Analytical Chemistry Course Research Articles

The Influence of Modern Instrumentation on the Analytical and General Chemistry Curriculum at Bates College

The availability of state-of-the-art instruments such as high performance liquid chromatograph, gas chromatograph-mass spectrometer, inductively coupled plasma-atomic emission spectrometer, capillary electrophoresis system, and ion chromatograph obtained through four Instructional Laboratory Improvement and one Course, Curriculum, and Laboratory Improvement grants from the National Science Foundation has led to a profound change in the structure of the analytical and general chemistry courses at Bates College. Students in both sets of courses now undertake ambitious, semester-long, small-group projects. The general chemistry course, which fulfills the prerequisite requirement for all upper-level chemistry courses, focuses on the connection between chemistry and the study of the environment. The projects provide students with an opportunity to conduct a real scientific investigation. The projects emphasize problem solving, team work, and communication, while still fostering the development of important laboratory skills. Cooperative learning is also used extensively in the classroom portion of these courses.

The Use of Disposable IR Cards for Quantitative Analysis Using an Internal Standard

Infrared spectroscopy is traditionally used to identify compounds and aid in structure elucidation. However, solid samples require tedious and sometimes messy preparation of KBr pellets or mineral oil mulls and solutions cannot be used because there are no solvents that do not absorb in the IR. Disposable IR cards have simplified sample preparation for IR spectrometry. Moreover, they allow samples to be preserved for long periods, so that results can be verified at a later time. We report an experiment suitable for the instrumental analysis portion of the analytical chemistry course. It employs an internal standard in order to utilize the disposable cards for quantitative analysis. We use potassium thiocyanate as the internal standard because it has few absorption bands in the IR and they do not interfere with the bands of the unknown, benzophenone. Acetone is used as the solvent because it evaporates readily, making no contribution to the spectrum. This lab is useful as a teaching tool to illustrate the use of internal standards and calibration curves and the principle of Beer's law. It can be adapted for the determination of any analyte, provided the analyte and internal standard have distinctly separate IR bands. It is particularly useful in areas such as forensic chemistry, in which lab results are likely to be contested and samples must be preserved for long periods of time.

Introducing Field Environmental–Analytical Chemistry in the Quantitative Analysis Laboratory

Advances in instrumentation and technology now provide the ability to perform many quantitative determinations in the field. Additionally, the potential for sample degradation and analyte decomposition make it necessary to determine certain analytes (e.g., dissolved oxygen) in the field when conducting environmental analyses. Unfortunately, field environmental—analytical chemistry is not a substantial portion of the analytical chemistry curriculum at many institutions. Students in lower-level analytical chemistry courses are often non-chemistry science majors, particularly at institutions with small chemistry departments. We report here on an experiment in which field environmental-analytical chemistry is introduced in the quantitative analysis laboratory. In the context of a water quality assessment of a local river, students determine temperature, pH, ORP, nitrate nitrogen, and ammonia nitrogen at several points in the river. The experimental objective is to determine the potential effects local agricultural practices and treated wastewater discharge may be having on the water composition. The pedagogical objective is to expose these students to the difficulties involved in making analytical determinations in unfamiliar and/or disruptive settings.

What Is Service Learning?

Contemporary models for teaching chemistry involve learning in the context of real-world problems. Service learning immerses students in the real world through activities that not only promote student learning but also serve the public. Environmental and analytical chemistry courses provide a background for introducing students to using their scientific skills to work with their community and thereby gain an understanding of their role as scientists in society. The American Chemical Society, recognizing the potential of service learning in the chemistry curriculum, convened a group of faculty to examine how service learning can best fit into its programs.

