GHK-Cu Copper Peptide: Research Overview, Purity Data and Where to Buy

GHK-Cu is a copper(II)-binding tripeptide — glycyl-L-histidyl-L-lysine complexed with a copper ion — first isolated from human plasma in the 1970s. Laboratory research examines its roles in copper transport, extracellular matrix signaling, antioxidant and anti-inflammatory pathways, and tissue-repair models. Evidence across these areas remains largely preclinical, and material is supplied for research use only.

What GHK-Cu Is and Where It Came From

The peptide backbone, glycyl-L-histidyl-L-lysine (GHK), is a three-residue sequence identified in human plasma during investigations into why old and young serum behaved differently in liver cell cultures. The histidine imidazole and the free amino terminus give the tripeptide an unusually high affinity for copper(II), and the resulting 1:1 chelate — written GHK-Cu — is the form most commonly studied and most commonly supplied to laboratories.

GHK also occurs as a fragment within larger extracellular matrix proteins, most notably collagen. The prevailing hypothesis in the literature is that proteolytic breakdown at sites of injury liberates GHK locally, where it can bind available copper and participate in the signaling environment of repair. Plasma concentrations of the free tripeptide are reported to decline with age, an observation that has driven much of the interest in GHK as a marker or mediator of regenerative capacity — though causation has not been established.

Nomenclature note. "GHK" refers to the apo-peptide; "GHK-Cu" refers to the copper complex. Cosmetic ingredient listings often use "copper tripeptide-1" or "copper peptide." These terms describe the same chemistry but not necessarily the same purity, counter-ion, or formulation, which matters when comparing published results across sources.

Reported Mechanism of Action

No single mechanism accounts for the range of effects described in the GHK-Cu literature. Instead, several partially overlapping models appear repeatedly:

• Copper coordination and shuttling. The complex binds copper with an affinity that sits between weaker serum ligands and higher-affinity intracellular copper proteins, positioning it as a plausible exchange intermediate. Copper is a required cofactor for lysyl oxidase, superoxide dismutase, and cytochrome c oxidase, so localized copper availability has downstream consequences for matrix crosslinking, redox balance, and mitochondrial function.
• Extracellular matrix signaling. Cell-culture work reports effects on collagen, elastin, glycosaminoglycan, and proteoglycan production by fibroblasts, alongside modulation of matrix metalloproteinases and their tissue inhibitors. The framing in most papers is remodeling balance rather than simple stimulation.
• Antioxidant and anti-inflammatory activity. GHK-Cu has been described as quenching reactive species and dampening inflammatory signaling. A 2024 study in Redox Biology reported that in a silicosis model the complex attenuated lung inflammation and fibrosis in a manner linked to peroxiredoxin 6, offering an unusually specific molecular target for a peptide often discussed in general terms.
• Transcriptional modulation. Gene-expression profiling studies have described broad shifts in transcript levels after GHK exposure, which is frequently cited as an explanation for the diversity of reported effects. This work is descriptive, and the pathways connecting copper binding to transcriptional output are not fully mapped.
• Sirtuin-linked signaling. Work published in 2023 in the Journal of Cachexia, Sarcopenia and Muscle reported that GHK-Cu improved cigarette-smoke-associated skeletal muscle dysfunction in a rodent model through a sirtuin 1-dependent pathway, tying the compound to a well-studied metabolic and mitochondrial regulator.

These mechanisms are complementary rather than competing, but each rests on model systems with different endpoints. Extrapolating from a fibroblast monolayer to whole-organism physiology remains speculative.

What the Research Literature Examines

Dermal and anti-wrinkle research

Skin is the largest single research area. A 2025 review in BioImpacts assessed topically applied GHK as an anti-wrinkle peptide and — importantly for method design — framed the discussion around advantages and problems, including the fundamental difficulty of moving a charged, hydrophilic metal complex across the stratum corneum. Early clinical work in cosmetic settings reports changes in skin appearance measures, but studies are typically small, variably blinded, and formulation-dependent, so evidence remains preliminary.

Delivery and formulation science

A substantial share of recent output is not about GHK-Cu's biology at all but about getting it where it needs to be and measuring whether it arrived. A 2025 Molecules paper asked directly whether current methods are adequate to measure skin permeation of GHK-Cu encapsulated in liposomes — a candid methodological question that shapes how permeation claims elsewhere should be read. Separately, a 2025 study in Colloids and Surfaces B described an injectable hydroxyapatite microsphere filler loaded with the tripeptide, characterized for anti-inflammatory and antioxidant behavior in a biomaterials context.

