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Frequently asked questions

Below you find the most frequently asked questions and answers on the use of the webshop. Click on the question to see the answer or hide it again. For general questions on CRMs and application notes, please visit our user support page. In case you have any other question you may contact us.

General: What is a CRM?
In a nutshell, a certified reference material (CRM) is a material which is used for method development, method validation, in particular to check for method bias, or for calibration. The formal answer - as defined in the Vocabulary of Metrology – is: a CRM is a reference material, accompanied by a certificate, one or more of whose property values are certified by a procedure which establishes traceability to an accurate realisation of the unit in which the property values are expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence.
General: What is the difference between CRM, RM, SRM, ERM?
Reference material (RM) is the generic term for a group of either pure substances or matrix materials, which are used for calibration, method validation, the establishment of metrological traceability, method development, and various quality control purposes (proficiency testing, charting, etc). If the reference material fulfils a number of requirements (proven homogeneity and stability, characterisation of the property values using suitable, well-described and validated methods) this information may be summed up in a certificate, thus being a certified reference material (CRM).

SRM® is a trademark registered by the US National Institute for Standards and Technology (NIST) for the certified reference materials they produce and stands for Standard Reference Material.

Any ERM® is a CRM carrying the trademark of the European Communities for CRMs produced by partners of the European Reference Material (ERM) co-operation and fulfilling stringent quality criteria.
General: Are CRMs generally produced under an accreditation scheme?
The appropriate standard for the production of reference materials is ISO Guide 34 “General quality requirements for the production of reference materials”, but it is understood that measurements must comply with the provisions of ISO 17025. There are only very few reference material producers accredited to ISO Guide 34 yet. We were the first organisation in Europe to achieve accreditation to ISO Guide 34 for the production of CRMs.
General: What does the CRM uncertainty mean?
The uncertainty indicates the range where the “true” property value can be expected with a stated probability. This information can be used directly, if the material is used for calibration. When the material is used to estimate method bias, the uncertainty range for the result obtained in the laboratory of the user should overlap with the uncertainty range given on the certificate. If this is true, the method applied by the user for determining the property is unbiased. The CRM user should take care to compare only equivalent statistical parameters, i.e. for instance confidence intervals (and not the SD from a measurement with expanded uncertainties from a certificate).
General: What does traceability mean for CRMs?
The Vocabulary of Metrology defines traceability as a property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties. In more practical terms this means to anchor the results to standards which do not change over time and place in order to make measurement results comparable. Consequently, the certified value(s) of a CRM shall be traceable to such internationally accepted standards, preferably to the International System of Units (SI). Use of a CRM is a convenient way to demonstrate traceability.
General: Why do certified values and uncertainties of replacement batches differ from the first released batch of a CRM?
Replacement batches are usually produced from different raw materials than the first batch of a CRM. Therefore, they do not have the same property values (analyte content etc.). Although we try to match the first batch, this is sometimes impossible or even not desirable: changes in the analyte content routinely encountered in the laboratory should be reflected by changes in the concentration levels of the CRM.
General: What is the difference between net and gross mass?
Net mass is the mass of the product in the unit. Gross mass is the mass of the content plus the mass of the packaging (vial, box etc). For example, an ampoule (mass 10 g) contains 1 mL water. Net mass = 1 g; gross mass = 11 g
Documentation: What is the difference between certified, indicative and information values?
Certified values are values that fulfil the highest standards of accuracy. Uncertainty and metrological traceability is clearly defined and they can be used as a metrological reference, for example in calibration, validation and bias tests.
Indicative values are values where either the uncertainty is deemed too large or where too few independent datasets are available to allow certification and are therefore less reliable than certified values. Great caution should be used when using these values.
Additional material information are values that were obtained in the course of the study. They are usually derived from single measurements only and are stated without an uncertainty and give merely information about other material properties that may be of interest for the user.
Documentation: What is the purpose of the certification reports?
We believe that transparency is important to ensure trust in our CRMs. For this reasons, we publish detailed certification reports for all CRMs. These reports contain details of the production process, describe how stability and homogeneity was assessed and how the certified values were designed. They also give information on the methods used and potential problems encountered by the participants in the production process and are therefore a very useful source of information for method development and error diagnostics. While these reports contain many data, the only official values are the certified values stated on the certificate.
Documentation: Where can I get additional information on my material?
We publish for each material an extensive report available on this web site. This report gives valuable information on methods used by the participants and potential problems besides giving more detailed information on the production of the material.
Order process: Why do you only confirm receipt of the order, but not the order itself?
Some of our CRMs require special export permits, because they are dual-use goods or covered by other export or import restrictions. As we cannot guarantee that we will get the necessary permits from the Belgian/Flemish authorities, we can only confirm receipt, but not execution of an order.

