凯氏定氮法测N元素
采用凯氏消煮法用硫酸钾-硫酸铜为加速剂，其时间虽然较长，但只要控制好加速剂用量，不易导致氮素损失，消化程度容易掌握，测定结果稳定，准确度较高。消煮后氮的测定用蒸馏法。测定结果由北京林业大学生物中心提供。
1材料与方法
1.1 材料
取新鲜草莓叶片，编号称重，95°C烘干后研磨至粉末状。
1.2 仪器
凯式定氮仪KDY-9820
1.3 试剂激励的成语
400g/L氢氧化钠溶液，甲基红-溴甲酚绿混合指示剂，20g/L硼酸溶液，20g/L硼酸-指示剂溶液，0.02mol/L1/2Na2B4恭祝商祺O7标准溶液，1mol/L盐酸溶液，0.02mol/L盐酸标准溶液。
1.4 方法
消煮：用浓硫酸消化样品，硫酸钾-硫酸铜为加速剂。
蒸馏：往250mL锥形瓶中加入15mL20g/L硼酸-指示剂溶液，将锥形瓶置于定氮蒸馏装置冷凝器的承接管下，管口置于硼酸溶液面上3～4cm处。把盛有全部消煮液的凯氏瓶安装在蒸馏装置上，打开冷凝水。经三通管加入30mL400g/L氢氧化钠溶液。立即打开蒸汽夹，以每分钟8mL速度进行蒸汽蒸馏，当锥形瓶内溶液达半小瓶时，用广泛pH试纸在冷凝管口测试蒸馏液，如无碱性反应，表示氮已蒸馏完毕；否则需继续蒸馏。
滴定：吸收在硼酸溶液中的氮，用0.02mol/L盐酸标准溶液滴定，由蓝到紫红色为终点，记下用去的盐酸标准溶液的毫升数，同时进行试剂空白试验。
2结果
样品名称 | 全氮含量 |
A1 | 3.2884% |
A2 | 3.3018% |
A3 | 3.2513% |
A4 | 3.0729% |
A5 | 0.2221% |
b1 | 3.0167 |
b2 | 2.7785 八哥幼鸟 |
世博会博物馆b3 | 2.5330 |
b4 | 2.4976 |
| |
说明1=2# Albion 2=2# San Andreas 3=3# Albion 4=3# San Andreas 5=3# soil
A 12月 B1月 2#=2号温室 3#=3号温室
Kjeldahl determination to measure N elements
Kjeldahl Digesting Method using potassium sulfate and copper sulphate for accelerating agent consumes longer time, but it is difficult to lead to nitrogen loss, easy to know the digesting extent, stable with measurement results and high accuracy as long as the amount of control the accelerator. The nitrogen after digesting is detected by distillation method. Determination results were made in the biological center of Beijing Forestry University.
1 Materials and methods
恐怖的
1.1 Materials
Fresh strawberry leaves were weighed, we pestle them into powder after 95℃ drying (1 to 2 # Albion, 2 to 2 # San Andreas, 3 to 3 # Albion, 4 to 3 # San Andreas)
1.2 Instruments
Kjeldahl apparatus KDY-9820
1.3 Reagents带万字的成语
400g / L sodium hydroxide solution, methyl red - bromocresol green mixed indicator, 20g / L 假如有个星期八boric acid, 20g / L boric acid - indicator solution, 0.02mol/L1/2Na2B4O7 standard solution, 1mol / L hydrochloric acid solution, 0.02mol / L hydrochloric acid standard solution.
1.4 Methods
Digestion: samples digested with concentrated sulfuric acid, potassium sulfate - copper sulfate as accelerator.
Distillation: to 250mL conical flask 15mL20g / L boric acid - indicator solution, the flask placed in fixed nitrogen distillation unit to undertake the condenr tube, the tube port pla
ced in boric acid solution at the surface of 3-科技发展作文4cm. The solution containing all of the Kjeldahl digestion flask in the distillation unit installed, open the condensate. The three-way pipe to join 30mL400g / L sodium hydroxide solution. Now open the steam folder, 8mL speed per minute steam distillation, when the conical flask half a vial of solution when the pH test paper in the condenr with a wide mouth test distillates, such as non-alkaline reaction, distillation has been completed, said nitrogen; otherwi need to continue distillation.
Titration: absorption of nitrogen in the boric acid solution with 0.02mol / L hydrochloric acid standard solution titration, from blue to purple as the end point, a note of spent hydrochloric acid standard solution in ml, while the reagent blank test.
2 Results
Sample | Full N content |
A1 | 3.2884% |
A2 | 3.3018% |
A3 | 3.2513% |
A4 | 3.0729% |
A5 | 0.2221% |
b1 | 3.0167 |
b2 | 2.7785 |
b3 | 2.5330 |
b4 | 2.4976 |
| |
Introduction: 1=2# Albion 2=2# San Andreas 3=3# Albion 4=3# San Andreas 5=3# soil
A= December B=January 2#=greenhou number 2 3#= greenhou number 3
