Quality control techniques

The criteria which a primary standard chemical substance should satisfy are fully stated in many textbooks (e.g., V3), and few compounds satisfactorily meet all these exacting requirements. Furthermore, the primary standards of quantitative inorganic analysis are, for the most part, made to take part in reactions occurring in aqueous protein-free solution during the calibration of secondary standards the conditions under which these secondary standardizations are performed are as nearly ideal as possible, and solutions are kept free from contaminants which might interfere with the stoichiometry of the reactions. 

In clinical chemistry, the closely controlled reaction conditions of quantitative inorganic and organic chemistry cannot always be obtained, since estimations have to be performed on complex mixtures. This means that both simple aqueous and protein-containing standards have to be considered, and the criteria adopted when choosing a standard for use in clinical chemistry may be unable to meet the criteria of primary standards used in other branches of quantitative chemistry. For some determinations, the accuracy of a method cannot be established at present since pure materials for standardization are not yet available the best examples of such methods are provided by determinations of enzyme activity in serum, but suitable control preparations exist for monitoring the precision of these assays (e.g., H8). 

The inability always to define accuracy of clinical chemical procedures does not necessarily render such analyses any less valuable, as long as the method of performance is adequately validated and criteria of reproducibility are established. Such nonstandardized data can be used in the application of the procedure to the investigation of different disease states, by comparison with findings obtained in normal individuals, and the standards of technique required for the quantitative performance of 

Standards should be included with every batch of determinations, and most laboratories base the calculations of concentration for patients specimens included in each batch of analyses on the readings obtained with the standards that have been processed as part of that batch. Henry and Segalove (H7a), however, have suggested that the standard value which ought to be used for these calculations should be the mean of a previously determined series (say 20) of values for that reference standard. The authors have no experience of this method of calculation, which in some ways is tantamount to using a calibration curve (Bla), and prefer to base their calculations on the performance of standards analyzed as part of the batch of specimens under investigation. 

Standard materials used in clinical chemistry include the following  

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J. A. Newton. Applications of spectroscopic quality control techniques for oilfield chemicals. NACE Corrosion 88 (St Louis, MO, 3/21-3/25), 1988. 

By using the combination of specific method accreditation and generic accreditation it will be possible for laboratories to be accredited for all the analyses of which they are capable and competent to undertake. Method performance validation data demonstrating that the method was fit-for-purpose shall be demonstrated before the test result is released and method performance shall be monitored by on-going quality-control techniques where applicable. It will be necessary for laboratories to be able to demonstrate quality-control procedures to ensure compliance with the EN 45001 Standard,3 an example of which would be compliance with the ISO/AOAC/IUPAC Guidelines on Internal Quality Control in Analytical Chemistry Laboratories.12... 

When sampling in the enviromnent, it is often impossible to determine which chemical mixtures are causing a total petroleum hydrocarbons reading, which is one of the major weaknesses of the method. At minimum, before using contaminants data from diverse somces, efforts should be made to determine that field collection methods, detection limits, and quality control techniques were acceptable and comparable. This will help the analysts compare the analysis in the concentration range with the benchmark or regulatory criteria concentrations should be very precise and accmate. 

Quality control techniques are applied to ensure and verify that all design features are as intended and that any changes to the design have been authorized, distributed, accomplished, and recorded. 

The apparatus used to measure membrane bubble points is shown in its simplest form in Figure 7.7 [4], Bubble point measurements are subjective, and different operators can obtain different results. Nonetheless the test is quick and simple and is widely used as a manufacturing quality control technique. Bubble point measurements are also used to measure the integrity of filters used in critical pharmaceutical or biological operations. 

Validation is a defined program, which, in combination with routine production methods and quality control techniques, provides documented assurance that a system is performing as intended and/or that a product conforms to its predetermined specifications. When practiced in a life-cycle model, it incorporates design, development, evaluation, operational and maintenance considerations to provide both operating benefits and regulatory compliance [3]. 

One of the salutary effects of the widespread adoption of quality control techniques based on gas chromatography has been to inject clarity into this formerly somewhat murky area. Thanks to these techniques, the purchaser is now in a position to know to what extent a so-called natural material is pure. As a result genuinely and reliably pure essential oils, absolutes and resinoids are again available in the market today. Synthetic essential oils that are honestly designated as such may be thought of as quasi-natural materials rather than as bases. 

Accordingly, it would be desirable for the alkaline solubilization sampling atomic spectrometric procedures to be accepted both as a routine quality control technique and/or as a screening approach in different processes involving foodstuffs. In this respect, the reduced sample manipulation, the low turnaround time and the relative low cost are primary merits. While single-element determinations using methods such as AAS will continue to play an important role in this Feld, multielement and multiisotope measurements will play an ever more important role in food science in the years to come. 

Tools to enable the coupling of quality control techniques with those required for process control are another interesting area for continued investigation. If the two tasks can be harmonized, less instrumentation may be needed. 

Establishment of good quality control techniques and good manufacturing practices and of facilities for formulation and packaging development activity to undertake compatibility and stability tests as well as safety testing and bioavailability studies. 

The radiochemical purity of the Re-HEDP, ascertained using the ITLC quality control technique, is shown in Fig. 7.1. 

Section 3 discusses quality control techniques, together with criteria for selecting satisfactory standards for the evaluation of a method and the subsequent use of standard materials as part of a control program. The tendency to use the word standard in several different contexts is potentially confusing, and has given rise to the misconception that control sera can be used at one and the same time both as standard materials and as an objective means of checking the quality of results. Because of the dangers inseparable from such potential confusion, it has been considered advisable to discuss some of the differences between standards and controls in this section on definitions. 

Thomas, A. (1987) Microhardness measurement as a quality control technique for thin, hard coatings. Surf. Eng., 3, 117-122. 

Recovery conditions should also be validated against a range of microorganisms as described above. Variation in recovery characteristics of laboratory media should be guarded against through application of rigorous batch-to-baich quality control techniques. 

Quality control techniques are crucial components of any high-throughput biological analysis workflow. In summary, quality control procedures should include ... 

Much like polymers, organic chemicals have their own set of properties that can be used to provide quality control techniques. These properties can be very similar to those used in polymer systems and can include glass transition temperatures, melting (temperature, endialpy), crystallization (temperature, enthalpy), decomposition (thermal, oxidative), reaction (widi various other materials) and more. Thus, the techniques that could be used for quality control of starting materials, process intermediates and final products are similar to those used for polymers. 

Uchikawa, H., "Advances in Physico-Chemical Characterization and Quality Control Techniques for Cement and Concrete," 9th International Congress on the Chemistry of Cement, New Dehli, 1992, pp.797-876. 

Indoor Air Quality Control Techniques Radon, Formaldehyde, Combustion Products, Eds., W.J. Fisk, R.K. Spencer, D.T. Grimsrud, EJ. Offerman, B. Pedersen and R. Sextro, Noyes Data Corporation, Park Ridge, NJ, USA, 1987. 

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