牛奶或奶制品中酸值检测方案(自动电位滴定)

Julabo VISCOAnalysis And Testing Technology Application Application Use This method is used for the quantitative determination of acidity (acid degree) in milk and milkproducts. The acidity is calculated either as SH-， Dornic-or Therner degree. The different degree usesdifferent concentrations of NaOH titrant. Appliances Titrator： TL 6000/7000 (TL 6000/7000 M2/20) consists of Basic device Magnetic stirrer TM 235 20 mL Exchange unit WA 20， with nrown glass bottle for titrant complete And pH combination electrode A 162 DIN ID Electrodes Electrode： A 162 DIN ID Calibration： DIN buffer pH= 4.00 and pH= 7.00 Application Reagents Titrant： sodium hydroxide solution 0.1mol/l (Therner)， 0.25 (SH) or 0.11 (Dornic) mol/l Soda lime for carbon dioxide uptake of the reagent. Titer： potassium hydrogenphthalate (reference material) Description Calibration The pH combination electrode is calibrated in technical buffer pH=4.00 and pH= 7.00 or in DIN bufferpH= 4.01 and pH= 6.87. Example of the calibration documentation： Calibration Buffers used pH buffer 1： TEC 4.000 pH buffer 2： TEC 7.000 Measured values pH buffer 1： TEC 4.000 165.6 mV/23.4°℃ pH buffer 2： TEC 7.000 -11.2 mV/23.0°℃ Calibration data slope： 99.4%/-58.8 mV/pH Zero point： pH 6.81/-11.2 mV Temperature： 23.4°C (a) Date and time： 07.03.13/ 15：04 Determination of the exact concentration of the standard solution By carbon dioxide absorption from the air occurs in the sodium hydroxide solution of sodiumbicarbonate， which changes the pH of the titrant. To prevent this， a drying tube filled with soda lime isplaced on the reagent bottle. The exact concentration of the sodium hydroxide solution is determinedusing the standard potassium hydrogen phthalate. The potassium hydrogen phthalate is dried in theoven before the titer determination for 2 hours at 120°C and cooled in a desiccator. Implementation In a 50 mL beaker， 0.2 to 0.3g potassium hydrogen phthalate were weighed accurately and dissolvedin 30 mL of dist. water with stirring. It is titrated with 0.1 mol/l sodium hydroxide solution. For 0.25 mol/lNaOH you need 0.5 -0.75 g potassium hydrogen phthalate. Application Standardisation titration (result) GLP documentation Titration graph 'ml M p[H/ml ·dpH/dml Method data Method name： Titre NaOH Titration duration： 2 m 15 s End date： 08.01.13 End time： 15：46：03 Titration data Weight： 0.20490 g Start pH： pH 4.065 End pH： pH 9.667 Start temperature： 25.0°℃(m) End temperature： 25.0°C(m) Zero point： pH 6.85 /-8.9 mV Slope： 98.7%/-58.4 mV/pH EQ： 10.032 ml /pH 8.498 Titre： 0.1000 mol/l Mean value： RSD： Calculation formula Titre： (W*F2)/((EQ1-B)*M*F1)->WA Mol (M)： 204.22000Weight (W)： 0.2049 g (m) Factor 2 (F2)： 1000.0000Blank value (B)： 0.0000 ml Factor 1 (F1)： 1.0000Statistics： Application Standardisation titration (method Method data Method name： Titer NaOH Created at： GLP Method type： Automatic titration Last modification： Measured value： pH Documentation： Titration mode： Dynamic Dynamic： average Measuring speed / drift： Normal： e： minimum holding time： 02 s maximum holding time： 1 15 s measuring time： 02 S drift： Initial waiting time： Os Titration direction： Increase Pretitration： Off End value： 10.500 pH EQ： On slope value： Steep Value： 700 Dosing parameter 1/1 Application Titration of the sample Pipette accurately in 100 ml beaker either： 25 ml milk for SH degree 11 ml milk for Dornic degree 9 ml for Therner degree Add app. 25 ml - 40 ml CO2 free water into and mix the sample on the magnetic stirrer for a fewseconds. Titrate with the suitable NaOH titrant to a fixed pH endpoint (8.2-8.7， depending on nationalnorms). Example GLP documentation Titration graph 1.81 mlpH 8.200 ·pH/ml Method data End date： 29.04.13 End time： 13：47：45 Titration data Sample ID： Milk 4 Weight： 24.67000 g Start pH： pH6.768 End pH： pH 8.215 Start temperature： 19.1℃ (a) End temperature： 19.3 °C (a) Zero point： pH 6.82/-10.3 mV Slope： 98.8%/-58.4mV/pH EP1： 1.806 ml /pH 8.200 Acidity： 7.321 °SH Calculation formula Acidity： (EP1-B)*T*M*F1/(W*F2) Mol (M)： 1.00000 Blank value (B)： 0.0000 ml Titre (T)： 1.00000000 (a) Factor 1 (F1)： 100.0000 Weight (W)： 24.67000 g (m) Factor 2 (F2)： 1.0000 Statistics： Off Application Method parameters： (optimized for SH degree) Method data overall view Method name：acidity in milkCreated at： 04/29/13 13：24：34Method type：Automatic titrationLast modification： 04/29/13 13：44：18Measured value：pHDamping settings： NoneTitration mode：End pt.Documentation： GLPLinear steps：0.050 mlMeasuring speed / drift：Normal：minimum holding time： 02 smaximum holding time： 15sMeasuring time： 02 sDrift： 20 mV/minInitial waiting time：0 sTitration direction：IncreasePretitration：OffEndpoint 1：pH 8.200delta endpoint 1： pH 1.000Endpoint delay 1： 5 sEndpoint 2：Off Dosing parameter Dosing speed： 20.00 % Filling speed： 30 s Maximum dosing volume： 50.00 ml Unit values Unit size： 20ml Unit ID： 00360005 Reagent： NaOH Batch ID： no Charge Concentration [mol/l]： 1.00000 Determined at： 04/29/13 20：26：19 Expire date： 01/01/13 Opened/compounded： 02/01/12 Test according ISO 8655： 01/01/00 Last modification： 04/29/1313：26：21 Device information Device： TitroLine 7750 Serial number： 10018602 Software version： 1316 Hard Disk\result\acidity_in_milk_29_04_13-13_45_40.pdf Application Notes The acidity can also calculate as % lactic acid instead of acid degree. In this case the calculation is： % lactic acid： (EP1-B)*M*T*F1/(W*F2) EP1： ml consumption to pH endpoint B： blank value in ml. Here =0 M： molecular weight of lactic acid： 90.08 T： exact concentration of the NaOH in mol/l (e.g. 0.2510 mol/l F1： 0.1 (conversion factor to%) W： sample amount in g F2： 1 If you have any questions on the application， you can feel free to contact us. JULABO TECHNOLOGY(Beijing)Co.，LTD地址：北京市朝阳区酒仙桥东路1号院M8号楼C厅3层301室Add ： Room 301，C hall，M8 office building，No.1 jiuxianqiao east road ，Chaoyang District，Beijing，ChinamTel.：4008092068昌Fax： +86 (0)1064390585E-Mail ： info@julabo.cn优莱博技术(北京)有限公司③Web： www.julabo.cn， www.julabo-visco.com Seite von date： Seite von date：