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).