凯氏定氮仪的发展史

July05/KJChina_KjeldahlSolutions1凯氏定氮一个使用了120年的依旧年轻的技术BÜCHILabortechnikAGKatharinaJehleFlawil,SwitzerlandJuly05/KJChina_KjeldahlSolutions2主题：蛋白的基本概念凯氏定氮的方法方法的发展Büchi’s消化单元Büchi’s消化单元Kjeldahl法问题解决July05/KJChina_KjeldahlSolutions3蛋白的基本概念BasicsProteinJuly05/KJChina_KjeldahlSolutions4为什么要分析蛋白?蛋白质是：Basicnutrient－基本的营养Impactoncaloricvalue(17kJresp.4kcal)－热量来源Parameterforquality(e.g.meat)－品质参数Influenceonproductionprocess(e.ggelation,extrusion)－影响产品的中间处理（例，冻结，压榨）Influenceonflavourandcolouroffood(e.g.bakingprocessbread,roastingprocesscoffee)－影响食品的风味和颜色July05/KJChina_KjeldahlSolutions5蛋白的基本结构是氨基酸，分子式如下：Thereareabout200aminoacidsfoundinnature自然界已发现的大概有200种氨基酸Thereareabout20aminoacidsinaproteinhydrolysate蛋白水解后大概有20种氨基酸July05/KJChina_KjeldahlSolutions6怎么测定蛋白质？－通过检测氮的含量计算蛋白含量Thenitrogencontentinproteinisinasmallrange(15%-18%,mean:16%)蛋白中氮的含量在15％－18％波动，平均16％Proteinisdeterminedbyanalysingthenitrogencontentandcalculatingtheprotein通过氮含量计算蛋白含量July05/KJChina_KjeldahlSolutions7凯氏定氮概述July05/KJChina_KjeldahlSolutions8谁是凯氏?JohanKjeldahl1849–19001849borninDenmark1867graduationfromuniversity1876ScientistatCarlsbergBreweriesFermentationstudiesDevelopmentofamethodforexactdetermi-nationofnitrogeninanimalandvegetablematerialResearchoncarbohydratesinbarleyandmalt1883PublicationoftheKjeldahlmethodJuly05/KJChina_KjeldahlSolutions9凯氏定氮的原理1.Digestion消化ConversionofProtein-NitrogentoNH4+将蛋白中氮转化为NH4+2.Distillation蒸馏分离收集NH3SeparationofNH33.Titration滴定用酸中和滴定MeasureoftheAmountofAcidthatwasneutralisedbyNH3July05/KJChina_KjeldahlSolutions10Digestion消化(I)BlankSample1.0722tabsofCatalystSulphuricacidWeighsample称重•1gofdryorganicmaterial(homogeneous)•1克干的有机物质（均质）SampleBlank空白•addeverythingexceptsampleAddreagents加试剂•10gor2tabsofKjeldahlcatalystmixture•10g或2片凯氏消化片•20ml硫酸样品均质，称重后加入试剂July05/KJChina_KjeldahlSolutions11Digestion消化(II)vapourstoScrubberDigestion•digestat370°Cfor90minoruntilthemixtureisclear(green/bluecolor)+30min370℃90mins或消化澄清后30分钟DigestionJuly05/KJChina_KjeldahlSolutions12Distillation蒸馏(I)manuallyorautomatedDilution•dilutethecooleddigestionsolutionwith50mldeionisedwater•加入50ml去离子水稀释Dilution稀释July05/KJChina_KjeldahlSolutions13Distillation蒸馏(II)Boricacidtitration硼酸滴定•add60mlofBoricacid4%•加4％60ml的硼酸•add2to3dropsofindicatoraccordingtoSher•加两至3滴的指示剂Backtitration反滴定•add20.0mlofsulphuricacidstandardsolution(0.5Norequivalent)加20ml的硫酸标准液（0.5N)•add2to3dropsofindicatoraccordingtoSher加2到3滴指示剂PreparationofReceiver准备接受液July05/KJChina_KjeldahlSolutions14Distillation蒸馏(III)SodiumhydroxideNaOH•add90mlofNaOH32%tothediluteddigestionsolution•加90ml32％的NaOH到溶液中Distillation蒸馏•distillfor4min.