土壤中物理指标检测方案

pH of SoilspH of Soils pH of Soils Star SeriesMethod Note M-1016-E 03/05 RevB 6 Place the electrode， ATC probe， and stirrer into the beaker with the pH 10.01 buffer. ·pH Introduction 7. When arrow stops flashing， press MEASURE key to accept AUTOBUFFER recognition as secondpoint calibration and to move to the measure mode of the meter. Press the STIRRER key to turn thestirrer off. ·Soils · pH Electrode 8. Rinse electrode and stirrer thoroughly with deionized water. This method describes a procedure for the determination of the pH in Soils. The pH of soil indicates thestrength of acidity or alkalinity in the soil solution and can help determine which crops would be mostsuccessful or most beneficial for the soil. in this procedure， soil samples are suspended in water and pH istaken on the supernatant liquid. The Epoxy-Body， Sure-Flow°Combination pH electrode is ideal for dirty，difficult samples such as soils and offers stable， fast results regardless of sample composition. 9. Place the electrode， ATC probe， and stirrer into the beaker with prepared sample such that theelectrode tip is fully immersed in the solution. Press the MEASURE key on the meter； the stirrer willturn on. The pH icon will flash as the measurement is being made. The pH icon will become solidand the display value will freeze when a stable reading is achieved. This value is logged and printedautomatically and the stirrer turns off automatically.V. 10. Repeat steps 8 and 9 for additional samples. Remember， rinse electrodes with deionized water between measurements. Penetrate each sample to thesame depth to reproduce sample measurement. Upon completion of samples， rinse the electrode withdeionized water and store the electrode according to instructions in the Electrode Storage section of thismethod note. pH Application Package (includes all items with a catalog number) 1010117 1. 3 Star benchtop pH meter 1112000 2. Epoxy-Body，ROSS° Sure-Flow°combination pH electrode 9165BNWP 3. ATC probe 927007MD 4. Orion benchtop stirrer (or magnetic stir plate and bar) 096019 5. Orion benchtop electrode stand 111001 6. Beakers (50 mL) Required Solutions CatNo. 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. Filling solution， 4 M KCl saturated with AgCl 900011 5.pH storage solution 910001 6 Deionized water Optional Solutions Cat No. 1. pH cleaning kit， 4 pack 900020 Calibration Standard Preparation 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 10.01 buffer into a 50 mL beaker. Note： Select two buffers with bracket the expected sample pH. The first should be near theelectrode isopotential point (pH 7) and the second near the expected sample pH. Sample Preparation 1.Weigh 20 g of soil into a beaker， add 20 mL of deionized water. Mix within a 30-minute period. Environmental InstrumentsWater Analysis Instruments166 Cummings CenterBeverly， MA 01915 USAM-1016-E 03/05 RevB248076-001 Toll Free：1-800-225-1480Tel：1-978-232-6000Dom.Fax： 1-978-232-6015Intl Fax：978-232-6031www.thermo.com/waterO 2005 Thermo Electron Corporation RegisteredIS O9001：2000 2 Repeat this procedure for additional measurements. All rights reserved Results Five soil samples were prepared and measured for pH. The obtained pH results demonstrated good repeatability. Soil sample pH Sample #1： 7.96 Sample #2： 7.94 Sample # 3： 7.91 Sample # 4： 7.98 Sample # 5： 7.92 Mean： 7.94 Standard Deviation： 0.03 %CV： 0.36 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°pH electrode storage solution. If not available， as a temporary substitute， use about 200 mL of Orion° pH 7buffer with 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-ROSS° Sure-Flow° 1.Remove the protective shipping cap from sensing element and save cap for storage. 2. Clean any salt deposits from exterior by rinsing with deionized water. 3. Uncover filling hole by removing plastic sleeve and add ROSS" internal 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. Meter Setup -3 star portable 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. 2. Connect the ATC probe to the meter. Connect the electrode to the meter 3. Press the POWER key on the meter to turn the meter on. 4. Note 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. 5. 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. 6.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. 7. P1ress the LINE SELECTION key to select the middle line， and press the UP or DOWN arrow key toselect “bUF”which is pH buffer. 8.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. 9. Press the LINE SELECTION key to accept and select the pH setup menu line (top line). 10. 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 Setupbefore analysis， please see the Quick Start Guide for instructions. 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 and pH 10.01 buffers， stirring the solutions at a uniform rate. 3. Place the electrode， ATC probe， and stirrer into the beaker with the pH7 buffer such that the electrode tipis fully immersed in the solution. The stirrer should be positioned slightly below the tip of the electrode.Press the STIRRER key on the meter to turn the stirrer on. Press the CALIBRATE key. 4 When arrow stops flashing， press CALIBRATE key to accept AUTOBUFFER recognition as first pointcalibration. www.thermo.com of of off