Quantitative Analysis

An Inexpensive Electrodeposition Device and Its Use in a Quantitative Analysis Laboratory Exercise

This experiment describes the construction of a simple apparatus for effecting the electrodeposition of nickel onto a tared copper electrode. Results are compared to the determination of nickel by the classical gravimetric precipitation of the dimethylglyoxime complex.

The full citation is here: Parker, R. H.  J. Chem. Educ. 2011, 88, 1428–1430 and a link to the article is provided below (subscription to the journal required).

http://dx.doi.org/10.1021/ed101202t

How Much Cranberry Juice is in Cranberry-Apple Juice?

Students determine the amount of cranberry juice (as a volume percent) in mixtures of cranberry juice and apple juice by measuring the absorption of mixtures and comparing to a calibration curve prepared for cranberry juice. The experiment assumes that the absorbance of apple juice is negligible at the analytical wavelength, which isn’t strictly true. The experiment can be modified easily by a simultaneous analysis at two or more wavelengths.

The full citation is here: Edionwe, E., Villarreal, J. R., Smith, K. C.  J. Chem. Educ. 2011, 88, 1410–1412 and a link to the article is provided below (subscription to the journal required).

http://dx.doi.org/10.1021/ed2002237

Leeching of Silver from Silver-Impregnated Food Storage Containers

Food storage containers may contain micro-particles of Ag, which serves as an anti-microbial agent to limit the growth of molds, fungi, and other microorganisms. Students study the leeching ability of three solvents — deionized water, tap water, and acetic acid — by measuring the concentration of silver in the leechate using graphite-furnace atomic absorption spectrophotometry. An analysis of variance is used to evaluate the relative importance of container type, solvent, extraction time, and the application of heat during the extraction.

The full citation is here: Hauri, J. F., Niece, B. K.  J. Chem. Educ. 2011, 88, 1407–1409 and a link to the article is provided below (subscription to the journal required).

http://dx.doi.org/10.1021/ed101042y

Using a Flatbed Scanner to Measure Detergency

Using a flatbed scanner to measure the reflectance from samples of a white polyester fabric impregnated with linseed oil, students determine detergent efficiency. Scans of samples are stored as RGB (red, green, blue) coordinates and the blue channel used as the analytical signal. Detergent efficiencies for different amounts of sodium dodecyl sulfate are measured relative to a reference standard (a non-impregnated sample) and the sample before and after cleaning. Results are compared to reflectance measurements made using a conventional spectrometer.

The full citation is here: Poce-Fatou, J. A., Bethencourt, M., Moreno-Dorado, F. J., Palacios-Santander, J. M.  J. Chem. Educ. 2011, 88, 1314–1317 and a link to the article is provided below (subscription to the journal required).

http://dx.doi.org/10.1021/ed100635z

Laboratory Inquiry for Determining the Chemical Composition of a Component in a Laboratory Detergent

Students determine the concentration of sodium sesquicarbonate in an alkaline laundry detergent though a combination of an acid-base titration and thermal gravimetry, both of the thermal decomposition and the decomposition by reaction with acid.

The full citation is here: Koga, N., Kimura, T., Shigedomi, K.  J. Chem. Educ. 2011, 88, 1309–1313 and a link to the article is provided below (subscription to the journal required).

http://dx.doi.org/10.1021/ed1011212

The Shell Seeker: What is the Quantity of Shell in the Lido di Venezia Sand? A Calibration DRIFTS Experiment

This experiment uses a novel approach to introduce students to the method of standard additions. To approximate the contribution of shell fragments in sand collected from a beach (in this case, from the seashore at Lido di Venezia, Italy). After obtaining DRIFT spectra of the sand and a powdered seashell (a cockleshell in this case), students identify peaks that serve as markers of the shell’s principle component – CaCO3. Students then measure the response for the sand and the sand spiked with known quantities of the powdered shell.

The full citation is here: De Lorenzi Pezzolo, A.  J. Chem. Educ. 2011, 88, 1298–1303 and a link to the article is provided below (subscription to the journal required).

http://dx.doi.org/10.1021/ed100832e

Have Biofuel, Will Travel: A Colorful Experiment and a Different Approach to Teach the Undergraduate Laboratory

This experiment describes a  quantitative UV-Vis analysis of mixtures of diesel/ethanol and diesel/biofuel based on the absorption of a solvochromatic probe dye. Students first synthesize the dye and then monitor the change in the dye’s λmax for different known mixtures, creating an empirical scale of solvent polarity. Mixtures containing unknown (to the student) mixtures of diesel/ethanol and diesel/biofuel are then analyzed using calibration curves of solvent polarity as a function of the concentration of ethanol or biofuel.

