The method describes how to determine the nitrate content of water photometrically with a cuvette test.
In an acidic sulfurous solution containing phosphorus, nitrate ions react with 2,6-dimethylphenol to produce 4-nitro-2,6-dimethylphenol.
The method is suitable for determining approx. 0.5–25 mg/l NO3-. If the ratio of chloride to nitrate ions is larger than 10, this may interfere with the reaction (if this is the case, according to DEV D 9-3, follow DIN 38405); likewise, nitrite ions exceeding approx. 0.2 mg/l may also interfere with the reaction. For their removal, refer to Remarks below.
The method describes how to determine the nitrite content of water photometrically with a cuvette test.
In an acidic solution, nitrite reacts with primary aromatic amines, producing diazonium salts. Together with aromatic compounds, they form azo compounds, which contain an amino or hydroxyl group and exhibit an intense color.
Malt intended for use in beer brewing or elsewhere in the food industry
A (modified) Congress wort is produced from malt samples prior to analysis. NDMA present in the Congress wort is extracted using dichloromethane followed by concentration of the eluate. The determination is performed with a gas chromatograph using a packed Carbowax 20M column with a specific TEA detector (thermal energy analyzer); nitrosodipropylamine (NDPA) serves as an internal standard.
This detector analyzes nitrosamine according to the following procedure:
After exiting the GC column, the separated substances are heated to 500 °C in a pyrolyzer. At this temperature, the N-NO bond of the nitrosamine is broken, thus forming an NO radical (NO۰):
The gas mixture then flows through a special filter (CTRTM gas stream filter), which only allows the carrier gas and the NO radicals to pass. After exiting the filter, the NO radicals flow into a reaction chamber along with ozone, which is created by a special generator. The following chemical reactions take place in the chamber:
|
NO• + O3 |
→ |
NO2• |
|
NO2• |
→ |
NO2 + h•ν |
These NO radicals react with ozone, forming nitrogen dioxide in an excited state (NO2•). The NO2• molecules decompose spontaneously to form nitrogen dioxide in its common form (NO2), emitting radiation (h•ν) with a wavelength of approx. 600 nm.
Applicable for all (laboratory) worts
Medium and high molecular weight proteins are precipitated by phosphomolybdic acid. The nitrogen is determined in the filtrate. Therefore, the results express the amount of low molecular weight proteins.
Determination of the concentration of the anions bromide, chloride, fluoride, nitrate, nitrite, oxalate, phosphate and sulfate through ion chromatography
Water, wort, beer, NAB and beverages as well as malt and hops
Separation of bromide, chloride, fluoride, nitrate, nitrite, oxalate, phosphate and sulfate through ion chromatography followed by conductivity detection
Determination of the proportional composition of grist fractions through sieve analysis
Malt grist, grist from adjuncts
The extract yield in the brewhouse is highly dependent on optimal milling of the malt or other grain. The composition of the brewery grist should therefore be monitored on a regular basis.
The sieve analysis is performed on a sample of brewery grist of a known weight with a shaking device containing a set of sieves (according to DIN ISO 3310-1 specifications or a Pfungstädter plansifter sieving device).