Epitalon peptide quality: purity testing, COA and laboratory verification

4 September 2026

Epitalon, also referred to as Epithalon, is a tetrapeptide described by the sequence Ala-Glu-Asp-Gly, abbreviated as AEDG. The analytical characteristics of this compound include several distinct issues: chemical identity, chromatographic purity, peptide content, the presence of other components, and changes in the material properties over time.

A single percentage value does not present a full description of the sample. The result regarding purity does not necessarily determine the identity, quantity or stability of the substance. Also, the document entitled „certificate of analysis” presents information on a specific scope of tests, rather than a universal confirmation of all properties of the material.

In the scientific description of Epitalon's quality, therefore, it is important to distinguish between what has actually been measured and what cannot be determined on the basis of a given measurement. This applies both to a single chromatogram and to extensive laboratory documentation.

What does the analytical characteristic of Epitalon mean?

Analytical characterisation consists in describing the composition and properties of a material using appropriate testing. It is not a single measurement, but a collection of information answering various questions.

With Epitalon, the primary issue is the conformity of the data with the expected AEDG molecule. Subsequent issues concern the quantity of this substance, the presence of additional ingredients, and the extent of changes occurring in the material.

Parameter	What question describes?	What does he not resolve on his own?
Chemical identity	Do the data correspond to the expected molecule?	How much of this substance is in the sample?
Chromatographic purity	What signal share has been assigned to the specific component?	Does the result correspond to the mass fraction in the whole material?
Peptide content	How much of the labelled peptide is in the sample?	Have all the remaining components been characterised?
Pollution profile	What additional substances were detected?	Have all possible contaminants been ruled out?
Chemical species	How is the chemical form of the material described?	Does the material remain unchanged over time?
Stability	Do specific parameters change over time?	Have properties outside the range of observation been investigated?

Such a distinction prevents a single result from being treated as the answer to all questions regarding the sample. The material may contain a correctly identified peptide and at the same time require a separate determination of its content or the characterisation of the remaining components.

Chemical identity — what does the sequence AEDG mean?

The Ala-Glu-Asp-Gly sequence describes the order of four amino acid residues: alanine, glutamic acid, aspartic acid and glycine. The AEDG abbreviation uses the single-letter designations of these amino acids.

The name of the substance and its sequence record are elements of the chemical description. However, they do not constitute a test result of the sample in themselves. The information included in the documentation specifies the expected identity, whereas the analysis provides data enabling the assessment of the material's compliance with this description.

It is also important to distinguish between the sequence and the full characterisation of the material. The sequence does not automatically describe the water content, counterions, excipients or other substances present in the sample.

Two materials described by the same name may therefore require separate analytical characterisation. Conformity of naming does not replace the comparison of results.

What is a certificate of analysis, also known as a COA?

COA is the abbreviation for the English term Certificate of Analysis. The document presents the results of analyses relating to an identified material, sample or batch.

The certificate may contain the substance name, sample designation, batch identifier, testing date, analytical methods, obtained results, and criteria for their evaluation. Individual documents vary in scope and level of detail.

The mere presence of the acronym COA does not indicate whether solely chromatographic testing, identification, quantification or a broader set of analyses was performed. The significance of the document derives from its content.

Test result vs specification

The specification describes the adopted requirements or evaluation criteria. The test result presents the outcome obtained for a specific sample.

In the documentation, both types of information may be located next to each other. However, the limit value in the „specification” column is not the same as the measured value.

Similarly, the term „compliant” implies a comparison of the result against a specific criterion. Without information about this criterion and method, it does not present a complete picture of the assessment carried out.

Numerical result versus descriptive result

Not every analysis leads to a numerical value. An identification test may end with a descriptive statement of conformity with the expected material, whereas a content assay usually presents a quantitative result.

A lack of a number does not automatically mean a lack of scientific value. What matters is whether the form of the result corresponds to the aim of the study and whether it is clear on what basis the conclusion was formulated.

On the other hand, the mere presence of numerous figures does not prove that the document describes all the relevant properties of the sample.

CoA and full analytical report

The certificate may serve as a summary of broader documentation. Chromatograms, spectra, calculations, and method details may be stored in a separate laboratory report.

The absence of a chromatogram in the CoA itself does not prove that chromatography was not performed. However, it means that the signal profile cannot be analysed in detail on the basis of this document.

