PW (Purified water) and WFI (water for injection) Specification-pH, Conductivity

Table of Contents

There are many different grades of analytical water used for pharmaceutical purposes. Different grades of water quality are required depending on the different pharmaceutical uses.

Different grades of Pharmaceutical water-USP, IP

PW (Purified water)
WFI (Water for Injection)
SWFI (Sterile Water for Injection)
BWFI ( Bacteriostatic Water for Injection)
WBET (Water bacterial endotoxin test)

1. Purified water (PW)

PW is used as an excipient in the production of non-parenteral preparations (tablets, capsules, creams, lotions, etc.) and in other pharmaceutical applications, such as cleaning of certain equipment and non-parenteral product-contact components.
Purified Water must meet the requirements for ionic and organic chemical purity and must be protected from microbial contamination.
Unless otherwise specified, Purified Water is also to be used for all tests and assays.
The source or feed water for the production of Purified Water is Drinking Water/potable water. Drinking water may be purified using unit operations that include deionization, distillation, ion-exchange, reverse osmosis, filtration, or other suitable purification procedures.
The Limit for the microbial population for purified water is 100 CFU/mL (USP & IP)

PW(purified water) Specification

Description/test	Criteria
Feed water	Drinking Water/potable water ( obtained by a suitable process (distillation, ionexchange (deionized, demineralised), reverse osmosis)
Limit for the microbial population	100 colony forming units/CFU per ml
Added substance	No
Conductivity	not exceed 1.3 mS/cm at 25°C
Total organic carbon (TOC)	not exceed 500 ppb

PW Specification

-Purified water is prepared from water complying with the federal regulations for drinking water.
-Purified water contains no added substance.
-Purified water is obtained by a suitable process (distillation, ionexchange (deionized, demineralised), reverse osmosis, or other methods).
-Its conductivity does not exceed a set level (1.3 mS/cm at 25°C).
-Its total organic carbon (TOC) does not exceed set level (500 ppb).
-purified water should have not more than 100 colony forming units/CFU per ml (CFU/ml)

2. Water for Injection (WFI)

Water for injection (WFI) is used as an excipient in the production of parenteral and other preparations where product endotoxin content must be controlled and in other pharmaceutical applications, such as cleaning of certain equipment of parenteral production.
The minimum quality of source or feed water for the generation of Water for Injection is Drinking Water as defined by the U.S. EPA, EU, Japan, or the WHO.

WFI complies with the test for purified water with additional requirements for bacterial endotoxins (not more than 0.25 IU of endotoxin per ml), conductivity & total organic carbon.

WFI (water for injection) Specification

Test/Description	Criteria
Appearance	Clear, colorless & odorless
pH	5.0-7.0 (varying with temp.)
Conductivity	not more than 1 micromho (1 megohm, approximately 0.1 ppm NaCl)
Total organic carbon (TOC)	not more than 500 ppm.
Endotoxin	not more than 0.25 USP endotoxin units per milliliter.
Limit for the microbial population	not more than 0.1 CFU/ml
osmolarity	osmolarity is 0
Ammonia	Less than 0.2 ppm
Heavy Metals	Less than 0.1 ppm
Nitrates	Less than 0.2 ppm
Residue on evaporation	Less than 0.001 ppm

Water for Injection (WFI) specification- USP

WFI Specification

-A pH of WFI is about 5. it may range from 5.0 to 7.0 (varing temp.).
-Storage of WFI: at room temperature 24 hrs; & for more than 24 hrs it must store at 80-degree centigrade.
-WFI is not intended to sterile water and is not a final dosage form.
-Water for Injection normally should not have a conductivity of more than 1 micromho (1 megohm, approximately 0.1 ppm NaCl) and total organic carbon (TOC) not more than 500 ppm.

– meets all the requirements for Purified Water.
– is obtained by distillation or reverse osmosis and contains not more than 0.25 USP endotoxin units per milliliter.
– is prepared using suitable means to minimize microbial growth
-WFI should have not more than 0.1 CFU/ml.

3. Sterile Purified Water USP

It is Purified Water , packaged and rendered sterile.
It is used in the preparation of non-parenteral compendial dosage forms or in analytical applications requiring Purified Water

4. Sterile Water for Injection (SWFI)

As per USP monogram, Sterile Water for Injection is Water for Injection packaged and rendered sterile (i.e Sterile WFI)
It is used for extemporaneous prescription compounding (as solvent for powder or Injection) and as a sterile diluent for parenteral products.
SWFI is packaged in single-dose containers not larger than 1.0 L in size.

5. Bacteriostatic Water for Injection (Bacteriostatic WFI)

As per USP monogram, Bacteriostatic Water for Injection (USP monograph) is sterile Water for Injection to which has been added one or more suitable antimicrobial preservatives.
It is intended to be used as diluent in the preparation of parenteral products, most typically for multi-dose products that require repeated content withdrawals.
It may be packaged in single-dose or multiple-dose containers not larger than 30 mL.

6. Sterile Water for Irrigation

As per USP monogram, It is Water for Injection packaged and sterilized in single-dose containers of larger than 1 L in size that allows rapid delivery of its contents.

7. Sterile Water for Inhalation

As per USP monogram, it is Water for Injection that is packaged and renderedsterile and is intended for use in inhalators and in the preparation of inhalation solutions.

Non-monographed Analytical Waters

1. Distilled Water

This water is produced by vaporizing liquid water and condensing it in a purer state.
It is used primarily as a solvent for reagent preparation, but it is also specified in the execution of other aspects of tests, such as for rinsing an analyte, transferring a test material as a slurry, as a calibration standard or analytical blank, and for test apparatus cleaning.
It is also cited as the starting water to be used for making High Purity Water.