Some Aspects of the Spontaneous Solubility Equilibria of Solid Carbonates

In order to adequately carry out the laboratory procedures usually taught in a general analytical chemistry course, students must master the subject of multiple equilibria in aqueous solution, both conceptually and mathematically. The use of a computer program to solve the concentrations of all species at equilibrium with a slightly soluble compound is frequently recommended in the chemical education literature, due to its simplicity and quickness. But, when this calculation procedure fails to consider other important reactions aside from the solubility equilibrium itself, significant differences in the numerical results may be obtained. For several metal carbonates, the usual procedure to calculate their solubilities is to consider carbonate ion hydrolysis as the only additional reaction. In this paper it is shown numerically and graphically that for magnesium and silver carbonates, the precipitation reaction of metal (hydr)oxides would occur at the pH value calculated from the carbonate dissolution plus the anion hydrolysis equilibria. An analytical procedure to solve these complex multiple equilibria system is presented. The final solution to the problem is obtained through a high-order equation that is easily solved by a simple iterative method. The correct solubility-pH curve for the metal carbonates is calculated, and the pH values for the metal hydroxide precipitation onset for several important representative and transition metal carbonates are shown. It is concluded that the overall procedures to solve these multiple equilibria problems are not beyond the comprehension of any chemistry student with a acceptable background in general, inorganic, and analytical chemistry, and that by focusing on tasks such as these, important critical-thinking skills can be obtained.

Determination of Anionic Surfactants Using Atomic Absorption Spectrometry and Anodic Stripping Voltammetry

An experiment has been developed for our undergraduate analytical chemistry course that demonstrates the indirect analysis of anionic surfactants by techniques normally associated with metal ion determination; that is, atomic absorption spectroscopy (AAS) and anodic stripping voltammetry (ASV). The method involves the formation of an extractable complex between the synthetic surfactant anion and the bis(ethylenediamine)diaqua copper(II) cation. This complex is extracted into chloroform and then back-extracted into dilute acid. The resulting Cu(II) ions are determined by AAS and ASV. Students are required to determine the concentration of a pre-prepared "unknown" anionic surfactant solution and to collect and analyze a real sample of their choice. After the two extraction processes, students typically obtain close to 100% analytical recovery. Correlation between student AAS and ASV results is very good, indicating that any errors that occur probably result from their technique (dilutions, extractions, preparation of standards, etc.) rather than from the end analyses.The experiment is a valuable demonstration of the following analytical principles: indirect analysis; compleximetric analysis; liquid-liquid (solvent) extraction; back-extraction (into dilute acid); analytical recovery; and metal ion analysis using flame-AAS and ASV.

A Practical Guide for the Preparation of Specimens for X-ray Fluorescence and X-ray Diffraction Analysis (Buhrke, V. E.; Jenkins, R.; Smith, D. K.)

Although its principal thrust is geared towards the analytical chemist in an X-ray diffraction (XRD) or X-ray fluorescence (XRF) service laboratory, this text will be of use primarily as a reference source in all milieus dealing with undergraduate research projects and advanced laboratory courses in physical and analytical chemistry. It contains dozens of suggestions for preparing randomly oriented small samples of nearly anything.

Sulfides in the Anaerobic Environment: The Determination of Hydrogen Sulfide and Acid-Soluble Metallic Sulfides in Sea-Floor Sediment

A procedure for the determination of hydrogen sulfide and acid-soluble metallic sulfides in sea floor sediment has been developed and tested as part of a laboratory course in analytical and environmental chemistry. The procedure includes (i) anaerobic sampling of sediment, (ii) a volatilization method, which discriminates between hydrogen sulfide and acid-soluble metallic sulfides in the sediment, and (iii) a quantitative determination of these sulfide components using an ion-selective electrode approach. The paper describes all experimental details and gives a brief summary of sulfide generation processes in sea-floor sediments, underlining the importance of sulfides in anaerobic environments. Representative results obtained during the laboratory course are discussed.

Using Bad Science To Teach Good Chemistry

Many undergraduate college students view the traditional topics of general and analytical chemistry with trepidation and consider them boring and irrelevant to their future careers. While a number of remedial efforts have been made to increase relevancy and interest potential, an area that has not been extensively explored is the incorporation of topics relating to into lecture and laboratory curricula. This paper presents examples of bad science ranging from unintentional mistakes to fraud that can be used as part of traditional courses in general and analytical chemistry to encourage scientific reasoning and ethical behavior, and to provide a classroom atmosphere that encourages students to think and learn.

