Interlaboratory studies

Nilsson, T, Ferrari, R., and Facchetti, S., Interlaboratory Studies for the Validation of Solid-phase Mieroextraction for the Quantitative Analysis of Volatile Organic Compounds in Aqueous Samples, Anu/yrica Chimica Acta 356, 1997, 113-123. 

An interlaboratory study using mixed vegetable reference material showed average relative standard deviations (RSDs) of 23% ranging from 11% for lutein and a-carotene to 40% for lycopene." Triplicate HPLC injections of the same extract showed RSD values of 0% for P-carotene and 6.8% for lutein. ... 

Scott, K. et al.. Interlaboratory studies of HPLC procedures for the analysis of carotenoids in foods. Food Chem., 57, 85, 1996. 

Takacs-Novak, K., Avdeef, A. Interlaboratory study of log P determination by shake-flask and potentiometric methods. J. Pharm. 

Qubvauviller Ph and Maier EA 1999), Interlaboratory Studies and Certified Reference Materials for Environmental Analysis. Elsevier Publishers B.V., Amsterdam. 

Value assignment based on selected data from interlaboratory studies... 

Fig. 3.4 Results from the interlaboratory study used for certification of benzo[b]fluoranthene in BCR CRM 088 Sewage Sludge...

DE VooGT P, HinschbergerJ, Maier EA, Griepink B, Muntau H, and Jacob J (1996) Improvements in the determination of eight polycydic aromatic hydrocarbons through a stepwise interlaboratory study approach. Fresenius J Anal Chem 356 41-48. 

Quevauviller Ph, and Maier EA (1999) Interlaboratory studies and certified reference materials for environmental analysis - the BCR approach. Elsevier, Amsterdam Quevauviller Ph, Drabaek I, Muntau H, Biahchi M, Bortoli A, and Griepink B (1996a) Certified reference materials (CRMs 463 and 464) for the quafity control of total and methyl mercury determination in tuna fish. Trends Anal Chem 15 160-167. 

DE Boer J (1997) The preparation of biological reference materials for use in interlaboratory studies on the analysis of chlorobiphenyls, organochlorine pesticides and trace metals. Mar Poll Bull 35 84-92. 

DE Boer J, van der Meer J, Brinkman UATh (1996) Determination of chlorobiphenyls in seal blubber, marine sediment, and fish interlaboratory study. ( Assoc Off Anal Chem 79 83-96. 

Tuinstea LGMTh, Roos AH, Werdmuller WA (1985) Capillary gas chromatographic determination of some chlorobiphenyls in eel fat interlaboratory study. J Assoc OffAnal Chem 68 756-759. 

Fig- 5-7 Results (lU/mg) of an interlaboratory study to determinate the potency of tylosin CRS 1 by microbiological assay (diffusion method). 

The enormous difference in certified values between methods and between analytes illustrates well how much care is needed in matrix/method matching. Further evidence of the importance of matrix matching is provided by an interlaboratory study on trace elements in soil reported by Maier et al. (1983) and the certification of a sewage sludge described by Maaskant et al. (1998). 

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. 

Bugner, E. and Feinberg, M. (1992). Determination of mono and disaccharides in foods by interlaboratory study Quantitation of bias components for liquid chromatography. /. Assoc. Ojfic. Anal. Chem. 75,443-464. 

Sakai, S., Adachi, R., Akiyama, H., Teshima, R., Doi, H., and Shibata, H. (2010a). Determination of walnut protein in processed foods by enzyme-linked immunosorbent assay interlaboratory study. /. AOAC Int. 93,1255-1261. 

Sonication of polychlorinated biphenyls (PCBs) from soils has been the subject of an interlaboratory study [196] with 129 participants. Two standard methods of extraction were evaluated EPA method 3540 for Soxhlet extraction and EPA method 3550 for sonication... 

