根据美国药典测量纯水及注射用水的电导率

1、Conductivity test for Purified Water andWater for Injections according to USP-NFAn application for Mete止ab ?SummaryThe con ductivity of a water is a measure of the ion mobilitythrough this water. The con ductivity partly depe nds on the pH, the temperature and the amou nt of atmospheric carb on diox

2、ide, which has bee n dissolved in the water to form ions (in tri nsic con ductivity). The con ductivity also depe nds on the chloride, sodium and ammonium ions in itially prese nt in the water (extra neous con ductivity). The con ductivity (intrin sic and extra neous) of the water is measured and co

3、mpared to values listed in a table to evaluate if the studied water is suitable or not for use in pharmaceutical application s. If the sample fails Stage 1, additi onal tests have to be performed (Stages 2 and 3) in order to determ ine if the excessive conductivity value is due to in tri nsic factor

4、s or extra neous ions.USP Requireme nts Automatic temperature correcti on by this meter must not be used.In strume nt specificati ons:Mi ni mum resoluti on of 0.1 S/qm on the lowest ran ge. Excludi ng the cell accuracy, the in strume nt accuracy must be ±1 S/cm.Meter calibrati on:It is accompli

5、shed by replac ing the con ductivity cell with precisi on resistors traceable to primary sta ndards (accurate to 0.t% of the stated value) or an equivale nt- ly accurate adjustable resista nee device.Cell calibrati on:Water con ductivity must be measured accurately using calibrated in strume ntati o

6、n. The con ductivity cell con sta nt must be known within 2%.Comme ntsRadiometer An alytical produces a KCl 0.01D con ductivity sta ndard which has a certified con ductivity value of 1408 S/cm ±0.5% at 25 C traceable to internationally recog ni sed Stan dard Refere nee Material (SRM) from the N

7、atio nal In stitute of Stan dards and Tech nol- ogy (NIST) and accredited by COFRAC, the official Fre nch ac- creditati on authority.This means that there is a 95% con fide nee level that the true value of the con ductivity sta ndard is 1408 pS/cm ±7 /S/cm at 25 °. For such a low un certa

8、inty con tri- buti on, the un certa inty associated to the cell con sta nt determ in ati on can be reduced to less tha n 1%.The cell constant can be verified directly by using this con ductivity sta ndard.ApparatusFor Stages 1 & 2:CDM230 Co nductivity Meter with calibration certificate.For Stage

9、 3:Stages 1 & 2 equipme nt, plus: PHM210 Standard pH Meter with verification certificate.ElectrodesFor Stage 1:CDC511T Con ductivity Cell, Circu- lati on/Pipette, 4-pole with temperature sensor, with calibration certificates for flow type cell and temperature sen sor.For Stage 2:Stage 1 equipme

10、nt, plus:Epoxy tube for CDC511T, Part No. X31M013 with calibrati on certificate.For Stage 3:Stage 1 & 2 equipme nt, plus: pHC2085-8 Combi ned pH Electrode, Red Rod with temperature sen sor.Reage ntsFor Stages 1 & 2:Certified Con ductivity Sta ndard: Part No. S51M003, KCI 0.01 D.For Stage 3:S

11、tage 1 & 2 soluti ons, plus: Certified pH Sta ndards, IUPAC Series, pH4.005, Part No. S11M002 and pH7.000, Part No. S11M004Saturated KCl Solution, 100 ml, Part No. S21M002Other apparatusE190 Electrode Sta nd, Part No. 809-206Thermostatic bathSAM7 Sample Sta nd with the sta ndard bay onet electro

12、de head,Part No. X31T022X31T031 Adapter (2 pcs)X51T015 Thermostated Vessel for SAM7X31T052 Tubi ng kit for thermostated vesselSTAGE 1Determ ine the temperature and con ductivity of the water.Cable resista nee <0.000>Cab. Capacita nee <500> pFPress the Method ” key for approx. 3 sec on ds

13、:Method<Con ductivity>Con ductivity<Autora nge>Reset reading<no>Un it selecti on<S/cm>Pri nt format<all>Warning beep<yes>Result beep<yes>Reset method<no>Press the T；f ”key for approx. 3sec on ds, select:Temp correcti on<none>Press the Sample ” ke

14、y for approx. 3 sec on ds:Sample result<Autoread>Stability crit.<1.0>%/minAccept time<60> sProcedure table, find the temperature value that is no greater tha n the measured temperature. The corresp ond- ing con ductivity is the limit at that temperature.3) If the measured con ducti

