During aerobic and anaerobic decomposition reactions nitrogen from nitrogen-containing organic substances is first converted to ammonium. The subsequent two-step microbial oxidation of ammonium to nitrate via nitrite is called nitrification. In soil as well as in water it is performed by nitrifying bacteria, a fact which is used for the purification of waste water in sewage plants. Nitrification is an important step during waste water purification in order to keep the concentration of ammonium ions in the effluents of the sewage plant as low as possible. Additionally, nitrification is prerequisite for the denitrification for complete nitrogen elimination, which is required for waste water treatment in many countries. With BioFix® nitrification inhibition tests you can now easily determine the nitrification inhibition in waste waters of all kinds as well as nitrification inhibition by individual substances or substance mixtures. Advantages of BioFix® nitrification inhibition tests ▪high sensitivity ▪easy procedure (by far less effort than for the DIN procedure) ▪speed (considerable time-saving: test time 10 min; 4 hours for the DIN test) ▪ready-to-use reagents ▪reagents and preserved bacteria have a shelf life of at least 1 year under the temperatures indicated for storage ▪ability to differentiate between inhibition of the different steps of nitrification (ammonium and/or nitrite oxidation) ▪very good reproducibility due to defined bacterial strains used in defined concentrations As biomass these tests use nitrifying microorganisms which are typical for sewage plants, preferably Nitrosomonas and Nitrobacter. The bacteral strains are applied as inoculum for the test preparation in defined composition – concerning the precise bacterial strain as well as their concentration – either as pure cultures or as mixed cultures. Measurement of the metabolic activity of the test organisms is performed with an apparatus for oxygen determination using a commercial oxygen electrode. The result is obtained as % inhibition of the oxygen consumption of the sample solution compared to a non-inhibited control. Amperometric measurement of the oxygen consumption Amperometric method of determining the specific retardation effect of the substances contained in a sample on nitrite oxidation in connection with microbial nitrification with the aid of defined bacterial strains, preferably of the genus Nitrobacter. The results are specified as % retardation of oxygen consumption in the sample solution in comparison to a non-inhibited control solution. ▪Sufficient for 10 - 19 determinations ▪Shelf life at least 1 year at -20°C