This analysis is performed by means of atomic absorption spectrometry. Lead exists in water both as a solute as lead(II) ions and undissolved in the following forms: lead hydroxide, lead carbonate, lead phosphate, lead sulfide and lead sulfate. Of particular significance is the capacity for the lead in pipes to dissolve in aggressive or oxygen-rich water.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
The lead content is determined by employing a flameless method which utilizes graphite furnace atomic absorption spectrophotometry. This technique is suitable for determining the lead content of water with very little lead contamination. Any matrix effects can be eliminated by using the standard additions calibration technique.
An aliquot of the sample is dosed into a graphite tube and is subsequently subjected to a program comprising a three-step temperature regime through electrothermic resistance heating. As the temperature increases in each step, the consecutive steps include drying, matrix pyrolysis (incineration) and thermal dissociation into free atoms (atomization). These can be carried out separately. During the analysis, the graphite tube is under an inert gas atmosphere (argon).
Also important for graphite furnace AAS is background correction, which can be achieved using a continuum radiation source (deuterium) or through the Zeemann effect. Background correction with the Zeemann effect is used for particularly difficult sample matrices.
A hollow-cathode lamp or an electrodeless discharge lamp, which contains the relevant element in gaseous state, usually serves as the light source.