Quality control interlaboratory studies

Quality Control Interlaboratory Studies Reference Materials Clinical Applications. 

See also Quality Assurance Quality Control Interlaboratory Studies Reference Materials Production of Reference Materials Accreditation. 

CRMs are products of very high added value. Their production and certification are very costly and, therefore, these materials should not be used for routine quality control or external quality assurance (interlaboratory studies). In order to fulfil the needs related to these uses, noncertified RMs may be prepared, linking them to one or several CRMs as a means of evaluating the accuracy of the values assigned to the so-called secondary materials. This approach is straightforward in the case of calibrants (pure compovmds or calibrating solutions), but is more difficult in the case of matrix CRMs owing to the likely matrix differences. 

Maaskant j, Boekholt A, Jenks P and Rucinski R (1998) An international interlaboratory study for the production of a sewage sludge certified reference material for routine use in inorganic quality control. Fresenius J Anal Chem 360 406-409. 

Aspila et al. [338] reported the results of an interlaboratory quality control study in five laboratories on the electron capture gas chromatographic determination of ten chlorinated insecticides in standards and spiked and unspiked seawater samples (lindane, heptachlor, aldrin, 5-chlordane, a-chlordane, dield-rin, endrin, p, p -DDT, methoxychlor, and mirex). The methods of analyses used by these workers were not discussed, although it is mentioned that the methods were quite similar to those described in the water quality Branch Analytical Methods Manual [339]. Both hexane and benzene were used for the initial extraction of the water samples. 

The previous chapters of this book have discussed the many activities which laboratories undertake to help ensure the quality of the analytical results that are produced. There are many aspects of quality assurance and quality control that analysts carry out on a day-to-day basis to help them produce reliable results. Control charts are used to monitor method performance and identify when problems have arisen, and Certified Reference Materials are used to evaluate any bias in the results produced. These activities are sometimes referred to as internal quality control (IQC). In addition to all of these activities, it is extremely useful for laboratories to obtain an independent check of their performance and to be able to compare their performance with that of other laboratories carrying out similar types of analyses. This is achieved by taking part in interlaboratory studies. There are two main types of interlaboratory studies, namely proficiency testing (PT) schemes and collaborative studies (also known as collaborative trials). 

Briefly, to assure quality assurance and quality control, samples are analyzed using standard analytical procedures. A continuing program of analytical laboratory quality control verifies data quality and involves participation in interlaboratory crosschecks, and replicate sampling and analysis. When applicable, it is advisable, even insisted upon by the EPA, that analytical labs be certified to complete the analysis requested. However, in many cases, time constraints often do not allow for sufficient method validation. Many researchers have experienced the consequences of invalid methods and realized that the amount of time and resources required to solve problems discovered later exceeds what would have been expended initially if the validation studies had been performed properly. 

Maier, E A., Quevauviller, Ph, and Griepink, (1993), Interlaboratory studies as a tool for many purposes proficiency testing, learning exercises, quality control and certification of matrix materials. Analytica Chimica Acta, 283 (1), 590-99. 

The interlaboratory studies supported the beliet that, if a laboratory performs well with the methods using distilled water, it should be able to obtain good results with surface waters and industrial waste waters. On the basis of these studies, the multilaboratory regression equations for accuracy and single-analyst overall precision for distilled or reagent water have been incorporated into the quality assurance and quality control provisions of Methods 601, 602, 604-613, 624, and 625. These provisions will be discussed later. 

Interlaboratory Quality Control. In addition to the mandatory quality control practices just outlined, the laboratory is encouraged to participate in interlaboratory programs such as relevant performance evaluation (PE) studies, analysis of standard reference materials, and split sample analyses. Participation in interlaboratory analytical method validation studies is also encouraged. 

A high degree of motivation is required from laboratory staff to achieve a good quality control of chemical analysis. Participation in interlaboratory studies is... 

