Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
The nickel content is determined by employing a flameless method which utilizes graphite furnace atomic absorption spectrophotometry. This technique is suitable for determining the nickel content of water with very little nickel 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 usually serves as the light source.
Suitable for beer
Aside from carbohydrates composed solely of glucose molecules (with, for example, 0.69 g/100 ml of utilizable carbohydrates remaining in the beer), in highly attenuated beer there are small amounts of pentose molecules (approx. 300 mg/l) and also various glycosides (approx. 100–200 mg/l).
According to their degree of digestibility, additional utilizable carbohydrates amount to 500 mg/l at the most (equal to 0.05 g/100 ml). As a rule, 0.05 g/100 ml is also added to the total value for carbohydrates.
Determination of the nickel content using an AAS graphite furnace
Suitable for all types of wort, beer and beer-based beverages
Nickel is measured using the flameless graphite furnace atomic absorption spectrometry. The determination is carried out at 232.0 nm. This process is well-suited for determining trace quantities of nickel in beer. Matrix effects, which may occur, are eliminated through the use of a standard addition calibration procedure. A palladium magnesium modifier reduces interference from compounds in the beer matrix.