Leaching sample preparation methods

This chapter gives an overview of decomposition methods and recent developments and applications of the decomposition of different materials. Other sample preparation methods, such as chemical extraction and leaching, solubilization with bases, enzymatic decomposition, thermal decomposition, and anodic oxidation, are beyond the scope of this contribution and are not discussed. 

Another example of ultrasound use is leaching of organic impurities from different kinds of samples. The main analytes of interest are PAHs, which are widespread in soil, sediment, dust, and particulate samples [55]. USE is recommended as a fast, efficient, and direct environmental sample preparation method for determination of PCBs, nitrophenols, pesticides, or polymer additives. Organometallic and biologically active compounds (such as vitamins A, D, and E) present in samples in trace quantities, can be extracted from animal and plant tissues with the aid of ultrasonic wave energy [59]. Table 6.6 presents some typical applications of USE in trace analysis of biological and environmental samples [60]. 

Polychlorinated biphenyls (PCBs) are also frequently included in pollutant monitoring programmes owing to their substantial persistence and accumulation in the environment. This has raised the need to develop methods for their routine analysis. USAL as a sample preparation method is an effective choice for the fast, efficient and straightforward removal of these compounds, as shown by the method for the determination of 146 PCBs in heron eggs [119], where ultrasonic leaching resulted in improved precision, efficiency and reliability under the operational conditions proposed. USAL was used prior to the... 

For the precise AMS analysis of Be and A1, Hunt et al. (2008) reported an efficient sample preparation method, where quartz was separated from rocks following a sequence of pulverization, size fractionation, acid etching and leaching, and liquid density separation. This protocol yields pure quartz mineral phase, however, trace-level contamination is expected. Most of the time quartz is contaminated due to lattice imperfections with some combination of native Al, Fe, Ti, alkalis, and alkaline earth metals. 

All reagents and solvents that are used to prepare the sample for analysis should be ultrapure to prevent contamination of the sample with impurities. Plastic ware should be avoided since these materials may contain ultratrace elements that can be leached into the analyte solutions. Chemically cleaned glassware is recommended for all sample preparation procedures. Liquid samples can be analyzed directly or after dilution when the concentrations are too high. Remember, all analytical errors are multiplied by dilution factors therefore, using atomic spectroscopy to determine high concentrations of elements may be less accurate than classical gravimetric methods. 

The selectivity of amperometric detection has been useful in simplifying the sample pretreatment steps in the determination of a number of drug products [82-86]. A method requiring no sample preparation using an amperometric detector and UV detector in series was developed for lido-caine hydrochloride injectable solutions [87]. The drug epinephrine is quantified with the amperometric detector, whereas lidocaine and methyl para-ben are detected by ultraviolet light. Disodium EDTA had to be added to the mobile phase to eliminate a peak response from iron leached from the stainless steel. 

Solid-phase microextraction (SPME) is a technique that was first reported by Louch et al. in 1991 (35). This is a sample preparation technique that has been applied to trace analysis methods such as the analysis of flavor components, residual solvents, pesticides, leaching packaging components, or any other volatile organic compounds. It is limited to gas chromatography methods because the sample must be desorbed by thermal means. A fused silica fiber that was previously coated with a liquid polymer film is exposed to an aqueous sample. After adsorption of the analyte onto the coated fiber is allowed to come to equilibrium, the fiber is withdrawn from the sample and placed directly into the heated injection port of a gas chromatograph. The heat causes desorption of the analyte and other components from the fiber and the mixture is quantitatively or qualitatively analyzed by GC. This preparation technique allows for selective and solventless GC injections. Selectivity and time to equilibration can be altered by changing the characteristics of the film coat. 

C before pyrolysis started. During decomposition of the oxalate at higher temperatures, cavities were formed by the release of C02- These cavities were then filled up with molten CoTMPP. EHie to the successive pyrolysis of CoTMPP within the cavities, carbon was formed and partially covered the reaction products of the oxalate decomposition. The surface area of leached samples was determined. It ranged from 400 to 700 m /g. This new preparation method led to an enhanced activity in terms of current densities. The catalyst was more active than that made at the same pyrolysis temperature by impregnation of CoTMPP on Vulcan. Pyrolysis of pure CoTMPP led only to dense particles with low catalytic activity. 

The quantitation of inorganic ions in sludge, leachates, and similar solid wastes by ion chromatography is similar, in practice, to the analysis of soil samples. Such samples are typically leached under aqueous conditions, then filtered and pretreated using solid-phase extraction (SPE), if necessary, before injection. Sludges and solid-waste samples can be prepared for analysis by ion chromatography using combustion methods. 

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