The motivation and dedication of the laboratories participating in the various interlaboratory studies and certifications organised by BCR represent one of the keys to the success of the projects with a clear impact on the improvement of quality control of speciation measurements. All project coordinators and participants in the projects are gratefully acknowledged and are listed in the RSC book on speciation (Quevauviller, 1998b). 

CRM for road dust (BCR-723) containing 81.3 2.5 Jg/kg Pt, 6.1 1.9 ig/ kg Pd, and 12.8 1.3 Jg/kg Rh, was introduced [49, 228]. It is widely used for quality control of results obtained in the analysis of environmental materials (e.g., airborne particulate matters, dusts, soils, and sediments). Comparison of results obtained using different analytical procedures and interlaboratory studies are recommended when there is a lack of suitable CRM (e.g., in examination of clinical samples). The use of standards based on real matrices (e.g., saliva, plasma, ultrafiltrates, and lung fluids) instead of synthetic solutions is recommended in such analyses. Difficulties with the identification and quantification of different metal species in examined samples make the reliability of results of great importance. The use of various instrumental techniques for examination of particular samples can be helpful. The application of chromatography, mass spectrometry, and electrochemistry [199] HPLC ICP MS and HPLC MS/MS [156] ESI MS and MALDI [162] micellar electrokinetic chromatography, NMR, and MS [167] AAS, ESI MS, and CD spectroscopy [179] SEC IC ICP MS and EC ESI MS [180] and NMR and HPLC [229] are examples of such approaches. 

Due to the high workload of analysing such large series, trueness is usually not determined during method validation, but rather from the results of a great number of quality control (QC) samples during routine application or in interlaboratory studies. 

The role and use of reference materials are in principle well known, in particular for Certified Reference Materials (CRMs) used as calibration materials or matrix materials representing - as far as possible - real matrices used for the verification of the measurement process, or (not certified) laboratory reference materials (LRMs also known as quality control (QC) materials) used, for example, in interlaboratory studies or in the maintenance of internal quality control (control charts). Examples of reference materials relevant to WFD monitoring (water, sediment and biota) are described in the literature (Quevauviller, 1994 Quevauviller and Maier, 1999). 

The programme to improve the quality control of organotin determinations in environmental matrices started in 1988 [9] by a consultation of European experts. It was decided to follow a stepwise approach for the evaluation of the performance of methods used in butyltin analyses. The overall programme consisted in a series of interlaboratory studies which started by an intercomparison on organotins in solutions followed by an intercomparison on a TBT-spiked sediment. 

Before participating in interlaboratory studies the laboratory must have set-up all adequate internal quality assurance and quality control systems [7]. This also means that all basic investigations have been performed for possible mistakes, that these have been noticed and corrected. In other words the laboratory has validated the method to be applied. For a laboratory performance study, this also implies that in the laboratory the method is under statistical control for a given type of matrix, that this control is monitored and that results are evaluated. 

When the matrix has been chosen with regards to the feasibility as discussed above and when the parameters to be measured are clearly defined, the collection and the preparation of the test material may start. All requirements of quality, except the certification of the content of certain substances, are valid for all type of reference materials used in interlaboratory studies. These detailed requirements, the preparation and control procedures should be available from the organiser in a production report. They are discussed in more detail in the chapter 4 dealing with (C)RM. 

To have a real impact on the quality of the laboratory performance the participation in interlaboratory performance studies should be done on a regular basis and should be an integral part of the laboratory quality assurance and quality control system. The common project of lUPAC/AOAC/ISO, leading to a harmonised protocol [3] gives several indications and recommendations on the organisation and evaluation of such interlaboratory studies. 

Baldi F, Bianchi M and Muntau H (1996) Interlaboratory study to improve the quality control of mcthylmercury determination in sediment. Appl Organomet Chem 10 537-544. 

Quality Control/Quality Assurance Interlaboratory comparison studies for arsenic and arsenic speciation in blood, urine and biological samples have been... 

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