Section: Science

157) Paper chromatography can be used to identify metal ions in wastewater. A drop of sample solution is placed on filter paper. The bottom of the paper is set in a solvent that travels up the paper (see Figure 1).



The solvent carries the ions up the paper. Some ions move faster, and therefore farther than others, resulting in a separation as they move up the paper. The paper is dried, then stained, causing the ions to appear as colored spots. Rf values are calculated for each spot:



Table 1 shows Rf values for 5 ions. Table 2 shows Rf values from 3 samples of wastewater. The same solvent was used for all ions and samples.





Table 1 adapted from Thomas McCullough, CSC, and Marissa Curlee, “Qualitative Analysis of Cations Using Paper Chromatography.” ©1993 by the American Chemical Society.

Note: Samples contain only the metal ions listed in Table 1.



Based on the information in Tables 1 and 2, one can conclude that Sample 2 contains: