In-house reference materials

Do you use In-House Reference Materials (IHRM) and how are they obtained For example, specify the concentration(s) matrix type(s). 

After this the trainee nses the method nnder supervision with material analysed before, e.g. in-house reference material. Can he achieve the performance stated in the method He has to learn to think ahead, making sure that all material/solutions are ready when required. 

Reference Materials or other materials of suitable purity and stabihty. In-house reference materials may be prepared from typical, well-characterized materials checked in-house for stability and retained for in-house (Quality Control. 

CRMs would be the ideal control samples, but they normally are too expensive and very often not available. In-house reference materials that are regularly checked against a CRM under repeatability conditions are a good alternative. 

If retained sample material from an interlaboratory test is available and it is stable after the test is finished, this also can be used as an in-house reference material. 

The samples that are used for proficiency tests should be similar to routine samples in order to get an information about the routine capabilities of the laboratory. In some cases it is useful to distribute a larger amount of sample than is needed for the determination, to give the laboratories the opportunity to use this material as an in-house reference material. But the surplus can be also used to cany out more analyses compared to routine, which is not desired. 

Traceable property values of in-house reference materials... 

Abstract The traceability of in-house reference materials (IHRM) is discussed. It is shown that a systematic error in results of a measured value, specific to a measurement method or to a laboratory developing an IHRM, can be overcome if a comparative approach to IHRM characterization is used. 

More than 220 producers of CRMs throughout the world produce today 12,000 20,000 materials with dif ferent matrixes, analytes and properties [4]. However, many testing (analytical) laboratories cannot find suitable CRMs in the market and develop in-house reference materials (IHRMs) themselves. Often IHRMs are developed in a laboratory to conserve the corresponding expensive CRMs. For example, a pharmaceutical company Chemagis Ltd. produces 30 active pharmaceutical ingredients steroids, benzodiazepines, antihistamines, hipolipidaemics, blood flow reactants, etc. Only for a few of them Mo-metasone Furoate, Fluticasone Propionate and Dobutamine Hydrochloride are of fi-cial reference standards for assay supplied by US, British and European Pharmacopoeias with prices of about 180 per unit (50 200 mg). Thus, to support its customers Chemagis is forced to develop IHRMs for assay as well as for impurities and related substances of each produced compound. Therefore, certification of such IHRMs that leads to traceable values is very important. 

Precision of the analysis was calculated using three in-house replicates, and two blind duplicates submitted by the authors. Accuracy was determined using ACME s in-house reference material, DS2 (HMTRI, 1997) (Table 16.1). 

Another important use of CRMs is for the validation of in-house reference materials. Since CRMs are fairly expensive and perhaps not as specific as necessary for certain analysis, it would be cost-effective to prepare in-house reference materials when possible. By analyzing a specific sample (that is homogenous and available in a reasonably large quantity) along with a similar CRM, traceability of the found value is established to the certified value. Then this in-house material can be used as a complement to the CRM. A recently published procedure describes how to get the most complete information out of CRMs [16]. 

Certified reference material (CRM) In-house reference material Matrix reference material... 

An in-house reference material is an RM prepared by an organisation solely for its own internal purposes. The values for this material may have been obtained by comparison with a CRM. 

The case presented here is simple because all six samples can be analysed as one set of samples in one analytical run. For a single run the estimation of uncertainty can be reduced to the calibration of the method with an in-house reference material and the uncertainty of the analysis itself. In this example inhomogeneity of the sample, the evaluation uncertainty and the uncertainty of the reference material (i.e. inhomogeneity) as given in Table 1 can be neglected because the results of only one analysis are compared. The weighing uncertainties can be neglected because they are small compared to the sampler uncertainty. 

Various types of control charts, a tool that is most often used for internal quality control purposes, are often based on values given by reference materials. For this purpose, in-house reference materials should be preferably used, as certified reference materials are too expensive to be used to monitor the stability of the measurement process. 

