Quality control Materials

To ensure quality control material suppliers and developers routinely measure such complex properties as molecular weight and its distribution, crystallinity and crystalline lattice geometry, and detailed fracture characteristics (Chapter 6). They use complex, specialized tests such as gel permeation chromatography (2, 3), wide- and narrow-angle X-ray diffraction, scanning electron microscopy, and high-temperature pressurized solvent reaction tests to develop new polymers and plastics applications. 

Taylor A (1988) The use of internal quality control materials for the preparation and maintenance of reliable methods for measurement of lead in blood. Fresenius Z Anal Chem 332 732-735. 

Surprisingly, few certified reference materials or quality control materials for use in the measurement of airborne contaminants are commercially available from world-wide producers. The main reason for the scarcity of such materials is related to great difficulties in producing realistic samples and the lack of interest from... 

On most occasions CRMs are used as Quality Control materials, rather than as calibrations . As outlined above, this common application adds significantly to the user s uncertainty budget, since at a minimum it is necessary to consider at least two independent measurement events (Um). so increasing the combined uncertainty of the results. Again this process rapidly increases the combined uncertainty with increasing complexity of the analytical system and so the usefulness of a control analysis may be downgraded when a correct uncertainty budget is formulated. 

The establishment of performance criteria for a given tumor marker test is not a simple process because accuracy and precision are unique for each type of analyte and its application. Establishing methodological limits for accuracy, precision, sensitivity, and specificity often requires standard reference materials, quality control materials, comparative studies, and actual clinical specimens. Accuracy and precision must be measured over the analyte reportable range for which the device is intended to be used. Sensitivity and specificity must be considered with respect to the intended clinical use of the device. Also, the indications for use should be carefully considered in the design of the study protocol. The indications for class II should be to monitor residual tumor after surgery (or radiation), the recurrence of tumor, or response to therapy. A 510(k) must provide clear evidence that the device is accurate, safe, effective, and substantially equivalent to a device legally marketed in the United States. 

If repeatability is the only estimate of precision that is obtained, this is unlikely to be representative of the variability observed when the method is used over a long period of time. Intermediate precision is often more relevant - this expresses the within-laboratory variation or within-laboratory reproducibility (different days, different analysts, different equipment, etc.). This is initially obtained from validation studies and confirmed later by examining the results obtained for quality control material measured over a period of about three months (see the quality control (QC) charts in Chapter 6). 

Note (4) is very important as it highlights the fact that the reference material used for the method validation cannot be used again when the method is in routine use for calibration purposes. The same type of material can be used, but it needs to come from a different supplier. The same material cannot be used for calibration purposes and then as a quality control material. 

Control charts Routine charting of data obtained from the analysis of quality control materials to check that the results lie within predetermined limits. 

Quality control material A material that is fully characterized in-house or by a third-party, similar in composition to the types of samples normally examined, stable, homogeneous and available in large quantities so that it can be used over a long period of time for monitoring method performance. 

GFAAS end analysis of Pb in blood was critically discussed in a review, including methods of introducing the sample into the furnace, matrix interferences and ways of improving the precision of the method, such as use of a stabilized temperature platform40. An evaluation program was carried out for quality control materials and proficiency for... 

Abuse of CRM Instead use in-house materials or quality control materials... 

Figure 1.1. Steps and materials in an analysis. Procedures are shown in dashed boxes. Quality control materials that are presented to the analytical system are not shown.

The Royal Australian Chemical Institute has supported metrology in chemistry through its Hitchhiker s Guide to Quality Assurance series of seminars and workshops. These have been excellently organized by Maree Stuart and John Eames and have been well attended by the analytical community. I particularly thank John Eames for allowing me to use his approach for quality control materials in chapter 4. 

Quality control material is available from Bio Rad or Chromsystems (Munich, Germany). We also use an abnormal patient urine stabilized with 1% azide and kept in... 

After calibration of the HPLC, a food-based quality control material or reference material should be analyzed on a routine basis to validate the performance of the method. The chromatograms illustrated in the following sections of this chapter are of a food matrix created from a mixture of baby foods and infant formula however, a similar standard food reference material (SRM 2383) may be directly purchased from the National Institute of Standards and Technology (NIST). 

The number of analytical methods developed for the study of the distribution of metal- and metalloid-containing species in the last decade has been impressive. However, a majority of these are as yet to be applied to real biological materials. With the greater appreciation of the pre- and post-sampling factors that influence chemical speciation, and the development of appropriate quality control materials the results of these studies will become more reliable. Consequently, the use of chemical speciation data will become indispensable to accurate environmental impact assessment, and to our understanding of the roles that metals and metalloids play in biological systems. 

In-source transformation effects can only be perceived during method development if extracts of biological samples are analyzed under extended chromatographic runs. Interference by in-source transformation will not become evident if only spiked quality control materials are used which do not contain relevant metabolites. If one or more additional peak in the SRM trace of the target analyte is observed in comparison to analyte reference solutions, chromatography may only be accelerated to such degree that these peaks still remain baseline separated from the analyte. 

Fraser, C. G., Fudge, N. A., and Penberthy, L. A. (1978). Evaluation of precision using lyophilized quality control material. Arm. Clin. Biochem. 15, 121-122. 

Control objectives for a chemical process originate from certain regulation tasks (i.e. product quality control, material balance control, safety, environmental regulations, etc.) and economic objectives (i.e. optimizing the economic performance). Such a classification of control objectives automatically formulates the different design activities for the regulatory and optimizing control structures. 

The drug-free material must first be analysed by the relevant analytical technique for which the quality control material is being prepared to ensure that there is no interference from endogenous compounds or contaminants introduced during collection and pooling. For example, serum stored in some plastic containers may become contaminated with a plasticiser which interferes with the assay of phenytoin by gas chromatography. 

Quality control materials using serum or urine are commercially available for many drugs which are assayed routinely for therapeutic or toxicological purposes. Such preparations are generally lyophilised and their stability is guaranteed by the manufacturer. The concentration values assigned by the manufacturer should be verified in the user s laboratory before they are used for the construction of control charts. 

The particle size distributions of 15 International Atomic Energy Agency and 16 National Institute of Standards and Technology reference materials (RMs) were measured by laser diffraction to determine their potential as reference or quality control materials in that less than 100 mg are required. Most of the materials are commercially available as environmental and biological reference materials (RMs) [137]. 

E441 Hill, S.A., Heathcote, J.C. and McQueen, M.J. (1988). Variable behaviour of lyophilized quality control material in the Kodak Ektachem LD assay. Clin. Biochem. 21, 384, Abstr. MC-17. 

E676 Schneider, A., Ko, B. and Magneson, G. (1990). An evaluation of the performance of a lyophilized, comprehensive quality control material. Clin. Chem. 36, 1178, Abstr. 1054. 

R136 Brandford, S., Sobecki, S. and Bais, R. (1989). Whole-blood quality-control material for Reflotron assays of cholesterol. Clin. Chem. 35, 1255-1256. 

Aqueous quality control materials are commercially avail-able for free calcium. Because simple aqueous controls may not reliably detect changes in performance with patient specimens, serum-based quality control materials should be used daily. Serum-based controls may be prepared by acidifying serum with 10 pL of 1 mol/L HCl and leaving it exposed in the refrigerator for 1 week to remove carbon dioxide. The pH is then adjusted to 7.4, and the serum is ahquoted and frozen. Alternatively, serum-based controls can be equilibrated with carbon dioxide before their analysis. 

Table 5.1.1 Quality control materials produced within the SWIFT-WFD Project... 

TABLE 1.5 Types and Purposes of Daily Quality Control Materials for IHC ... 

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