Catalogue / Ostarine
Ostarine
Also written as Enobosarm, MK-2866, S-22, GTx-024.
A non-steroidal aryl propanamide and the most widely distributed compound in this class, supplied as the single (2S) enantiomer.
| Molecular formula | C19H14F3N3O3 |
| Average mass | 389.33 Da |
| Monoisotopic mass | 389.0987 Da |
| Molecular target | Androgen receptor |
| Electrospray polarity | Negative |
| Class | Androgen receptor modulators |
| Determination | Small molecule analysis, catalogue compound |
| Price | 267 USD |
Computed at build time from the composition shown on this page, not transcribed from a supplier datasheet.
Ostarine has an average molecular weight of 389.33 daltons and a monoisotopic mass of 389.0987 daltons, computed from the molecular formula C19H14F3N3O3. Identity is confirmed by matching the measured mass against a certified reference standard, and purity is reported separately by reversed-phase chromatography at the compound's own ultraviolet maximum rather than at the 214 nm used for peptides. Neither figure states which enantiomer is present, which is a third determination on a chiral stationary phase.
| Ion | m/z |
|---|---|
| [M+H]+ | 390.106 |
| [M-H]- | 388.0914 |
Usable response for this compound is in negative mode. The other ion is given because it is the one a wrongly configured method looks for.
A molecule of this size does not produce the multiply charged envelope a peptide does. It produces one singly charged ion, and which polarity that ion appears in is decided by the functional groups rather than by convenience. A nitro or cyano aromatic responds in negative mode; a basic amine responds in positive.
That is why a screen acquired in a single polarity misses part of its own compound list, and why a non-detect from such a screen is not evidence that a substance is absent. The polarity used belongs on the certificate alongside the result.
| The (2R) enantiomer has the same formula, the same mass and the same retention on an achiral C18 column. Enantiomeric purity is only established on a chiral stationary phase, and a certificate that does not name one has not measured it. |
| The compound responds far better in negative electrospray than in positive, with the diagnostic ion at [M-H] minus. A laboratory that runs the class in positive mode alone reports a weak response and can record a non-detect on material that is present. |
| It is the cheapest compound in the class, which makes it the commonest substitute for the expensive ones. Material labelled as another modulator but containing ostarine is separated on mass in a single injection and not at all by a label. |
Every compound fails in its own way. A generic peptide method applied without regard to these specifics produces a number that looks like a result and is not one.
Non-steroidal small molecules, most of them a single enantiomer of an aryl propanamide. They are not peptides and almost nothing carried over from peptide work applies: there is no amide backbone to detect at 214 nm, the molecules are a fraction of the mass of the smallest peptide in this catalogue, and the impurity that matters most is a mirror image that no achiral column separates from the target.
LC-MS identity against a certified reference standard, acquired in the ionisation polarity the compound actually responds in rather than in whichever polarity the instrument was left in. Purity by HPLC-UV at the compound's own absorbance maximum, not at 214 nm. Enantiomeric purity is a separate determination on a chiral stationary phase and is reported as a separate figure, because an achiral method cannot see it.
Where the delivered milligram figure matters rather than the percentage, assay against a certified reference standard gives content directly, and where no such standard exists quantitative NMR against a certified internal standard gives an absolute purity that needs no standard of the analyte at all.
| LC-MS identity | Measured mass |
| HPLC-UV purity | Area at the UV maximum |
| Enantiomeric purity | Chiral stationary phase |
| Water content | Karl Fischer |
| Elemental impurities | ICP-MS |
| Residual solvents | GC-MS |
What is the molecular weight of Ostarine?
The average molecular weight is 389.33 daltons and the monoisotopic mass is 389.0987 daltons, computed from the molecular formula C19H14F3N3O3 shown on this page. Both figures are calculated rather than transcribed, so they can be checked against the stated composition.
How is Ostarine tested for purity and identity?
LC-MS identity against a certified reference standard, acquired in the ionisation polarity the compound actually responds in rather than in whichever polarity the instrument was left in. Purity by HPLC-UV at the compound's own absorbance maximum, not at 214 nm. Enantiomeric purity is a separate determination on a chiral stationary phase and is reported as a separate figure, because an achiral method cannot see it. Purity is an area ratio measured at the compound's own ultraviolet maximum, and it describes the chromatographable fraction only. It says nothing about which enantiomer is present, because mirror images are not separated by an achiral column.
What goes wrong when Ostarine is analysed?
The (2R) enantiomer has the same formula, the same mass and the same retention on an achiral C18 column. Enantiomeric purity is only established on a chiral stationary phase, and a certificate that does not name one has not measured it.
What does Ostarine analysis cost at ANALYTON?
Small molecule analysis, catalogue compound is priced at 267 US dollars, covering the determinations described on this page. Content, safety and elemental determinations are ordered alongside and are priced separately on the price list.
Updated 2026-09-01. Masses computed at build, not transcribed.