Reproducibility intralaboratory

The infralaboratory calibration study was performed by the Institute for Environmental Studies. Sediment was extracted and cleaned up as indicated here. The determination of dioxin and/or dioxin-like content was according to the method indicated under the section DR CALUX analysis. For the intralaboratory study, the following parameters were investigated limit of detection (LOD), limit of quantitation (LOQ), and reproducibility and repeatability of the bioassay. 

Table 1 Intralaboratory repeatability and reproducibility of the dioxin response-chemically activated lucerferase (DR CALUX ) bioassay for sediment extracts 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) TEQ = toxic equivalent.

As with the determination of the intralaboratory repeatability, the intralaboratory reproducibility was determined by analyzing a cleaned sediment extract and a 3-pM 2,3,7,8TCDD standard on 10 separate days and by multiple persons. The reproducibility for the 3-pM 2,3,7,8-TCDD standard was found to be 13.8%, whereas the reproducibility for the cleaned sediment extraet was shown to be 19.9%. Since the observed reproducibilities are in the range of relative standard deviations for two sediment extracts analyzed in 10-fold on the same day (intralaboratory repeatability), the DR CALUX bioassay can be evaluated as a stable and robust bioanalytical tool. 

Precision measures are divided into (1) repeatability precision measures s or SD (sT or SDr) and RSD (RSDr), (2) intralaboratory reproducibility precision or intermediate-precision measures SD and RSD, and (3) interlaboratory reproducibility precision s or SD (sR or SDR) and RSD (RSDr) [66]. 

Any or all of these conditions can be varied. To provide some guidance, intralaboratory reproducibility is used to express changes only within a laboratory, and interlaboratory reproducibility" is used to refer to the changes that occur between laboratories, for example in proficiency testing, interlaboratory method validation studies, and the like. Interlaboratory reproducibility is usually two to three times the repeatability. 

Accurate temperature calibration using the ASTM temperature standards [131, 132] is common practice for DSC and DTA. Calibration of thermobalances is more cumbersome. The key to proper use of TGA is to recognise that the decomposition temperatures measured are procedural and dependent on both sample and instrument related parameters [30]. Considerable experimental control must be exercised at all stages of the technique to ensure adequate reproducibility on a comparative basis. For (intralaboratory) standardisation purposes it is absolutely required to respect and report a number of measurement variables. ICTA recommendations should be followed [133-135] and should accompany the TG record. During the course of experiments the optimum conditions should be standardised and maintained within a given series of samples. Affolter and coworkers [136] have described interlaboratory tests on thermal analysis of polymers. 

Table I lists the catalyst materials characterized and available for use as reference materials. For each property measured, the number of the ASTM Standard Test Method used in the determination is identified the material is specified the consensus mean value determined is listed the interlaboratory reproducibility and the intralaboratory repeatability from round robin tests are presented and the number of the ASTM research report describing the round robin data is listed. These round robins were conducted in accordance with ASTM E-691 -- Standard Practice for Conducting an Interlaboratorv Study to Determine the Precision of a Test Method.

Temperature is an important and often ignored parameter in method optimization. A lack of temperature control can result in poor inter- and intralaboratory reproducibility. Increased temperatures can speed up and alter separations and may improve efficiency and throughput, especially of macromolecules. High-temperature work using superheated water can eliminate organic solvents from the mobile phase, simplifying detection and solvent interferences in detection. At lower temperature the reduction in molecular motion can resolve interconverting chiral and structural analytes. 

Reproducibility is defined as the long-term variability of the measurement process, which may be determined for a method run, within a single laboratory, but on different days. Reproducibility also applies to a method, either run by different operators, different instruments, or a combination of the above. The reproducibility standard deviation is typically twofold to threefold larger than that for repeatability. Precision is often expressed relative to 1 day as intraday (within-day) precision or relative to a period of days, as interday (between days) precision. Reproducibility, in the sense of intralaboratory precision, is related to the procedure being performed at two or more laboratories as in, e.g., a collaborative study. 

The results of local tissue irritation tests are subject to considerable variability due to relatively small differences in test design or technique. Well and Scala arranged and reported on the best known of several intralaboratory studies to clearly establish this fact. Though the methods presented previously have proven to give reproducible results in the hands of the same technicians over a period of years and contain some internal controls (the positive and vehicle controls in the PDI) to minimize large variations in results or the occurrence of either false positives or negatives, it is still essential to be aware of those factors that may systematically alter test results. These factors are summarized as follows ... 

