Quality control applications

It should be pointed out that when using ethidium bromide the sensitivity of the assays varies depending on the physical state of the nucleic acids (see Table I). Ethidium does not discriminate between RNA and DNA, although dyes are available which bind DNA exclusively, so the relative amounts of each may be determined by taking two sets of measurements. Alternatively, nucleases (DNA-ase or RNA-ase) can be used to exclusively remove one or the other in a mixture. Nucleic acids from different sources (see Table II) also show a variation in sensitivity, and the fluorescence assay lacks the selectivity of the hybridization technique. Nevertheless, for rapid screening or quality-control applications the fluorescence assay is still the method of choice. 

These three NIST SRMs have a number of important quality control applications for forensic DNA profiling, medical diagnostics and mutation detection. The main applications are summarized below ... 

The need for complete compositional analysis of additive packages in industrial plastics for both research and quality control applications has led to the development of numerous analyte-specific test procedures in recent years. 

Columns filled with polymer solutions are extremely simple to prepare, and the packing can easily be replaced as often as desired. These characteristics make the pseudostationary phases excellent candidates for use in routine CEC separations such as quality control applications where analysis and sample profiles do not change much. However, several limitations constrain their widespread use. For example, the sample capacity is typically very low, pushing typical detection methods close to their sensitivity limits. Additionally, the migration of the pseudostationary phase itself may represent a serious problem, e. g., for separations utilizing mass spectrometric detection. The resolution improves with the concentration of the pseudostationary phase. However, the relatively low solubility of current amphiphilic polymers does not enable finding the ultimate resolution limits of these separation media [88]. 

Traditionally, most pharmaceutical assays are isocratic analysis employing the same mobile phase throughout the elution of the sample. Isocratic analyses are particnlarly common in quality control applications since they nse simpler HPLC eqnipment and premixed mobile phases. Notable disadvantages of isocratic analysis are limited peak capacity (the maximnm nnmber of peaks that can be accommodated in the chromatogram), and problems with samples containing analytes of diverse polarities. Also, late eluters (such as dimers) are particularly difficult to quantitate in isocratic analysis due to excessive band broadening with long retention times. 

Assumptions. Limitations, and Quality Control Applications in Practical Settings... 

Quality control Applications of NMR relaxation experiments, NMR imaging, NMR MOUSE and (multi) hyphenated TGA techniques for quality control are discussed in Chapters 1, 7 and 10. 

If one is interested in quality control applications and solely looking for qualitative differences between different batches of the same or similar supports, the errors associated with these methods... 

The simplest color sensing systems are responsible for monitoring only one color across a scene. These are typically used in quality control applications such as monitoring of paints, to ensure consistency between batches made at different times. More sophisticated color sensors look at the color distribution across a two-dimensional image. These systems are capable of complex analysis and can be used for checking multi-colored labels or for identifying multi-colored objects by their color patterns. 

In general, analytical techniques/methods intended for routine manufacturing and quality control applications must be very robust and rugged, and not rely on what are considered to be advanced technologies in these areas (e.g., GC/MS and LC/MS). Also, such methods must be thoroughly validated according to the accepted industry practice and standards. To these ends, it is common industry practice to do the following ... 

Statistical diameters are often used in microscopy as they can be easily and rapidly measured, but the disadvantage is that they do not give information about the particle properties such as volume, mass, or surface area. However, for quality control applications this information may not be important. Figure 5 illustrates the most commonly used diameters. The USP <776> defines Martin s and Feret s diameter and other less commonly used diameters as (7) ... 

One quality control application of near-IR spectroscopy is the nondestructive determination of tablet hardness. Near-IR prediction of tablet hardness has been used and investigated by Drennen for a number of years. In 1991, the first publication of the near-IR technique for this application appeared [26]. Ciurczak and Drennen published similar results in 1992 [60] and Drennen and Lodder in 1993 [61]. Results of a study presented at the 1994 annual meeting of the American Association of Pharmaceutical Scientists were published in a 1995 paper [62]. In that paper, Kirsch and Drennen identified the utility of the technique in the determination of multiple film-coated tablet properties, including tablet hardness. In a review paper regarding the use of near-IR in the analysis of solid dosage forms, Kirsch and Drennen discussed the historical aspects of near-IR prediction of tablet hardness [27]. 

The use of low-field NMR in quality control applications has increased because of the ease of operation and reliability of the data. Most of the applications involve the measurement of Tj and/or T relaxation times, to yield quantitative information relating to the concentrations of individual components. The applications include the determination of viscosity and the measurement of moisture, fat, hydrogen, fluorine, and carbon contents. One of the most common uses of this technique is the quantitative determination of the state of water in soils, foodstuffs, coals, and catalysts. ... 

All methods for the determination of tensile strength described above are too complicated and time consuming to be suitable for routine industrial quality control applications. In those cases it is the task of the test procedure to determine a specific characteristic of the agglomerate easily, quickly, and reliably. The results must only be reproducible and comparable within the own organization and a relation to theoretical predictions is normally not required comparisons with results from other plants are often not necessary or, in case of competing products, not desired. 

In many analytical applications in biomedical and pharmaceutical sciences it is desirable to probe, noninvasively, the composition of deep layers of samples with high chemical specificity. Examples include the diagnosis of bone disease and breast cancer, as well as the noninvasive probing of pharmaceutical products in quality control applications and drug authentication. 

Flow-based analytical procedures are already used in many fields, e.g., environment, food and health. In tandem with the developments described above, flow analysers will also be used in new and emerging fields of application such as the "omics" (metallomics, genomics and proteomics), biotechnology (enzymatic assays, platforms for bio-sensors and flow immunoassays) and quality-control applications in general. Economic resources will also be a driver for more multi-parametric flow-based methods, particularly with spectrophotometric detection. 

Capillary columns are potentially useful in methods research and quality control applications because they are effective, especially with complex samples, as in environmental analyses easy to use in developing separation methods and more reproducible in terms of performance than packed columns. This last point follows from the fact that capillary columns are available that are individually tested and guaranteed on the basis of performance specifications guaranteed packed columns are not available normally. 

Plasma emission spectrometers have shown a rapid growth. This holds also for NMR spectrometer sales because of new applications in biomedical research and more sophisticated experimental methods using increased computing power. Similarly, Raman spectroscopy, traditionally used in academic research, is gaining acceptance in industrial R D and quality control applications. Materials research and surface analysis in a variety of industries keeps the sales of electron microscopic, electron spectroscopic, ion spectroscopic, and X-ray instruments growing. Details of the various techniques on surface and interface characterization which are also important in R D of chemical sensors themselves, can be found in Chapter 3, Section 3.4.2. 

DSC finds many applications in characterizing materials. Quantitative applications include the determination of heals of fusion and the extent of crystallization for crystalline materials. Glass transition temperatures and melting points arc useful for qualitative classification of materials, although thermal methods cannot be used alone for identification. Melting points are also very useful in establishing the purity of various preparations. Hence, Ihcrmal methods are often used in quality control applications. 

Utility-grade pH meters usually cost about 100-300. Most are battery operated, and thus portable generally they offer enough sensitivity to be used in many quality-control applications and out in the field. Their relative accuracy is about +0.1 pH unit, and they have taut-band meter movements. General-purpose pH meters are more often line operated, and cost about 300-700. For the extra cost, they usually offer better stability and accuracy ( 0.05 pH or 3 mV), larger taut-band scales, and extra features such as a recorder output, mV scales, and a constant-current jack for performing polarized electrode measurements or dead-stop titrations such as the Karl Fischer titration for water determination. 

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