A 19F NMR Study of Enzyme Activity

This basic enzyme activity laboratory experiment demonstrates how 19F NMR can be used in biochemical studies and presents the advantages of 19F NMR over 1H NMR for studies of this nature. N-Trifluoroacetylglycine was selected as a commercially available model fluorine-tagged substrate that readily undergoes acylase I-catalyzed hydrolysis to produce trifluoroacetic acid and glycine. Progress of the reaction was monitored by following conversion of the trifluoroacetyl moiety peak of N-trifluoroacetylglycine to trifluoroacetic acid. The extent of hydrolysis was determined by comparing integrated ratios of the two 19F NMR peaks. A plot of percent hydrolysis versus enzyme concentration was used to calculate unit activity of the enzyme. This is a viable laboratory experiment for junior/senior-level courses in instrumental analytical chemistry, biochemistry, molecular biology, or spectroscopy.

Fourier Transform Nuclear Magnetic Resonance Spectroscopy Experiment for Undergraduate and Graduate Students

Many NMR experiments in analytical chemistry courses utilize commercial Fourier transform (FT) instruments that do little in teaching the students about the components of the spectrometer. We have designed a FT-NMR spectrometer composed of self-contained components (i.e. mixers, switches, amplifiers) that has been successfully incorporated into laboratory experiments for both undergraduate and graduate students. The undergraduate instrumental analysis experiment allows students to examine the spectrometer on a component by component basis. The individual components of the spectrometer were mounted on a board and connected by coaxial cables, which easily permits changes in the configuration of the spectrometer. Topics covered in the experiment included filtering, amplification, phase cycling, and quadrature detection as well as quantitative determination of the amount of ethanol in an unknown sample. In the graduate analog instrumentation course, the graduate students were required to take the same compone...

Determination of caffeine content in coffee using Fourier transform infra-red spectroscopy in combination with attenuated total reflectance technique: a bioanalytical chemistry experiment for biochemists

In this report we describe an experiment to estimate the amount of caffeine present in common beverages with the use of Fourier transform infra-red spectroscopy (FTIR), using an attenuated total reflectance accessory as a sampling system. The absorbance band at 1655 cm −1 was used to estimate caffeine in standards and in the samples. The sensitivity of the technique was 5 ppm. The experiment provides a good demonstration of a bio-analytical technique that can be adopted either for a biochemistry or an analytical chemistry course.

Low-budget flow-injection device for teaching: A $10 six-port valve

A novel sample introduction valve, based on the tubing clamp operation principle, is described for teaching flow-injection analysis. It was developed to overcome the shortage of instrumentation in elementary instruction courses in analytical chemistry at Fachhochschule Hamburg. The materials for one valve, which can be easily build-up by the students, is <$10.

Determination of Blood Glucose by Quantitative TLC on Preadsorbent Silica Gel Plates

A thin layer chromatography method was developed for quantification of glucose in human blood serum using preadsorbent silica gel plates, acetonitrile-water (85:15) mobile phase, methanolic sulfuric acid detection reagent, and scanning densitometry. Results are reported for the measurement of glucose by the TLC method before and after consumption of a sucrose solution. The method was validated by determining the precision for replicate analyses and accuracy by analyzing a spiked sample and also comparing results with those given by a commercial kit intended for use by diabetics for home monitoring of glucose levels. The TLC method is simple to perform and can serve for the analysis of other sample types and as an interesting experiment illustrating quantitative TLC in college analytical chemistry or biochemistry laboratory courses.

Complexometric Titration of Zinc: An Analytical Chemistry Laboratory Experiment

Complexometric titrations with EDTA have traditionally been performed in undergraduate analytical chemistry courses to determine the calcium or magnesium content of water. These titrations are performed at a basic pH, where the formation constants of Ca-EDTA and Mg-EDTA complexes are high. These types of problems are well-treated in the analytical chemistry textbooks. In contrast, treatment of metal ions whose EDTA complexes occur significantly at low pH (e.g., Zn2+, Fe3+, Cu2+, Ni2+, Pb2+, Al3+) is sparse. An incorrect conclusion can be reached by the student that practical EDTA titrations are only performed at high pH. In addition, widening the window of possible metal ions for complexometric titration affords the possibility of analyzing real world products, such as the cold lozenges discussed in the article.