Precision studies can be performed under different conditions, and are strongly influenced by variables such as temperature, source and quality of reagents, reproducibility of reagent delivery, and instrumental noise. Therefore, if all precision studies are done in the same laboratory (intralaboratory study) higher precision is expected in comparison with interlaboratory studies, where several laboratories produce the data used to prepare the method precision profile. 

The revised version of this guide gives an approach for the use of CRMs. After having validated his method (see Chapter 2) with intralaboratory tools, the analyst analyses the CRM. He calculates the mean value X of at least five determinations, possibly ten. These determinations have to be fully independent. This means that he starts five or more times from a fresh test sample and does a new calibration of the instrument. If the same operator does the job, in a short period of time, it can be considered as having being done under repeatability conditions (r). Otherwise a reproducibility value is established (R). Having calculated the mean X and the standard deviation... 

For completeness it should be noted that intralaboratory reproducibility is sometimes used to refer to the standard deviation of measurement results obtained within the same laboratory, but perhaps by different analysts and/or different equipment and/or different days. 

As palaeoceanographic reconstructions based on bulk fossil chemistry proliferate, comparability of measurements between laboratories has become an important issue. A recent calibration exercise involving thirteen laboratories by Rosenthal et al. (2004) evaluated the reproducibility of analyses of synthetic standard solutions within and between laboratories. The study found that intralaboratory instrumental precisions were generally better than 0.5% for both Mg/Ca and Sr/Ca measurements, but interlahoratory precisions (r.s.d) were significantly worse (up to 3.4% and 1.8%, respectively). This could be a result of differences between cahbration standards used by laboratories, or because the circulated standard solutions had become contaminated in the interval between their... 

Reproducibility (ICH) Precision of repeated measurements between analytical laboratories also termed intralaboratory precision. 

Reproducibility precision is a standard deviation of a mean under conditions in which one or more aspects of the measurement system are changed. Interlaboratory reproducibility perforce changes the analyst, instrument, reagents, and so on. Intralaboratory reproducibility (sometimes known as intermediate... 

The use of CRMs for validation purposes is, however, not limited to the above intralaboratory verification of trueness (checking the absence of significant systematic errors). They also enable the user to estimate the precision of a method (repeatability and reproducibility), which should actually represent one of the first steps of the method validation. In this respect, the evaluation will have to take into account specific characteristics of the CRM, in particular, possible sources of uncertainties linked to the material heterogeneity which should in principle be considered for the calculation of the uncertainty of the certified values. 

Method that is implemented by different analysts on different instruments Precision - intralaboratory reproducibility, trueness, ruggedness Calibration, precision, (limits, recovery)... 

As mentioned in the introduction, this article is aimed at the practicing homogeneous catalysis chemists in academic, corporate, and national research laboratories, who perform small-scale bench-top organic synthesis. These scientists should be concerned that their experiments are reproducible, at both an intralaboratory as well as an interlaboratory level. As this article tried to emphasize that reproducible mass transfer is an integral component of obtaining reproducible rates, and more importantly of reproducible regio-, chemo-, and stereoselectivities. The main issues and conclusions of the article can be condensed into a succinct checklist. 

To a first approximation, good interlaboratory reproducibility of the pyrolysis profile is obtainable however, intralaboratory matchings have been disappointing. Several major parameters influence pyrolysis reproducibility ... 

SA Margolis, DL Duewer. Measurement of ascorbic acid in human plasma and serum stabihty, intralaboratory repeatability, and interlaboratory reproducibility. Clin Chem 42 1257-1262, 1996. 

However, the relative deviations for interlaboratory reproducibility sr are considerable, i.e. 26.6% (AO-1) and 12.3% (AO-2). These results (Table 6.23) show that the determination of antioxidants in polyolefins is not a trivial matter. For cases where the interlaboratory precision is much larger than the intralaboratory precision there is obviously lack of robustness of the analytical methods used. 

Fig. 6.2. Solvent extraction of NBR/DEHP films by 25 laboratories participating in a round-robin. Mean value 21.72% DEHP Sr rel. 0.97%, sr rel. 7.87%, Sr abs. 0.210, sr abs. 1.711 (cfr Table 6.24). Intralaboratory error bars are indicated. Outlier values beyond dotted (3a) lines. After Affolter et al [47]. Reproduced by permission of M. Schmid,...

Performs zero- and double-blind studies. Intralaboratory reproducibility (including ruggedness and robustness for real samples) should be demonstrated additional validation using an authentic standard reference material of the analyte in the sample matrix. Definition of criteria for revalidation. 

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