METHOD OF ASSESSING QUALITY OF NITROGEN-CONTAINING MINERAL FERTILISERS WITH APPLICATION OF BIOSENSORS Russian patent published in 2015 - IPC G01N30/62 

FIELD: chemistry.

SUBSTANCE: as test-device used is piezo-quartz resonator with natural frequency of fluctuations 10 MHz, electrodes of which are modified by application on them of polydiethyleneglycolsuccinate from individual acetone solution in such a way that weight of sorbent film after removal of solvent by drying in drying chamber at temperature 40-50°C for 15-20 min constituted 15-20 mcg, which is placed into closed compartment of detecting static monochannel gas analyser and kept in it for 5 min to establish stable zero signal. After that, sample of nitrogen-containing mineral fertiliser weighing 0.050 g is sampled into sampler and dissolved in distilled water (10 cm³). After that, it is tightly closed with polyurethane plug, through which 1 cm³ of sodium hydroxide solution with concentration 4 mol/dm³ is introduced, obtained solution is kept at temperature 20±1°C for 15 minutes to saturate gas phase with ammonia vapours. After that, 1 cm³ of balanced gas phase is sampled through polyurethane plug with syringe and injected into closed detection compartment of static monochannel gas analyser, fixed for 60 s with changing frequency of fluctuations of piezo-sensor, analytic signal - maximal change of fluctuation frequency ΔF_max for 60 s ΔF_max=f(τ) is calculated and content of ammonia is determined by calibration curve, built in ΔF_max coordinates of concentration of ions NH₄ ⁺(ΔF_max=f (C_NH4 ⁺, %)), content of ammonia is determined. Calibration curve is built by standard solutions of ammonia nitrate, for fertilisers, containing nitrogen in different forms, by content of ammonia nitrogen its content is calculated in terms of total nitrogen, for which purpose obtained by calibration curve ammonia concentrations are multiplied by correction factor 82.4.

EFFECT: elaboration of method of assessing quality of nitrogen-containing mineral fertilisers with application of piezo-sensors, making it possible to assess quality of nitrogen-containing mineral fertilisers and extend range of determination of total nitrogen concentrations with application of piezo-quartz converter with thin-film coating, characterised by high sensitivity, with low limits of ammonia detection, accuracy, expressiveness and selectivity of analysis, objectivity of measurement and decision-taking.

2 dwg, 1 tbl