Bone, vasculature, and conjugate chemistry

Work published in Bioconjugate Chemistry in 2025 described copper complexes of new GHK–hyaluronan conjugates showing antioxidant properties along with osteogenic and angiogenic synergistic effects. Covalent conjugation to a polysaccharide carrier is an approach to stability and residence time that also changes the molecule's identity, so results from conjugates should not be read as results for free GHK-Cu.

Pulmonary fibrosis and systemic inflammation

The silicosis work noted above extends GHK-Cu research well beyond dermatology into organ fibrosis, where the reported peroxiredoxin 6 involvement gives a testable hypothesis for follow-up. Findings are from animal models; no clinical translation should be assumed.

Muscle and metabolic models

The sirtuin 1-linked skeletal muscle work sits in a similar category: a defined insult model, a defined pathway, and a rodent readout. It broadens the mechanistic picture without establishing generalizable outcomes.

Non-biomedical and analytical applications

Two lines of work are easy to overlook but useful to anyone characterizing the molecule. GHK-modified asymmetric nanochannels have been described for ultrasensitive, label-free detection of copper ions, exploiting exactly the coordination chemistry that defines the complex. And in industrial biotechnology, copper-GHK has been reported as a high-efficiency inducer of laccase production in Trametes versicolor. Both underline that the copper-binding behavior is robust enough to be engineered around.

Laboratory Handling: Reconstitution and Storage

GHK-Cu is normally supplied as a lyophilized powder, often with the characteristic blue-to-violet cast of a Cu(II) complex. In that dry state it is comparatively stable when kept cold, dark, and dry; once it enters solution, it becomes a peptide plus a redox-active metal in an aqueous environment, and the stability calculus changes.

General laboratory practice for handling the material includes:

1. Equilibrate before opening. Allowing a cold vial to reach ambient temperature before breaking the seal limits condensation onto hygroscopic powder.
2. Introduce solvent gently. Directing diluent down the vial wall rather than onto the cake, then swirling rather than shaking, reduces mechanical stress and foaming at the air–liquid interface.
3. Inspect the resulting solution. A clear, evenly tinted solution is the expected outcome. Persistent haze, visible particulates, precipitate, or a marked color shift are grounds for setting the vial aside and documenting the observation.
4. Protect from light and heat. Amber storage or foil wrapping, refrigeration for working stock, and deeper freezing for longer-term aliquots are standard; repeated freeze–thaw cycling is generally avoided by aliquoting.
5. Log everything. Solvent identity, date of reconstitution, storage location, and any appearance changes belong in the notebook. Reproducibility problems in peptide work are more often handling artifacts than chemistry.

Deeper treatments of these topics — cold-chain requirements, what cloudiness after reconstitution indicates, how long an opened vial remains usable, recognizing degraded material, lyophilized powder handling, and transporting material between facilities — are covered in dedicated articles elsewhere on this hub. This page deliberately keeps handling guidance at the level of laboratory technique and does not address administration of any kind.

Regulatory and Research-Use Status

GHK-Cu is not FDA-approved as a drug for any of the biological effects described in the research literature above. It has no approved indication for skin conditions, wound repair, fibrosis, muscle function, or bone. Copper tripeptide-1 appears as an ingredient in cosmetic products in various markets, but cosmetic ingredient status is a regulatory category concerning topical products and their claims — it is not evidence of therapeutic efficacy and does not extend to research-grade powder.

Material supplied by research vendors, including Real Peptides, is intended for research use only: in vitro work, analytical method development, and laboratory investigation by qualified personnel. It is not intended for human or veterinary use, not for diagnostic use, and not for incorporation into consumer products. Institutional oversight, biosafety review, and applicable local regulation govern any experimental work involving it.

How Researchers Evaluate Supplier Quality

Because peptide identity and purity drive every downstream result, sourcing is a methodological decision, not a purchasing one. The checks below are what experienced labs ask for before a lot enters an experiment.

