss what sort of information about samples is provided by XPS, and what limitations there are on sample analysis by XPS. 70C. Porous samples present some intriguing analytical problems, particularly when the pores are very small. Describe a method for measuring the surface area of a porous sample that has pores that are smaller than 50 nm. Describe what is measured and what physical model is used to analyze the data. 71C. Energy-dispersive X-ray (EDX) analysis is available in most modern electron microscope instruments. Explain what is measured in the EDX technique, describe what information about samples is provided, and discuss some advantages and limitations on sample analysis by this technique. 72C. The technique of ellipsometry is used to study thin films. What is ellipsometry? How is ellipsometry performed? What information may be obtained about samples using the technique of ellipsometry? 73C. Infrared (IR) spectroscopy is often performed in transmission mode but it may also be performed in an external specular reflection mode, to obtain information about molecular layers on surfaces. Provide a simple sketch of an external specular reflection IR experiment and discuss the similarities and differences between transmission IR spectroscopy and external specular reflection IR spectroscopy. Discuss one attribute of a sample that may be studied by external specular reflection IR spectroscopy that could not be studied by transmission IR spectroscopy. 74C. The quartz crystal microbalance (QCM) is a powerful means of analyzing certain kinds of samples. What is a QCM? How does it work? What information does it provide about samples? Describe an analytical application of a QCM, being sure to say what sample attribute is measured.

75C. A concept that is particularly important in the statistical treatment of analytical data in the confidence interval. Explain what a confidence interval is and how it could be determined for a given data set. Give an example of how a confidence interval could be used in analysis. 76C. The method of standard addition is a commonly used calibration method in analytical chemistry. Explain what the method of standard addition is, how it could be implemented for a particular type of sample, and what sorts of problems the method solves that are not solved by other calibration methods. 77C. Internal standards are commonly used in analytical chemistry. What is an internal standard? Provide an example of how an internal standard could be used in analysis, focusing on what problem the internal standard solves that could not be solved without an internal standard. 78C. Errors in measurement may be classified as random or systematic. Discuss the difference between random and systematic errors in analytical chemistry. Give a specific example of how one could distinguish between random and systematic errors in a particular analysis. 79C. Significance testing in analytical chemistry often make use of “t-testing”. Give an example of a t-test in analytical chemistry. Be sure to clearly describe how the test is performed and what the test is testing. 80G. 81G. Using the software of your choice and the attached data file, plot the electropherogram corresponding to the separation of five compounds, appearing in the detector in the 5-12 min range. You will observe an additional peak at about 2 min, corresponding to the EOF. 81G. Using the previous electropherogram, calculate the resolution for the two closest peaks, the number of theoretical plates, and describe if there is any peak skew 82G. One of the most active areas of research for gas sensing is the development of electronic noses. Explain what they are, how they work, and what analytical performance can be reasonably expected from them. 83G. How would you analyze samples containing the following compounds. Provide a critical assessment of the selected methodologies considering typical LOD, analysis time, instrumental needs, and cost. o

Ethanol in wine

o

Carbohydrates in beer

o

Lithium in pegmatite

o

Polyphenols in chocolate

o

Benzene in fuel

84G. Although its features poor limits of detection (typically in the high uM range), cyclic voltammetry is one of the most useful electrochemical techniques to characterize electrode surfaces. Describe how would you apply this technique to calculate the electrochemically active are of an electrode. 85G. In this regard, various electrochemical couples can be selected. Describe what would be the advantage of selecting an outer-sphere redox system for the characterization 86G. Briefly explain what electrochemical impedance spectroscopy is, what information can be obtained from it, and how is the experiment typically interpreted. 87G. Provide a basic circuitry required to perform electrochemical measurements and explain the function of each component. 88G. Describe the difference between primary, secondary, tertiary, and quaternary structure of proteins and explain which one(s) can be affected during their immobilization to a solid surface. 89G. Perform a critical assessment of 3 enzyme immobilization methods and provide their main advantages and disadvantages. 90G. What chemical route would you select to attach a protein to a glass surface. Describe conditions, reactants, etc. 91G. Schematically draw the basic structure of an immunoglobulin and explain how they can be applied for the development of immunosensors. Explain the role of Protein C in these sensors. 92G. Schematically draw the basic structure of an immunoglobulin and explain how they can be applied for the development of immunosensors. Explain the role of Protein C in these sensors. 93G. Glucose sensors are probably the most common example of a portable sensor in the today’s market. How would you adapt one of these sensors to measure lactate? 94G. Most microfluidic devices feature “low Reynolds numbers”. Describe what the number is and what can be considered “low”. 95G. Explain why carbon nanotubes (and other carbon allotropes) can be used to perform sample preconcentration.