Exploring Emission and Absorption Spectroscopy in the First-Year General Chemistry Laboratory

Abstract

In the first-year general chemistry laboratory course, instrumental data collection involving sample quantification has often been limited to absorption spectroscopy due to the inaccessibility of emission techniques suitable for large enrollments and novice users. In this laboratory experiment, students explore the complementary techniques of emission and absorption spectroscopy, in which sample quantification respectively occurs via the measurement of light emitted or absorbed by the sample. Calibration curves are constructed for both techniques. Eschewing atomic absorption spectroscopy (AAS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES), instrumentation not typically available for large general chemistry courses, quantitative data is instead collected using a series of carefully implemented flame tests. Students perform flame tests on alkali, alkaline earth, and transition metal compounds using the emitted light to gain a thorough understanding of emission spectroscopy. In Week 1, students are introduced to emission spectroscopy through the identification of unknown components in air, lamps, and contaminated soil samples. In Week 2, students carry out quantitative emission and absorption characterization of Na and Cu solutions, comparing the two techniques through experimental observations and analyzed results. Calibration curves with high linear regressions (r 2 > 0.992) are prepared and used to determine the concentrations of provided reference samples, with averaged student data resulting in reasonably low percent errors (<12% for Na emission, <11% for Cu emission, and <2% for Cu absorption) when compared to the known concentrations. Students then compare experimental flame emission results to provided ICP data to gain experience with a sensitive, quantitative emission technique.

A Smart Phone Based Low-Cost Flame Photometer Constructed from a Scrap Oil Tin Container for Lithium Detection from Psychotropic Drugs for Undergraduate Students

“…The Analytical Chemistry undergraduate syllabus of any curriculum includes FES in both theory and practical courses. − Practical experiments are crucial for a better understanding of instrumental techniques, but the unavailability of sophisticated instruments in undergraduate laboratories can be a challenge. Students can benefit greatly from an active learning experience in assembling instrument components and conducting real sample analysis.…”

Exploring the Potential of Sewage Sludge as Agricultural Fertilizer: Determination of Heavy Metals and Nutrients by Microwave-Assisted Digestion Followed by ICP-OES Analysis

“…The prevalence of this analytical technique with applications across multiple fields makes it an important teaching topic. There are a few educational publications on the matter, commonly addressing multielement analysis in different samples, 15−18 or even singleelement applications, 19−21 while others focus on the comparison between emission and absorption spectrometry 22 or the selection of emission lines and ICP-OES spectral interferences. 23 The present laboratory experiment consists of a three-step learning activity: (1) execution of a microwave-assisted digestion procedure followed by an ICP-OES instrumental analysis; (2) validation of the analytical method, using external calibration with internal standardization and a certified reference material (CRM) for accuracy and precision evaluation; (3) determination of heavy metal and nutrient contents of a real sewage sludge sample, with critical interpretation of results and comparison to legislated values.…”

“…The prevalence of this analytical technique with applications across multiple fields makes it an important teaching topic. There are a few educational publications on the matter, commonly addressing multielement analysis in different samples, − or even single-element applications, − while others focus on the comparison between emission and absorption spectrometry or the selection of emission lines and ICP-OES spectral interferences …”