The full citation is here: El Seoud, O. A., Loffredo, C., Galgano, P. D., Sato, B. M., Reichardt, C.  J. Chem. Educ. 2011, 88, 1293–1297 and a link to the article is provided below (subscription to the journal required).

http://dx.doi.org/10.1021/ed1009464

Quantitative Investigations of Biodiesel Fuel

In this experiment students complete four tasks: monitoring the production of biodiesel by a transesterification of a commercial oil; quantifying mixtures of biodiesel and petroleum-based diesel; using a Karl-Fisher titration to determine the impact of water on the quantification of biodiesel; and determining the figures of merit for several IR sampling platforms.

The full citation is here: Ault, A. P.; Pomeroy, R.  J. Chem. Educ. 2012, 89, 243–247 and a link to the article is provided below (subscription to the journal required).

http://dx.doi.org/10.1021/ed101097n

What if There is no Quantitative Analysis Course?

What happens if an institution does not have a quantitative analysis course? Where are  students introduced to the concepts of analytical chemistry and the importance of analytical measurements? This post describes how one institution approached this when the needs of the curriculum required eliminating the Quantitative Analysis class.

With the rapid growth of biochemistry and its increasing importance in the undergraduate chemistry curriculum, finding space for biochemistry classes and topics is a challenge. At DePauw University — a small, wholly undergraduate, liberal arts college — the desire to provide all chemistry majors with an introductory course in biochemistry and the desire to create a biochemistry major lead us, in 2001, to significantly reinvent our curriculum. One “victim” of this reorganization was the traditional sophomore course in Quantitative Analysis.

To ensure that we continued to provide all students — both chemistry majors and biochemistry majors — with an introduction to analytical chemistry, we transformed our old second semester general chemistry course into a new course focusing on three essential ideas: thermodynamics, equilibria, and kinetics. In addition to these traditional topics, we built time into the class and the lab to introduce additional analytical content.

Although the classroom portion of the course — Chem 260: Thermodynamics, Equilibria, and Kinetics — focuses on the three primary topics, approximately two weeks of classes are set aside for data analysis exercises covering topics such as uncertainty in measurements, the statistical comparison of data sets, regression analysis and the modeling of data, and the handling of outliers.

The laboratory portion of Chem 260 is designed to introduce students to analytical measurements and the importance of thinking like an analytical chemist. The lab meets for 14 weeks, with each week consisting of a single three-hour lab. Students work in teams of three, with each team having an instrument suite consisting of a Vernier LabPro data interface with pH, oxidation-reduction potential, and temperature probes, a drop counter for titrations, and an Ocean-Optics USB-2000 visible spectrometer.

After completing several case studies on ethics in science, the students complete four one-week preliminary labs that introduce them to the instrumentation, software, and analytical techniques they will use later in the semester. The students then complete four two-week project-based labs. For each of these project-based labs the students are given a question to answer and a set of issues to consider—the students are responsible for designing an experiment that provides an answer to the lab’s question. A summary of the experiments is provided here:

Preliminary Experiments (and analytical concepts)

  1. Preparing Solutions
    1. uncertainty in measurements
    2. summary statistics
  2. Newton’s Law of Cooling
    1. fitting theoretical models to data
    2. significance testing
  3. Determination of Acetic Acid in Vinegar
    1. pH calibration and measurement
    2. acid-base titrations
    3. primary and secondary standards
  4. Characterizing an Oscillating Reaction
    1. Beer’s law
    2. external standardization
    3. boxcar filters and ensemble averaging

Project-Based Experiments (and questions to answer)

  1. Decomposition of H2O2
    1. What is ΔH for the reaction?
    2. Can you verify that Fe3+ is acting as a catalyst?
  2. Thermodynamics of Ca(OH)2 Solubility
    1. What are the values of ΔG, ΔH, and ΔS for the solubility reaction?
    2. How does temperature affect the solubility of Ca(OH)2?
  3. Acid Dissociation Constants of Organic Dyes
    1. What is the pKa value for your assigned dye?
  4. Kinetics of the Bleaching of Dyes
    1. What is the rate law for the reaction?
    2. How does the solution’s pH affect the reaction’s rate?

For additional details a PowerPoint presentation on DePauw’s analytical curriculum is available here and a copy of the lab manual for Chem 260 is available here.