15、vity is no greater than the table value, the water meets the requireme nts of the test for con ductivity. If the con ductivity is higher tha n the table value, proceed with Stage 2.Stage 1Temperature and con ductivity requireme nts(for non-temperature-compensated conductivity measurements only)Tempe

16、rature °CConductivity Use the CDC511T Con ductivity Cell, Circulation/ Pipette in the pipette version, and place it on the E190 Electrode Sta nd.Note: If you want to determ ine the cell con sta nt, the calibrati on can be performed either in pipette or circulati on mode.Rinse the cell carefully

17、 with deionised water. Perform a measurement with a sample from the con- tai ner using the CDC511T. Check that the 4 rings and the temperature sen sor are immersed in the sample and that no air bubbles are trapped. Fit the stoppers on the Luer adapters. Conn ect the CDC511T to the meter, press theSa

18、mple ” key and perform a tem - perature and con ductivity meas- ureme nt (us ing a non-temperature corrected con ductivity read in g). 6) Perform the followi ng test within approximately 5 minutes of the con ductivity determ in ati on while mai ntai ning the sample temperature at 2515C.Add the Satur

19、ated KCl Solution to the same water (0.3 ml per 100 ml of the test specime n). and determine the pH to the n earest 0.1 pH unit.7) Referri ng to the Stage 3 pH and con ductivity requireme nt table determine the conductivity limit at the measured pH value. If the measured con ductivity in step 4 is p

20、S/cm00.650.8100.9151.0201.1251.3301.4351.5401.7451.8501.9552.1602.2652.4702.5752.7802.7852.7902.7952.91003.1(1) Values from USP-NF Fifth SupplementPhysical Tests / Water Conductivity (645) 3465-3467STAGE 2Determi ne the in flue nce of COCDM230 programmi ng:Press the cal ” key for approx. 3 sec on ds

21、.If you use a certified CDC511T, no cell calibrati on is performed, en ter the following parameters directly as follows:Cell 1 Con sta nt<en ter below>Cell 1 Co nsta nt <1.100*> cm-1 Cable resista nee<0.000>Cab. C apacita nee<500> pF (*) En ter the value written on the calibr

22、ation certificate delivered with the CDC511T epoxy tube vers ion.Note: If you want to determ ine the value of the cell con sta nt. en ter:Calibrate using Stability crit. Accept time Calibrate every Cable resista nee Cab. C apacita nee<0.01 KCl> <1.0>%/min<60> s <7> Days <0

23、.000> <500> pFPress the Sample ” key for approx. 3 sec on ds:Sample result Stability crit. Print In terval<At in tervals><0.5>%/min<30> sNote: Stability criteria < 0.5%/min corresp onds in fact to a cha nge in con ductivity < 0.02 S/cm per min ute (equivale nt to 0.1

24、 S/cm per 5 min utes), as required in the Stage 2 USP document.ProcedureStart the measureme nts by pressing the Sample ” key.When the con ductivity value is stable. ' STAB on the display. note the con ductivity.5) If the con ductivity is not greater tha n 2.1S/cm. the water meetsthe requirements

25、 of the test for con ductivity. If the con ductivity is greater tha n 2.1S/m. proceedwith Stage 3.STAGE 3Determ ine the comb ined effectof CO 2 and pHPHM210 programmi ng:Select the type of buffer to be used for the calibrati on. We recomme nd you to use the IUPAC Series pH4.005 and pH7.000. Adjust a

26、nd main tain the temperatureat25 ± °C for the calibration.Select the AUTOREAD fun ctio n for pH measureme nts.Conn ect the pHC2085-8 Combi ned pH Electrode to the meter. Rinse it carefully. Place it on the SAM7 Sample Sta nd.Press the cal ” key to perform a calibrati on.When the calibrati

27、on has bee n performed. rinse the electrode. immerse it in the sample and stir.Procedurenot greater tha n the con ductivity requireme nts for the pH determi ned in step 6. the water meets the requireme nts of the test for con ductivity. If the measured conductivity is greater tha n this value or the

28、 pH is outside of the range of 5.0 to 7.0. the water does not meet the requireme nts of the test for con ductivity.Stage 3pH and con ductivityrequireme nts(For atmosphere and temperature equilibrated samples only)pHCon ductivity pS/cm5.03.02.46.0

29、3.87.04.6LiteratureUSP -NF Fifth SupplementPhysical Tests / Water Con ductivity (645) 3465-3467CDM230 programmi ng:Press the cal ” key for approx. 3 sec on ds.If you use a certified CDC511T, no cell calibrati on is performed, en ter the following parameters directly as follows:Cell 1 Con sta nt<en ter below>Cell 1 Co nsta nt<1.100* *> cm-1Cable