Quick answer
CJC-1295 (DAC) is verified by two complementary tests: reversed-phase HPLC for purity and mass spectrometry for identity.
- Identity: average mass about 3647 Da, roughly 280 Da above the no-DAC peptide (about 3368 Da)
- Key impurity: hydrolyzed maleimide, +18 Da, no longer able to bind albumin
- HPLC caveat: a percentage is only meaningful with the method, trace and integration table
- Stock: V8 carries CJC-1295 (No DAC), not the DAC form
- Concentration: mg ÷ mL; see the calculator
For laboratory research use only; not for human consumption.
What CJC-1295 (DAC) is, analytically
CJC-1295 with DAC carries an albumin-binding modification on top of the base GHRH-fragment sequence, and verifying that both the fragment and the modification are correctly present is the point of lot-level testing. The base sequence is the first 29 residues of GHRH carrying four stabilizing substitutions, the same backbone described in the no-DAC overview. The DAC form adds a C-terminal lysine bearing a maleimidopropionyl group. In the albumin-binding design, that maleimide is the reactive handle: it forms a covalent thioether bond with the free cysteine of serum albumin, which is how the molecule gains its long persistence in model systems. The chemistry and its research context are covered in the CJC-1295 (DAC) research overview.
That reactive group is what makes the DAC variant analytically distinctive, and also somewhat more fragile than its unmodified sibling. A maleimide that has reacted with water, with a buffer nucleophile, or with another thiol is no longer the same molecule even though the 29-residue backbone is untouched. A purity test for this compound therefore has two questions to answer: is the backbone intact and free of deletion products, and is the maleimide still functional?
| Feature | CJC-1295 (DAC) | CJC-1295 (No DAC) |
|---|---|---|
| Backbone | GHRH(1-29) with four stabilizing substitutions | Same four-substitution backbone |
| C-terminal modification | Lysine carrying a maleimidopropionyl group | None; free C-terminus (amide) |
| Approximate average mass | About 3647 Da | About 3368 Da |
| Reactive group | Maleimide, thiol-reactive and hydrolysis-prone | None |
| Main analytical risk | Ring opening, thiol adducts, incomplete coupling | Oxidation and deletion sequences |
Reversed-phase HPLC
HPLC separates the DAC-modified peptide from unmodified fragment, partially reacted intermediates, and other synthesis byproducts, with purity read per understanding HPLC purity. Reversed-phase separation on a C18 column with a water/acetonitrile gradient and an ion-pairing acid is the standard method for peptides of this size.
The maleimide ring is susceptible to hydrolysis, which opens the ring and yields a species that can no longer react with albumin's free thiol. Ring-opened material is a characteristic impurity for this compound and typically appears as a closely eluting peak beside the main one. Because it is only 18 Da heavier and slightly more polar, a short or steep gradient can hide it inside the main peak; a shallow gradient over the elution window of the peptide is what makes it visible.
Impurity classes to look for
| Species | Expected mass shift | Typical chromatographic behavior |
|---|---|---|
| Intact DAC peptide | Reference, about 3647 Da | Main peak |
| Ring-opened (hydrolyzed) maleimide | +18 Da | Closely eluting, usually slightly earlier |
| Unmodified backbone (no linker) | About −280 Da | Earlier than DAC form; matches the no-DAC peptide |
| Oxidation products (for example at tryptophan or tyrosine) | +16 Da per site | Earlier-eluting shoulders or small peaks |
| Deletion sequences | Minus one residue mass | Close to main peak; need shallow gradient |
| Thiol adducts on the maleimide | Plus the adduct mass | Variable; often later or broad |
A 29-residue backbone plus a modified lysine means roughly thirty coupling cycles, and each one that fails produces a deletion sequence. These are the byproducts most likely to co-elute, which is why the stated method matters as much as the percentage.
Mass spectrometry for identity
Because the DAC modification adds measurable mass relative to the no-DAC form, mass spectrometry can confirm not just that a peptide is present but that the albumin-binding modification described in the chemistry article is actually attached. See HPLC vs. mass spectrometry for why the two methods answer different questions.
The DAC form has a theoretical average mass near 3647 Da, about 280 Da heavier than the no-DAC peptide at roughly 3368 Da. Hydrolysis of the maleimide adds 18 Da, so a spectrum can separate intact DAC peptide, hydrolyzed DAC peptide, and unmodified backbone in a single run. Electrospray ionization spreads a peptide of this size across several charge states, commonly in the 4+ to 6+ range, and software deconvolutes them to one neutral mass. The reading to look for on a report is observed mass next to theoretical mass, with agreement of well under one Da on a high-resolution instrument.
The mass gap between forms is far larger than instrument error, so identity is unambiguous when the spectrum is shown. A report that quotes only a pass/fail statement for identity, with no spectrum or masses, cannot be checked by the reader. The side-by-side comparison of the two forms is developed in the DAC vs. no-DAC comparison.
Why this matters for a long-acting research tool
DAC CJC-1295's extended research half-life depends entirely on the modification being intact; an incompletely reacted or degraded lot could behave more like the shorter-acting no-DAC form without that being obvious from appearance alone. A lyophilized cake looks the same whether the maleimide is intact or hydrolyzed, and a purity figure that counts the ring-opened species as part of the main peak would not reveal the difference.
This is why moisture control matters more for the DAC form than for most lyophilized peptides, and why a test date close to the time of use is valuable when a study depends on extended persistence in a model system. A lab building an albumin-binding experiment would reasonably ask for a spectrum that resolves the +18 Da species and show its relative abundance, not only a single purity number.
