Absorption spectroscopy at work
Atoms absorb certain wavelengths of light that are able to promote their valence electrons to higher energy levels. The more of this wavelength that is absorbed the greater the number of atoms present. Light of a specific wavelength is passed through a solution and its intensity measured by an electronic detector. The amount of light absorbed indicates the quantity of the element tested for.

Before we can measure the concentration of an element, in this case lead, we must first graph the absorbance of known concentrations of the element. This is shown below.
The absorbance of known solutions were

Absorbance
2
4
6
8
10
Concentration of lead in ppm
5
10
15
20
25

Once the absorbance of known solutions is graphed we can measure the absorbance of an unknown sample and using the graph, read the concentration, as shown below.

A sample of oyster was tested for lead content using atomic absorption spectroscopy and was found to have a lead concentration of 11.25 ppm.
Oysters from an unknown source were suspected of having a high lead content. An oyster was cut from its shell and the meat finely chopped into small pieces. 2.00 grams were placed in a 10 ml solution of nitric acid. The mixture was filtered and a 1ml sample of the filtrate was analysed in the atomic absorption spectrometer. The experiment is animated below.

Construct an absorption vs concentration graph.

What is the lead concentration of the 1 ml sample?

What is the lead content present in the 2.00 gram of oyster sampled?

What is the lead concentration in the oyster per gram of oyster flesh?

If the recommended limit of lead in oysters for human consumption is 3.00 ppm in every gram, can you recommend the oysters for sale?
Continue with some past exam paper questions on spectroscopy