碳酸饮料中pH检测方案

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pH inCarbonated Beverages pH inCarbonated Beverages Calibration and Analysis 1. Allow all the standards and the samples to attain room temperature for precise measurements since themeasurement is temperature sensitive. 2. Calibrate the meter using the pH 7.00 buffer followed by the pH 4.01 buffer， stirring the standards at auniform rate. 3. Place electrode，ATC probe and Orion stirrer into beaker with pH 7.00 buffer standard such that theelectrode tip is fully immersed in the solution. The stirrer should be positioned slightly below the tip ofthe electrode. Press the STIRRER key on the meter to turn the stirrer on. Press the CALIBRATE key. 4. Wait for stable reading (1-2 minutes). Enter standard value of 7.00 using the UP and DOWN arrowkeys and the DECIMAL /DIGIT key. 5Press CALIBRATE key to accept 7.00 standard and press the STIRRER key to turn the stirrer off.6 Rinse electrode， ATC probe， and stirrer thoroughly with deionized water. Gently remove excess solutionfrom the outer sleeve of the electrode by dabbing with a clean paper tissue. Do not wipe or rub thesensing element of the electrode. 7. Place the electrode and stirrer into beaker with the pH 4.01 buffer standard such that the electrodetip is fully immersed in the solution. The stirrer should be positioned slightly below the tip of theelectrode. Press the STIRRER key on the meter to turn the stirrer on. 8. Wait for a stable reading (1-2minutes). Enter standard of 4.01 using the UP and DOWN arrow keysand the DECIMAL /DIGIT key. 9. Press MEASURE key to accept 4.01 standard and to move to the measure mode of the meter. Press theSTIRRER key to turn the stirrer off. 10. Rinse the electrode， ATC probe and stirrer thoroughly with deionized water. Gently remove excesssolution from the outer sleeve of the electrode by dabbing with a clean paper tissue. Do not wipe or rubthe sensing element. 11. Place the electrode and stirrer into beaker with the pH 1.68 buffer standard such that the electrodetip is fully immersed in the solution. The stirrer should be positioned slightly below the tip of theelectrode. Press the STIRRER key on the meter to turn the stirrer on. 12. Wait for a stable reading (1-2 minutes). Enter standard of 1.68 using the UP and DOWN arrow keysand the DECIMAL /DIGIT key. 13.Press MEASURE key to accept 1.68 standard and to move to the measure mode of the meter. Press theSTIRRER key to turn the stirrer off. 14. Rinse the electrode， ATC probe and stirrer thoroughly with deionized water. Gently remove excesssolution from the outer sleeve of the electrode by dabbing with a clean paper tissue. Do not wipe or rubthe sensing element. 15. Place the electrode， ATC probe and stirrer into prepared sample such that the electrode tip is fullyimmersed in the solution. Press the MEASURE key on the meter； the stirrer will turn on. The pH iconwill flash as the measurement is being made. The pH icon will become solid and the display value willfreeze when a stable reading is achieved. This value is logged and printed automatically and the stirrerturns off automatically. Remember， rinse electrodes with deionized water between measurements. Penetrate each sample to the samedepth to reproduce sample measurement. Upon completion of samples， rinse the electrode with deionizedwater and store the electrode according to instructions in the Electrode Storage section of this method note. Toll Free：1-800-225-1480Tel：1-978-232-6000Dom. Fax：1-978-232-6015Intl Fax：978-232-6031www.thermo.com/water2005 Thermo Electron CorporationAll rights reserved pH inCarbonated Beverages Introduction The new Orion 3-Star pH meter and ROSS Ultra pH electrode (Cat No.8104BNUWP) assuresbeverage manufacturers the most stable and fast pH measurements for testing purposes. pH together withtemperature， rank as the most important indicators of food quality and safety. The pH of carbonatedbeverages is measured to ensure that quality standards have been properly met. pH is also monitored atdifferent stages to guarantee safety， improve production and enhance taste. Recommended Equipment Cat.No. pH in Carbonated Beverages Application Package (includes all items with a catalog number) 1010143 1.3 Star benchtop pH meter 1112000 2.ROSS Ultra pH electrode 8104BNUWP 3. ATC temperature probe 927007MD 4. Orion benchtop stirrer (or magnetic stir plate and bar) 096019 5. Benchtop electrode stand 1110001 6. Beakers (50 mL) 7. Graduated cylinder (50 mL) Required Solutions Cat. No. 1. pH 4.01 buffer， color coded pink 910104 2. pH 7.00 buffer， color coded yellow 910107 3. pH 10.01 buffer， color coded blue 910110 4. pH electrode storage solution 910001 Deionized water Calibration Standard Preparation 1.Using a graduated cylinder， transfer 30 mL of the pH 7.00 buffer into a 50 mL beaker. 