Two failure modes recur. The first is a generic COA reused across lots — a document that cannot fail, and therefore cannot inform. The second is mislabeled or substituted material; for a copper complex, gross discrepancies in color, solubility behavior, or mass spectrum are often the first clue. Related articles on this hub cover identity verification and distinguishing authentic from counterfeit material in more detail.

Where the Open Questions Are

An honest reading of the GHK-Cu literature leaves several large gaps:

• Delivery and bioavailability. The 2025 permeation paper's framing — are current methods even adequate to measure it — is a reminder that many claims about topical delivery rest on assays whose validity is still being argued.
• Free peptide versus complex versus conjugate. GHK, GHK-Cu, liposomal GHK-Cu, and hyaluronan conjugates are chemically distinct entities with distinct behavior. Literature that blurs them produces confusion that propagates.
• Copper concentration dependence and redox risk. Copper is both essential and potentially pro-oxidant. Where the beneficial window sits in a given model system, and how it shifts with matrix and concentration, is under-characterized.
• Mechanistic convergence. Peroxiredoxin 6 and sirtuin 1 are concrete targets identified in specific models. Whether they represent parts of one upstream mechanism or independent, tissue-specific effects is unresolved.
• Clinical translation. Nearly all of the compelling data is in vitro or in animals. Controlled human trials of adequate size and design are scarce, and evidence remains preliminary.

For researchers, those gaps are the opportunity. Careful characterization of the material, disciplined handling, and precise reporting of which chemical species was used are the low-cost steps that make new GHK-Cu work worth citing.

Research-grade GHK-Cu: Real Peptides supplies GHK-Cu for laboratory research with a published third-party Certificate of Analysis for every batch. Research use only.

Explore GHK-Cu research on Real Peptides

The articles below go deeper on the questions researchers ask most about GHK-Cu.

Reconstitution, storage & handling

• How to Store GHK-Cu After Reconstitution — Shelf Life &
• GHK-Cu Refrigeration: Essential or Overkill in 2026?
• Maximizing Your GHK-Cu Vial’s Life: Our Expert 2026 Guide
• GHK-Cu Refrigeration: The Real Truth About Peptide Storage
• Does GHK-Cu Cosmetic Need Refrigeration Storage?
• GHK-Cu Reconstituted Cloudy — Still Good or Ruined?
• How to Mix GHK-Cu Cosmetic Calculator — Real Peptides

Safety & side effects

• GHK-Cu on Empty Stomach Safety — What Research Shows
• GHK-Cu Contraindications: A 2026 Safety Deep Dive
• Is GHK-Cu Safe Side Effects — Real Peptides
• Navigating GHK-Cu Cosmetic Contraindications Safely

Research timelines & mechanisms

• How Long GHK-Cu Stays in System — Clearance Timeline
• GHK-Cu Half Life: What Researchers Need to Know in 2026
• How Long GHK-Cu Cosmetic Stays in System? (Clearance
• GHK-Cu for Keloid Scars Research — Mechanism Evidence

Research questions

• Signs GHK-Cu Gone Bad Degraded — Real Peptides
• Signs GHK-Cu Cosmetic Gone Bad Degraded — Real Peptides
• GHK-Cu Cosmetic Lyophilized Powder: Handling Guide
• Travel With GHK-Cu Cosmetic: A 2026 Pro’s Checklist
• GHK-Cu Cosmetic Oral Taste: A Deep Dive for Researchers
• GHK-Cu Needles Syringes: Precision in Peptide Research

Stacks & comparisons

• GHK-Cu vs KLOW: Which Peptide Is Right for Your Research?
• GHK-Cu Real vs Fake: How to Tell | Real Peptides
• GHK-Cu Cosmetic Real vs Fake — How to Tell the Difference
• Difference Between GHK-Cu and KLOW — Real Peptides
• GHK-Cu Cosmetic Quality: Real vs. Fake in 2026
• GHK-Cu for Scar Reduction: A Deep Dive for Researchers

Legal & regulatory

• Is GHK-Cu Banned by WADA? The Unflinching Answer for Athletes
• Is GHK-Cu FDA Approved? The Unflinching Truth for Researchers

Ordering GHK-Cu for research

Real Peptides supplies GHK-Cu as a research-use-only reference material: lyophilized powder in a sealed vial, labeled with the lot number that matches its published certificate of analysis. Every batch is tested by an independent laboratory before it ships, and the certificate is published before purchase, so a researcher can read the purity result for the exact lot they are ordering.

