Examples
Worked examples
- Is an instance
A manufacturer specifies USP Type I borosilicate glass vials for a lyophilized injectable biologic that is sensitive to trace alkali leaching and pH shift over a multi-year shelf life; the vial supplier's certificate of analysis documents the USP <660> powdered glass test result supporting the Type I classification.
- Is an instance
A laboratory buys borosilicate volumetric flasks marked 'Type I' under ASTM E438 for general bench use — chosen for thermal-shock resistance and chemical durability during routine titrations and heating, with no USP <660> container testing involved, since the flasks are not pharmaceutical primary packaging.
Counter-examples
Looks similar, but isn't
- Not an instance
A non-aqueous, chemically stable oil-based injectable is packaged in USP Type III glass because its formulation's compatibility data supports that lower category — specifying Type I here would not be incorrect, but it also would not be required by the product's actual chemistry, and procurement over-specifying it adds cost without a documented quality justification.
- Not an instance
A general chemistry lab's borosilicate beaker, never submitted to USP <660> testing, is 'borosilicate glass' by material and may even meet ASTM E438 Type I for laboratory apparatus — but it is not correctly described as 'USP Type I' in a regulatory or pharmaceutical procurement context, because that designation applies only within the pharmacopeial container-testing system, not to lab glassware generally.
Editorial commentary
Type I borosilicate glass is the highest hydrolytic-resistance category in the United States Pharmacopeia’s glass-container classification system (USP General Chapter <660>, Containers—Glass). It designates a borosilicate glass formulation and container that has been tested and shown to release the least alkali into a stored liquid, making it the default choice for parenteral (injectable) drug products, especially those that are sensitive to pH shift or trace ion leaching. The name is also used, in a related but distinct sense, for general laboratory glassware under ASTM E438 — the two systems overlap in terminology but classify different things, which is a common source of confusion and is addressed below.
What “Type I” Means Under USP <660>
USP <660> sorts glass intended for pharmaceutical containers — vials, ampoules, cartridges, syringes — into four categories based on chemical composition and, more specifically, on how much alkali the glass releases when it is in contact with an aqueous solution (its hydrolytic resistance). A container earns a Type designation by passing the corresponding test in the chapter, not simply by being made of a particular raw material; composition determines the likely outcome, but the classification itself is a tested, documented result.
| USP Type | Composition | Hydrolytic resistance | Typical use |
|---|---|---|---|
| Type I | Borosilicate glass (silica network modified with boron trioxide and, typically, aluminum oxide) | Highest | Parenteral products sensitive to pH shift, alkali leaching, or long shelf life; the default for injectable biologics and reactive small-molecule formulations |
| Type II | Soda-lime-silica glass with a chemically treated (dealkalized) inner surface | High, but achieved by surface treatment rather than bulk composition | Aqueous parenterals at or below approximately neutral pH, where Type I is not required by a stability or compatibility case |
| Type III | Soda-lime-silica glass, untreated | Moderate | Non-aqueous parenterals, powders for injection reconstituted immediately before use, and many oral or topical liquids |
| NP (General purpose, non-parenteral) | Soda-lime-silica glass, untreated | Lowest of the four | Oral and topical dosage forms only — not for parenteral use |
Type I is not a claim about clarity, strength, or thermal performance on its own — it is specifically a statement about how little the glass interacts chemically with what is stored in it, evaluated under defined test conditions.
How Hydrolytic Resistance Is Tested
USP <660> (and the corresponding European Pharmacopoeia chapter 3.2.1 and ISO 719/720 methods, which are harmonized in substance) rely on titration-based tests rather than a simple compositional assay:
- Powdered glass test — a sample of the glass is crushed to a controlled particle size, exposed to high-purity water under defined time and temperature conditions, and the amount of alkali extracted is measured by titrating the resulting solution against a standard acid. This test establishes the baseline hydrolytic-resistance category of the glass itself and is the method used to distinguish Type I from Type III.
