Matrix types, samples

If the sample and standard have essentially the same matrices (e.g., air particulates or river sediments), one can go through the total measurement process with both the sample and the standard in order to (a) check the accuracy of the measurement process used (compare the concentration values obtained for the standard with the certified values) and (b) obtain some confidence about the accuracy of the concentration measurements on the unknown sample since both have gone through the same chemical measurement process (except sample collection). It is not recommended, however, that pure standards be used to standardize the total chemical measurement process for natural matrix type samples chemical concentrations in the natural matrices could be seriously misread, especially since the pure PAH probably would be totally extracted in a given solvent, whereas the PAH in the matrix material probably would not be. All the parameters and matrix effects. Including extraction efficiencies, are carefully checked in the certification process leading to SRM s. 

Problem evaluation in turbomachinery is complex, but with the aid of performance and mechanical signals, solutions can be found to diagnose various types of failures. This is done by using several inputs and a matrix. A sample of some of the problems are given in the next few sections. 

The revised database holds over 23 000 analyte values for 660 measurands and 1670 reference materials produced by 56 different producers, from 22 countries. The database is restricted to natural matrix materials (i.e. made from naturally occurring materials, excluding calibration standards manufactured from pure chemicals). Information has been extracted from the relevant certificates of analysis, information sheets, and other reports provided by the reference material producers. As a general rule, the authors have only included in the compilation reference materials for which a certificate of analysis or similar documentation is on file. Information included in the survey is on values for measurands determined in reference materials, producers, suppliers, the cost of the materials, the unit size supplied, and the recommended minimum weight of material for analysis, if available. The new searchable database has been designed to help analysts to select reference materials for quality assurance purposes that match as closely as possible, with respect to matrix type and concentrations of the measurands of interest and their samples to be analyzed see Table 8.3. 

To demonstrate the validity of an analytical method, data regarding working range/ calibration, recovery, repeatability, specificity and LOQ have to be provided for each relevant sample matrix. Most often these data have to be collected from several studies, e.g., from several validation reports of the developer of the method, the independent laboratory validation or the confirmatory method trials. If the intended use of a pesticide is not restricted to one matrix type and if residues are transferred via feedstuffs to animals and finally to foodstuffs of animal origin, up to 30 sets of the quality parameters described above are necessary for each analyte of the residue definition. Table 2 can be used as a checklist to monitor the completeness of required data. 

Origin of sample Matrix type Main study Independent lab. validation" Confirmatory method"... 

On-line SFE-SFC method development for validated quantitative analysis of PP/(Irganox 1010/1076, Tinuvin 327) has been reported [93]. SFE conditions required optimisation of extraction time and pressure, matrix type (particle or film) and matrix parameters (particle size, film thickness, sample weight). About 30% of extracts were lost during collection. Very poor recoveries (20-25 %) were reported from ground samples (particle size 100 p,m dependent recoveries of 45-70% for 30-p.m-thick films. Biicherl... 

The standard curve should be three levels, typically ranging from 25 to 2,500 ng/mL (may be lower or higher as needed). Each standard is 10 times the one below (a typical set is 25, 250, and 2500 ng/mL). The matrix of the calibration curve should be from the same animal species and matrix type as the samples. 

Dams, R., Huestis, M. A., Lambert, W. E., and Murphy, C. M. (2003). Matrix effect in bio-analysis of illicit drugs with LC-MS/MS influence of ionization type, sample preparation, and biofluid. Am. Soc. Mass Spectrom. 14, 1290—1294. 

Optimal conditions for the extraction of polygalacturonase (PGase) depend on the sample matrix (type of food product) and the source of the enzyme (plant versus microbial origin). The extraction scheme presented below is that developed for the PGase of tomato (Pressey, 1986). 

Chemical interferences, which can be highly dependent on matrix type and the specific analyte element, are characterized by molecular compound formation, ionization effects, and solute vaporization effects. If such effects are observed, they can be minimized by careful selection of operating conditions, by buffering the sample, by matrix matching, and by standard addition procedures. 

Matrix spike (one per 20 samples of each matrix type)... 

One may be inclined to suppose that for each type of chemical measurement there is a need to build a measurement system based on the pyramid concept [7, 32], For the practicing chemist, however, this would be seen only as an unhelpful imposition. Previously discussed limitations of such a pyramid system would apply equally to the use of RMs. In addition, there is a major difficulty due to the previously discussed differences between RM matrix and sample matrices. Whereas for extrinsic measurements the composition of an RM or other traveling standard is of little or no concern, intrinsic amount-of-substance measurements are generally affected by the internal composition, structure, and texture of the RM. 

Whilst pure substance RMs are mainly used for calibration purposes (determining Fc and Uc), matrix RMs are most often required to validate a measurement or method (determining R and UR). To be of use matrix RMs must closely match the real sample in terms of analyte, matrix type, and concentration. In addition, the analyte must be incorporated into the matrix in the same way as in the real sample. RMs may be prepared by gravimetrically mixing the components or by characterizing the amount of the analyte(s) of interest in normal production or naturally occurring material. The former provides a more ready route to traceability, but in many cases such materials do not sufficiently closely match the real samples. 

A question of increasing importance to both suppliers and users of RM is the scope of a matrix RM, i.e. the extent to which a reference matrix of a particular type (e.g. a sediment) may properly be used to validate methods used for the routine analysis of test sample matrices of a different type (e.g. a soil). Relating different matrix types in this way is sometimes referred to as com-... 

Whilst this conclusion is valid for data of the type described here (where the deviations of the results from the reference values are large), where laboratories are consistently producing results of very low bias (e.g. deviations of less than a few percent), a correlation between two matrix types is likely to be much harder to demonstrate. Thus for such laboratories and such analytical methods, matrix RMs that are a very close match in composition to the routine test samples are likely to be required. 

From the viewpoint of a DL, sampling will be the responsibility of the OPCW inspectors or SP representatives. Sample preparation and subsequent analysis of the samples is carried out on-site or in a DL in a case where further analysis is required. For a DL, the ROPs (7) give instructions for sample preparation and instrumental analysis. Rather than being the best choice for a single analyte or matrix type, ROPs provide an optimal approach for all in an unknown situation. The following ROPs exist for the analysis techniques ... 

---