Alternative Laboratory Methods

Thermogravimetry is an attractive experimental technique for investigations of the thermal reactions of a wide range of initially solid or liquid substances, under controlled conditions of temperature and atmosphere. TG measurements probably provide more accurate kinetic (m, t, T) values than most other alternative laboratory methods available for the wide range of rate processes that involve a mass loss. The popularity of the method is due to the versatility and reliability of the apparatus, which provides results rapidly and is capable of automation. However, there have been relatively few critical studies of the accuracy, reproducibility, reliability, etc. of TG data based on quantitative comparisons with measurements made for the same reaction by alternative techniques, such as DTA, DSC, and EGA. One such comparison is by Brown et al. (69,70). This study of kinetic results obtained by different experimental methods contrasts with the often-reported use of multiple mathematical methods to calculate, from the same data, the kinetic model, rate equation g(a) = kt (29), the Arrhenius parameters, etc. In practice, the use of complementary kinetic observations, based on different measurable parameters of the chemical change occurring, provides a more secure foundation for kinetic data interpretation and formulation of a mechanism than multiple kinetic analyses based on a single set of experimental data. 

Sample Pre-treatment Automation Alternative Laboratory Methods... 

Alternative (laboratory) methods for making phosphoric acid are the direct oxidation of white phosphorus with nitric acid and the oxidation of phosphorons acid (4.22), (5.216). 

In 2000, an interlaboratory trial was organized, involving 26 laboratories using the draft standard ISO 15061 IC method with conductivity detection and/or alternative methods. Three alternative laboratory methods based on IC coupled with different detection systems were developed ICP-MS, colorimetry, and fluorimetry. The performance data of these three methods are comparable to the respective data of standard IC with conductivity detection. 

The full dynamical treatment of electrons and nuclei together in a laboratory system of coordinates is computationally intensive and difficult. However, the availability of multiprocessor computers and detailed attention to the development of efficient software, such as ENDyne, which can be maintained and debugged continually when new features are added, make END a viable alternative among methods for the study of molecular processes. Eurthemiore, when the application of END is compared to the total effort of accurate determination of relevant potential energy surfaces and nonadiabatic coupling terms, faithful analytical fitting and interpolation of the common pointwise representation of surfaces and coupling terms, and the solution of the coupled dynamical equations in a suitable internal coordinates, the computational effort of END is competitive. 

Alternatively a mixture of almost any solid chloride and manganese-(IV) oxide will yield chlorine when warmed with concentrated sulphuric acid. These are the most common laboratory methods but there are many others. 

A number of processes have been devised for purifying thionyl chloride. A recommended laboratory method involves distillation from quinoline and boiled linseed oil. Commercial processes involve adding various high boiling olefins such as styrene (qv) to react with the sulfur chlorides to form adducts that remain in the distillation residue when the thionyl chloride is redistilled (179). Alternatively, sulfur can be fed into the top of the distillation column to react with the sulfur dichloride (180). Commercial thionyl chloride has a purity of 98—99.6% minimum, having sulfur dioxide, sulfur chlorides, and sulfuryl chloride as possible impurities. These can be determined by gas chromatography (181). 

Rapid equivalent methods - Generally based on a principle different from that of the corresponding laboratory method, alternative or surrogate systems are used more and more often for on-line and off-line monitoring. For example, the spectrophotometric methods or biosensors proposed for the measurement of organic compounds or electrochemical techniques for metals must be considered as alternative methods. 

Methods have successfully been transferred to various laboratories in inter-company cross-validation exercises for a chiral separation, for an assay of the main component in a formulation and for drug stoichiometry. Revalidation is an alternative to method transfer in case of changes in product composition or analytical procedure (cf. Section I.L). Although a method transfer in CE is not a major difficulty, some aspects have to be considered, especially if a method is transferred to an instrument of another manufacturer. 