• Product page: GHK-Cu for research, with the vial formats currently stocked and the certificate for the batch shipping now.
• Certificates: search any lot number at the certificate lookup; reports stay on file after a batch sells out.
• Shipping: orders dispatch within 24 hours on business days from inventory in Florida and California to every US state; see research peptides by location.
• Related compounds: browse the full research peptide catalog.

Nothing on this page is medical advice or guidance on administering any compound. GHK-Cu is not for human or animal use, and buyers confirm they are 21 or older and purchasing for laboratory research.

What should a certificate of analysis for GHK-Cu include?

A certificate of analysis (COA) is the primary document a laboratory buyer uses to decide whether a GHK-Cu lot is fit for benchwork. At minimum, it should identify the peptide sequence (glycyl-L-histidyl-L-lysine) and its copper(II) complex, state the lot number and manufacture date, report chromatographic purity with the method and gradient noted, and confirm molecular identity by mass spectrometry. Supporting entries often include appearance, water content by Karl Fischer, residual solvent screening, and net peptide content, since lyophilized material typically carries counter-ions and bound water that affect gravimetric calculations.

Because GHK-Cu is a metal complex rather than a simple peptide, copper content analysis — commonly by ICP-MS or atomic absorption — is a meaningful extra data point, as discussed in the overview of copper delivery chemistry and the comparison of GHK versus its copper-bound form. Documentation should be lot-specific rather than a generic template reused across batches.

Researchers assembling procurement checklists often cross-reference the buying guide for researchers and the parallel cosmetic-grade sourcing guide to confirm which analytical fields they consider non-negotiable before a lot enters an experimental workflow.

How is GHK-Cu purity confirmed by HPLC and mass spectrometry?

Reversed-phase high-performance liquid chromatography (RP-HPLC) is the standard first-pass purity assay for GHK-Cu. A C18 column with a water/acetonitrile gradient and trifluoroacetic acid or formic acid modifier separates the target species from truncated sequences, deletion peptides, and synthesis by-products. Purity is reported as the area percentage of the main peak at a stated wavelength, usually 214–220 nm where the amide bond absorbs. Metal complexes can produce peak broadening or split peaks on acidic gradients, so some laboratories run the free tripeptide and the copper complex separately to interpret the trace correctly.

Mass spectrometry — typically ESI-MS or LC-MS — supplies orthogonal identity confirmation by matching the observed mass to the calculated monoisotopic mass of the tripeptide, with copper adducts recognisable by their characteristic isotope pattern. HPLC alone confirms homogeneity; MS confirms that the homogeneous material is the intended molecule.

Analytical rigour matters most when results are being compared across sources, a theme explored in the summary of comparative GHK-Cu studies and in discussions of absorption and bioavailability variables. Procurement considerations for verified lots are collected in the researcher buying guide and the free-peptide versus complex comparison.

How should lyophilized GHK-Cu be stored and shipped for research use?

Lyophilized GHK-Cu is supplied as a blue to blue-violet powder, the colour arising from the copper(II) coordination sphere. In dry form it is comparatively stable, but it remains sensitive to moisture, heat, and prolonged light exposure. Common laboratory practice is storage at −20 °C in the sealed original vial, protected from light, with the container allowed to equilibrate to ambient temperature before opening so that condensation does not deposit water onto the cake. Short periods at refrigerated or ambient temperature during transit are generally tolerated by lyophilized peptides, which is why many suppliers ship without cold chain and rely on the dry state for stability.

Repeated temperature cycling is the more common degradation risk, so dividing bulk material for separate freezer storage at receipt is typical. Visible colour fading, caking, or discoloration are reasons to re-verify identity analytically before use.

Background on why the copper centre influences handling is covered in the copper delivery discussion, while general orientation for new laboratory users appears in the beginner-oriented overview. Sourcing and documentation expectations are detailed in the cosmetic-grade buying guide, and redox-related stability context is summarised in the antioxidant mechanisms guide.

What has hair follicle research examined with copper tripeptides?

Follicular research involving GHK-Cu and related copper tripeptides generally uses cultured dermal papilla cells, hair-follicle organ culture, or rodent models of hair cycling. Endpoints reported in the literature include dermal papilla cell proliferation, expression of growth factors associated with the anagen phase, markers of follicle miniaturisation, and the duration of growth versus resting phases in cycling models. Some investigators have also assessed copper tripeptides in the context of 5-alpha-reductase biology, which is the mechanistic bridge most often drawn to androgen-driven follicular change.

