Direct analysis

The chloroplatinates prepared as above are sufficiently pure for direct analysis without recrystallisation. The chloroplatinates of the amines are usually freely soluble in hot water, but recrystallisation (when required) should not be attempted until the process has been found to be successful with a small test-portion of the chloroplatinate. The chloroplatinates of many primary and secondary amines decompose in hot water, the amine being oxidised, and the chloroplatinate reduced to the metal some amines furthermore co-ordinate readily with the metal when the chloroplatinate is boiled with water and a mixed product is obtained on cooling. 

In electrogravimetry the analyte is deposited as a solid film on one electrode in an electrochemical cell. The oxidation of Pb +, and its deposition as Pb02 on a Pt anode is one example of electrogravimetry. Reduction also may be used in electrogravimetry. The electrodeposition of Cu on a Pt cathode, for example, provides a direct analysis for Cu +. 

Quantitative Calculations In precipitation gravimetry the relationship between the analyte and the precipitate is determined by the stoichiometry of the relevant reactions. As discussed in Section 2C, gravimetric calculations can be simplified by applying the principle of conservation of mass. The following example demonstrates the application of this approach to the direct analysis of a single analyte. 

This is an example of a direct analysis since the iron in the analyte, Fe304, is part of the isolated precipitate, Fe203. Applying a conservation of mass to Fe, we write... 

This is an example of a direct analysis in which the two analytes are determined without a prior separation. The weight of the original precipitate and the ignited precipitate are given by the following two equations... 

Two methods have been proposed for the analysis of sulfur in impure samples of pyrite, EeS2. Sulfur can be determined in a direct analysis by oxidizing it to S04 and precipitating as BaS04. An indirect analysis is also possible if the iron is precipitated as Ee(OH)3 and isolated as Ee203. Which of these methods will provide a more sensitive determination for sulfur What other factors should be considered in deciding between these methods ... 

Calcium ion plays an important role in many aqueous environmental systems. A useful direct analysis takes advantage of its reaction with the ligand ethylenedi-aminetetraacetic acid (EDTA), which we will represent as... 

The following example demonstrates the application of this approach in the direct analysis of a single analyte. 

Selection and Standardization of Titrants EDTA is a versatile titrant that can be used for the analysis of virtually all metal ions. Although EDTA is the most commonly employed titrant for complexation titrations involving metal ions, it cannot be used for the direct analysis of anions or neutral ligands. In the latter case, standard solutions of Ag+ or Hg + are used as the titrant. 

Scale of Operation The scale of operations for atomic emission is ideal for the direct analysis of trace and ultratrace analytes in macro and meso samples. With appropriate dilutions, atomic emission also can be applied to major and minor analytes. 

Three common quantitative applications of radiochemical methods of analysis are considered in this section the direct analysis of radioactive isotopes by measuring their rate of disintegration, neutron activation, and the use of radioactive isotopes as tracers in isotope dilution. 

Direct Analysis of Radioactive Analytes The concentration of a long-lived radioactive isotope is essentially constant during the period of analysis. As shown in Example 13.6, the sample s activity can be used to calculate the number of radioactive particles that are present. 

The direct analysis of short-lived radioactive isotopes using the method outlined in Example 13.6 is less useful since it provides only a transient measure of the isotope s concentration. The concentration of the isotope at a particular moment... 

For solids, there is now a very wide range of inlet and ionization opportunities, so most types of solids can be examined, either neat or in solution. However, the inlet/ionization methods are often not simply interchangeable, even if they use the same mass analyzer. Thus a direct-insertion probe will normally be used with El or Cl (and desorption chemical ionization, DCl) methods of ionization. An LC is used with ES or APCI for solutions, and nebulizers can be used with plasma torches for other solutions. MALDI or laser ablation are used for direct analysis of solids. 

It is interesting to compare data for headspace volatiles of the living vs picked and both of these with respect to the direct analysis of the extracts shown ia Table 19. 

Compaction Cycles Insight into compaction performance is gained from direct analysis of pressure/density data over the cycle of... 

The concentration of acid impurities is an important indication of the quality of petroleum products and the purity of organic solvents, plasticizers, mineral oils, food fats, and polymers. Methods are used to detect organic acids in such compounds have many disadvantages the alkalimetry - low sensitivity, especially in the determination of weak acids, the extraction-photometric method is laborious, instmmental methods are expensive. In addition, most of methods are commonly unsuitable for direct analysis. 

DIRECT ANALYSIS OF UNSTABLE GAS CONDENSATE USING HIGH-PRESSURE SUPPLY OF THE SAMPLES INTO A GAS CHROMATOGRAPH... 

There are two main approaches to its solution. Traditional approach is based on preliminary separation of UGC samples to gaseous and liquid phases and their subsequent analyses [1]. This approach is well-developed and it allows obtaining quite precise results being used properly. However, this method is relatively complicated. Multi-stage procedure is a source of potential errors, then, it makes the analyses quite time consuming. More progressive approach is based on the direct analysis of the pressurized UGC samples. In both cases the determination of heavy hydrocarbons (up to C ) is made by capillary gas chromatography. 

Sample conductivity Conductors and semiconductors direct analysis insulators (>10 (ohm-cm) ) pulverize and mix with a conductor... 

ICP-OES is one of the most successful multielement analysis techniques for materials characterization. While precision and interference effects are generally best when solutions are analyzed, a number of techniques allow the direct analysis of solids. The strengths of ICP-OES include speed, relatively small interference effects, low detection limits, and applicability to a wide variety of materials. Improvements are expected in sample-introduction techniques, spectrometers that detect simultaneously the entire ultraviolet—visible spectrum with high resolution, and in the development of intelligent instruments to further improve analysis reliability. ICPMS vigorously competes with ICP-OES, particularly when low detection limits are required. 

In situ quantitation The direct analysis was carried out at A = 510 nm if the zones were red in color and at Z = 620 nm if they were violet. 

Direct analysis with the fluoride lon-selective electrode requires addition of total ionic strength adjustor buffer solution (TISAB) to the standard and to unknown samples Some advantages of this addition are that it provides a constant background ion strength, ties up interfenng cations such as aluminum or iron, which form a complex with fluoride ions, and maintains the pH between 5 0 and 5 5 According to the manufacturer s claim, reproducibility of direct electrode measurement IS 2 0%, and the accuracy for fluonde ion measurement is 0 2% [27]... 

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