肥料中硝酸盐和氨检测方案(定氮仪)

APPLICATION NOTEF&F-K-004-2018/A1 DEVARDA'S METHOD ON FERTILIZERSUDKDISTILLATION UNIT Nitrate and Ammonia Determinationin Fertilizersaccording to the Devarda Method Reference： UNI EN ISO 15476：2009， AOAC 892.01 Tested with VELP Scientifica UDK 149 Kjeldahl Distillation Unit (Code F30200140) Introduction Healthy plants often contain 3 to 4 percent nitrogen in their above-ground tissues. This is a much higher concentrationcompared to other nutrients. Nitrogen is so vital because it is a major component of chlorophyll， the compound by which plants use sunlight energy toproduce sugars from water and carbon dioxide (i.e.， photosynthesis). Plants thus have the ability to take up several chemical forms of nitrogen from the soil. The most common are： ammonium(NH4*)， nitrate (NO3)， and urea，((NH2)2CO). Many commercial fertilizer mixes contain a combination of all three nitrogenforms. Determination of nitric and ammonia nitrogen in fertilizer samples This method describes the procedure for the determination of nitrate and ammoniacal nitrogen with reduction usingDevarda's alloy. When a solution of nitrate ions and Devarda’s alloy is mixed with aqueous sodium hydroxide， the mixture gently liberatesammonia gas. This conversion under the form of ammonia， requires some minutes. The method is applicable to all nitrogenous fertilizers， including compound fertilizers， in which nitrogen is found exclusivelyin nitrate form or in ammoniacal and nitrate form. Samples Two samples of ammonium nitrate fertilizer have been tested： Fertilizer 1 expected value： 34.69 %N Fertilizer 2 expected value： 26.79 %N Reagents and equipment Magnetic stirrer Burette 50 ml， precision 0.1 ml Sodium Hydroxide 32 % Devarda Alloy， powder Sodium hydroxide 0.1 N Sulfuric acid 0.2 N Methyl red in ethanol， as indicator Sample Preparation 300-350 mg of sample have been weighed in a beaker and transferred to the test tube. The beaker is flushed severaltimes with distilled water， then poured to the test tube. Just before starting the distillation Devarda's alloy powder， about 1.5 g， is added manually to the test tube. Distillation and titration Distill the samples with the following parameters (set a customizable method)： H2O： 10 ml●Distillation time： 5 min●NaOH： 50 ml●Steam power： 80 %Receiving solution： 0 mlPause： 12 minutes Set No automatic distillation residues discharge at the end of the distillation. As receiving solution in a 250 ml Erlenmeyer flask， 50.0 ml of sulphuric acid 0.2 N (measured with a marked volumetricflask) and 4-5 drops of methyl red indicator solution are added manually. Titrant solution： NaOH 0.1 N， dosed manually using the 50 ml burette， up to the colour change. Typical Results on Fertilizer samples From the ml of titration solution， %N have been calculated by the following formula： where： V1： ml of the receiving solution (50 ml) N1： Normality of the receiving solution (0.2 N) V2： ml of NaOH dosed for titration of the sample N2： Normality of the NaOH solution (0.1 N) V1B： ml of the receiving solution for the blank (10 ml) V2B ： ml of NaOH dosed for titration of the blank MN： Nitrogen molecular weight (14.007 g/mol) msample： sample quantity (mg) The following table shows the obtained results： Sample Sample quantity (mg) V2 (ml NaOH) %N Fertilizer 1 324.7 19.6 34.55 Fertilizer 1 330.0 17.5 34.89 Fertilizer 1 395.5 1.30 34.85 Average±SD% 34.76±0.18 RSD%* 0.53 Recovery % 100.2 Fertilizer 2 336.2 35.2 26.87 Fertilizer2 301.2 42.0 26.83 Fertilizer 2 342.9 34.3 26.72 Average± SD% 26.81±0.08 RSD%* 0.31 Recovery% 100.1 Fertilizer 1： expected value： 34.69%N Fertilizer 2： expected value： 26.79 %N The blank value (V2B) is 19.7 ml of NaOH. *RSD%=(Standard Deviation * 100) / Average The distillation process was verified by using ammonium chloride as standard solution (1000 ppm N)， as referencesubstance. Conclusions The determination of nitrate and ammoniacal nitrogen in fertilizer according to Devarda Method by using VELP UDK 149Distillation Unit has proven to guarantee accurate and precise results corresponding well to specifications.VELP UDK Distillation Unit is the perfect response for all laboratories looking for reliability， rapidity and ease-of use，producing results that corresponds to the expected values.     健康的植物地上组织通常含有3%到4%的氮。这比其他营养物质的浓度高得多。氮之所以如此重要，是因为它是叶绿素的主要成分，叶绿素是植物利用太阳能从水和二氧化碳(即光合作用)中产生糖的化合物。因此，植物有能力从土壤中吸收几种化学形式的氮。最常见的是:铵(NH4 +)、硝酸盐(NO3 -)和尿素((NH2)2CO)。许多商业肥料混合含有这三种氮形态的混合物。实验样品：Two samples of ammonium nitrate fertilizer have been tested:                  Fertilizer 1  expected value: 34.69 %N      Fertilizer 2 expected value: 26.79 %N实验仪器：VELP UDK149凯氏定氮仪实验结果：以氯化铵为标准溶液(1000ppm N)，作为标准物质，对蒸馏过程进行了验证。实验结论：用VELP UDK149法测定肥料中硝酸盐氮和氨氮,经实践证明，该蒸馏装置能较好地保证计算结果的准确和精确。VELP UDK蒸馏装置是所有实验室寻求可靠性、快速性和易用性的完美响应，产生符合期望值的结果。