The evidence base here is thinner and more heterogeneous than the dermal matrix literature, with differences in species, model system, and delivery format making cross-study comparison difficult. Many reports are preliminary, and replication across independent laboratories is limited.

Mechanistic discussion of the androgen-related hypotheses is set out in the overview of GHK-Cu and androgenetic alopecia mechanisms, with study-level detail in the companion piece on alopecia research insights. Facial-follicle model work is summarised in the beard growth research article, and the analogue comparison is covered in GHK-Cu and AHK-Cu skin and hair research.

How does research-grade GHK-Cu differ from cosmetic-grade copper peptide material?

The two categories differ in specification rather than in the underlying molecule. Research-grade GHK-Cu is typically supplied as a lyophilized solid with a lot-specific COA documenting chromatographic purity, mass-spectrometric identity, water content, and copper assay, and is labelled for laboratory use only. Cosmetic-grade copper peptide raw material is usually sold as an ingredient intended for incorporation into finished formulations, where the relevant documentation centres on INCI naming, microbiological limits, preservative compatibility, and formulation stability data rather than on high-resolution analytical purity.

Concentration conventions also differ. Finished cosmetic products contain the tripeptide at low percentages within a complex base, which complicates any attempt to compare them directly with defined-concentration laboratory preparations. Formulation pH and chelating excipients can additionally affect whether the copper complex remains intact.

These distinctions are explored in the comparison of topical formulations and isolated GHK-Cu and in the article on cosmetic bioavailability and absorption efficacy. Reported endpoints in cosmetic-science literature are summarised in the cosmetic benefits overview, and sourcing expectations for either category are detailed in the cosmetic buying guide for researchers.

Which compounds are studied alongside or compared with GHK-Cu?

GHK-Cu rarely appears in isolation in the current literature. Comparative work most often places it next to other matrix-active agents: retinoids, which act through nuclear retinoic acid receptors and have a far larger clinical dataset; vitamin C derivatives, which function as cofactors for collagen hydroxylation; and other signalling peptides such as palmitoyl pentapeptide analogues studied in cosmetic-science contexts. Because these agents operate through different receptor and enzymatic routes, investigators sometimes examine them in combination to test whether effects are additive or redundant.

In peptide research more broadly, GHK-Cu is also assessed alongside repair-oriented sequences in multi-agent experimental designs, where the analytical challenge is separating contributions of each compound from one another and from vehicle effects. Interpretation of such studies depends heavily on controls, and single-arm reports provide weak evidence of synergy.

Comparisons with retinoid chemistry are discussed in the article on GHK-Cu versus vitamin A derivatives. Multi-compound experimental designs are reviewed in the piece on GHK-Cu combined with other peptides and the anti-aging research stack overview, while the broader substitute landscape is mapped in the peptide alternatives review.

How does GHK-Cu compare with AHK-Cu in laboratory research?

AHK-Cu (alanyl-L-histidyl-L-lysine copper) is a structural analogue in which the N-terminal glycine of GHK is replaced by alanine. Both tripeptides coordinate copper(II) through the histidine imidazole and the terminal amine, and both appear in the cosmetic-science and cell-culture literature as copper-carrying signalling peptides. The single methyl-group difference alters hydrophobicity and complex stability, which is the usual explanation offered for why the two analogues are often investigated in different model systems.

GHK has the deeper research history, having been isolated from human plasma and subsequently examined across fibroblast, keratinocyte, and wound-repair models, as reviewed in the published literature on GHK as a modulator of cellular pathways in skin regeneration (PubMed (PubMed PMID 26236730)). AHK-Cu is more frequently described in follicular and dermal papilla cell work, though its dataset is smaller and less replicated.

Side-by-side discussion of the two analogues appears in the review of GHK-Cu and AHK-Cu skin and hair research and in the write-up on combined copper-tripeptide follicle models. Broader analogue landscape context is covered in the comparative studies summary and the peptide alternatives overview.

Why is the copper(II) ion central to GHK-Cu biology?

