凯氏定氮仪和发展史课件.ppt
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1、凯氏定氮一个使用了120年的依旧年轻的技术BCHI Labortechnik AGKatharina JehleFlawil,SwitzerlandJuly 05/KJ1China_Kjeldahl Solutions主题:蛋白的基本概念 凯氏定氮的方法 方法的发展 Bchis 消化单元 Bchis消化单元Kjeldahl法问题解决July 05/KJ2China_Kjeldahl Solutions蛋白的基本概念Basics ProteinJuly 05/KJ3China_Kjeldahl Solutions为什么要分析蛋白?蛋白质是:Basic nutrient基本的营养 Impact o
2、n caloric value(17 kJ resp.4 kcal)热量来源 Parameter for quality(e.g.meat)品质参数 Influence on production process(e.g gelation,extrusion)影响产品的中间处理(例,冻结,压榨)Influence on flavour and colour of food(e.g.baking process bread,roasting process coffee)影响食品的 风味和颜色July 05/KJ4China_Kjeldahl Solutions蛋白的基本结构是氨基酸,分子式如下
3、:There are about 200 amino acids found in nature 自然界已发现的大概有200种氨基酸 There are about 20 amino acids in a protein hydrolysate 蛋白水解后大概有20种氨基酸Basics ProteinJuly 05/KJ5China_Kjeldahl Solutions怎么测定蛋白质?通过检测氮的含量计算蛋白含量The nitrogen content in protein is in a small range(15%-18%,mean:16%)蛋白中氮的含量在1518波动,平均16Prot
4、ein is determined by analysing the nitrogen content and calculating the protein 通过氮含量计算蛋白含量Basics ProteinJuly 05/KJ6China_Kjeldahl Solutions凯氏定氮概述July 05/KJ7China_Kjeldahl Solutions谁是凯氏?Johan Kjeldahl 1849 19001849 born in Denmark1867 graduation from university1876 Scientist at Carlsberg Breweries F
5、ermentation studies Development of a method for exact determi-nation of nitrogen in animal and vegetable material Research on carbohydrates in barley and malt1883 Publication of the Kjeldahl methodJuly 05/KJ8China_Kjeldahl Solutions凯氏定氮的原理1.Digestion消化消化Conversion of Protein-Nitrogen to NH4+将蛋白中氮转化为
6、NH4+2.Distillation蒸馏蒸馏分离收集NH3Separation of NH33.Titration滴定滴定用酸中和滴定Measure of the Amount of Acid that was neutralised by NH3 July 05/KJ9China_Kjeldahl SolutionsDigestion消化(I)BlankSample1.0722 tabs ofCatalystSulphuric acidWeigh sample称重称重 1 g of dry organic material(homogeneous)1克干的有机物质(均质)Sample Bla
7、nk 空白空白 add everything except sampleAdd reagents加试剂加试剂 10 g or 2 tabs of Kjeldahl catalyst mixture 10g 或2片凯氏消化片20ml 硫酸 样品均质,称重后加入试剂样品均质,称重后加入试剂July 05/KJ10China_Kjeldahl SolutionsDigestion消化(II)vapours to ScrubberDigestion digest at 370 C for 90 min or until the mixture is clear (green/blue color)+3
8、0 min 370 90 mins 或 消化澄清 后30分钟 Digestion July 05/KJ11China_Kjeldahl SolutionsDistillation 蒸馏(I)manually or automatedDilution dilute the cooled digestion solution with 50 ml deionised water加入50ml 去离子水稀释Dilution稀释稀释July 05/KJ12China_Kjeldahl SolutionsDistillation蒸馏(II)Boric acid titration硼酸滴硼酸滴定定 add
9、60 ml of Boric acid 4%加 460ml 的硼酸 add 2 to 3 drops of indicator according to Sher 加两至3滴的指示剂Back titration反滴定反滴定 add 20.0 ml of sulphuric acid standard solution(0.5 N or equivalent)加20ml的硫酸标准液(0.5N)add 2 to 3 drops of indicator according to Sher加2到3滴指示剂Preparation of Receiver 准备接受液准备接受液July 05/KJ13Ch
10、ina_Kjeldahl SolutionsDistillation蒸馏(III)Sodium hydroxide NaOH add 90 ml of NaOH 32%to the diluted digestion solution加90ml 32的NaOH到溶液中Distillation蒸馏蒸馏 distill for 4 min.蒸馏4分钟 Neutralisation and DistillationJuly 05/KJ14China_Kjeldahl SolutionsTitration滴定7.15Boric acid titration 硼酸滴定硼酸滴定 titrate the c
11、ondensate with sulphuric acid standard solution(0.5 N or equivalent)to the end point of pH 4.65 用0.5N的硫酸标准液中和滴定至 终点PH4.65Back titration 反滴定反滴定 titrate the condensate with sodium hydroxide standard solution(0.5 N or equivalent)用0.5N的NaOH标准液中和滴定 TitrationJuly 05/KJ15China_Kjeldahl SolutionsCalculation
12、计算%P =(Consumption-Blank)x 1.4007 x N x PF x 100Sample Size1.4007:1ml 0.1N Volumetric Solution 1.4007mg NN:Normality AcidPF:Protein factor N Protein July 05/KJ16China_Kjeldahl SolutionsProtein Factors蛋白转换因子Sample typeProtein FactorGelatine5.55Dairy products6.38Meat6.25Fish6.25Nuts,oilseeds5.4Cereals
13、6.25Fruit,Vegetable6.25Corn6.25Eggs6.25July 05/KJ17China_Kjeldahl Solutions凯氏定氮法的发展July 05/KJ18China_Kjeldahl Solutions最早July 05/KJ19China_Kjeldahl SolutionsBuchi公司开始凯氏分析于:1961开始生产上市凯氏定氮仪市场上第1个带有内置蒸汽发生器的蒸馏仪,大大提高蒸馏效率July 05/KJ20China_Kjeldahl Solutions定氮仪在 Bchi的发展演变July 05/KJ21China_Kjeldahl Solution
14、sBchi 今日Digestion Units and Scrubber 消化单元和排废装置Distillation Units蒸馏单元July 05/KJ22China_Kjeldahl SolutionsBchis Digestion Units 消化单元July 05/KJ23China_Kjeldahl Solutions消化加热方式Infrared Heating红外加热Block Heating整体铝块加热July 05/KJ24China_Kjeldahl Solutions红外消化炉特点 红外加热,通过辐射方式,非接触式加热 升温速度快(10min预热)可以升温至650C消化管
15、排废和消化管紧密联接 6 管消化仪(K-424)或12 管(K-435)加热步骤可控,定时器 12 管(K-435)K-424K-435July 05/KJ25China_Kjeldahl Solutions整体铝块加热消化炉的特点K-437K-438 铝块加热 -接触式加热 可以升温到450C 温度时间可控消化管排废和消化管紧密联接 酸气回收装置可控 20个消化位置 自动提升(K-438 only)K-438:程序化(时间延迟,升温梯度,自动停止,)July 05/KJ26China_Kjeldahl SolutionsDigestion红外和整体铝块消化炉的区别 Block铝块铝块 IR红
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