Standard Addition

Multiple Point Standard Addition Method

A 3.12g stick of chewing gum is ashed at high temperature, dissolved in 5 mL of concentrated nitric acid and then diluted to the mark in a 100mL volumetric flask. To 25 mL volumetric flasks are added 5.00 mL aliquots of the dissolved chewing gum sample and an additional volume of 300.0 ppm aluminum. After dilution to volume, the solutions are analyzed for aluminum by graphite furnace atomic absorption spectrometry at 309 nm. The data are shown in the following table.

Volume of spike                        Absorbance Signal

           (mL)                              (arbitrary units)

0.00                                        0.214

0.10                                        0.386

0.20                                        0.554

0.30                                        0.728

What is the concentration of aluminum in the 5 mL sample of dissolved chewing gum?