Draft standard CEI-MS-19: Purity determination for peptides… — submissions
The 16 submissions received, published in full with declared interests and secretariat responses.
§2Submissions and responses
16 submissions were received. Each is published in full below with its declared interest, the secretariat response and the disposition. The Institute publishes submissions it did not accept in the same form as those it did.
The matrix interferes with the determination and no control is required
Having read the draft of CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase…, the respondent puts one point to the secretariat.
The respondent states that the matrices in scope can suppress or enhance the response, and that without an inhibition and enhancement control a result cannot be attributed to the analyte.
Data showing recovery outside acceptable limits in an uncontrolled matrix accompanied the submission.
The secretariat accepts this submission. A determination on an interfering matrix without a validated control establishes nothing, and the draft permitted one.
An inhibition and enhancement control is now required for every determination under this standard, with stated recovery limits, and a determination reported without it is recorded as not conformant rather than as a low result.
The standard does not require retention of the primary data
The respondent read CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase… in draft. The point applies to it and to the series generally.
The respondent states that a reported figure cannot be checked without the chromatogram or spectrum from which it was derived, and that the draft requires only the figure.
The respondent proposes a retention requirement with a stated period.
The respondent notes submission 001 above and does not repeat the ground it covers.
The secretariat notes this submission. Retention is addressed in the certificate-of-analysis minimum data standard, which requires that primary data be retained and be identifiable from the certificate, and which applies to every determination reported on a certificate.
No amendment arises. The requirement exists in the standard that governs reporting rather than in each determination standard, and the cross-reference has been added here so that a reader working from this document alone can find it.
Nothing prevents a chromatogram being reprocessed until it passes
The respondent read the draft of CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase… and has confined this submission to a single requirement.
Integration parameters can be adjusted after acquisition, and nothing in the draft requires the sequence of processing to be recorded. A result presented as a single determination may be the last of several.
The respondent proposes that the standard require an audit trail of processing, retained with the primary data.
The secretariat accepts the principle and adopts a narrower requirement.
The standard now requires the processing method and its version to be recorded with every result and the primary data to be retained. A full audit trail is recommended and not required, since it depends on software many laboratories in scope do not run.
The reporting threshold is not tied to a demonstrated limit of quantitation
The respondent has read CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase… and submits on a matter of presentation.
The draft sets a reporting threshold as a fixed percentage. The respondent states that whether a laboratory can quantify at that threshold depends on the signal-to-noise achieved, and that the threshold should be conditional on demonstrating it.
The respondent proposes that a determination be reportable only where the signal-to-noise at the threshold is demonstrated in the run.
The secretariat accepts this submission. A threshold no one has demonstrated is a convention rather than a limit.
The reporting threshold is now conditional on demonstrating the required signal-to-noise at that threshold within the run, and a determination that cannot demonstrate it reports the achievable threshold instead of the nominal one.
The draft prescribes a procedure where it should state performance
The respondent submits on CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase…, on a matter that is not specific to this draft but is visible in it.
Several clauses specify a gradient, a column chemistry and a temperature. The respondent states that fixing these prevents a laboratory from using a validated equivalent, and that the Institute settled on stating performance when it scoped the series.
The respondent proposes that the prescriptive clauses be converted into performance requirements with the prescribed conditions retained as a worked example.
The secretariat accepts this submission. The draft departed from the position settled when the series was scoped, and the departure was not deliberate.
The prescriptive clauses are converted to performance requirements, the specific conditions are retained as a worked example clearly labelled as one, and a laboratory using a different validated procedure that meets the stated performance reports a conformant determination.
The standard would be applied more consistently with a worked example
The respondent notes that CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase… will be cited by suppliers as a warrant for a purity figure, and submits with that in view.
The respondent states that the requirement most often misapplied in practice is the one the draft states most briefly, and that a worked calculation would settle it.
The respondent proposes a worked example showing the same data treated correctly and incorrectly, with both results stated.
The respondent supports submission 005 so far as it goes and adds the matter set out here.
The secretariat accepts this submission. An example showing only the correct treatment does not show the reader what they are doing wrong.
A worked example is added showing the same primary data treated two ways, with both resulting figures stated and the difference between them quantified, so that the consequence of the misapplication is visible rather than described.
The standard should require documented operator competence
The draft of CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase… was read against the instrumentation in general use in a hospital laboratory rather than against a research configuration.
The respondent states that the determination described requires judgement, particularly at the integration step, and that a competence requirement would improve consistency more than any change to the criteria.
The respondent proposes that conformance be conditional on documented operator training.
The secretariat does not accept this submission. Operator competence is a quality-system matter governed by accreditation requirements the Institute does not administer and cannot verify.
The standard states performance and remains silent on competence. Where judgement affects the result, as at the integration step, the standard requires the judgement to be recorded rather than the operator to be qualified, which is the part the Institute can check from a report. The submission remains published in full.
The document set should be published in translation
The respondent has read CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase… in draft and makes one submission.
The respondent notes that the assessments concern compounds supplied internationally and that publishing only in English restricts access to the assessment to readers who work in it.
The respondent proposes machine translation of the document set as an interim measure, with human review of the certainty language.
The secretariat does not accept this submission, and records that the underlying point is sound and that the proposed remedy is the difficulty.
A translation whose certainty language has drifted is a different assessment carrying the Institute's name, and the Institute cannot review translations it does not have the capacity to review. The documents remain in English. The submission is published in full because the access problem it identifies is real and unresolved.