Similarly, the enclosed chromatogram is only part of the documentation. Its interpretation depends on its correlation with the method, the sample, and the method of calculating the result.

What does HPLC describe in the Epitalon analysis?

PLC, or high-performance liquid chromatography, is a technique for separating sample components. Compounds that differ in their interactions within a specific chromatographic system can be recorded as separate peaks.

The chromatogram shows the detector response over time. Information about the position, shape and area of the peaks is interpreted in relation to a specific method.

In peptide analysis, chromatography can provide data on the main component and accompanying substances. However, its capabilities are not unlimited: not every method separates all compounds and not every component is detected equally well.

Retention time

Retention time describes the moment a given component is registered in a given chromatographic system. It is a feature dependent on the conditions of the analysis.

It should not be treated as an invariant molecular identifier, independent of the method used. The same compound may have a different retention time in a different system, and different compounds may exhibit similar times in a single analysis.

Retention time consistency can form part of a comparison, but its significance arises from the entire analytical context.

Peak area

Peak area refers to the integrated detector signal. Its interpretation depends, among other things, on the detector's response to a given component.

It is not an independent, universal measurement of the mass of a substance. In the quantitative method, the relationship between the signal and the amount of analyte requires appropriate determination.

Therefore, the chromatogram used to assess the relative peak area does not necessarily have to represent the determination of the total Epitalon content.

Does one peak represent one substance?

Not always. Different components may not be separated and can form an overlapping signal. This phenomenon is known as co-elution.

Therefore, the dominant peak does not confirm on its own that it contains exclusively a single compound. Nor does it prove that this compound has the expected identity.

Assessment of chromatographic homogeneity and confirmation of chemical structure remain distinct issues.

What does chromatographic purity mean?

If the result was calculated by peak area normalisation, it describes the contribution of the selected peak to the sum of the areas included in the calculation.

This value applies to the signal obtained under specific conditions. It does not necessarily correspond to the mass fraction of the peptide in the entire material.

Among other things, the resolution of the method, the type of detector, the detectability of individual substances, and the integration principles are important.

Why does a percentage result require context?

Different components can generate a different detector response. Some may be detected poorly, while others may remain outside the scope of a given analysis.

Water, specific inorganic components or other substances do not need to be included in the peak area calculation. A high proportion of the main signal therefore does not automatically mean that the entire material consists almost exclusively of the peptide.

Also, even small differences between percentage results do not always allow samples to be ranked by quality. Without knowledge of the methods and their properties, the comparison can be ambiguous.

What does mass spectrometry describe?

Mass spectrometry, abbreviated as MS, analyses ions based on their mass-to-charge ratio. This data can support the assessment of whether a tested component conforms to the expected molecule.

The method provides a different type of information than chromatography. Chromatography separates components in a specific system, whereas mass spectrometry describes the properties of the recorded ions.

The combination of these techniques, namely LC-MS, enables the correlation of chromatographic information with mass information.

Molecular mass versus mass-to-charge ratio

On the mass spectrum, the mass-to-charge ratio is presented, usually denoted as m/z. Each value on the spectrum axis should not be directly equated with the mass of a neutral molecule.

The interpretation takes into account the type of registered ion and its charge. The mere reading of a single number, without signal assignment, does not constitute a full identification.

The identification report links the observed signals with the expected properties of the test compound.

Mass compliance versus full structure

Mass match is evidence of a specific scope. It does not always resolve all issues concerning the structure of the molecule.

Some compounds may have the same mass, despite structural differences. Some issues related to isomerism or stereochemistry require additional information.

Tandem mass spectrometry, or MS/MS, analyses ion fragmentation and can provide further structural data. The range of possible conclusions still depends on the specific problem and the analysis used.

Does the MS signal alone determine the content?

Detection of the signal assigned to the peptide is not automatically a quantification of its amount.

MS can be part of a quantitative method, but this requires appropriate development and calibration. A result obtained solely for identification purposes does not replace such a procedure.

It also cannot be assumed that the strongest signal in the spectrum always corresponds to the largest mass fraction of the component.

Why are HPLC and MS complementary methods?

Both techniques describe different properties of the sample. Their combination can limit the ambiguity of the interpretation, but does not automatically create a complete characterisation of the material.

