01/2008:512005.12.REFERENCE STANDARDS This chapter is published for information.1.INTRODUCTION ‘Reference standard’is ud in this chapter as a general term covering reference substances,reference preparations and reference spectra.Reference standards are frequently necessary to achieve adequate quality control of substances for pharmaceutical u and pharmaceutical preparations.Reference standards are established using suitable procedures and their continued suitability for u is monitored according to a predefined programme.Where a reference standard is needed,it
is an integral part of the
pharmacopoeial monograph or the manufacturer’s specification.Where a European Pharmacopoeia reference standard is referred to in a monograph or general chapter,it reprents the official standard t
hat is alone authoritative in ca of doubt or dispute.Reference materials and certified reference materials are defined below but are not otherwi dealt with in this chapter.In veral parts of the chapter,detailed information is given for
chemical reference substances but not for biological reference preparations.The general principles given apply to the latter,but in view of their heterogeneous nature and frequently their complexity compared to chemical reference substances,detailed information
on
their u,establishment
and
the
re-test programmes applied is not included.For peptide and protein reference standards,a specific approach is ud for certain aspects,notably the establishment of an assigned content;this chapter does not deal with that approach.2.TERMINOLOGY Primary standard .A standard shown to have suitable properties for the intended u,the demonstration of suitability being made without comparis
on to an existing standard.Secondary standard .A standard established by comparison with a primary standard.International standard .An international standard is a primary standard that defines
an
International Unit.The equivalence in International Units of an international standard is stated by the World Health Organisation.European Pharmacopoeia
reference
standard .A reference standard established under the aegis of and approved by the European Pharmacopoeia Commission.European Pharmacopoeia
Chemical Reference Substance (CRS).A substance or mixture of substances intended for u as stated in a monograph or general chapter of the European Pharmacopoeia.European
Pharmacopoeia
Chemical Reference Substances are primary standards,except for tho (notably antibiotics)that are calibrated in International Units.The latter are condary standards traceable to the international sta
ndard.European Pharmacopoeia Biological Reference Preparation (BRP).A substance or mixture of substances intended for u as stated in a monograph or general chapter of the European Pharmacopoeia.European Pharmacopoeia Biological Reference Preparations are either condary standards calibrated in International Units
or primary standards,
which
may be ud
to define a European Pharmacopoeia Unit.Other assigned values may also be ud,for example,virus titre,or number of bacteria.Reference Material (RM).A material or substance,one or more
of who property values are sufficiently homogeneous and well established to be ud for the calibration of an apparatus,the asssment of a measurement method,or for assigning values to materials.Certified Reference
Material (CRM)
.
A reference
material,
accompanied by a certificate,one or more of who property values are certified by a procedure that establishes its traceability to an accurate realisation of the unit in which the property values are expresd,and for which each certified value
is accompanied by an uncertainty at a stated level of confidence.NOTE :pharmacopoeial reference standards are to be
distinguished from reference materials and certified reference materials,which may be ud in veral contexts using a variety of analytical techniques for quantitative purpos.The u of reference materials is required or recommended in a number of monographs and general chapters of the pharmacopoeia,
notably for calibration or verification of satisfactory performance of instruments.The specificity of pharmacopoeial reference standards has been officially recognid in the introduction of ISO Guide
34-
General requirements for the competence of reference material
producers -(Second Edition 2000):“Pharmacopoeia standards and substances are established and distributed by
pharmacopoeia
authorities following the general principle
of this guide.It should be noted,however,that a different approach is ud by the pharmacopoeia authorities to give the
ur the information provided
by
the certificate
of analysis
and
the expiration dates.Also,the uncertainty of their assigned values is not stated since it is negligible in relation to the defined limits
of the method-specific assays of the pharmacopoeias for which they are ud.”3.USE OF REFERENCE STANDARDS
Reference standards
are employed in the identification,purity testing and assay of substances for pharmaceutical u and pharmaceutical preparations.Reference standards
are shown to
be suitable for their intended purpo;they are not necessarily suitable for other purpos.If a reference standard is to be
ud for any purpo other than that for which it has been
established,its suitability for the new u has to be fully demonstrated.Any value assigned to a reference standard is
valid for the intended u and not necessarily for other us.A European Pharmacopoeia reference standard with an assigned content/potency for u in the assay of a substance for pharmaceutical u may be suitable to determine the content of that substance in a pharmaceutical preparation where all the following conditions are fulfilled:
—the chromatographic assay method described in the active substance monograph is employed;
—the ur verifies the applicability of the method to the particular pharmaceutical preparation (abnce of
interference);
—any pre-treatment of the sample (action)is validated
for the particular pharmaceutical preparation;—the u is approved by the competent authority.
