Quantitative analysis general

De Bibvre and H. Giinzler, Measurement Uncertainty in Chemical Analysis, Springer-Verlag, Berlin (2003). 

de Levie, Principles of Quantitative Chemical Analysis, McGraw-Hill, New York, NY (1997). 

Prichard, Quality in the Analytical Chemistry Laboratory, J. Wiley Sons, Chichester (1997). 

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Most cells used in infrared spectrometry have sodium chloride windows and the path length is likely to vary with use because of corrosion. For quantitative work, therefore, the same cell should be used for samples and standards. In general, quantitative analysis in the infrared region of the spectrum is not practised as widely as in the ultraviolet and visible regions, partly because of the additional care necessary to obtain reliable results and partly because the technique is generally considered to be less sensitive and less precise a precision of 3-8% can be expected. 

In general, quantitative analysis by EDS in EM is similar to that of XRF. The analytical methods, however, are different for two main reasons. First, the interactions between the electron beam and specimen are different from those of primary X-ray radiation. Second, an EM specimen for chemical analysis cannot be modified as in the internal standard method. For accurate quantitative analysis of EDS in EMs, separate standard samples containing the elements in the specimen to be analyzed are necessary. The standards should be measured at identical instrumental conditions to the specimen. It means that the spectra of specimen and standard should be collected under the same conditions with regard to the following parameters ... 

We have also added an entirely new section dealing with semi-microanalysis. In our original Introduction (p. ix) we justified the retention of macro-methods of quantitative analysis on the grounds that they formed an excellent introduction to micromethods and also afforded a valuable training in exact manipulation generally. By now, however, the macro-estimation particularly of carbon and hydrogen and of nitrogen has disappeared entirely from most laboratories. On the other hand, the micro-... 

The comparatively wide prevalence of micro-methods of quantitative organic analysis, applied more particularly to the estimation of the constituent elements in an organic compound, may cause the advisability of including the macro-methods in Part IV to be questioned. Quite apart, however, from the fact that the micro-methods still find no place in many laboratories, we consider that thorough practice in the macro-methods of quantitative analysis to be not only an excellent introduction to the micro-methods themselves, but also a valuable training in exact manipulation generally. 

In an ideal separation = I, Rj = 0, and Sj a = 0. In general, the separation factor should be approximately 10 for the quantitative analysis of a trace analyte in the presence of a macro interferent, and 10 when the analyte and interferent are present in approximately equal amounts. 

Chemical kinetic methods of analysis continue to find use for the analysis of a variety of analytes, most notably in clinical laboratories, where automated methods aid in handling a large volume of samples. In this section several general quantitative applications are considered. 

Noncatalytic Reactions Chemical kinetic methods are not as common for the quantitative analysis of analytes in noncatalytic reactions. Because they lack the enhancement of reaction rate obtained when using a catalyst, noncatalytic methods generally are not used for the determination of analytes at low concentrations. Noncatalytic methods for analyzing inorganic analytes are usually based on a com-plexation reaction. One example was outlined in Example 13.4, in which the concentration of aluminum in serum was determined by the initial rate of formation of its complex with 2-hydroxy-1-naphthaldehyde p-methoxybenzoyl-hydrazone. ° The greatest number of noncatalytic methods, however, are for the quantitative analysis of organic analytes. For example, the insecticide methyl parathion has been determined by measuring its rate of hydrolysis in alkaline solutions. 

Local and state forensic laboratories generally do not engage ia excipient testing. Most provide quaUtative and quantitative analysis of the evidence to determine if an Ulegal substance is present and if so, the amount of the dmg present. The quantity of dmg seized by the authorities may be important ia jurisdictions which give enhanced sentences for larger amounts of the pure dmg, or ia some cases the total weight on the dmg and diluent ia possession of the defendant. 

High Pressure Liquid Chromatography. This modem version of the classical column chromatography technique is also used successfully for separation and quantitative analysis of dyes. It is generally faster than thin-layer or paper chromatography however, it requires considerably more expensive equipment. Visible and uv photometers or spectrophotometers are used to quantify the amounts of substances present. 

Qualitative analysis methods should have well-grounded and generally adopted quantitative reliability estimations. At first the problem was formulated by N.P. Komar in 1955. Its actuality increased when test methods and identification software systems (ISS) entered the market. Metrological aspects evolution for qualitative analysis is possible only within the scope of the uncertainty theory. To estimate the result reliability while detecting a substance X it is necessary to calculate both constituents of uncertainty the probability of misidentifications and the probability of unrevealing for an actual X. There are two mutual complementary approaches to evaluate uncertainties in qualitative analysis, just as in quantitative analysis ... 

The accuracy of quantitative analysis has been reported to be better than 2% relative for major concentrations, using well-polished standards having a composition similar to the sample. A more conservative figure of 4—5% relative should be expected for general analysis using pure element standards. For analysis without... 

In addition to qualitative identification of the elements present, XRF can be used to determine quantitative elemental compositions and layer thicknesses of thin films. In quantitative analysis the observed intensities must be corrected for various factors, including the spectral intensity distribution of the incident X rays, fluorescent yields, matrix enhancements and absorptions, etc. Two general methods used for making these corrections are the empirical parameters method and the fimdamen-tal parameters methods. 

In the discussion so far we have considered the typical LEIS experiment only, i.e. large angles of incidence of exit relative to the surface plane. Under these conditions, in general, quantitative composition analysis is possible, because the ion-target interaction can be considered as a binary collision, because of the absence of matrix effects (see below). 

So far, as in Equation (3.33), the hydrolyses of ATP and other high-energy phosphates have been portrayed as simple processes. The situation in a real biological system is far more complex, owing to the operation of several ionic equilibria. First, ATP, ADP, and the other species in Table 3.3 can exist in several different ionization states that must be accounted for in any quantitative analysis. Second, phosphate compounds bind a variety of divalent and monovalent cations with substantial affinity, and the various metal complexes must also be considered in such analyses. Consideration of these special cases makes the quantitative analysis far more realistic. The importance of these multiple equilibria in group transfer reactions is illustrated for the hydrolysis of ATP, but the principles and methods presented are general and can be applied to any similar hydrolysis reaction. 

It is important to note that the solubility product relation applies with sufficient accuracy for purposes of quantitative analysis only to saturated solutions of slightly soluble electrolytes and with small additions of other salts. In the presence of moderate concentrations of salts, the ionic concentration, and therefore the ionic strength of the solution, will increase. This will, in general, lower the activity coefficients of both ions, and consequently the ionic concentrations (and therefore the solubility) must increase in order to maintain the solubility product constant. This effect, which is most marked when the added electrolyte does not possess an ion in common with the sparingly soluble salt, is termed the salt effect. 

This expression enables us to calculate the exact concentration at the equivalence point in any redox reaction of the general type given above, and therefore the feasibility of a titration in quantitative analysis. 

In the following sections, a brief account of general laboratory apparatus relevant to quantitative analysis will be given. The commonest materials of construction of such apparatus are glass, porcelain, fused silica, and various plastics the merits and disadvantages of these are considered below. 

The stability of the reagent in acid solution, together with its ability to complex a wide range of metals, make it a very useful general extracting reagent, especially for heavy metals. The chief applications of APDC in quantitative analysis are as follows ... 

Solvent extraction is generally employed in analysis to separate a solute (or solutes) of interest from substances which interfere in the ultimate quantitative analysis of the material sometimes the interfering solutes are extracted selectively. Solvent extraction is also used to concentrate a species which in aqueous solution is too dilute to be analysed. 

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