Nitrogen contains not less than 99.0 percent by volume of N2. Nitrogen (N­2) is plentiful, inert, and commonly used for blanketing, purging, pressurizing, and mixing. It also protects precursors, reagents, and products from reacting with oxygen in the air. Additionally, nitrogen is used as a pressurizing agent to check for leaks in tanks, vessels, and other processing equipment or to transfer fluids.

Carbon dioxide contains not less than 99.0 percent by volume of CO2. Like nitrogen, carbon dioxide (CO2) is inert, making it highly useful for blanketing and packing, and is a widely used supercritical fluid. Carbon dioxide also plays an important role in micro and nanoparticle production.

Because it is one of the most effective oxidizing agents organic chemists have in their toolbox, oxygen (O2) has a key role in many processes. 

• Oxygen contains not less than 99.0 percent by volume of O2 (oxygen produced by the air liquefaction process is exempt from the requirements of the tests for carbon dioxide and carbon monoxide).
• Oxygen 93 percent is oxygen produced from air by the molecular sieve process. It contains not less than 90.0 percent and not more than 96.0 percent by volume of O2, the remainder consisting mostly of argon and nitrogen.

Testing based on required purity classes of compressed air with respect to both viable and non-viable particles, water, and oil & hydrocarbons.

Bacteriostatic water for injection that is free of ammonia.

Bacteriostatic water for injection that is free of calcium.

Bacteriostatic water for injection that is free of carbon dioxide.

Bacteriostatic water for injection that is free of carbonizable substances.

Bacteriostatic water for injection that is free of chloride.

Microorganisms and certain microbes are prone to colonize pharmaceutical water systems. This test addresses microbiological examination of water samples to show that the water meets pharmaceutical requirements. All water must be free of coliforms.

Electrical conductivity in water measures the ion-facilitated electron flow through it. Water molecules dissociate into ions as a function of pH and temperature and result in a very predictable conductivity. Conductivity tests assess the conductivity of:

• Bulk water (e.g., PF, WFI, water for hemodialysis, and condensate of pure steam)
• Sterile water (e.g., sterile purified water [SPW], sterile water for injection [SWI], sterile water for inhalation and sterile water for irrigation)

Elemental impurities are defined as residual catalysts or environmental contaminants that may be present in drug substances, excipients, or drug products. Whether these impurities occur naturally, are added intentionally, or are introduced inadvertently, testing is required for assurance of the specified levels.

Microorganisms and certain microbes are prone to colonize pharmaceutical water systems. This test addresses microbiological examination of water samples to show that the water meets pharmaceutical requirements.

Identifies particulate matter in injections and parenteral infusions, other than gas bubbles, unintentionally present in the solutions. 

pH measurements are characterization assays to determine or confirm pH levels for drug compatibility, quality control, and/or shelf-life stability concerns. For compendial assays, pH is measured by a properly calibrated, potentiometric sensor and measuring system.

Stronger Rose Water is a saturated solution of the odoriferous principals of the flowers of Rosa centifolia L. (Fam. Rosaceae) prepared by distilling the fresh flowers with water and separating the excess volatile oil from the clear, water portion of the distillate.

Total organic carbon (TOC) is an indirect measure of organic molecules present in pharmaceutical waters that can be measured as carbon. Organic molecules can be introduced to the water from purification and distribution system materials, biofilm growing in the system, and packaging sterile and nonsterile waters.