This quarter, CHE261 – Instrumental Analysis is running again after being defunct for a significant amount of time. This lab-based course was recently re-incorporated into our curriculum for several reasons, the most important being to give our students more hands-on experience with modern research instrumentation. This class is offered every spring, and it should be taken the same year that CHE204/205 is taken (CHE204/205 – Analytical Chemistry Lecture and Lab are pre-requisites for CHE261).
The course is being co-instructed this quarter by Drs. Grice, Griffin, and Niedziela. It started out with several workshop days in which Dr. Griffin helped the class learn about electronics and circuits, including hands-on time building and examining circuits with various arrangements of resistors and capacitors. Students then used UV-Vis spectroscopy of metal salts to learn how to understand Limit of Detection (LOD) and Limit of Quantification (LOQ) values.
After this, the bulk of the course involves hands-on work with four important instrumental techniques: Gas Chromatography-Mass Spectrometetry (GC-MS), Cyclic voltammetry, Atomic Absorption Spectroscopy (AAS), and Liquid Chromatography-Mass Spectrometry (LC-MS).
All of these modules involve creating various solutions for samples and for calibration curves of known standards . Solution-making is an important skill that comes with practice, and is critical to getting accurate measurements.
The GC-MS experiments allow analysis of volatile components of organic mixtures. The samples are heated to a gas then pushed through a column. The interaction with the column’s packing materials separate out the components, which are then analyzed by mass spectrometry. The mass spectrum of each compound gives identifying information about a molecule based on its molecular mass and fragmentation pattern.
Cyclic voltammetry (CV) allows for analysis of redox-active compounds in solution. For this module, students learn about CV and use it to analyze the amount of acetaminophen in children’s Tylenol. The acetaminophen can be quantified because it can be oxidized at an electrode in aqueous solution. The PINE potentiostats are relatively small and can be used on the bench-top with a laptop computer.
Atomic Absorption Spectroscopy (AAS) is an adaptation of optical spectroscopy that relies on the characteristic absorption properties of elements. It can be used to quantify the amounts of specific elements in a sample, such as Pb, Hg, Ca, and Mg. In this module, students use AAS to analyze Ca, Pb, and/or Mg content in various water samples.
The 4th technique that students learn is LC-MS. LC is a widely used technique, sometimes called HPLC or UPLC (depending on the specifications of the instrument). We recently obtained a LC-MS and students use it to identify the active components in Excedrin as well as quantify caffeine in coffee and yerba mate. The LC-MS offers several benefits over GC-MS, particularly in that samples do not need to be in the gas phase, so ionic or very polar species can be separated and analyzed in complex mixtures.