Sample Preparation Using Microwave Acid Digestion

2 Sample Preparation Using Microwave Acid Digestion 

Program Power (W) O/ /o power Time (min) Pressure (psi) Temp. (°C) Hold (min) 

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Table 5.18 Results of comparative study of analysis of 250 ggkg-1 of spiked toxic metals after sample preparation using microwave acid digestion and oxygen bomb combustion. Results in brackets are percentage recovery...

Table 6.8 Results of analysis of metal for metal content of Type A and Type B anaerobic adhesives after sample preparation using microwave acid digestion...

Results. The results of the analysis of epoxy samples after sample preparation using microwave acid digestion are shown in Table 6.19. 

Results. The results obtained by this experiment were between 95 and 109% which is indicative of a good recovery for the listed elements using the ashing method. The metals Pb and Sn were included to test for their volatility in this type of sample (Table 5.13). The method works well for some metals but not for volatile metals. These samples can also be prepared using microwave acid digestion or bomb combustion methods. 

Dry ashing of cmde oils can cause serious loss of ash or elements through volatility of some metals, even in the presence of metal-retaining compounds. The methods using microwave acid digestion or bomb combustion are suitable for sample preparation for most trace metal analysis because they are retained in solution. This includes those that are volatile. Unfortunately, these methods are time-consuming and can be erroneous, and require experience skilled operators, but are necessary because they are precise, accurate and quantitative. 

The benefit of sample preparation techniques using microwave acid digestion and bomb combustion is that the sample is totally enclosed during the decomposition. These methods remove matrix interference and generate aqueous solutions, which can be analysed using ICP-OES. Sub-trace concentrations can be detected when hyphenated attachments are used, e.g. ultrasonic nebuliser, hydride generation or continuous cold vapour method. These methods are essential where trace levels of toxic elements are present that need to be identified and quantified. 

Sample Preparation of Anaerobic Adhesives Using Microwave Acid Digestion... 

Sample preparation using the bombing combustion method has an advantage over the microwave digestion method in that it does not require very strong multi-acidic solutions... 

Table 6.27 Results of analysis of polyurethane (PU) adhesives spiked with 0.1 % organometallic catalysts using destructive methods ashing, microwave acid digestion and bomb combustion methods of sample preparation...

The selectivity and sensitivity offered by atomic spectroscopy techniques can be used for direct and indirect determination of metals in a range of pharmaceutical preparations and compounds. Metals can be present in pharmaceutical preparations as a main ingredient, impurities, or as preservatives which can be prepared for analysis using non-destructive (direct or solvent dilution) or destructive methods (microwave acid digestion, bomb combustion, extraction, etc.) and the metal of interest measured against standards of the metal prepared in the same solvents as the sample. Methods associated with some pharmaceutical products are already described in the international pharmacopoeias and must be used in order to comply with regulations associated with these products, e.g titration techniques are carried out according to methods that are the same for all pharmaceutical products. 

Mercury salts that are present in the formulations in Table 7.8 are used in low and controlled concentrations and must be analysed for their concentration prior to use. Therefore, sample preparation is usually carried out in closed vessels such as microwave acid digestion or bomb combustion and diluted in deionised water to a known volume. 

Microwave acid digestion of the tissue, blood, serum, etc., can be used to prepare samples for metal analysis. The ICP-OES method is useful for monitoring the distribution of platinum compounds in the body but the information alone is not sufficient to support rigorous pharmacokinetic studies required to fully understand the total functionality as a cancer killing drug. 

Analysis of urine samples for metals content is a useful way to study the presence of toxic metals in humans. The metal content can give an indication of the performance of kidneys in regulating the body electrolyte, water metabolism and rate of excretion of metals from the body. ICP-OES can be used to measure the level of heavy metals in urine of both healthy and pathological cases. Sample preparation for analysis of these samples must involve an acid digestion in a microwave oven or bomb combustion to destroy the interfering organics present. Metals such as Pb, Cd, Tl, Se, Sn and Hg are the usual metals requiring analysis. 

The correct choice of sample preparation and analysis will give excellent confidence in the reported results. Microwave acid digestion methods can be used to prepare almost all... 

Principles and Characteristics Instead of thermal initiation, microwave decomposition may be of use for sample preparation involving combustion or acid digestion. The advantages over thermal initiation lie in the shorter time needed (minutes instead of hours). Microwave oven digestion (MOD) systems are not analytical instruments. Functionally, they are chemical... 

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