Chromatography may indicate the presence of a dominant component. Mass spectrometry data can support the assignment of this component to the expected molecule.

However, questions regarding quantitative content, undetected components, chemical form or stability still remain. The scope of the response depends on the measurements actually performed.

The concept of complementary methods therefore means the combination of various pieces of evidence concerning the same material. It does not mean that any two results are sufficient to resolve all aspects of quality.

Why does the peptide content require separate determination?

The content describes the amount of the analyte in the sample. It differs from the relative contribution of the chromatographic signal.

The total mass of the material may include peptide, water, counter-ions, excipients and other substances. Individual components do not necessarily need to be represented in the chromatogram in a manner corresponding to their mass.

Therefore, the percentage peak area should not be automatically used as a conversion factor for the actual peptide amount.

Basis of the expression of the result

A quantitative result requires an indication of what it refers to. It may describe the material as received, dry matter or another specified basis.

Two numbers presented in similar units can have different meanings if they are calculated with respect to different forms of the material.

The documentation should allow the measured quantity to be distinguished from the way in which it is presented. Without this, comparing results may lead to apparent contradiction.

What role does the reference material play?

A reference material provides a point of comparison for specific analytical properties. It may be involved in identification or in establishing the relationship between a signal and the amount being determined.

Its meaning depends on which properties have been characterised and for what purpose it is used. The name „standard” alone does not describe the full range of characteristics assigned to it.

Comparison with the reference material also does not mean that both samples are identical in every respect. The conclusion applies to those parameters that were included in the comparison.

Anti-ion, water and auxiliary ingredients

Peptide material may contain substances not included in the amino acid sequence. Their presence affects the description of the entire sample.

A counterion is an ion that accompanies an ionic species of opposite charge. Its type and content constitute information separate from the name and sequence of the peptide.

A specific counterion should not be assumed solely on the basis of the term „Epitalon”. The characteristics of a given form require appropriate information regarding the material.

Similarly, the water content or excipients cannot be reliably determined from the appearance of the powder. The volume and shape of the dry sample do not describe its quantitative composition.

The presence of a specific additive component does not in itself determine whether the material complies with the specification. What is important is whether this component has been defined and characterised.

What does a contaminant profile mean?

The impurity profile describes additional substances detected within the scope of the analyses performed. It may include compounds related to the synthesis, purification or transformations of the material.

In the case of synthetic peptides, various types of accompanying substances are possible. Their presence depends on the specific sequence and the history of the sample.

General knowledge about peptide impurities does not, however, prove the presence of a specific compound in Epitalon. The conclusion regarding a particular material requires direct data.

Recognised and unrecognised contaminants

An additional peak may indicate the presence of a component whose identity has not yet been established. The detection of the signal and the identification of the substance are different stages of the characterisation.

Not every small peak can be automatically assigned to a specific degradation product. Such assignment requires adequate evidence.

On the other hand, the lack of full identification of an additional component does not mean that its signal is irrelevant to the characterisation of the sample.

Non-detection versus absence

The „not detected” information refers to the capability of a specific test. It is not proof of the absolute absence of the substance.

A targeted analysis does not automatically describe all other potential constituents. The scope of the application remains tied to the scope of the method.

In scientific documentation, therefore, it is important to distinguish between the absence of a signal and the universal statement that the sample contains no contaminants.

Why do the characteristics of an analytical method matter?

A technique name, such as HPLC or MS, does not describe the entire procedure. Two methods using the same technique can be developed for different purposes.

One may serve primarily for identification, another for denoting the contents, and yet another for separating specific impurities. Their results should not be treated as interchangeable solely because of the common name of the apparatus.

The ICH Q2(R2) guideline describes the evaluation of analytical procedures with respect to their purpose. It lists, amongst other things, accuracy, precision, specificity, and detection and quantification limits. Its scope covers specific pharmaceutical analyses; the reference to the document does not confer the status of an approved product upon Epitalon. Source: EMA, ICH Q2(R2).

Even the phrase „validated method” requires context. Validation relates to a defined purpose and scope, and not to all possible measurements.

Sample and batch traceability

Traceability makes it possible to link a result with the material under test. This is achieved through sample labels, batch identifiers, report numbers and laboratory records.

It is not the same as representativity. A correctly labelled sample can be unequivocally linked to the report, but extending the result to the entire batch requires additional justification.