•蒸馏4分钟NeutralisationandDistillationJuly05/KJChina_KjeldahlSolutions15Titration滴定7.15Boricacidtitration硼酸滴定•titratethecondensatewithsulphuricacidstandardsolution(0.5Norequivalent)totheendpointofpH4.65用0.5N的硫酸标准液中和滴定至终点PH4.65Backtitration反滴定•titratethecondensatewithsodiumhydroxidestandardsolution(0.5Norequivalent)用0.5N的NaOH标准液中和滴定TitrationJuly05/KJChina_KjeldahlSolutions16Calculation计算%P=(Consumption-Blank)x1.4007xNxPFx100SampleSize1.4007:1ml0.1NVolumetricSolution1.4007mgNN:NormalityAcidPF:ProteinfactorNProteinJuly05/KJChina_KjeldahlSolutions17ProteinFactors蛋白转换因子SampletypeProteinFactorGelatine5.55Dairyproducts6.38Meat6.25Fish6.25Nuts,oilseeds5.4Cereals6.25Fruit,Vegetable6.25Corn6.25Eggs6.25July05/KJChina_KjeldahlSolutions18凯氏定氮法的发展July05/KJChina_KjeldahlSolutions19最早…July05/KJChina_KjeldahlSolutions20Buchi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July05/KJChina_KjeldahlSolutions21定氮仪在Büchi的发展演变July05/KJChina_KjeldahlSolutions22Büchi今日DigestionUnitsandScrubber消化单元和排废装置DistillationUnits蒸馏单元July05/KJChina_KjeldahlSolutions23Büchi’sDigestionUnits消化单元July05/KJChina_KjeldahlSolutions24消化加热方式InfraredHeating红外加热BlockHeating整体铝块加热July05/KJChina_KjeldahlSolutions25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650°C消化管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-435July05/KJChina_KjeldahlSolutions26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450°C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-438only)K-438:程序化(时间延迟,升温梯度,自动停止,…)July05/KJChina_KjeldahlSolutions27红外和整体铝块消化炉的区别Block铝块IR红外预热时间60min5min温控Temperatureeasydifficultcontrol加热单元最大加热温度450°C600°CJuly05/KJChina_KjeldahlSolutions28铝块Block红外IRWatersamples++++++++upto100mlLiquidsamples++++++++++upto15mlDryorganicmaterial++++++++++0.2gto5gHumidorganicmaterial++++++++++0.2gto5gFoamysamples+++++++Mineraloil++++++++++DifferencesIR–Block红外和整体铝块消化炉的区别July05/KJChina_KjeldahlSolutions29如何处理消化过程中的酸雾？Sulphuricacidvapoursarecorrosiveandvitriolic酸雾具有腐蚀性和毒性，解决方法：1)消化炉排废装置，标准配置2)中和酸雾的废气循环回收装置July05/KJChina_KjeldahlSolutions30ScrubberB-414模块化设计,可达4步高效能泵系统,34l/min大的回收试剂腔,3l大的气液接触面积,提高操作性能可加NaOHor碳酸钠(最高NaOH20%但推荐浓度NaOH10%)可以选择抗酸，提供特殊密封垫（抗酸）吸收步骤使用活性炭吸附July05/KJChina_KjeldahlSolutions31Step1(optional)冷凝Step2(standard)中和Step3(standard)吸收Step4(optional)反应ScrubberB-414July05/KJChina_KjeldahlSolutions32消化炉特殊附件Suctionmoduleforaqueoussamples水类样品吸收模块带有冷凝漕的吸收模块，专门处理水类样品，防止交叉污染用于H2O2消化的吸收模块(仅适用于K-424andK-435)用于连续添加H2O2