The results of biological assays should be expressed in units of activity calibrated against an international or national reference standard, when available and appropriate for the assay utilized. Where no such reference standard exists, a characterized in-house reference material should be established and assay results of production lots should be reported as in-house units. 

FIGURE 6.5 Reference materials differences in immunoreactive signal observed in an ELISA. Circles standard prepared from a concentrated stock from the commercial supplier. Squares standards prepared from a concentrated stock from in house reference material. Triangles standards prepared from a kit. 

Every analytical laboratory should have its own reference materials for internal quality assurance, and such materials should conform to the same standards of appropriateness, homogeneity and long term stability as are required for certified reference materials (see section "preparation of reference materials). In practice, however, most analytical laboratories do not use their own "in-house" reference materials for internal quality assurance but rather rely on internationally available reference materials. In the opinion of the present author, this is undesirable since much larger amounts are required for internal quality assurance than for externai quality assurance, and thereby the available stocks of expensively prepared certified reference materials will be consumed much too quickly. 

Reference materials which are prepared for in-house control by the laboratories are often referred to as laboratory reference materials (LRMs) or in-house reference materials (HRMs). 

Run secondary in-house reference materials (control samples) in order to further check on recovery. Due to the limited supply and high cost of CRMs, in-house reference standards (control samples) should be used. They are also useful in the preparation of quality control charts . 

Table 19.2 contains the results of niacin determinations performed in MRM mode for some grain-based food materials, including appropriate reference materials, and compares them to expected levels. For the commercial food materials, expected values are as listed on the packaging. The US National Institute of Standards and Technology (NIST) does not provide a reference value for niacin for RM 8437 however, there have been determinations of its niacin value reported in the literature (LaCroix et al. 1999 Tanner et al. 1988). The expected value for RM25C, an in-house reference material used by an analytical testing and consulting laboratory, was provided by the producer. 

D. Rizkov, O. Lev, J. Gun, B. Anisimov, and 1. Kuselman. Development of in-house reference materials for determination of inorganic polysulfide in water. Accredit. Qual. Assur., 9, 399-403, 2004. 

Characterisation of method performance involves a judgement as to whether the capabilities of the new method are sufficient to meet the needs of the end user (this is also known as method validation). Various options exist for characterisation of method performance. The trueness of a new method could be assessed against that of established methods, repeatability could be assessed using reference materials, and reproducibility through interlaboratory comparisons. In R D, many of these options may not readily be available. Validation tools may be limited to the use of in-house reference materials. 

At the different level of in-house reference materials, Nagourney et al. [60a] have described the practical case of Witco s approach for obtaining or preparing materials to be used in quality assurance of metals (Ba, Zn, Cd) in vinyl stabilisers (i) purchase of commercially available organometallic reference solutions, traceable to certified standard solutions (EMPA/BAM or NIST) [60b] (ii) solubilisation of salts of known stoichiometry in small quantities of acid and 2-butoxyethanol, thereby obtaining a solution with a known quantity of metal or (Hi) utilisation of well-characterised in-house materials (either intermediates of finished products) as QA reference materials. Also other authors have shown that suitable polymer reference materials can be produced relatively easily at the laboratory level [61],... 

As part of the quality control programme and to support accreditation according to the EN lEC/ISO 17025 2005 [6], each batch of samples should contain a reference material to validate the results. As there are currently no suitable and traceable certified reference materials available, several in-house reference materials (RMs) were developed. One iron ore and one sinter dust were selected to be developed as RMs for the alpha spectrometry method and the same sinter dust along with a blast furnace dust were selected for the gamma spectrometry method. When analysing stack emission samples, one blank filter was spiked with a known amount of a certified Pb standard solution (R22-02, National Physical Laboratory, UK) and used as a reference for result validation. 

Bulk chemical composition of in-house reference materials (RMs) and associated mass attenuation coefficients... 

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