Reference standards are also established for the determination
of
the content of components of herbal drugs and herbal drug preparations.The may be:the active principles themlves;marker constituents ud for quantification;or extracts.
Reference standards consisting of extracts are established
using well-characterid samples of active principles or marker constituents.
It is the policy of the European Pharmacopoeia to supply
reference standards in adequate quantities for immediate u after opening of the container.U in other conditions is the responsibility of the analyst.If an unopened container is stored in the recommended conditions,it remains suitable for u as long as it is of the current batch.Information on current batch numbers is provided in the reference standards catalogue
available from the European Directorate for the Quality of Medicines &HealthCare (EDQM).Storage of solutions of reference standards is not recommended unless suitability has
been demonstrated by the ur.
Secondary
standards .A condary standard may be ud for routine quality control purpos for any of the us described
above for primary standards,provided that it is established with reference to the primary standard.A condary standard is established and employed to reduce the u of the primary
standard,which requires more extensive characterisation and
evaluation and may be available only in a limited quantity.
A condary standard is ud only for the same purpo as
the primary standard with reference to which it has been
established.
4.ESTABLISHMENT OF REFERENCE STANDARDS
4-1.PRIMARY STANDARD
A substance or preparation to be established as a primary
standard is characterid by a variety of analytical techniques
chon to demonstrate its suitability for u.
For substances for pharmaceutical u and their impurities,
relevant parts of the following test programme are usually
applied.
—Characterisation of the substance(structural elucidation)by
appropriate chemical attributes such as structural formula,
empirical formula and molecular weight.A number of
techniques may be ud including:
—nuclear magnetic resonance spectrometry;
—mass spectrometry;
—infrared spectrophotometry;
—elemental analysis.
—Determination of the purity:
清脆反义词—determination of the content of organic impurities by
an appropriate paration technique or spectrometric
method,where applicable;
—
quantitative determination of water;
—determination of the content of residual solvents;
—determination of loss on drying,which may in certain
circumstances replace the determinations of water and
residual solvents;
—determination of inorganic impurities(test for heavy
metals,sulfated ash,atomic spectrometry,inductively
coupled plasma spectrometry,X-ray fluorescence);the
results are not ud in determining an assigned content,
except where they would have an appreciable impact
upon it;
—
determination of the purity by an absolute
differential scanning calorimetry or pha solubility
analysis where appropriate;the results of the
determinations are ud to support and confirm the
results obtained from paration techniques;they are not
ud in the calculation of the assigned value).
For a primary chemical reference substance to be established
for assay purpos,the assigned content is generally calculated
from the values obtained from the analys performed for the
determination of impurities(organic,inorganic,water and
solvents)by applying the principle of mass balance;other
suitable methods are also ud.
An establishment report for the reference standard is prepared
and approved by the qualified person.
4-2.EUROPEAN PHARMACOPOEIA REFERENCE
STANDARDS
The candidate standards are tested against a wide variety of
analytical methods.The extent of testing and the number of
laboratories involved depends on the u of the reference
standard.Compliance with the relevant monograph is usually
required,unless otherwi justified.
Where a collaborative trial is carried out during establishment,
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a protocol is provided for each participant and only valid results
derived according to the protocol are ud for establishing an
assigned value or otherwi confirming suitability.
For chemical reference substances,relevant parts of the
following programme are typically applied.
4-2-1.Identification.In general,a batch lected from the
normal production of the substance is satisfactory.It is shown
to comply with the requirements of the monograph;full
structural elucidation is carried out for the first batch.
4-2-2.Related substances test.A reference standard
corresponding to an impurity is characterid for identity and
purity.Where a reference standard is ud to determine the
content of a given impurity,the preferred minimum content
is95.0per cent;where this is achieved no assigned value is
given,the content being considered as100.0per cent;this涠洲岛火山口
approximation is acceptable since there will be no appreciable
effect on the determination of impurities.When this minimum
content cannot be obtained,the standard has an assigned
content.
