Usp Water Purity Monitoring; What Is Usp; What Is Conductivity Measurement According To Usp; Usp In The Sc202 - YOKOGAWA SC202G (S) User Manual

9-1 USP

9. USP WATER PURITY MONITORING

9-1. What is USP ?

USP stands for United States Pharmacopeia and it is responsible for issuing guidelines for the
pharmaceutical industry. Implementing these guidelines is highly recommended for companies wishing
to market drugs in the US. This means that USP is important for pharmaceutical companies worldwide.
USP recently issued: - USP - recommendations for conductivity measurement. This new USP, aims at the
replacement of 5 antiquated laboratory tests by simple conductivity analysis.

9-2. What is conductivity measurement according to USP?

Life would be easy, if the limits for the conductivity of injection water were set to be 1.3 µS/cm at
a reference temperature of 25°C. However, the committee (PHRMA WQC) who made the USP
recommendations, could not agree on a simple Sodium Chloride model for water quality determination.
Instead, they chose a Chloride-Ammonia conductivity-pH model in water atmospherically equilibrated (CO2)
at 25 °C.
The objective of the WQC was to find an easy way to establish the water quality, so on-line analysis
at process temperature was a necessary requirement. However, if it is not possible to choose one
temperature response model to work to, then it is also not possible to choose one temperature
compensation algorithm.
We as a manufacturer of analytical equipment do not want to go into the details of whether the limiting
conductivity values for water quality are based on the Chloride model or the Ammonia model. Our job is to
develop on-line analyzers that make it simple for our customers to meet the water quality that is specified
as "stage 1: Conductivity Limit as a Function of Temperature."
If the water exceeds the limits of stage 1, then it can still be acceptable, but requires the customer to
proceed to Stage 2, and possibly Stage 3, to validate the water quality. It is our objective to assure that our
customers do not exceed the limits in stage 1 to avoid them having to carry out the complicated laboratory
checks in Stages 2 and 3.

9-3. USP in the SC202

1. In SC202 we have defined an Error Code: E13. This is independent of what range the customer is
measuring or what temperature compensation method he is using for water quality monitoring. When
the display shows E13, then the water quality exceeds the USP limits, and the FAIL flag on the display is
activated to signal that the system needs urgent attention.
2. We have introduced uncompensated conductivity in the DISPLAY menu. In the LCD display the user can
read the temperature and the raw conductivity to compare his water quality with the USP table.
3. We have kept all the EXA functionality: It is even possible to have the mA Output and Display readings
in resistivity units. Most users will have very good water quality and in the resistivity mode they will
have better resolution on the recorder or DCS. The readings are simply the reciprocal values of the
conductivity values. In the example mentioned above the contact will close at an uncompensated
resistivity of 1/1.76 µS/cm. = 0.568 MΩ.cm.
IM 12D7B3-E-E