Determination of Total Nitrogen in Soil by Automatic Determination of Nitrogen
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When the soil sample was digested, two blank measurements were made, except that no soil sample was used, and all the other operations were the same as when the KDN-08A automatic nitrogen determination instrument was used to determine the soil sample. Before the distillation, inspect the KDN-08A automatic nitrogen determination instrument according to the instruction manual, and steam the tube for 0.5 hours. Then add 50 mL of ion-free water, 25 mL of 10 indicator mixture, etc. in the instrument. Input sample mass and standard acid concentration. Place the digestion tube on the automatic nitrogen determination instrument for distillation and titration, and do two blank tests first. , Blank determination of the volume of the standard solution used, KDN-08A Automatic Determination of nitrogen automatically deduct blank value, automatically calculate and record the sample nitrogen content, the test can be directly printed measurement results.
The results of the spiked recovery test in the whole process show that the KDN-08A automatic nitrogen determination instrument has a recovery rate of 96.79% to 104.49% of the total nitrogen in the soil, which is in line with the permissible requirements of the current standard semi-micro Kjeldahl method. The determination of total nitrogen content in soil using automatic nitrogen determination instrument is of high accuracy. The method can be used to select standard samples with different nitrogen content under the same laboratory conditions, and arrange for different test personnel to perform measurements according to the same regulations, from the automatic determination of nitrogen. The test results verify that the precision meets the requirements.
Because the boiling temperature of the KDN-08A automatic nitrogen determination boiler is better than that of conventional elimination to form a complete set of boiler heat preservation performance, and the temperature can be set, and the distillation temperature is not in accordance with the specified standard, different temperature gradients in the furnace are used. The comparison test selects the best measurement temperature. The results show that as the temperature increases, the measurement value of the KDN-08A automatic nitrogen determination instrument also increases. When the temperature reaches 420°C or more, the measurement value of the furnace temperature is in the range of 360-400°C. The range of uncertainty of the label value of the product and the standard is 360-380°C which is the best measurement temperature.