Interlaboratory quality control

Booth E. Crofton P and Roberts LB (1974) The influence of standards on interlaboratory quality control programmes. Clin Chim Acta 55 367-375. 

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. 

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. 

Interlaboratory Comparison Program for trace elements in biological fluids includes Al in a serum (http //www.ctq.qc.ca), and they distribute samples six times per year. The Worldwide Interlaboratory Quality Control Aluminium program of the Centre Hos-pitalier Universitaire de Poitiers Hopital Jean Bernard distributes serums and dialysis fluids six times yearly (Guillard et al. 1988) (communication chu-poitiers.fr). 

OPs and CMs are used as pesticides, and some OPs are also potential warfare nerve agents. Pesticides are used worldwide, and warfare agcni.s may also be used extensively. To detect absorption of anticholinesterases, a standardized protocol for measuring AChE and BuChE activities in human blood is needed that is simple in technical terms but reliable and well reproducible. This would enable a better comparison of data from different laboratories and an exchange of samples for analysis and confirmation of results. It seems that a protocol based on the Ellman method would meet the outlined requirements, but further studies including interlaboratory quality control are required, particularly when field methods are developed. 

There are other routinely practiced procedures in terms of intralaboratory and interlaboratory quality control, such as the control chart, round-robin interlaboratory testing, and various proficiency tests offered by different agencies, such as the PATs (Proficiency Analytical Testing) by AHA in the US and WASPs (Workplace Analysis Scheme for Proficiency) by the Health and Safety Laboratory in Great Britain. In normal circumstances, a combination of these quality control measures should be used in performing workplace air analysis. 

Interlaboratory quality control studies are designed to determine the degree of compatibility of the data generated by participating laboratories. Furthermore, such studies help to determine interlaboratory precision and accuracy and to standardize analytical methodology. They also provide valuable data for the certification of standard reference materials. 

A well-designed multisample interlaboratory quality control program provides ... 

It must be remarked that terminology is not consistent and there are many widely used synon)ms. Quality control in this Chapter refers to practices best described as internal quality control. Quahty assessment is often referred to as external quality control, proficiency testing, interlaboratory comparisons, round robins or other terms. Internal Quality Control and External Quality Assessment are preferred because they best describe the objectives for which the RMs are being used, i.e. the immediate and active control of the results being reported from an analytical run or event, and an objective, retrospective assessment of the quality of those results. 

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. 

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). 

Quality control, however, needs more attention. For example, it has been reported that much of the chemical data produced by the International Indian Ocean Expedition is unusable because of doubts about its accuracy. Such reports are a perennial source of confusion in marine chemistry. Better calibration, universal standards, and interlaboratory comparison are essential if we are to continue our present field methods, in which independent investigators make measurements that are presumably comparable (NRC, 1971, pp. 54-55). 

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. 

Youden, W.J. (1959), Graphical Diagnosis of Interlaboratory Test Results, Industrial Quality Control, 15(11), 24,... 

Interlaboratory tests are a powerful tool for external quality control (see chapter 15). A laboratory should take part wherever possible. The participation has to be planned. The results and if necessary the corrective actions have to be documented. Procedures have to be accordingly described in the quality manual. 

Procedures carried out in the laboratory, as opposed to proficiency testing or other interlaboratory collaborations, are known as in-house or internal quality control procedures. When running batches of samples with calibration solutions and unknowns, there are a number of extra samples that can be analyzed that cover different aspects of quality control (QC samples). These QC samples should be documented in the quality manual and be part... 

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. 

What would the resulting Youden plots look like if the method was rugged If the method was not rugged If the laboratories were precise, but each was biased If the laboratories were imprecise, but accurate [See, for example, Youden, W.J. (1959). Graphical Diagnosis of Interlaboratory Test Results , Industrial Quality Control, 24(May), p. 24.]... 

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). 

Quevauviller, Ph., Wang, Y., Turnbull, A.B., Dirkx, W.M.R., Harrison, R.M. and Adams, F.C. (1995b) Interlaboratory programme for the quality control of trimethyllead determination in the environment. Appl. Organometal. Chem., 9, 89. 

The ISO/IEC GUIDE 25 [1] stresses, in paragraphs 5.6 and 9.3, the importance of participation in proficiency testing programs or other interlaboratory comparisons, as appropriate and when suitable programs are available. This would imply that such activities are an important part of a laboratory s quality control procedures. 

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