Fluorescence quenching is an analytical technique and a common undergraduate laboratory exercise. Unfortunately, a typical quenching experiment requires the use of an expensive fluorometer that measures the relative fluorescence intensity of a single sample in a closed compartment unseen by the experimenter. To overcome these shortcomings, we designed an “open-box” fluorescence quenching method that uses an iPad screen as the excitation source and a digital single-lens reflex (SLR) camera as the detector. This setup enables a complete fluorescence quenching experiment to be performed and an accurate Stern–Volmer plot to be generated by analyzing a single image of six fluorescein samples and applying correction factors. The Stern–Volmer quenching constant (KSV) calculated using this method was 9.62 ± 0.27 L mol–1; fluorometer value, 9.52 ± 0.40 L mol–1; literature values, 9.0 ± 0.2 L mol–1 and 9.608 L mol–1. These results demonstrate that, in addition to allowing direct visualization of the chemical processes and simultaneous measurement of multiple samples, this simple method yields quantitative results comparable in accuracy to the more expensive fluorometer.

Complex error propagation is reduced to formula and data entry into a Mathcad worksheet or an Excel spreadsheet. The Mathcad routine uses both symbolic calculus analysis and Monte Carlo methods to propagate errors in a formula of up to four variables. Graphical output is used to clarify the contributions to the final error of each of the individual variables as well as illustrate how well the results conform to the normal distribution. The Excel routine allows direct entry of the formula and evaluates the error by numerical approximation of the necessary partial derivatives. Students find the routines much more user friendly and informative than traditional error propagation techniques.Keywords: Analytical Chemistry; Computational Chemistry; Mathematics/Symbolic Mathematics; Physical Chemistry; Problem Solving/Decision Making; Upper-Division Undergraduate;