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BACKGROUND

Water is one of the most widely used raw materials inthe pharmaceutical plant. Several grades of water areused throughout the plant. One grade, Water forInjection (WFI), is water purified by reverse osmosisor distillation as specified by the United StatesPharmacopeia (USP). Specific tests for Conductivityapply to WFI Water produced on site for manufactur-ing purposes.

PROCESS

The process starts with raw water conforming to US

EPA National Primary Drinking Water Regulations orcomparable standards of the European Union orJapan. The water contains no added substances. ForReverse Osmosis systems, the raw water is passedthrough semi-permeable membrane filtration wherethe pores in the membrane effectively reject dis-solved ions, salts and organic compounds. Filtrationunits are located before and after the membranemodules, a booster pump to increase net pressureacross the membranes, and storage tanks.

For Distillation systems, a phase change from liquidto vapor occurs, enabling the pre-treated feed waterto be stripped of any residual ion materials, particu-late, colloids and non-volatile organic compounds.

Demisters and separation devices remove any mate-rial that may be entrenched in the purified vapors.Single effect distillation units consist of a series ofcolumns where the phase change occurs, the evapo-ration and subsequent condensation being consid-ered a single effect. Multiple effect units may be useddepending on the water usage demand. The distillateis gravity fed to a storage tank.

CONDUCTIVITY SOLUTIONS

Water for Injection systems must consistently pro-duce water that is compliant with the latest the USPrevision; meaning raw conductivity is measured and

compared to the water temperature. Conductivity lev-els exceeding limits as designated by the USP can-not be classified as WFI Water unless additional testsare performed (refer to table 1). Conductivity sensorsmust be accurate below 1.3 microSiemen/cm and

must include an accurate temperature measurement.The analyzer must be able to output the raw, uncom-pensated conductivity value and the temperature.

Preferred material of construction for wetted compo-nents is polished and passivated stainless steel tominimize the number of micropores in the metal sur-faces, which prevents corrosion or microbial growth.WFI Systems are validated to installation qualification(IQ), operational qualification (OQ), and performancequalification (PQ). Component level equipment mustinclude proper documentation to facilitate the valida-tion proces. Typically there are two conductivity sen-sors per system so a percent passage or percent

rejection can be determined. Additional conductivitysensors may be placed on storage tank outletsdepending on the facility's WFI demand.

INSTRUMENTATION SOLUTION

The Rosemount Analytical Model 403 EnduranceConductivity Sensor with either the Solucomp ModelXmt or Solucomp II Model 1055 is the conductivitysolution for the Water for Injection System.

The Model 403 Conductivity Sensor accurately mea-sures conductivity below 1 microSiemen/cm. All wet-ted components have a surface finish better than 16micro inch Ra. All elastomers are FDA compliant and

USP Class VI traceable. The insulator material usesFDA compliant material. The sensor includes a highlyaccurate RTD. Documentation is standard with eachModel 403 sensor that includes lot traceability tofacilitate the validation process.

The Solu Comp II Model 1055 outputs raw conductiv-ity and temperature. The Model 1055 can also accepttwo sensor inputs to make a percent rejection or per-cent passage measurement. The 1055 includes aUSP alarm option that will generate a discreet signalif the water conductivity exceeds the USP value atthe measured temperature. The Solu Comp ModelXmt with FOUNDATION FIELDBUS is a digital solu-

tion. The Model Xmt can send raw conductivity val-ues and temperature values to a well-designed DCSsuch as Delta V, which can have the USPConductivity vs. Temperature tables residing in thesystem.

WATER FOR INJECTION MEASUREMENTS

Application Data SheetADS 2834-02/rev.A

September 2005Pharmaceutical Industry

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Emerson Process Management

Rosemount Analytical Inc.2400 Barranca Parkway

Irvine, CA 92606 USA

Tel: (949) 757-8500

Fax: (949) 474-7250

http://www.raihome.com

Rosemount Analytical Inc. 2005

INSTRUMENTATION

Model 403EnduranceonductivitySensor

Highly accu-rate conduc-tivity sensor

Better than16 microinch Rasurface finish

Highly accurate internal RTD

Documented Lot traceability onwetted components

.

Solu Comp II Model1055 ConductivityAnalyzer

Two sensor inputs

Output raw conductivi-ty and temperature

Easy to use menu structure

Easy to read display

Solu Comp ModelXmt ConductivityAnalyzer

FOUNDATIONFieldbus and HARTcompatible

Continuous diagnostic monitoring ofsensor performance and for warningor failure

Easy to use menu structure

Easy to read display

TABLE 1: RAW CONDUCTIVITY VS. TEMPERATURE USP 28 SECTION

Temp

DegC

Cond

uS/cm

Temp

DegC

Cond

uS/cm

Temp

DegC

Cond

uS/cm

0 0.6 35 1.5 70 2.5

5 0.8 40 1.7 75 2.7

10 0.9 45 1.8 80 2.7

15 1.0 50 1.9 85 2.7

20 1.1 55 2.1 90 2.7

25 1.3 60 2.2 95 2.9

30 1.4 65 2.4 100 3.1