Quality Tests

We conclude this chapter with a brief description of some tests that may be applied to judge the accuracy or self-consistency of a particular approximation method. Ideally, one could compare the approximation method results with the exact results for the measurable properties of the same model. Since such exact solutions are seldom available except for very simple models (e.g., hard spheres in one dimension), one must use Monte Carlo or molecular dynamics calculations as the standard. These too represent approximations, however, and are more expensive and less reliable for ionic solution models than for nonionic systems. 

Among the most useful quality tests are those for self-consistency, which determine whether the pair correlation functions calculated using a particular approximation method give identical results when used to calculate a certain thermodynamic function by different routes. For example, in an ionic solution calculation we can apply the virial-compressibility consistency test as follows From the pair correlation functions, we calculate the osmotic coefficient 4  

We now define S4 as the difference between the value of calculated from Eq. (71) and that calculated from Eq. (171). For a satisfactory approximation method S should be no larger than the experimental uncertainty in as measured for an appropriate real system. The required percentage accuracy in f is often very stringent, since it is really 1—0 rather than f that is the excess function. 

For calculations involving mixed electrolyte solutions there are many independent self-consistency tests of this kind. In addition, there is another class of self-consistency tests based upon calculating the effect of small changes in the model Hamiltonian or in the independent thermodynamic variables. One can then by successive approximation adjust the model until the method yields consistent results. All of the work to date involving self-consistency tests indicates that they are reliable guides to the quality of the calculation with respect to those particular measurable properties that are calculated in the test. 

Another valuable quality test for electrolyte solution calculations is based upon the zeroth and second moment conditions of Stillinger and Lovett. To apply these conditions, the first of which is equivalent to the requirement of local electroneutralitywe define the zeroth and second moment defects for an ion of species a as follows  

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Standards also give definitions for the characteristics of a material or product, or they provide the means and methods to implement quality tests for them. The difference lies in their method of preparation, therefore, in their legal status. A standard is the result of a consensus between all parties concerned. These parties represent the manufacturers of the product or material, the consumers who are the industries or user services or, ultimately, consumer associations, as well as, finally, governments. 

Describe several instruments suitable for indoor air quality testing. 

Step 1.3 Identify and Allocate Additional Resources. The audit may require external resources, such as laboratory facilities and possibly equipment for air sampling, flow measurements, energy measurements, and product-quality testing. 

Air resource management The enforcement of set standards to reduce contamination supported by control regulations, planning, and quality testing facilities. 

S. T. Adam, Quality test of a mechanical switching valve for two-dimensional open tubular gas cliromatography , 7. High Resolut. Chromatogr. Chromatogr. Commun. 11 85-89(1988). 

K. Groh Jr., G. Groh and K. Groh, Comprehensive quality test for glass capillary columns , / Chromatogr. 156 1-20(1978). 

Abbott studied the corrosion of contacts, and proposed quality tests in dilute mixtures of hydrogen sulphide, nitrogen dioxide and chlorine in air at controlled temperature and humidity . These gave good results in a project seeking improved procedures for British and lEC standards . 

The high-conversion bromine product quality tests at 300°C and 335°C gave greater than 99 % HBr conversion. Analysis of the resulting bromine showed no detectable chlorine. 

As discussed in Chapter 4, chemicals can be a nuisance or pose health risks if they become airborne as a result of inadequate process control, operation and maintenance malpractice, inadequate maintenance, incomplete understanding of the process etc. Hazards may arise if the oxygen concentration in the air fluctuates beyond its normal level of 21% by volume, and fire/explosion dangers may arise from the presence of flammable gases, vapours or dusts in the atmosphere. Thus air quality tests may be required for a variety of purposes such as ... 

Each of the countries operates a quality analysis system for post-marketing control of drug quality, albeit with vast differences in capacity. Data on the outcome measure for drug quality— the number of dmg samples that failed quality tests compared with the total number of samples collected— are available in all the countries, except the Netherlands. Failure rates are high in some countries, e.g. Tunisia and Uganda. In Australia, high failure rates are found for herbal and other complementary products, compared with prescription dmgs. Empirical data on sanctions applied in such instances are not available. 

Standardized Quality Test for Coated Open Tubular Columns... 

On-line SFE-GC finds use especially in petroleum-related applications [54], but has also been applied to polymer additives [47,55]. PBT polymers were extracted at 200 bar and 55 °C for the determination of carbonic acid diphenyl esters and other volatiles, using on-line SFE-GC-MS [47]. Extraction of entrained volatiles is a quality test for some polymers. SFE-GC-FTIR-MS has been employed to reveal the cause of odour of a smelly hose (a plasticiser) [56]. SFE-GC can also profitably be used for the determination of residual solvents in polymers such as benzene, toluene and o-xylene [57]. Oligomers of PE (up to 1000 Da) were determined by GC after supercritical fluid extraction [58]. 

In a study comparing organic and conventional apples (variety Golden Delicious) from a range of commercial orchards it was found that reproducible differences between apples from organic and conventional systems can be detected (Fig. 16.6). Additionally, the vitality index produced based on the picture forming method was found to be correlated with the technical standard index based on chemical quality tests and the sensory test results (Fig. 16.7, left) (Weibel et al., 2004a). 

Fig. 16.7 Correlations between the vitality quality index (based on data from picture forming methods and the index of technical quality (based on classical fruit quality tests, see text) in the first year (left) and the second year (right) of the study (filled symbols = organic, open symbols = conventional same symbol form = same village).

Possible industrial applications include screening of substances with antiradical activity, quality testing of raw materials, pharmaceuticals, cosmetic products, fruit juices, wines, beers, edible oils, detection of food irradiation, and many more. 

Quality techniques, 27 172-173 Quality testing, of methyl chloride,... 

Quality tests, of phenol, 78 753 Quantitative affinity chromatography, 6 404 05... 

Materials purchased for the purpose of mixing with other materials in the preparation of pharmaceutical products are called raw materials. Pharmaceutical companies often purchase solid raw materials as powders in large drums. Quality assurance laboratories require samples of the material in the drums for the purpose of performing quality tests to see if the raw materials meet the specifications required for the company s products. 

In all the above design problems, the manufacturing process is not included but instead, the application process is included and evaluated to identify the optimal product. Note that the formulated product, which may also be defined as products that are sold based on their properties during use and not their molecular structure, may need to pass a set of quality tests. 

Several in vitro tests are currently employed to assure drug product quality. These include purity, potency, assay, content uniformity, and dissolution specifications. For a pharmaceutical product to be consistently effective, it must meet all of its quality test criteria. When used as a QC test, the in vitro dissolution test provides information for marketing authorization. The dissolution test forms the basis for setting specifications (test, methodology, acceptance criteria) to allow batch release into the market place. Dissolution tests also provides a useful check on a number of physical characteristics, including particle size distribution, crystal form, etc., which may be influenced by the manufacturing procedure. In vitro dissolution tests and QC specifications should be based on the in vitro performance of the test batches used in in vivo studies or on suitable compendial specifications. For conventional-release products, a single-point dissolution... 

For batch-to-batch quality testing, selection of the dissolution medium is based, in part, on the solubility data and the dose... 

The process of evidence gathering, timeline development, scenario determination, and causal factor identification is somewhat iterative, and therefore some of the tools and quality tests previously described may assist in causal factor identification. More specifically, barrier analysis and change analysis, together with a completeness test, can ensure that all valid causal factors are identified. 

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