Arsenic is a toxic element to which humans are primarily exposed through food and water; it occurs as a result of human activities and naturally from the earth’s crust. An experiment was developed for a senior level analytical laboratory utilizing an Inductively Coupled Plasma–Mass Spectrometer (ICP–MS) for the analysis of arsenic in household sinus wash and tap water. This powerful instrumental technique can be used to elucidate the elemental composition of a complex sample while offering the benefits of high-precision quantitative analysis. The chosen matrices further provided the opportunity to demonstrate two important analytical concepts. First, the sinus wash samples displayed signal suppression, illustrating the necessity for employment of the internal standard calibration technique. Second, the high chloride matrix of the sinus wash led to the formation of the ArCl+ polyatomic ion in the argon plasma, which overlapped with arsenic’s single isotope at m/z = 75. Analysis was performed in no gas mode and also with the collision cell in helium mode, allowing the students to observe firsthand the false positive results for arsenic by comparing 75 m/z results in the two modes. In addition, in a third objective, students were able to compare the sinus wash and tap water to current federal drinking water regulations. This laboratory exercise provided a novel and engaging application of ICP–MS and allowed the students to use modern instrumentation and analytical techniques to investigate the current and relevant issue of arsenic in our environment.