Sample Preparation Using Leaching Method

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. 

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. 

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... 

Liquid and gas chromatography were used for determination of emcamide and oleamide in body organs, containing nanogram quantities of additives per gram of sample. Chromatographic methods were also used to identify leached slip additives from containers for pharmaceutical preparations. ... 

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