USP L1 column: C18 (octadecyl silane)
Octadecyl (C18) groups chemically attached to silica or ceramic particles (porous or non-porous) of 1.5-10 um, or to a monolithic rod.
Mode: reversed-phase Typical pH range: about 2-8 for classic silica; wider (about 1-12) if hybrid or specially bonded
Typical uses
- Assay and impurity tests for most small-molecule drugs
- Dissolution and content uniformity testing
- Preservative and degradation product methods
Common sizes (length x internal diameter, particle size)
- 250 x 4.6 mm, 5 um
- 150 x 4.6 mm, 5 um
- 100 x 2.1 mm, 1.7-1.8 um
Very broad class: C18 columns from different makers can differ a lot in carbon load, endcapping, silanol activity and selectivity. If a monograph names a brand in its column notes, start with that. USP <621> allows limited changes in length/particle size.
Example columns sold as USP L1
From the makers' own USP code lists and product pages, checked October 2026. Examples only, not an endorsement. Columns with the same code can still differ in selectivity; if the monograph names a column in its notes, start with that one.
| Maker | Product family | Particle | pH range |
|---|---|---|---|
| Agilent | InfinityLab Poroshell 120 EC-C18 | superficially porous silica | not stated in source |
| Waters | XBridge BEH C18 | fully porous BEH hybrid 2.5/3.5/5/10 um | not stated in source |
| Thermo Fisher Scientific | Hypersil GOLD (C18) | fully porous silica 1.9/3/5/12 um | 2-11 |
| Phenomenex | Luna C18(2) | fully porous silica 2.5/3/5/10/15 um | 1.5-9 (gradient), 1.5-10 (isocratic) |
| Merck (Supelco) | Purospher STAR RP-18e | fully porous silica | not stated in source |
| YMC | YMC-Triart C18 | fully porous organic/inorganic hybrid 1.9/3/5 um | 1-12 |
| Shimadzu | Shim-pack GIST C18 | fully porous silica | not stated in source |
| Macherey-Nagel | NUCLEODUR C18 Gravity | fully porous silica | not stated in source |
| Nacalai Tesque (Cosmosil) | COSMOSIL C18-MS-II | fully porous silica 2.5/3/5/15 um | 2-10 |
| Welch Materials | Ultisil XB-C18 | fully porous silica | not stated in source |
10 makers listed, so a tender written by USP code stays open to competition.
Tender wording (brand-neutral)
HPLC column with USP L1 packing (C18 (octadecyl silane)), 250 x 4.6 mm, 5 um (length x internal diameter, particle size); stainless-steel or equivalent hardware with standard fittings; recommended pH and temperature range to be stated by the bidder; each column supplied with its certificate of analysis and test chromatogram, batch/lot number and serial number; shelf life not less than 2 years from delivery; any make meeting the USP L1 designation and the stated dimensions is acceptable.
Size:
Changing length or particle size
You can keep the USP L1 packing and use a different length, particle size or diameter within the harmonized USP 621 limits. Check your columns with the calculator.
Related column types
L7 C8 (octyl silane) | L10 Cyano (CN, nitrile) | L11 Phenyl | L13 C1 (trimethylsilane) | L21 PS-DVB polymer (rigid) | L26 C4 (butyl silane) | L29 Polybutadiene-coated alumina (RP) | L43 PFP (pentafluorophenyl) | L60 Polar-embedded alkyl amide, endcapped | L62 C30 | L67 Polymer C18 (vinyl alcohol copolymer) | L68 Alkyl amide, not endcapped
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