ECVAM is the leading international center for alternative test method validation. Hartung et al. (29) summarized the modular steps necessary to accomplish stage 3 (test validation). The seven modular steps are (I) test definition, (2) within-laboratory variability, (3) transferability, (4) between-laboratory variability, (5) predictive capacity, (6) applicability domain, and (7) performance standards (29). Steps 2-4 evaluate the test s reliability steps 5 and 6 evaluate the relevance of the test. Successful completion of all seven steps is necessary to proceed to stage 4 (independent assessment or peer review). This modular approach allows flexibility for the validation process where information on the test method can be gathered either prospectively or retrospectively. The approach is applicable not only to in vitro test methods but also to in silico approaches (e.g., computer-based approaches such as quantitative structure-activity relationships or QSAR) and pattern-based systems (e.g., genomics and proteomics). 

An alternative laboratory preparation of cyanamide and a selection of references to the literature have appeared in Inorganic Syntheses. 1 The present method is that of Werner.8... 

Concentration and Recovery of Solutes. The RO method was evaluated by using small-scale concentrations and selected model organic solutes. Similar concentrations were performed by other researchers by using alternate sampling methods as part of a comparison study. The concentration provided a 50-fold volume reduction (500 L down to 10 L). Field applications of the RO method usually involve sample volumes of 2000-8000 L. No steps were taken to condition membranes and equipment prior to the laboratory tests. This laboratory performance evaluation was conducted, in many respects, as a worst case exercise. 

If an analytic method lacks sufficient specificity, chemical interferences will result in an erroneously high reported concentration. If a measured chemical is introduced as an artifactual contaminant during sample collection or analysis, reported concentrations will also be overestimated. For example, credibly estimating human exposure to phthalates was hindered by the difficulties involved in avoiding specimen contamination with these ubiquitous chemicals the problem was resolved by focus on the much less prevalent metabolic product, the phthalate half-ester (Silva et al. 2004). Alternatively, a chemical measured as a marker of exogenous exposure may be identical with a chemical formed by an unrelated endogenous metabolic pathway. In each of those cases, a rigorous laboratory-method validation should detect the problem before data are reported. More subtly, the measured biomarker of exposure may be chemically identical with a dietary... 

The essential criteria for a useful analytical technique are specificity, sensitivity, accuracy, precision, simplicity, rapidity, economy, wide applicability, and freedom from hazard. It is well known that radioimmunoassay (RIA) was developed in 1959 by Yalow and Berson (Yl). Since then the radioimmunoassay method has been widely used in the field of clinical chemistry. Radioimmunoassay has inherent in it the advantages listed above. However, this method always requires special facilities for use and disposal of radioisotopes and consideration must be given to the fact that the labeled substances have short half-lives. Immunoassay methods are explosively increasing in use and development as an analytic technique in basic science as well as in clinical laboratory medicine (L1-L3, VI). With these points as background, efforts have been made to develop nonisotopic immunoassay methods or alternative immunoassay methods that are based on antigen-antibody reactions but do not involve use of a radioisotope. 

Therefore, an alternative test method, such as heating at 80 °C for 2 h, an alkali modified Coomassie-dye assay (e.g. Boyes et al. 1997), or the more recently available reagent based test kits such as Proteotest or Prostab, could present an opportunity to decrease bentonite dose and reduce volume of wine occluded in bentonite lees if confirmed to predict more accurately haze formation in wine. If these alternative test methods could replace the current heat test method of 80 °C for 6 h, this would also reduce the amount of time and/or effort presently required by a winery s laboratory to conduct heat stability testing. 

ALA can be measured directly but is converted more usually into an Ehrlich s-reacting pyrrole by condensation with a reagent such as acetylacetone after separation from PBG by two-stage anion exchange chromatography. A method for the measurement of PBG and ALA, based on that of MauzeraU and Granick, is available commercially (Bio-Rad Laboratories, Hercules, Calif.). An alternative photometric method has been proposed for more rapid testing. 

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