If an impurity is not available in a sufficient quantity to establish
a reference standard,a number of other options exist:
—preparation of a reference standard that contains a mixture
of the compound(s)and the impurity or impurities;
—preparation of a reference standard containing a mixture of
specified impurities.
Where such a mixture is also ud to determine the content of
a given impurity,the content of the impurity in the reference
standard is determined by appropriate paration methods and
a value assigned to the reference standard.
4-2-3.Assay
4-2-3-1.Chemical assay.When a reference standard is to be
ud for quantitative determination of an active substance or
an excipient(assay standard),the extent of testing is greater.
In general,veral collaborating laboratories examine the
propod substance,following a detailed protocol that describes
the procedures to be followed.The results obtained are ud to
assign a content.It is particularly important to quantify the
impurities if a lective assay is employed.In such a ca,it is
best to examine the propod substance by additional analytical
procedures that are scientifically justified,including,where
possible,absolute methods.
If a reference standard is required for a non-chromatographic as-
say lorimetry or ultraviolet spectrophotometry),
the relative reactivity or relative absorbance of the impurities
prent in a substance must be checked to ensure that they are
not markedly different from tho of the substance.
A protocol is prepared and must be strictly followed by the
participants of the collaborative trial to assign the content.The
protocol usually requires:
—determination of water(or loss on drying);
—estimation of the organic impurities(including residual
solvents when appropriate)using the prescribed paration
techniques;
—and possibly,determination of the content of the substance
by an absolute method;this would be a confirmatory
determination not necessarily performed by all participants
and the results would not be ud in the calculation of the
assigned value.
The protocol also indicates the system suitability tests and
acceptance criteria for each of the tests performed.
Unless otherwi stated,an assigned value is given for the
substance or preparation as prented in the container(‘as
is’),and the contents are not to be dried before u.For assay仍然的反义词
standards prepared by lyophilisation the content of the pure
substance is indicated in milligrams or International Units per
vial.
4-2-3-2.Microbiological assay.A reference standard for
the microbiological assay is first shown to comply with the
monograph.If the results are satisfactory a collaborative
microbiological assay is carried out,using the international
standard.The potency is expresd in International Units.If an
international standard does not exist,European Pharmacopoeia
Units are ud.The assigned potency is calculated from the
results of a collaborative trial.Various validity criteria are
applied including parallelism,linearity,and quadratic fit,推倒和
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according to the usual statistical procedures(5.3).The assigned
potency with the confidence limits is calculated from statistically
valid results.
4-2-3-3.Assay of components of herbal drugs and herbal drug preparations .
Reference standards ud in monographs of herbal drugs vary in the extent of testing depending on the type of reference standard.—An active
component
or marker constituent is characterid
and evaluated for identity and purity;a value for content is assigned irrespective of the purity.—An extract is ud as a reference standard when insufficient active principle or marker constituent is available.The assigned content of the extract is established by means of a collaborative trial using a well-characterid sample of the active principle or marker component for which a value is to be assigned.4-2-4.Establishment report .A report containing
the results
of the establishment study as well as information concerning the u of the reference standard is pre
pared.The report for a chemical assay standard has a value assigned to the substance with the rationale for attributing that value.The estimated uncertainty of the assigned value is calculated,and where it is less than a predefined
value,
which is considered to be
negligible in relation to the acceptance criteria for the assay,then the study is accepted.Otherwi,the trial may be repeated,in whole or in part,
or the limits
defined
for the
pharmaceutical substance may be widened.The uncertainty of the assigned value is not given as part of the information provided with the reference standard,since the precision of the method
and the uncertainty of the value attributed to the reference standard are taken into account when tting the limit(s)in a monograph.4-3.SECONDARY STANDARD A condary standard should exhibit the same property or properties as the primary
standard,relevant for the test(s)for
which it is established.The extent of testing is not so great as is required for the establishment of a primary standard.The condary
standard
is established
by comparison
with
the primary standard to which it is traceable.An official primary standard is ud wherever possible for establishment of condary standards.Identification —For u in infrared spectrophotometry:the absorbance bands correspond in position and relative size to the absorbance bands of the primary standard.—For u in paration techniques:the migration distance,migration time and retention time of the condary standard
are the same as tho of the primary standard for thin-layer chromatography or electrophoresis,capillary electrophoresis and gas or liquid chromatography respectively.Purity test .For u in paration techniques:as for identification but when ud for quantification,a content relative to the signal from the primary standard is to be established.Assay .Secondary standards are assayed against a primary standard with an assigned content or potency.The property for which a value is to be assigned for the condary standard is
similar in magnitude to that of the primary reference standard with which it is compared.Both the number of independent replicate determinations to be performed and the acceptance criteria to be applied are predefined.5.PRODUCTION,LABELLING,STORAGE AND DISTRIBUTION 5-1.PRODUCTION All operations are carried out according to the relevant norms of best practice to ensure the traceability and integrity of the reference standard.