Nothing states how long a prepared standard solution remains usable
This is a submission on the draft of CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase…, from the standpoint of a laboratory that would have to demonstrate conformance with it.
The procedure requires a reference solution and does not say for how long it may be used. Peptide solutions at working concentration lose material to surfaces and to hydrolysis, and a solution used for a week will bias every result obtained against it in the same direction.
The respondent proposes that the standard require solution stability to be demonstrated over the period of use, or that a maximum period be stated.
The secretariat accepts this submission. A systematic bias applied uniformly to a sequence is the hardest kind to notice.
The procedure now requires solution stability to be demonstrated over the period of intended use, and the demonstration to be recorded with the result.
The preparation solvent is not specified and changes what is measured
The respondent submits on CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase…. The point would apply equally to any document in the series.
Material that has aggregated will dissolve to different extents in different solvents, so a preparation in one solvent can report a purity that a preparation in another does not reproduce, on the same vial.
The respondent proposes that the preparation solvent be specified rather than left to the laboratory.
The secretariat accepts the reporting requirement and declines to specify a single solvent across all materials in scope.
The preparation solvent is now a required reporting field and the procedure names an acceptable range. Specifying one solvent for every material in scope would exclude compounds the standard is intended to cover.
Results are reported without an estimate of measurement uncertainty
This submission concerns the draft standard CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase…. The respondent runs reversed-phase separations of peptides daily and the observation arises from that work.
The respondent, an analytical chemist, states that a figure reported to one decimal place implies an uncertainty the standard nowhere estimates, and that two determinations differing within the uncertainty will be read as a difference.
The respondent proposes that an uncertainty budget be required for every determination.
The secretariat accepts this submission in part. A repeatability figure and a stated reporting precision are required. A full uncertainty budget is not, because the standard is written to be usable by laboratories that do not maintain one and the requirement would exclude them without improving the reading.
Every determination now reports the repeatability observed in the run, the reporting precision, and a statement that two results differing by less than the stated repeatability are not distinguishable by this method.
Nothing addresses the container the material was held in
This is a submission on CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase….
Adsorption to the container and oxidation in the headspace both change what is measured, and both depend on the container rather than on the material. The standard treats the vial as neutral.
The respondent proposes that container type and headspace atmosphere be reported where they are known.
The secretariat accepts the reporting requirement where the information is held and declines to require it where it is not.
Container type and headspace atmosphere are now reported where known, and recorded as not held where they are not, rather than omitted.
Rounding conventions are not stated and change the reported result
This submission concerns CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase… and a convention used across the Institute’s output.
The respondent states that the draft reports figures to varying precision and does not specify when rounding occurs in the calculation chain, which can move a result across an acceptance limit.
The respondent proposes that rounding occur only at the reporting step and that the convention be stated.
The secretariat accepts this submission. Intermediate rounding is a silent source of disagreement between laboratories analysing the same material.
The standard now requires that no rounding be applied before the reporting step, states the reporting precision for each quantity, and states the rounding convention used at that step.
The scope does not say which materials the standard excludes
This submission addresses the draft of CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase… from the standpoint of a reader who will use a figure produced under it without having read it.
The scope states what the standard applies to. The respondent states that in practice the difficult question is whether a borderline material is in scope, and that the draft leaves it to be inferred.
The respondent proposes an explicit exclusion list.
The secretariat accepts this submission. A scope stated only positively is a scope that will be stretched.
The scope now states both what the standard applies to and what it does not, with the excluded classes named and, where another standard covers them, cross-referenced.
Quantitative claims are reproduced without the method that produced them
The respondent submits on the draft of CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase…. A chromatographic purity determination is the figure most often quoted from a certificate and the one whose meaning depends most completely on the method behind it.
Several figures in the draft are quoted from sources that determined them by different methods. A figure obtained by one determination and a figure obtained by another are not comparable, and the draft places them in the same sentence without distinguishing them.
The respondent, an analytical chemist, proposes that every quantitative claim carry the method that produced it at the point of use rather than in the reference.
The respondent notes submission 007 above and does not repeat the ground it covers.
The secretariat accepts this submission. Placing two figures side by side is an implicit claim that they are the same kind of quantity, and in the cases identified they were not.
Every quantitative claim now carries the determination that produced it at the point of use, and figures obtained by non-comparable methods are no longer presented in the same row or sentence.
A determination does not record the version of the standard it was made under
The respondent’s comment on the draft of CEI-MS-19, Purity determination for peptides not retained by conventional reverse-phase… arises from applying it to a real separation rather than to a specimen one.
The respondent states that the standard will be revised and that results reported under different versions will circulate together, indistinguishable from one another.
The respondent proposes that the standard identifier and version be carried on the face of every determination.
This point is adjacent to the one made in submission 007 and the respondent puts it in a form the secretariat can act on.
The secretariat accepts this submission. A conformance claim against an unspecified version is not a conformance claim.
Every determination reported under this standard now carries the standard identifier and version on its face, and a claim of conformance that does not identify the version is recorded by the Institute as not conformant.
References cited on this page
References are numbered in order of first citation in this document. Each superscript in the text links to its entry below.
- International Organization for Standardization. ISO/IEC 17025:2017 General Requirements for the Competence of Testing and Calibration Laboratories. ISO/IEC Standard 2017;3rd edition. identifier not held by the Institute
Identifiers are reproduced only where the Institute holds them. Where a digital object identifier or PubMed identifier is not shown, the Institute has recorded the journal and year and has not constructed an identifier.