牙膏中氟的测定

Fluoride inToothpasteFluoride inToothpaste Fluoride inToothpaste 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“0.020 % w/v"followed by the “0.20% w/v"standard， stirring thestandards at a gentle and uniform rate. 3P.lace the electrode and stirrer into the beaker with the“0.020 % w/v"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. Press the CALIBRATE key. 4.Wait for a stable reading (1-2 minutes). Enter the standard value of“0.020”using the UP andDOWN arrow keys and the DECIMAL/DIGIT key. 5. Press the CALIBRATE key to accept the "0.020 % w/v"standard and press the STIRRER key to turnthe stirrer off. 6R.inse electrode and stirrer thoroughly with deionized water. Gently remove excess solution from theouter sleeve of the electrode by dabbing with aclean paper tissue. Do not wipe or rub the sensingelement. 7. Place the probe and stirrer into the beaker with the “0.20 % w/v"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 (1-2 minutes). Enter the standard value of“0.20”using the UP and DOWNarrow keys and the DECIMAL/DIGIT key. 9..Press the MEASURE key to accept the"0.20 % w/v"standard and to move to the measure mode ofthe meter. Press the STIRRER key to turn the stirrer off. 10. Rinse electrode and stirrer thoroughly with deionized water. Gently remove excess solution from theouter sleeve of the electrode by dabbing with a clean paper tissue. Do not wipe or rub the sensingelement of the electrode. 11. Place the probe and stirrer in a prepared sample with the electrode tip fully immersed in the solution.Press the MEASURE key on the meter； the stirrer will turn on. The ISE：% icon will flash as themeasurement is being made. The ISE：% icon will become solid and the display value will freeze whena stable reading is achieved. This value is logged and printed automatically and the stirrer turns offautomatically. 12. Repeat steps 10 and 11 for additional samples. Upon completion of samples， rinse electrode with deionized water and store the electrode according toinstructions in the Electrode Storage section of this method note. Introduction Fluoride is incorporated in oral health products in several chemical forms， including sodium fluoride，sodium monofluorophosphate， amine fluoride and stannous fluoride. This method provides rapid，uncomplicated determinations for fluoride in the form of sodium fluoride in toothpaste. This procedureeliminates interferences associated with the presence of color agents and solids. The direct measurement offluoride ion with the fluoride ion selective electrode is a well-established technique that is frequently usedas a standard method of analysis. Cat. No. Recommended Equipment ISE Application Package (includes all items with a Cat.No.) 1010157 1. 4-Star benchtop pH/ISE meter 1115000 2. Orion ionplus° fluoride electrode 9609BNWP 3. Orion benchtop stirrer (or magnetic stir plate and bar) 096019 4. Orion benchtop electrode stand 1110001 ).100 mL and 500 mLvolumetric flask 100 mL beakers 7. 50 mL graduated cylinder .10 mL pipettes Required Solutions Cat.No. 1. Fluoride Standard， 100 ppm as F 940907 3. Reference Filling Solution， Optimum ResultsA 900061 4. TISABII 940909 5. Deionized water Calibration Standard Preparation 1 Using a graduated cylinder， transfer 25 mL of the 100 ppm (0.010 % weight/volume) standard into abeaker. Using a graduated cylinder add 25 mL ofTISAB II. This 100 ppm standard will be used as“0.200% w/v”in calibration.The“0.200% w/v"standard takes into account and corrects for the 1：20dilution of the sample (25 g dispersed in 500 mL). 2 Prepare a 10 ppm (0.0010 % w/v) standard by pipetting 10 mL of the 100 ppm fluoride standardinto a 100 mL volumetric flask. Dilute to the mark with deionized water. Mix well. This 10 ppmstandard will be used as”0.020% w/v”in calibration. The “0.020 %w/v"standard takes into accountand corrects for the 1：20 dilution of the sample. 3. Using a graduated cylinder， transfer 25 mL of the "0.02 % w/v" (10 ppm) standard into a beaker.Using a graduated cylinder， add 25 mL ofTISAB II. Sample Preparation 1Disperse 25g toothpaste in about 150 mL of deionized water.2 Quantitatively transfer to 500 mL volumetric flask. Dilute to the mark with deionized water.Mix well. 3 Using a graduated cylinder， transfer 25 ml of the prepared sample into a beaker. Using a graduatedcylinder add 25 ml ofTISAB II. 4. Repeat this procedure for additional measurements. Results Five aliquots of the diluted toothpaste were measured for fluoride. The data in the table below is representativeof the results expected for fluoride in toothpaste. Toothpaste with Sodium Fluoride % w/v Fluoride Sample #1： 0.111 Sample #2： 0.110 Sample #3： 0.111 Sample #4： 0.110 Sample # 5： 0.110 Mean： 0.110 Standard Deviation： 9001 %CV： 0.50 Electrode Storage For brief storage periods between sample measurements， store the electrode in the 10 ppm (0.0010 % w/v)fluoride standard. The filling solution in the fluoride electrode should not be allowed to evaporate， whichcauses crystallization. For longer storage periods， refer to the electrode instruction manual. Fluoride electrodes，whose response may become sluggish with time， can often be restored to working order by brushing the sensingelement on the flat tip of the electrode with fluoride toothpaste and a soft brush. Equipment Setup Electrode Setup 1. Remove the rubber cap covering the electrode tip. 2. Fill the outer chamber with Optimum Results A filling solution. .33. Lift the filling solution bottle's spout to a vertical position. 4 Insert the spout into the filling hole in the outer sleeve of the electrode and add a small amount of fillingsolution to the chamber. Then tip the electrode to moisten the o-ring at the top and return electrode to avertical position. .5 Holding the electrode by the barrel with one hand， use the thumb to push down in the electrode cap，allowing a few drops of filling solution to drain wetting the inner cone. 6. Release the electrode cap allowing the electrode's outer sleeve to return to its original position immediately，check to see if the o-ring is moist and repeat steps 4-6 until the outer sleeve has returned to its originalposition. Add more filling solution until the amount of filling solution within the electrode body is levelwith the bottom edge of the electrode filling hole. Meter Setup 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. Press the SETUP key. Use the UP or DOWN keys to enter ISE setup.. Press the LINE SELECTIONkey to select the bottom line. Press the UP or DOWN arrow keys to select“3”for“rES”which is anabbreviation for resolution or number of significant digits. Press the LINE SELECTION key to acceptvalue. 6. Press the LINE SELECTION key to select the middle line， and press the DOWN arrow key to select“nL Inwhich is an abbreviation for non-linear blank correction. Press the LINE SELECTION key to select the bottom line. Press UP or DOWN arrow keys to select “off’for"nL In". Press the LINE SELECTION key to accept setting. 8. Press the LINE SELECTION key to select middle line， and press the DOWN arrow key to select “rAng"which is an abbreviation for measurement range. 9 Press the LINE SELECTION key to select the bottom line. Press the UP or DOWN arrow keys to select“HigH” for “rAng". Press the LINE SELECTION key to accept setting. 10. Press the LINE SELECTION key to select middle line， and press the DOWN arrow key to select “Unit”. 11. Press the LINE SELECTION key to select the bottom line. Press the UP or DOWN arrow keys to select“PEr”(%) for“Unit". Press the LINE SELECTION key to accept setting. 12. 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：%”to theright 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