Sample and batch

The sample is the material subjected to analysis. The batch comprises a broader collection of material specified in the documentation.

Testing a sample does not mean testing every part of the batch. The scope of possible generalisations depends, amongst other things, on the method of material collection and data concerning homogeneity.

The matching of the numbers documents a link, but does not in itself confirm the identical composition of all units.

External laboratory

The information that the analysis was carried out by an external laboratory describes the organisation performing the test. It does not independently determine its scope or the properties of the method used.

The scientific significance stems from documented measurement. The phrase „independently tested” does not replace information about the sample, analysis, and results.

The authenticity of the document, the validity of the method and the representativeness of the sample are separate issues.

Chemical purity vs microbiological parameters

Chemical purity and microbiological parameters describe different material properties. A result for one area does not automatically provide information about the other.

Neither the standard HPLC chromatogram nor the MS identification result confirms sterility. Nor do they replace endotoxin testing.

Sterility, the presence of microorganisms and endotoxin content are not interchangeable concepts. Documentation regarding one of these parameters does not necessarily cover the others.

Also, the lack of microbiological information does not allow the result of the unperformed test to be predicted. This represents a limitation of the available characterisation.

What does the documentation say about stability?

Stability concerns the retention of specific material properties over time. Its assessment requires data relating to defined parameters and conditions.

The initial purity result does not automatically describe the condition of the sample at any later time. The test date indicates when the analysis was carried out, but does not replace the observation of changes.

No visible differences also do not confirm chemical stability. Not all transformations lead to a colour change, the appearance of a precipitate or any other perceptible phenomenon.

A Certificate of Analysis may contain information related to stability assessment, but its significance depends on the data on which they were based. The summary document itself does not automatically reveal the full course of such studies.

What are the limits of COA interpretation?

A certificate of analysis presents results within a specified range. It does not constitute standalone proof of the full characterisation of all components, the identity of the entire batch, or the unchangeability of the material after testing.

It also does not confirm properties that have not been indicated. The lack of information is a gap in the available documentation, rather than a positive or negative result.

The phrase „Epitalon quality” therefore requires clarification: it can refer to identity, purity, content or other parameters. Without this, it remains a general term.

Analytical results describe the material. They do not constitute confirmation of its suitability for use in humans or animals.

Frequently asked questions

What does the Epitalon COA mean?

A Certificate of Analysis (CoA) for Epitalon is a certificate of analysis presenting the results of specific tests on a sample or batch of material described as Epitalon. The document may include information on chemical identity, chromatographic purity, peptide content, or other tested parameters. Its significance depends on which analyses were actually performed, how the methods are described, and whether the results can be linked to a specific material. The name certificate of analysis itself does not indicate an identical scope of testing across all documents. A CoA therefore constitutes a record of specific analytical findings, rather than a general confirmation of all properties of the substance.

Does chromatographic purity confirm identity?

Chromatographic purity does not independently confirm chemical identity, because it describes the proportion of a specific signal in the chromatogram, rather than the complete structure of the substance responsible for that signal. A sample may show one dominant peak, but its assignment to Epitalon requires appropriate identification evidence. A high proportion of the main peak area does not rule out a situation where it corresponds to another compound or several unresolved components. The assessment of chromatographic purity and the identification of the compound therefore answer different questions. Only the combination of appropriate data makes it possible to describe both the nature of the main component and its proportion in the recorded signal.

Does a single HPLC peak mean no contamination?

A single PLC peak does not automatically mean an absence of impurities, because the chromatogram only shows components that were separated and detected under the conditions of a specific method. Some substances may co-elute, meaning they leave the column at a similar time and produce an overlapping signal. Others may be present below the detection limit or fail to generate a suitable response from the detector used. A single dominant peak therefore indicates a specific chromatographic profile, but does not provide a complete description of the sample's composition. Without additional information, the presence of components that are invisible in a given analysis cannot be ruled out on this basis.

Does the matching mass confirm the full structure?

The consistency of the mass spectrometry result with the expected value supports the identification of the compound, but does not in every situation confirm its complete structure. Different molecules can have the same mass despite a different arrangement of atoms or stereochemical differences. Furthermore, the interpretation of the spectrum requires taking into account the type of registered ion and its charge, since the mass-to-charge ratio is measured. Additional data, such as fragmentation in MS/MS or the results of other relevant methods, can help in resolving specific ambiguities. The scope of structural confirmation therefore depends on the entire set of evidence, rather than solely on the consistency of a single signal.