GHK binds copper(II) with high affinity through a square-planar coordination involving the N-terminal amine, the deprotonated amide nitrogen, and the histidine imidazole nitrogen, with the lysine side chain remaining free. This arrangement is frequently described as mimicking the copper-transport chemistry of albumin, and it is the structural basis for the hypothesis that GHK functions as a physiological copper shuttle rather than simply as a signalling peptide.

The bound metal is relevant for two reasons discussed in the literature. First, copper is a cofactor for enzymes involved in connective-tissue cross-linking and in superoxide handling, so delivery of the ion to cells is mechanistically distinct from receptor-level signalling. Second, the redox activity of free copper is tightly controlled in tissue; chelation within the tripeptide is proposed to permit transport without unregulated Fenton-type chemistry. Reviews of GHK tissue-remodelling chemistry describe this dual role in detail (PubMed (PubMed PMID 18644225)).

Further background on the coordination chemistry is set out in the copper delivery article, with redox considerations in the antioxidant mechanisms guide. Comparisons of metal-free and metal-bound forms appear in GHK versus GHK-Cu and the absorption factors overview.

What do fibroblast and extracellular matrix studies report for GHK-Cu?

Much of the foundational GHK-Cu dataset comes from cultured human dermal fibroblasts. Published work in this area has examined changes in collagen and glycosaminoglycan output, expression of matrix metalloproteinases and their tissue inhibitors, and gene-expression profiling that identifies broad shifts across matrix-remodelling pathways. The general picture described in review articles is that the tripeptide influences both the synthetic and the degradative arms of matrix turnover rather than acting on collagen production alone (PubMed (PubMed PMID 26236730)).

Animal models extend the same themes into tissue repair, where investigators evaluate granulation tissue formation, angiogenic markers, and histological quality of repaired dermis. Findings are model-dependent, and translation from culture systems to whole-organism outcomes remains an active research question rather than a settled one.

Mechanistic treatments of these pathways are collected in the article on GHK-Cu and collagen synthesis and the longer explainer on how collagen production is thought to work. Cosmetic-science framing of the same cell biology appears in the collagen stimulation overview, while in vivo repair literature is summarised in the review of animal wound-healing and tissue-repair research.

References

Peer-reviewed sources on GHK-Cu indexed in PubMed, listed for research context. Real Peptides supplies GHK-Cu for laboratory research use only.

1. Topically applied GHK as an anti-wrinkle peptide: Advantages, problems and prospective. BioImpacts : BI, 2025. PMID 39963574. doi:10.34172/bi.30071
2. Copper Complexes with New Glycyl-l-histidyl-l-lysine-Hyaluronan Conjugates Show Antioxidant Properties and Osteogenic and Angiogenic Synergistic Effects. Bioconjugate chemistry, 2025. PMID 40123442. doi:10.1021/acs.bioconjchem.4c00545
3. Are We Ready to Measure Skin Permeation of Modern Antiaging GHK-Cu Tripeptide Encapsulated in Liposomes?. Molecules (Basel, Switzerland), 2025. PMID 39795193. doi:10.3390/molecules30010136
4. An injectable hydroxyapatite microsphere filler loaded with GHK-Cu tripeptide for anti-Inflammatory and antioxidant. Colloids and surfaces. B, Biointerfaces, 2025. PMID 40716276. doi:10.1016/j.colsurfb.2025.114982
5. The glycyl-l-histidyl-l-lysine-Cu(2+) tripeptide complex attenuates lung inflammation and fibrosis in silicosis by targeting peroxiredoxin 6. Redox biology, 2024. PMID 38879894. doi:10.1016/j.redox.2024.103237
6. Glycyl-l-histidyl-l-lysine-Cu(2+) rescues cigarette smoking-induced skeletal muscle dysfunction via a sirtuin 1-dependent pathway. Journal of cachexia, sarcopenia and muscle, 2023. PMID 36905132. doi:10.1002/jcsm.13213
7. Improved laccase production by Trametes versicolor using Copper-Glycyl-L-Histidyl-L-Lysine as a novel and high-efficient inducer. Frontiers in bioengineering and biotechnology, 2023. PMID 37180036. doi:10.3389/fbioe.2023.1176352
8. Ultrasensitive and Label-Free Detection of Copper Ions by GHK-Modified Asymmetric Nanochannels. Analytical chemistry, 2023. PMID 37624577. doi:10.1021/acs.analchem.3c01174