Please check the detailed product sheet.A comment is added if such restrictions apply. Please do not pay such orders by credit card: we will first obtain the permit and then, when we are sure that we can execute the order, ask for prepayment (if applicable).

Order process: What are the special export documents mentioned for some CRMs?
Some of our materials are classified as dual-use goods according to Council Regulation 428/2009/EC, are classified under the chemical weapons convention or are radioactive. In this case we may have to ask the Belgian authorities for an export licence. Although this licence is usually granted, it is not guaranteed. We therefore ask not to prepay such items so that in case the licence is not granted, we do not have to refund the payment.
Order process: Why do some CRMs have the comment "Please do not pay by credit card"
There are two reasons for this comment: a) The material requires special export documents (see question on special export documents). In this case we ask not to prepay as it is not entirely sure that an export licence is granted. b) Some materials require shipment on dry ice or are classified as dangerous goods for transport. For some countries, the standard courier services do not accept dry ice/dangerous goods. In these cases we have to find alternative carriers, which may be more expensive. Please contact us before ordering to see whether this applies to your shipment.
Order process: What is the significance of the comment "Animal by-product category ..."
According to regulation 1069/2009/EC, all products derived from animals that are not intended for human consumption are animal by-products. Although this legislation is mainly intended for waste from slaughterhouses, also CRMs that are made from material fit for human consumption are, as the CRMs are not intended for human consumption, animal by-products according to this legislation. The category of such materials must be stated on the transport documents. There are no other obligations connected with this classification for our CRMs.
Order process: What is the significance of the comment "Export and transit control according Regul. 428/2009/EC"
Materials with such a description are classified as dual-use goods according to regulation 428/2009/EC, i.e. are goods that can potentially be used for military purposes (an example is ERM-AC059). There are no restrictions for shipment within the EU, but export to countries outside the EU requires a permit. For this reason, classification of a product under the regulation has to be mentioned on the transport documents.
Order process: Why are some products only available from authorised distributors?
Some products carry the comment "Only available at authorised distributors". These materials are close to exhaustion and only some authorised distributors still have samples on their consignment stock. It is therefore not possible to order these products online from us. In these cases, please contact our authorised distributors to see, who of them still has samples.
Order process: What means "cooled shipment by courier"
A test for suitable dispatch conditions is a part of the production process for all of our materials. If no change is observed after 4 weeks at 40-60 °C, shipment can proceed without special precautions. In other cases, cooled dispatch is needed. This means that we ship with cooling elements ("wet ice") if the transport is not longer than one day, otherwise we ship on dry ice.
Order process: Can I purchase bulk volumes of CRMs?
We do not sell bulk volumes of reference materials, but rather individually labelled samples (‘units’) of CRMs.
Stability: What does the shelf life mean?
Producers of reference materials guarantee within a specified time (=shelf life) the integrity of the material and the validity of the certificate accompanying the material, provided the sample is properly transported and stored. Furthermore, most producers guarantee this only for the material in an unopened container. In other words, once the original material container is opened material integrity can no longer be guaranteed. This does not automatically mean that the user has to throw away the unused sample. Normally, the material will remain stable when stored under suitable conditions (which are described on the certificate), but the producer cannot take responsibility for them any longer.
Stability: Do I have to throw my material away after the expiry date?
Producers of reference materials guarantee within a specified time (=shelf life) the integrity of the material and the validity of the certificate accompanying the material, provided the sample is properly transported and stored. Furthermore, most producers guarantee this only for the unopened container. In other words, once the original material container is opened material integrity can no longer be guaranteed. This does not automatically mean that the user has to throw away the unused sample, but it only means that the producer can simply not guarantee stability forever. For more information see ERM Application Note 7
Stability: How long can I store my material?
CRMs should be used completely as soon as possible after receipt, because the producers cannot guarantee the stability of materials when stored outside their premises. If stored under the same condition as at the JRC, the materials can in principle be stored until the end of their shelf life, but beware: if some stability problems are discovered, we will contact customers only down to a certain date.
Stability: What should I do with opened CRM containers?
Materials from opened containers should be used completely as soon as possible after opening. Producers usually have no information about the stability of material in open containers stored in the customer laboratory, which is why they cannot guarantee the correctness of the certified value after longer periods of opened storage. It is up to the judgement of the analyst whether a certain material will or will not change after opening of the container. For more information see ERM Application Note 6
Use: How much of the material do I need?