- Water attack test — run on the inner surface of the intact, formed container (not powdered glass) at a lower temperature. Because it tests the container’s actual surface rather than the bulk material, it is the test used to confirm that a soda-lime container has been successfully surface-treated to qualify as Type II — a soda-lime container that fails this test remains Type III or NP regardless of its bulk composition.
USP <660> also sets requirements for arsenic release and light transmission (relevant to light-sensitive formulations), which sit alongside, but are separate from, the Type I/II/III/NP hydrolytic-resistance classification itself.
Type I Borosilicate Glass vs. ASTM E438 “Type I” Lab Glassware
A separate standard, ASTM E438 (Standard Specification for Glasses in Laboratory Apparatus), also uses the label “Type I” — but for a different purpose. ASTM E438 classifies the borosilicate and soda-lime-silicate glass used to make general laboratory apparatus (beakers, flasks, graduated cylinders) into two types based on chemical durability for bench use, not pharmaceutical container suitability. Glass sold under trade names such as Pyrex or Duran is commonly ASTM E438 Type I borosilicate glass. It is chemically similar to, and in some cases produced from, the same class of borosilicate formulation used for USP Type I containers — but a beaker meeting ASTM E438 has not been through USP <660> container testing, and the two designations are not interchangeable on a regulatory submission or a purchase specification. For a full comparison of borosilicate and soda-lime glassware used on the bench, see Types of Laboratory Glassware: Volumetric vs. General-Purpose, Explained.
When to Specify Type I in Procurement
Type I is the safest default for parenteral primary packaging, but it is also the most expensive glass category, and specifying it where it is not required adds cost without a corresponding quality benefit. A container specification should generally be set by:
- The formulation’s actual stability and compatibility data — a compatibility study showing acceptable performance in Type II or Type III glass over the product’s shelf life is a legitimate basis for specifying a lower category, not merely a cost-driven shortcut.
- Route of administration — parenteral products generally require Type I, II, or III (never NP); oral and topical products can use NP glass.
- pH and formulation chemistry — aqueous solutions near neutral pH are the typical case for Type II; non-aqueous or reconstituted-at-use products are the typical case for Type III.
- Regulatory filing history — a change from the glass type used in an approved drug product’s original filing is a specification change that generally requires supporting stability data and, depending on jurisdiction and product risk category, regulatory notification.
A certificate of analysis or a supplier’s container qualification package should state the USP type explicitly, along with the test method and result used to support it — not simply assert “borosilicate” as if that word alone settled the classification. For related procurement and supplier-documentation topics, see Chemical Grades Explained: ACS, USP, Reagent, and Technical Grade Compared and Lab Equipment and Supplies Procurement Guide.
Frequently Asked Questions
Is Type I glass always borosilicate?
In practice, yes — Type I is defined by achieving the highest hydrolytic-resistance category under USP <660>, and borosilicate composition is what reliably achieves that result. Type II is also capable of high resistance, but only after surface treatment of what is otherwise soda-lime glass, not through borosilicate composition.
Can Type III glass be relabeled as Type I by treating it?
No. Surface treatment (dealkalization) can move untreated soda-lime glass from Type III performance up to Type II performance, because that treatment targets the surface layer the water attack test measures. It does not change the bulk composition measured by the powdered glass test, so it cannot produce Type I, which requires borosilicate composition throughout.
Does “USP Type I” mean the same thing as “USP grade”?
No, and this is a common mix-up. A “USP grade” chemical (as in USP-grade ethanol or USP-grade excipient) refers to purity specifications for a substance under the USP-NF monograph system. “USP Type I glass” refers to a container classification under USP <660>. They are both pharmacopeial designations from the same publication but apply to entirely different things — a substance’s purity versus a container’s chemical resistance.
Is Type I glass required for all injectable products?
No. USP <660> permits Type II and Type III glass for many parenteral products depending on the formulation’s pH, water content, and stability profile; NP glass is excluded from parenteral use entirely. Type I is required where the specific formulation’s compatibility data shows it is needed, not as a blanket rule for every injectable.
Related: HS Code for Chemicals, Chemical Grades Explained, Types of Laboratory Glassware.
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