Functional checks are separate from analytical ones. Intact-mass data show the maleimide is present and unhydrolyzed; they do not show how much of it reacts with albumin in a given buffer. Labs that need that answer usually run their own albumin-binding assay with a retained sample.
Reading the CJC-1295 (DAC) chromatogram
HPLC purity for CJC-1295 (DAC) is reported as area percent: the main peak's share of all UV-absorbing material detected, normally at 214–220 nm, where the peptide bond absorbs. Three things make that number trustworthy. First, the method must be stated, including column chemistry, mobile phases, and gradient slope, because resolution determines what counts as a separate impurity. Second, the trace should show a clean baseline and a main peak free of fronting, tailing, or shoulders that hint at co-eluting species. Third, the integration table should account for every minor peak, so the percentage reflects the whole sample and not a selectively drawn window.
Two reports quoting the same percentage are comparable only when column, gradient, and wavelength match. For a maleimide-bearing peptide there is one further point: the sample diluent and the time between preparing the sample solution and running it matter, because hydrolysis continues in aqueous solution. A report that notes sample preparation conditions is more informative than one that does not.
What an HPLC percentage leaves out
Two quantities are easy to confuse: purity and content. Purity is the proportion of UV-absorbing peptide that is the target molecule. Content is the proportion of the dry powder that is peptide at all, once counter-ions and residual water are subtracted. A lot can be very pure and still carry a meaningful salt and moisture fraction, which matters when preparing standards by mass. Trifluoroacetate or acetate counter-ions from purification, and water retained after lyophilization, are invisible at 214 nm.
Net peptide content is usually determined by amino acid analysis or elemental nitrogen analysis, and water by Karl Fischer titration. These are optional additions to a standard certificate. Labs preparing quantitative stock solutions can plan reconstitution volumes and resulting concentrations with the peptide calculator, applying a content correction when one is known.
Documentation to expect
A lot-specific certificate of analysis with HPLC purity and mass-spec identity is the baseline; see how to read a CoA and third-party testing explained. A useful CJC-1295 (DAC) certificate is specific and traceable.
| Item | What it should show | Why it matters for this compound |
|---|---|---|
| Lot number | Matches the vial label | Links the document to a physical vial |
| HPLC trace and method | Column, gradient, wavelength, integration table | Determines whether the ring-opened peak could be resolved |
| Mass spectrum | Observed and theoretical mass side by side | Confirms the DAC modification, about 3647 Da |
| Hydrolysis species | Mention or visibility of +18 Da signal | Shows whether the maleimide is intact |
| Test date and laboratory | Who ran it and when | Hydrolysis is time dependent |
Lot-level documents are available from the CoA library. Check that the compound named on any certificate is the one you are working with: documents for the no-DAC form do not apply to the DAC form, and the reverse.
Keeping a verified lot verified
Verified purity is not permanent. CJC-1295 (DAC) stored as dry powder in cold, dark conditions holds its profile far longer than material kept in solution, where hydrolysis, oxidation, and adsorption to container surfaces proceed more quickly. For a maleimide-bearing peptide, water is the main enemy, so desiccated storage and warming a vial to room temperature before opening it are not optional niceties. General practice is collected in storing research peptides.
Recording reconstitution dates, minimizing freeze-thaw cycles, and keeping a retained aliquot for re-analysis gives a lab a way to rule material degradation in or out when a result looks anomalous. A retained sample that reproduces an 18 Da shoulder weeks later is a direct explanation for lost albumin-dependent behavior.
Sourcing note
V8 Peptides currently stocks CJC-1295 (No DAC) and the CJC-1295 (No DAC) + Ipamorelin blend; the DAC form is not currently carried. The analytical principles above still apply when evaluating DAC material from any source, and the no-DAC product pages are the right place to look at how identity and purity are presented for the sibling compound. See also CJC-1295 (No DAC) purity testing and the No DAC product page for its listed specifications.
CJC-1295 (DAC) FAQ
Does V8 Peptides carry CJC-1295 with DAC?
Not currently. The catalog includes CJC-1295 (No DAC) and a blend with ipamorelin; the analytical principles on this page still apply when evaluating DAC material from any source.
How can a lab tell DAC and no-DAC CJC-1295 apart?
By mass. The two differ by roughly 280 Da, a gap far larger than instrument error, so a mass spectrum distinguishes them unambiguously. See CJC-1295 (No DAC) purity testing for the sibling compound.
What does an 18 Da mass increase indicate?
Addition of water, most often hydrolysis of the maleimide ring. The peptide backbone is unchanged, but the albumin-reactive group is no longer functional.
Is a high HPLC purity enough to confirm the DAC modification is intact?
No. A ring-opened species can elute very close to the intact peptide and be integrated into the main peak. Mass spectrometry, which resolves the +18 Da difference, is the complementary check.
Why is DAC material more sensitive to moisture than most peptides?
Water attacks the maleimide ring, and hydrolysis cannot be reversed. Dry, cold, dark storage and warming vials before opening them reduce exposure.
What is the difference between purity and peptide content?
Purity is the target peptide's share of UV-absorbing material; content is the peptide's share of the whole powder, with counter-ions and water subtracted. Both matter when preparing stock solutions by mass.
How should a lab check a lot that seems to behave differently over time?
Compare a retained, properly stored aliquot against current material by HPLC and mass spectrometry, looking for new peaks and for signals 18 Da or 16 Da above the parent mass.
Where can I see example lot documents?
The CoA library lists published batch documents, and how to read a CoA explains each field.
Research Use Only. For laboratory research use only; not for human consumption. This article is research education, not usage guidance.