MALDI-MS at the Ingenieurschule Burgdorf: The Technique, Some Applications and Expected Benefits for the Education in Modern Analytical Chemistry

Analytical chemistry is changing rapidly, new methods are developed and introduced in the analytical laboratories. Parallel to this progress, the chemical industry is undergoing pronounced changes: it is focusing more and more on the life sciences.Consequently, the importance of analytical biochemistry is increasing.The educational system has to keep pace with these developments and has to integrate the new methods, which are or will be tools in analytical laboratories, into the analytical chemistry courses.Therefore, we were looking for an appropriate method which would allow us to face these challenges in analytical education at the Ingenieurschule (college of engineering) Burgdorf. With the recent acquisition of a matrix-assisted laser desorption mass spectrometer (MALDI-MS), a new analytical technique which has the potential to fulfill our requirements can be offered to the chemistry students.This contribution presents some analytical applications such as the sequence analysis of a modified oligonucleotide, the characterization of a non-covalently bound antigen-antibody complex as well as the analysis of a synthetic polymer and copolymer. Projects how to implement the method in the analytical chemistry course and the expected benefits for the students are discussed.

Potentiometric Measurement of Transition Ranges and Titration Errors for Acid/Base Indicators

Sophomore analytical chemistry courses typically devote a substantial amount of lecture time to acid/base equilibrium theory, and usually include at least one laboratory project employing potentiometric titrations. In an effort to provide students a laboratory experience that more directly supports their classroom discussions on this important topic, an experiment involving potentiometric measurement of transition ranges and titration errors for common acid/base indicators has been developed. The pH and visually-assessed color of a millimolar strong acid/base system are monitored as a function of added titrant volume, and the resultant data plotted to permit determination of the indicator's transition range and associated titration error. Student response is typically quite positive, and the measured quantities correlate reasonably well to literature values.

Determination of Phosphate in Cola Beverages Using Nonsuppressed Ion Chromatography: An Experiment Introducing Ion Chromatography for Quantitative Analysis

The determination of inorganic anions was very difficult until the development of ion chromatography (IC). The two techniques for performing the conductivity detection are 'single column' or 'non suppressed' IC and 'suppressed' IC. Non suppressed IC (NSIC) is generally the selected technique because of its simple instrumentation: with the addition of a conductivity detector, any standard HPLC system can perform NSIC. Thus, according to the importance of IC, it is advisable the development of some IC experiments that could be integrated into existing laboratory courses in analytical chemistry. In this paper, the determination of phosphate in cola beverages by NSIC is introduced. Cola beverages are actually relatively rich in phosphoric acid, and may be considered as very suitable laboratory samples for the experiments.In the practical session, each student analyzes at least 3 different colas, and calculates the phosphate concentration and its relative standard deviation from replicate injections of the sam...

Determination of the Thermodynamic Solubility Product of PbI2 Assuming Nonideal Behavior: An Analytical Chemistry Experiment

Solubility equilibria are usually introduced in the general chemistry course with limited mention of the nonideal behavior of real solutions. Nonideal behavior is introduced in the qualitative analytical chemistry course in the context of gravimetry. Often this concept is left as an academic exercise with no experimental application. The determination of a solubility product constant as reported here differs from other experiments in that nonideality is taken into account through Debye-Hückel theory by making few simplifying assumptions.

Determination of Polychlorinated Biphenyls (PCBs) in River and Bay Sediments: An Undergraduate Laboratory Experiment in Environmental Chemistry Using Capillary Gas Chromatography with Electron Capture Detection

With the arrival of the capillary gas chromatograph into undergraduate chemistry laboratories, it is now possible for students to perform ppb-level analysis of environmental samples containing organochlorine compounds such as PCBs. This paper briefly discusses the history of PCB use and provides guidelines for finding and evaluating PCB-contaminated sites as a way to interest students by showing them an application of chemistry to the real world. A procedure for the extraction of PCBs from sediments in a 4-hour laboratory period is presented, as well as the instrumental parameters required to analyze the samples by gas chromatography using an electron capture detector. This laboratory experiment was tested on freshman chemistry and environmental science students, but would also be appropriate for an organic or upper-level analytical chemistry course.