USP L7 column: C8 (octyl silane)
Octyl (C8) groups bonded to fully or superficially porous silica particles 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
- Assays of hydrophobic drugs that are too strongly retained on C18
- Steroids and many related-substance tests
- Faster elution alternative to L1
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
Less retentive than L1; selectivity still varies by brand.
Example columns sold as USP L7
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 | ZORBAX SB-C8 | fully porous silica | not stated in source |
| Waters | Symmetry C8 | fully porous silica 3.5/5/7 um | not stated in source |
| Thermo Fisher Scientific | Hypersil GOLD C8 | fully porous silica 1.9/3/5 um | 2-9 |
| Phenomenex | Luna C8(2) | fully porous silica 3/5/10/15 um | 1.5-9 (gradient), 1.5-10 (isocratic) |
| Merck (Supelco) | Purospher STAR RP-8e | fully porous silica | not stated in source |
| YMC | YMC-Triart C8 | fully porous organic/inorganic hybrid 1.9/3/5 um | 1-12 |
| Shimadzu | Shim-pack GIST C8 | fully porous silica | not stated in source |
| Restek | Ultra C8 | fully porous silica 3/5 um | 2.5-8 |
| Avantor (ACE) | ACE C8 | fully porous silica 2/3/5/10 um | 2-8 |
| Welch Materials | Ultisil XB-C8 | 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 L7 packing (C8 (octyl 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 L7 designation and the stated dimensions is acceptable.
Size:
Changing length or particle size
You can keep the USP L7 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
L1 C18 (octadecyl 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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