The amount of material needed depends on the analytical method used. But it should be always at least the minimum sample intake stated on the certificate (otherwise the homogeneity is not guaranteed).
Use: What does the minimum sample intake mean?
The value stated on the certificate refers to the average analyte content of one unit of a reference material. All reference materials (with the exception of homogeneous solutions and gases) are intrinsically heterogeneous but sufficiently large sample intakes eliminate the effect of this heterogeneity. The minimum sample intake is the minimum amount of material that is still representative for the average of the bottle. If the sample intake is less, differences between the analytical portions significantly influence the variability of the results. Therefore, producers cannot guarantee the certified value for individual subsamples if these subsamples are smaller than the minimum sample intake stated on the certificate.
Use: How should I correct for moisture and water content?
The method for water and moisture correction specified on the certificate must be followed, because different methods may give different results. Naturally, the moisture content is determined on a separate subsample than the one used for analysis.
Use: How do I know whether the certified value is valid for my method?
There are two CRM properties that describe the usefulness of a material for a certain method, namely traceability and commutability. Traceability describes what the certified value actually refers to including the definition of the measurand: is it about total or extractable element content, Kjeldahl or Dumans N? Commutability describes whether a material behaves similarly as a certain routine sample for a given method. Therefore, one should check whether the certified value of a CRM is traceable to the same reference as one’s method. If this is not the case, the material is unsuitable. Example: Certified values for dietary fibre traceable to a certain ISO method are only valid, if exactly this method is used. Additionally, one should check whether commutability is ensured. If this is not the case, the material may be unsuitable.
Use: Which value do I use for calibration?
The value mentioned on the certificate is the certified value for the reference material and consequently the value to be used for calibration. But the uncertainty of the certified value has also to be included for the estimation of the measurement uncertainty.
Use: How do I compare my result with the certified values?
The underlying principle is that one has to check whether the difference between the measured result and the certified value is larger than the expanded combined uncertainty of measurement and certified value. This is described in detail in ERM Application Note 1
GMO CRMs: Are the GMO CRMs of the JRC checked for the presence/absence of other GM events than the one certified?
The GMO CRMs are gravimetric mixtures of pure GM and non-GM powders certified for a specific GM event as mass fraction (g/kg). IRMM verifies the purity of the two raw materials used for production with respect to the presence of the particular GM event that is certified. The CRMs are not certified for the absence or adventitious presence of other (contaminating) GM events.
GMO CRMs: Do you provide instructions how to perform PCR?
Event-specific detection methods submitted under the provision of Art. 47 of Regulation EC 1829/2003 and their validation reports are accessible on the web site of the EURL for GM food and feed (EURL-GMFF) under the section "Status of dossiers". Detection methods used during the certification of a GMO reference material are listed in the certification report.
GMO CRMs: Which DNA extraction method should I use?
Reliable results can only be guaranteed if an extraction method validated in a collaborative trial is used. Some extraction methods and their validation reports are accessible on the web site of the EURL for GM food and feed under the section "Status of dossiers".
GMO CRMs: Is the sequence information for GM varieties publicly available?
The sequence information is usually patented by the producer and can in some cases be retrieved from the patent application. The sequence information itself is confidential and therefore not always accessible, whereas the primer and probe sequences targeted by the event-specific detection methods provided according to Art. 47 of Regulation EC 1829/2003 are accessible on the web site of the EURL for GM food and feed under the section "Methods database".
GMO CRMs: Can I purchase 100% GMO CRMs?
We only produce for selected GMO events a pure certified GMO reference material (nominal 100%). However, such materials may be available from other organisations or the intellectual property owner of the GMO event.
GMO CRMs: Can I use the GMO CRMs to calibrate my ELISA measurements?
GMO reference materials from us can be used as calibrants for DNA-based and protein-based methods. You should set-up a calibration with a reference material (calibrant) with known GM concentrations in order to be able to translate your test result into GM% m/m (mass fraction).
GMO CRMs: How to calculate the measurement uncertainty of PCR measurements?
In the Guidance Document on Measurement Uncertainty for GMO Testing Laboratories two selected approaches for the estimation of measurement uncertainty are proposed. The first approach presented in detail is using data from collaborative trial in combination with in-house quality control data. In case no suitable collaborative trial data are available, an alternative approach, using data obtained on within-laboratory samples, is presented.
ERM: What is an ERM® -branded material?
An ERM is a CRM with the added value that very stringent quality criteria regarding production, homogeneity and stability testing, and of course characterisation measurements, have to be fulfilled.
ERM: Are ERM® materials only for Europeans?
No. ERM-CRMs are suitable for any user who requires reference materials of the highest level of assurance. ERM® materials are available from a number of reference material distributors who make them available worldwide.
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