Additional Reagents and Materials Required

The resin is equilibrated three times with two volumes of distilled/ deionized water. A 1 1 resin water slurry is used to prepare columns. 

Plexiglass column rack with disposable columns 

A gel-type fluid that allows counting of samples with a high aqueous content is required, as 5 ml of water are used to elute each column. 

Assays are set-up in triplicate using either 12x75 mm tubes (glass and polystyrene work equally well) or 1.1-ml Microtube strips (see Section 2.2.3). Components are added to each tube in the order shown in Table 2. Incubate for 60 min. at 30°C. 

After incubation, tubes are placed in an ice-water bath to slow the reaction. Duplicate 70-[xl samples from each tube are transferred to separate columns to yield duplicate measurements for each of the triplicate assays. 

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Separate sample blanking requires an additional analytical channel, and is therefore wasteflil of both reagents and hardware. An alternative approach that is used on several automated systems, eg, Du Pont ACA, BM-Hitachi 704, Technicon RA-1000, is that of bichromatic analysis (5) where absorbance measurements are taken at two, rather than one, wavelength. When the spectral curves for the interference material and the chromogen of the species measured differ sufficiently, this can be an effective technique for reducing blank contributions to assay error. Bichromatic analysis is effective for blanks of both the first and second type. 

The central idea in all radiometric techniques of analysis is to have a radioactive reagent R of known activity combine quantitatively with some unknown amount of material U to form a radioactive addition product R U. By measuring the activity of the product R U, the original amount of unknown material U is deduced. The advantages of such techniques are the high sensitivity due to the use of radioactivity and the requirement that the product R U need not be chemically pure. All that is required is the R U not contain any spurious radioactivity. The disadvantages of these techniques are that the reaction between R and U must be quantitative, and... 

In a number of cases, simple dissolution of a solid sample in an appropriate solvent is possible and some laboratory reagents may even be analysed without further treatment. Prior to flame analysis, the best solvent is dilute hydrochloric acid, provided of course that the major matrix elements are not silver, lead or another element which forms a sparingly soluble chloride. If additional oxidising ability is required, concentrated nitric acid may be added to the solvent. This acid is the preferred solvent when the analysis is to be completed by electrothermal atomisation. If the material contains large amounts of silica it may be necessary to add hydrofluoric acid after preliminary digestion with hydrochloric acid (see Chapter 4g). Care should of... 

Utilized in drug discovery will be the same as that used to provide commercial scale quantities. The discovery chemist may utilize a large number of synthetic steps, use a number of reagents that are expensive or not practical at scale-up, use a number of chromatographic steps for purification, and experience very low yields. For scale up, the process development chemist must factor in safety, economical, and ecological considerations while producing a robust and reproducible synthesis. Fie must consider operating limitations such as heat and mass transfer. Economic factors will dictate minimization of the synthetic steps, maximization of yield, and choice of raw materials. In addition, the process must meet environmental, occupational health, and safety requirements. 

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