家用清洁剂中pH的测定

pH inHousehold Cleansers pH inHousehold Cleansers Calibration and Analysis 1. Allow all the standards and the samples to attain room temperature for precise measurements since themeasurement is temperature sensitive. 2C.alibrate the meter using the pH 7.00 buffer followed by the pH 4.01 buffer， stirring the standards ata uniform rate. 3. Place electrode， temperature probe， and stirrer into beaker with pH 7.00 buffer standard with theelectrode tip 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. 5. Press CALIBRATE key to accept 7.00 standard and press the STIRRER key to turn the stirrer off. 6.Rinse electrode， temperature 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 orrub the sensing element of the electrode. 7.Place the probes and stirrer into beaker with the pH 4.01 buffer standard with the electrode tip fullyimmersed in the solution. The stirrer should be positioned slightly below the tip of the electrode. Pressthe STIRRER key on the meter to turn the stirrer on. 8.Wait for stable reading (1-2 minutes). 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. Pressthe STIRRER key to turn the stirrer off. 10. Rinse electrode， temperature 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 orrub the sensing element. 11. Place the probes and stirrer into prepared sample with the electrode tip fully immersed in the solution.Press the MEASURE key on the meter； the stirrer will turn on. The pH Icon will flash as themeasurement is being made. The pH icon will become solid and the display value will freeze when astable reading is achieved. This value is logged and printed automatically and the stirrer turnsoff automatically. 12. Repeat steps 10 and 11 for additional samples. Remember to rinse the electrodes with deionized waterbetween measurements. Penetrateeach sample to the same depth to reproduce sample measurement.Upon completion of samples， rinse the electrode with deionized water and store the electrodeaccording to instructions in the Electrode Storage section of this method note. *Fantastik is a registered trademark of The Betty Mills Company** Crystal Shine is a registered trademark of USA Detergents Inc Introduction This method describes a procedure for the determination of the pH in two household cleansers，“Fantastik"and "Crystal Shine". The Orion ROSS Ultra° electrode offers stable， fast results regardlessof sample composition. Results are three to five times more precise than those obtained withconventional electrodes. Recommended Equipment Cat. No. 2. ROSS Ultra Electrode 8102BNUWP 3. ATC probe 927007MD 4. Orion benchtop stirrer (or magnetic stir plate and bar) 096019 5. Orion benchtop electrode stand 1110001 6. Beakers (50 mL) 7. Beaker watch glass Required Solutions Cat. No. 1. pH 4.01 Buffer， 475 mL 910104 2. pH 7.00 Buffer， 475 mL 910107 3. pH 10.01 Buffer， 475 mL 910110 T.ROSS reference filling solution (included with 8102BNUWP) 810007 5p.H electrode storage solution 910001 6.Deionized water Calibration Standard Preparation 1. Allow all the standards and the samples to attain room temperature for precise measurements since themeasurement is temperature sensitive. 2. Select two buffers that bracket the expected sample pH. The first should be near the electrode isopotential point (pH 7) and the second near the expected sample pH. Sample Preparation 1. Ensure that the test sample is well conditioned to room temperature. 2. Dispense approximately 40-50 mL of sample into a beaker. Cover the beaker with a watch glass. 3. Repeat this procedure for additional measurements. Results Five aliquots of each household cleanser were measured and the results provide representative results expectedfor pH in household cleansers. All purpose cleaner pH Cleaner pH Fantastik@ Crystal Shine@ Sample #1： 12.201 Sample #1： 5.142 Sample #2： 12.199 Sample #2： 5.137 Sample #3： 12.200 Sample #3： 5.135 Sample# 4： 12.200 Sample #4： 5.130 Sample #5： 12.196 Sample #5： 5.181 Mean： 12.199 Mean： 5.145 Standard Deviation： 0.002 Standard Deviation： 0.021 %CV： 0.016 %CV： 0.400 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一 ROSS Ultra 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 the filling hole by removing the plastic sleeve and add ROSS internal filling solution. To maintainan adequate flow rate， the level of filling solution must cover the end of the coil and be at least one inchabove the sample level when immersed. The filling hole should be open whenever the electrode is in use. 4. Place the electrode in the electrode holder and suspend in air for 15 minutes to thoroughly wet thereference junction.Once junction is wet， do not allow the electrode to dry out. 5. Thoroughly wet the reference junction by pressing down on the electrode cap and allowing some ofthe ROSS internal filling solution to flow out of the electrode through the junction. Replenish lostfilling solution. 6Shake down the electrode to remove air bubbles.7 For initial meter setup， follow the steps on the Quick Reference Guide that is attached to the meter itself. TheQuick-Start Guide included with each meter also contains a layout of the meter keypad for reference. Thewords in all capital letters such as POWER indicate a key on the meter， and words in quotations such as “Unit”indicate information on the meter display. 1 Connect the electrode to the meter 2. Connect the stirrer 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 the top line is not active， press theLINE SELECTION key to change the selected line to the top line. Then press the UP or DOWN arrowkeys to change the measurement mode of the top line to pH. 5.1Press 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 setting. 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 “ISE： mg/L”tothe right of 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 Quickstart guide for instructions. ofof f f