IM 12A06S01-00EN-P
54
• Buffer solutions
The tables are derived from the Standards laid down in “International Recommendation No.
56 of the Organisation Internationale de Métrologie Legale”.
Table A5.1: SC buffer solutions
11.6 Appendix 6: USP <645>
First published in the USP23 (The United States Pharmacopeia, ed. 23), the USP <645>
describes a procedure of measuring the conductivity of Purified Water and WFI (Water for
Injection) instead of the previous complicated monitoring procedure. This procedure consists
of three stages for measuring the conductivity of Purified Water and WFI.
On the stage 1, firstly the temperature of the water and the non-temperature-compensated
conductivity of the water are measured, and this conductivity is compared with the
limit conductivity value of the corresponding temperature directed by USP<645>. If the
conductivity is higher than the limit value, the procedure will proceed to the stage 2.
The SA11 has the limit values of USP<645> built in the firmware. If activated in the error
configuration, the SA11 checks the non-temperature compensated conductivity with the
limit value. If the conductivity is higher than the limit value, a USP limit warning will be
generated. A safety margin to the limit value can be set to generate a USP margin warning
below limit value. When the safety margin is set at 20%, for example, a USP margin warning
will be flagged when the non-temperature compensated conductivity goes higher than the
80% of the limit value at all temperatures. For example, if the temperature is 64 ºC and the
safety margin is set at 20%, then USP warning will be flagged at 0.8 x 2.2μS/cm = 1.76μS/
cm (2.2μS/cm is the USP<645> limit value at 64ºC).
In resistivity mode, a USP warning will be generated at a non-temperature compensated
resistivity of 0.568 MΩ (=1/1.76μS/cm).
T
[°C]
10 12 14 16 18 20 22 24
1.000M
KCl
78,88731 83,00522 87,16523 91,38752 95,70937 100,09892 104,61466 109,12745
0.100M
KCl
9,10702 9,58240 10,06265 10,55008 11,04901 11,55576 12,07707 12,59804
0.010M
KCl
0,99809 1,05019 1,10282 1,15624 1,21092 1,26646 1,32359 1,38069
0.005M
KCl
0,50900 0,53557 0,56241 0,58966 0,61754 0,64586 0,67500 0,70412
0.002M
KCl
0,20666 0,21745 0,22835 0,23941 0,25073 0,26223 0,27406 0,28588
0.001M
KCl
0,10411 0,10955 0,11504 0,12061 0,12631 0,13210 0,13806 0,14402
T
[°C]
25 26 28 30 32 34 35
1.000M KCl 111,31000 113,69765 118,03818 122,72326 127,50286 132,04033 134,27021
0.100M
KCl
12,85000 13,12564 13,62672 14,16759 14,71936 15,24318 15,50060
0.010M
KCl
1,40830 1,43851 1,49343 1,55270 1,61317 1,67058 1,69879
0.005M
KCl
0,71820 0,73361 0,76161 0,79184 0,82268 0,85196 0,86634
0.002M
KCl
0,29160
0,29785 0,30923 0,32150 0,33402 0,34591 0,35175
0.001M
KCl
0,14690
0,15005 0,15578 0,16196 0,16827 0,17426 0,17720
Fig A6.1:
Conductivity limit values at process
temperatures directed by USP<645>