Spiking studies

This automated procedure was estimated to have a precision of 0.13-0.21mg Hg kg-1 at the lmg Hg kgr1 level with standard deviations varying from 0.011-0.02mg Hg kg-1, i.e. relative standard deviations of 8.4-12% at the 17.2-32.3mg Hg kg-1 level in sediments. Recoveries in methyl mercuric chloride spiking studies were between 85 and 125%. The detection limit for the automated method is dependent upon the weight of sample taken for analysis. It is 0.1 pg Hg L 1 in the aqueous samples. The results for the automated method are routinely reported to a lower limit of O.lmg kg 1 which corresponds to a dry sample weight of 0.25g. 

In a more recent TIMS Mo isotope double spike study using a multiple collector system, Wieser and de Laeter (Wieser and DeLaeter 2003) reported precision of better than 0.1 %o/ amu mass difference ( 2ct) using a Mo- Mo spike. 

The specificity of PCR should make validation efforts for the clearance of viruses, DNA, and host cell proteins more efficient by combining studies and increasing the speed of the assays. In the case of DNA, the assay sensitivity may enable validation to be performed at full scale and eliminate the need for more costly and less accurate small-scale spiking studies. 

Sound knowledge of method bias and recovery from thorough investigation of interferences and matrix effects and by use of matrix CRMs, and/or spiking studies. Consideration is given to any mismatch between standards and samples, such as concentration and matrix differences and differences in the way the analyte is incorporated into the matrix. 

One practical approach to1 testing the specificity of an analytical method is to compare the test results of samples containing impurities versus those not containing impurities. The bias of the test is the difference in results between the two types of samples [20]. The assumption to this approach is that all the interferents are known and available to the analyst for the spiking studies. 

An example of a GC-MS run is shown in Figure 2. Toluene is known and elutes at approximately 16.8 min. An unknown compound elutes at 26.3 min. The positive electron impact spectrum for the unknown and the top library search spectrum are shown in Figure 3. A library search identified the unknown component as 1,2-dimethylbenzene. This was confirmed by spiking studies on the sample with a standard of 1,2-dimethylbenzene. 

The number and type of viruses selected for spiking studies depends on the process materials (e.g., host cell) and product development stage [5]. Before phase... 

Recovery and Its Uncertainty. The trueness of the method must be considered in the calculation of the uncertainty estimate to cover uncertainties due to method bias. Barwick and Ellison describe several possibilities for estimating uncertainty related to trueness, including the use of data from the analysis of a representative certified reference material, comparison with a reference or standard method, and spiking recovery studies. Since no representative certified reference material was available for this analyte-matrix combination, the trueness was estimated using spiking studies. As stated in the previous section, the spiked samples in this example were assumed to be representative of the incurred tissue. 

Figure 5.13 Comparative spiking studies employing methyl oleate with catalysts 19 and 63.

The following year, Corti et al. [39] applied NIR reflection spectroscopy to the analysis of ranitidine and water content in tablets. These were production samples with a narrow distribution of concentrations, so the authors established two criteria for the calibration development. Eirst, the narrow range of sample concentrations allowed fewer samples to be included in the calibration set. Second, production samples had a normal concentration range of 4%, and the calibration was expanded to cover a 10% concentration range. These samples were prepared by adding either filler or drug to a commercial mixture (a spiking study). 

In order to validate, in part, this newer approach, both sample workup and GC-FPD/DCP detection, we have performed several separate, single blind spiking studies with different levels of TBT. Table 9.1 summarizes some of this data, wherein two flounder (fish) and one whiting (fish) sample were separately spiked by one analyst, at the levels indicated, and these were then analyzed by GC-FPD a second... 

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