Are PLC and MS interchangeable?

PL and mass spectrometry are not interchangeable methods because they provide information on different properties of the studied material. PL allows for the separation of components in a specific chromatographic system, whereas MS analyses ions based on their mass-to-charge ratio. Combining these techniques can link the chromatographic signal with information supporting the identification of a given component. However, this does not mean the automatic determination of all sample parameters. Quantitative content, the presence of specific additional components, stability, or microbiological parameters may require separate tests. The value of combining PL and MS stems from the complementarity of the data, rather than the mutual replacement of the methods.

Does the percentage of purity mean the peptide content?

The percentage purity does not necessarily indicate the actual peptide content, as the meaning of the percentage value depends on how it is determined. If the result represents the area of the main peak as a percentage of the total included chromatographic peaks, it refers to the recorded signal rather than directly to the total mass of the material. The sample may contain water, counterions or other components that are not adequately reflected in such a calculation. Determining the peptide content requires a suitable quantitative method and a clearly defined basis for the result. Chromatographic purity and content therefore remain separate parameters, even when both are presented as percentages.

Does a CoA have to include all raw data?

A COA can serve as a summary document and does not have to be a full record of all data obtained during the analysis. Chromatograms, spectra, detailed calculations, and information about the course of the testing may be located in a separate report or laboratory documentation. The scope of the required documentation depends on the relevant quality system and the context of the testing, therefore a single rule should not be assumed for all certificates. The lack of raw data in the COA itself does not prove that the analysis was not performed, but it limits the possibility of its detailed evaluation based on this document. Neither is a single attached chart equivalent to complete analytical documentation.

Is „compliant” a test result?

The term „compliant” may be a valid summary of an assessment in which a result has been compared against a previously defined criterion. However, it does not always present the measurement result itself or the detailed evidence forming the basis of this conclusion. In an identification test, it may signify the conformity of specified characteristics with a reference material, whereas in a quantitative assay, it may indicate that an accepted range has been met. The meaning of the record therefore depends on the tested parameter, the method used and the specification. Without this context, it is not known what precisely the compliance relates to, and it cannot be extended to material properties not covered by the assessment.

Does a single-sample report describe the entire batch?

A single-sample report does not automatically describe the entire batch, as it directly presents the results for the material actually analysed. The ability to relate these results to a broader batch depends on the sampling method, its representativeness and data concerning the homogeneity of the material. A matching batch number enables the documentary linkage of the sample to a specific set of material, but does not in itself prove the identical composition of every part of it. This does not mean that the result of a single sample is meaningless, but rather that the scope of generalisation requires justification. Traceability and representativeness are related but distinct elements of interpretation.

Does an external examination guarantee a full characterisation?

An assay conducted by an external laboratory does not guarantee full characterisation, as it covers a specific set of analyses performed on the submitted material. The independence of the organisation does not automatically extend the scope of measurements or provide information on properties that were not investigated. The purpose of the analysis, the properties of the methods, the results documentation and the way the sample is linked to the material remain significant. An authentic external report may present valuable data while simultaneously leaving other parameters undescribed. The term „independently tested” therefore informs about the organisation performing the test, but does not replace a detailed description of what was actually established.

Does „not detected” mean the complete absence of the substance?

The term „not detected” does not mean proof of the complete absence of a substance, but rather indicates that no signal meeting the detection criteria was found under the conditions of the specific analysis. The method has defined detection capabilities, and the sample composition and measurement method affect the scope of the information obtained. The substance may be present in a quantity too small to be detected by the given procedure. Furthermore, testing targeted at a single component does not determine the presence of all other compounds. Such a statement should therefore be interpreted in relation to the substance being quantified and the method used, without turning it into a general assurance of the absence of contaminants.

Does the appearance of the powder confirm its composition?

The appearance of the powder does not confirm its chemical composition, as colour, volume, porosity or degree of caking are physical characteristics insufficient for the identification of a substance. Materials with different compositions may look similar, and materials containing the same peptide may differ in appearance. Observation does not determine the Epitalon content, the amount of water, the type of counterion or the presence of excipients. Nor does it rule out invisible impurities or chemical transformations. A visual description may form part of sample documentation, but it does not replace analytical testing and does not justify independent conclusions regarding its identity, purity or stability.