The production record
includes information regarding filling,labelling and storage.Reference standards are dispend into containers under appropriate filling and closure conditions,to ensure the integrity of the reference
standard.The containers employed may be multi-u or single u,but the latter is preferred to minimi the risk of decomposition,contamination,or water uptake.5-2.LABELLING The labelling bears the name of the reference standard,the name of the supplier,the batch number,and any other
information
necessary to the proper u of the reference standard.If ud
as an assay standard the following information is also given:—the assigned percentage content;
—or,the content in milligrams or millilitres of the chemical entity in the container;—or,
the assigned potency (for biological assays or
microbiological assays)in units either per milligram or per vial.For
a manufacturer’s reference standard,the label indicates a
re-test or expiry date.For European Pharmacopoeia reference standards,no re-test or expiry date is given since the re-test
programme (e below)monitors continued fitness for u.
Leaflets
.An accompanying explanatory leaflet may also be provided giving information needed for correct u of the reference
standard.An explanatory leaflet is
considered as part of the labelling.Where stated in a monograph,a chromatogram is included in the leaflet.5-3.STORAGE AND DISTRIBUTION
Reference standards are to be stored and distributed in conditions suitable to ensure optimal stability.
European
Pharmacopoeia reference standards .European Pharmacopoeia reference
standards
are mostly stored in
temperature-controlled rooms at 5±3°C.However,a number
of reference standards that are relatively unstable are stored at
−
20
±
5°C or,in a few cas (e.g.live virus preparations),at −80±10°C,and for cell cultures,under liquid nitrogen
(−180°C).Special
packaging is employed to minimi the risk of damage during transport.
Reference
standards that are normally stored at 5±3°C
are dispatched by normal mail since short excursions from the long-term storage temperature are not deleterious to the reference standard.Reference standards stored at −20°C are packed on ice and dispatched by express courier.Reference standards
stored at −80°C or stored under liquid nitrogen are
packed on solid carbon dioxide and dispatched by express courier.6.RE-TEST PROGRAMME
A system is established and implemented to ensure the continued
fitness-for-u
of the reference
standards.
Normally,
早上祝福语
a re-test programme is applied,taking account of the known physico-chemical properties and stability data for the reference
standard.
Reference standards are periodically tested for stability during storage.A monitoring programme is applied that is designed to detect at an early stage any sign of decomposition using
appropriate
analytical
techniques.
The methods employed
should be chon from amongst tho performed during
establishment so that baline data are available.The
periodicity and extent of re-testing reference standards depends on a number of factors including:—电脑屏幕一直闪烁怎么解决
stability;
—container and closure system;
—storage conditions;
—hygroscopicity;
—physical form;
—intended u;
—prentation (single
u/multiple u).
Most reference standards are prented in powder form but
some are prepared as solutions.Preferably,reference standards
are prented as single-u units.However,if the standard
is prented in multi-u containers then re-testing may be more frequent for hygroscopic or oxygen-nsitive substances.The testing methods include the determination of water and
decomposition products (where known).The re-test period may be lengthened with the support of sufficient data.The
maximum permitted variation from the assigned value should be pre-defined,and if exceeded,the batch should be re-established or replaced.
European Pharmacopoeia reference standards.The monitoring programme of the EDQM includes a lection of the following tests,chon for their rapidity,nsitivity and applicability to small quantities:
—determination of water,loss on drying and/or
thermogravimetric analysis;—estimation of impurities by stability-indicating paration techniques;
—where appropriate,determination of the molar purity by differential scanning calorimetry;
—application of other specific tests for detecting impurities. Any significant differences obrved compared with the last examination will lead to more extensive examination of the batch and,if necessary,to the establishment of a replacement batch.