2. Using a graduated cylinder， transfer 30 mL of the pH 4.01 buffer into a50 mL beaker. Sample Preparation 1.Using a graduated cylinder， measure 30 mL of the sample into a 50 mL beaker. Mix sample withSirOrion stirrer. 2.Repeat this procedure for additional measurements. Results Five aliquots of carbonated beverage are measured and the results provide representative results expected for pHin carbonated beverages. Carbonated Beverage pH Sample #1： 2.450 Sample # 2： 2.454 Sample # 3： 2.459 Sample #4： 2.451 Sample #5： 2.455 Mean： 2.4538 Standard Deviation： 0.0036 %CV： 0.1452 Electrode Storage To ensure a quick response and free-flowing liquid junction， the sensing element and reference junction mustremain wet and not be allowed to dry out. For short-term storage (up to one week)， soak electrode in Orion pHelectrode storage solution. If not available， as a temporary substitute， use about 200 mL of Orion pH 7 bufferwith 1 gm KCl added. For prolonged storage， the reference chamber should be filled with the fill hole cover in place. Cover thesensing element and reference junction with the protective cap containing a few drops of pH storage solution.After prolonged storage， prepare the electrode as described in the Electrode Setup section of this method. Equipment Setup Electrode Setup 1. Remove the protective shipping cap from sensing element and save cap for storage. 2Clean any salt deposits from exterior by rinsing with deionized water.3 Uncover filling hole by removing plastic sleeve and add ROSSTMinternal filling solution. To maintain anadequate flow rate， the level of filling solution must cover the end of the coil and be at least one inch abovethe sample level when immersed. The filling hole should be open whenever the electrode is in use. 4. Shake down the electrode to remove air bubbles 5.Soak the electrode in pH electrode storage solution for one hour. For initial meter setup， follow the steps in the Quick Start Reference attached to the meter itself. The QuickStart Guide also contains a layout of the meter keypad for reference. The words in this method represented inall capital letters， such as POWER， indicate a key on the meter， and words in quotations such as “Unit"indicateinformation on the meter display. 1. . Connect the electrode to the meter. 2.Connect the ATC probe to the meter. 3.Connect the stirrer to the meter 4.1Press the POWER key on the meter to turn the meter on. 5. 1Note that the arrow on the left of the screen indicates the active line. If not the top line is not active， pressthe LINE SELECTION key to change the selected line to the top line. Then press the UP or DOWNarrow keys to change the measurement mode of the top line to pH. 6.Press the SETUP key to enter pH setup. Press the LINE SELECTION key to select the middle line. Pressthe UP or DOWN arrow keys to select “rES”which is resolution. 7.Press the LINE SELECTION key to select the bottom line. Press the UP or DOWN arrow keys to select“0.001”for "rES”which is an abbreviation for resolution or number of significant digits. Press the LINESELECTION key to accept value. Press the LINE SELECTION key to select the middle line， and press the UP or DOWN arrow key toselect“bUF”which is pH buffer. 9.Press the LINE SELECTION key to select the bottom line， and press the UP or DOWN arrow key toselect“USA”which is US/Orion buffers. 10. Press the LINE SELECTION key to accept and select the pH setup menu line (top line). 11. Press the MEASURE key to return to the measurement mode. If all steps were followed correctly the meter display will show three digits in the top line and“pH"to the rightof the top line. The meter and electrode are now ready for calibration. Note： The Orion Benchtop Stirrer must be turned on in General Instrument Setup before analysis， please see the Quick Start Guide for instructions Water Analysis InstrumentsCummings CenterBeverly， MA USAM-E RevBnvironmental Instrumentswww.thermo.com of f ff