Does chemical purity confirm sterility?

Chemical purity does not confirm sterility, as both concepts refer to different material properties. Chromatographic testing describes specific chemical components detected by a given method, whereas sterility assessment concerns a separate microbiological issue. A standard HPLC result or identification using MS does not replace appropriate microbiological testing. Furthermore, sterility and endotoxin content are not interchangeable concepts, so a result concerning one parameter cannot be automatically applied to the other. High chromatographic purity therefore does not constitute a general confirmation of the microbiological properties of the sample or its safety.

Does the initial COA confirm stability over time?

The initial COA does not on its own confirm stability over time if it presents solely the results of a single analysis. Such a document describes the material in relation to the tests performed, whereas stability requires data concerning the behaviour of specified properties under defined conditions and over a period. The absence of visible changes does not rule out chemical transformations, just as the date of issue of the certificate does not replace analytical observations. A COA may contain information based on separate stability studies, but their significance depends on the documentation forming the basis of those entries. The initial purity result alone does not allow one to assume the invariance of the material at any subsequent point in time.

Is a COA a safety guarantee?

A COA is not a guarantee of safety, as it presents test results concerning specific material properties rather than a comprehensive assessment of all possible consequences of its use. Confirmation of the identity, purity or content of a peptide does not in itself establish the suitability of the substance for use in humans or animals. Nor does the document provide information on parameters that were not covered by the analysis. Even a detailed and authentic certificate should therefore be interpreted in accordance with the scope of the documented measurements. Its function is to describe the tested material, not to replace separate evidence required for safety assessment.

Disclaimer

The article is exclusively of an educational and informational nature in the context of laboratory research. It does not constitute medical advice, product selection advice, injection instructions, or a recommendation for the use of Epitalon. Analytical confirmation of identity or purity does not confirm clinical safety, efficacy, sterility, or suitability for human administration. Appropriate quality control requirements depend on the intended laboratory application, and where peptide identity, purity, quantity, sterility, endotoxins, or stability are relevant to the experiment, the proper framework is provided by validated methods, qualified laboratories, and appropriate institutional or regulatory standards.

References

Araj, S. K., Brzezik, J., Mądra-Gackowska, K., & Szeleszczuk, Ł. (2025). Overview of Epitalon—Highly bioactive pineal tetrapeptide with promising properties. International Journal of Molecular Sciences, 26(6), 2691.
https://doi.org/10.3390/ijms26062691
Vanhee, C., Moens, G., Van Hoeck, E., Deconinck, E., & De Beer, J. O. (2015). Identification of the small research tetrapeptide Epitalon, assumed to be a potential treatment for cancer, old age and Retinitis Pigmentosa in two illegal pharmaceutical preparations. Drug Testing and Analysis, 7(3), 259–264.
https://doi.org/10.1002/dta.1771
McCarthy, D., Han, Y., Carrick, K., Schmidt, D., Workman, W., Matejtschuk, P., Duru, C., & Atouf, F. (2023). Reference standards to support quality of synthetic peptide therapeutics. Pharmaceutical Research, 40(6), 1317–1328.
https://doi.org/10.1007/s11095-023-03493-1
Sharma, N., Kukreja, D., Giri, T., Kumar, S., & Shah, R. P. (2022). Synthetic pharmaceutical peptides characterisation by chromatography principles and method development. Journal of Separation Science, 45(13), 2200–2216.
https://doi.org/10.1002/jssc.202101034
Li, M., Josephs, R. D., Daireaux, A., Choteau, T., Westwood, S., Wielgosz, R. I., & Li, H. (2018). Identification and accurate quantification of structurally related peptide impurities in synthetic human C-peptide by liquid chromatography–high resolution mass spectrometry. Analytical and Bioanalytical Chemistry, 410(20), 5059–5070.
https://doi.org/10.1007/s00216-018-1155-y
International Council for Harmonisation. (2024). ICH Q2(R2): Validation of Analytical Procedures. Current guideline for validation of analytical procedures used for purposes including identity, assay, purity and impurity testing.
https://www.ema.europa.eu/en/ich-q2r2-validation-analytical-procedures-scientific-guideline
US FDA version:
https://www.fda.gov/media/161201/download