It is not uncommon that extraction techniques are unfairly compared. Appropriate interlaboratory studies are few. Soxhlet and sonication extraction (EPA methods 3540 and 3550, respectively) were compared in an interlaboratory study (129 participants) for PCBs in soil. Results from laboratories using Soxhlet extraction were significantly more accurate than those obtained using sonication, especially at higher concentrations, but with equal precision [196]. This is rationalised by the observation that the Soxhlet procedure presents the sample with fresh solvent so that the extraction solvent is never saturated, unlike the sonication procedure. Sonication is very sensitive to the solvent polarity, nonpolar solvents producing considerably less accurate results than polar solvents. It is not as sensitive to clean-up procedures as... 

On the other hand, reproducibility is the closeness of the agreement between the results of measurements of the same measurand carried out under changed conditions of measurement . The changed conditions include principle of measurement, method of measurement, observer, measuring instrument, reference standards, location, conditions of use, and time. Such variable conditions are typical for interlaboratory studies (laboratory intercomparisons). 

Only in a few cases was there a distinction made between both concepts by their use in intra laboratory studies (robustness) and interlaboratory studies (ruggedness) see USP 23-NF18 [1995] USP 24-NF19 [2000] Rodriguez et al. [1998] Zeaiter et al. [2004]. Wahlich and Carr [1990] seem to be the first to use robustness and ruggedness in a hierarchical sense but in a reverse meaning as given above. 

Analytical laboratories need to check their performance with regard to the production of accurate results with satisfactory precision. The most desirable way to ensure the reliability of analytical results is the participation of laboratories into regular interlaboratory tests. An interlaboratory study has to be understood as a study in which several laboratories measure a quantity in one or more identical portions of homogeneous, stable materials under documented conditions, the result of which are compiled into a single document (IUPAC [1994] Prichard et al. [2001]). 

There are several types of interlaboratory studies (Horwitz [1994]) ... 

In general, the evaluation of interlaboratory studies can be carried out in various ways (Danzer et al. [1991]). Apart from z-scores, multivariate data analysis (nonlinear mapping, principal component analysis) and information theory (see Sect. 9.2) have been applied. 

Evaluation of data and validation multivariate data analysis (MULTI-VAR, Wienke et al. [1991]), evaluation of interlaboratory studies (INTERLAB, Wienke et al. [1991]), ruggedness expert system (RES, van Leeuwen et al. [1991]). 

The Kerridge-Bongard model of information is of great importance in quality assurance, in particular for the assessment of interlaboratory studies. Examples of the information-theoretical evaluation of analytical results within the context of interlaboratory comparisons have been given by Danzer et al. [1987, 2001], Wienke et al. [1991] and Danzer [1993]. 

Danzer K (1993) Information content of an analytical result and its assessment by interlaboratory studies. IDF Special Issue 9302 Analytical quality assurance and good laboratory practice in dairy laboratories. IDF, Brussels... 

Ruggedness can be determined by an interlaboratory study with a sufficient in > 8) participating laboratories following one and the same procedure as performed by different analysts, and using operational and environmental conditions that may differ but are still within the specified parameters of the assay [1, 41]. Detailed guidance for robustness and ruggedness testing is available [42, 43],... 

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). 

These two different types of interlaboratory study are discussed in detail in the following sections. 

Jemmali M, Ueno Y, Ishii K, Frayssinet C, Etienne M (1978) Natural occurrence of trichothecenes, nivalenol, deoxynivalenol, T-2 toxin and zearalenone in corn. Experientia 34 1333-1334 Josephs RD, Schuhmacher R, Krska R (2001) International interlaboratory study for the determination of the Fusarium mycotoxins zearalenone and deoxynivalenol in agricultural commodities. Food Addit Contam 18 417-430... 

A mass accuracy better than 1 ppm is routinely obtained by the better instruments when they are operated in a peak matching mode. An interlaboratory study of mass accuracy of different instruments and operating modes can be found in Reference 231. 

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