Sample preparation digestion

A web-site dedicated to sample preparation, which contains useft information about acid digestion and microwave digestion, is found at... 

Two methods of sample preparation were investigated. The former is dilution of blood semm with 0.1% Triton X-100, the latter is aeid mierowave digestion. As evaluated, the most adequate mineralization proeedure for determining the majority of elements in blood semm by ICP AES is aeid mierowave digestion. However, the ICP AES determination of abundant elements (B, Si, Mn), whieh present in semm at 0.001-0.01 ppm levels should be follow sample dilution with Triton X-100. 

Destructive solid sample preparation methods, such as digestion and mineralisation, are well known as they have been around for some time they are relatively cheap and well documented [13-15]. Decomposition of a substance or a mixture of substances does not refer so much to the dissolution, but rather to the conversion of slightly soluble substances into acid- or water-soluble (ionogenic) compounds (chemical dissolution). 

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... 

The use of microwave digestion-wet oxidation overcomes sample preparation problems for many polymer-based materials. However, this will result in a reduction in sensitivity compared with an ashing procedure, because of dilution. Use of an aqueous phase is not... 

Samples of digest were prepared using either the maxibomb digester shown in Figure 3 or a smaller digestion vessel (minibomb) described elsewhere (12). The maxibomb consisted of a length of 25 mm o.d. stainless steel tube closed at one end... 

The last sample preparation method for IMS is the transfer of a tissue section onto the PVDF membrane. Proteins in the section can be transferred onto the PVDF membrane and then analyzed on the membrane. The advantage of this method is that the enzyme can be digested for MS" measurement, because the information on protein localization in the organization is fixed on the membrane.5,20 This technique can denature, reduce, and digest the proteins in the tissue section efficiently and remove the salt from the tissue. This increases the efficiency with which biological molecules are ionized, making it possible to obtain sensitive mass imaging spectra. 

The choice of the appropriate time for the enzymatic cleavage is a critical point of sample preparation. All types of the reference proteinaceous binders (Section 6.2.3) were cleaved from 1 to 24 h at laboratory temperature 20 25 °C. The peptide peaks in the interval 900 2000 Da were registered below 900 Da the peaks of the matrix interfere and above 2000 Da the incompletely cleaved oligopeptides are present which makes interpretation difficult. The best result, i.e. the highest number of peaks, was obtained after digestion for 2 h at laboratory temperature [32]. 

If pronase digestion of the biotinylated protein is to be done, heat 100 pi of the sample at 56°C for 10 minutes, then add 10 pi of the pronase solution. Allow the sample to digest enzymatically at room temperature overnight. If no pronase digestion is desired, simply use the biotinylated protein solution prepared in step 3 without further treatment. 

Ammonium pyrrolidine dithiocarbamate (APDC) chelate coprecipitation coupled with flameless atomic absorption provides a simple and precise method for the determination of nanomol kg 1 levels of copper, nickel, and cadmium in seawater. With practice, the method is not overly time-consuming. It is reasonable to expect to complete sample concentration in less than 20 min, digestion in about 4 h, and sample preparation in another hour. Atomic absorption time should average about 5 min per element. Excellent results have been obtained on the distribution of nickel and cadmium in the ocean by this technique. 

Sample Preparation Effects Many methods require the sample to be treated in some way before the analyte can be determined. Examples include drying, grinding or blending of the sample, and extraction or digestion of the sample. Variations in the conditions under which these activities are carried out (e.g. extraction temperature and time, solvent composition) may affect the final result. 

A chloric acid digestion was used by Backer 2 391 for the preparation of tissue samples. The digest is simply diluted to determine iron, zinc, and copper. The tantalum sampling boat technique was used by Emmermann and Luecke 2531 to measure lead, zinc, and silver in prepared soil solutions. White 1S81 treated ashed plants with hydroxylamine in IN hydrochloric acid to reduce and dissolve oxides of manganese, prior to its determination by atomic absorption spectroscopy. 

The micropipette tip containing solid phases is a relatively new sample preparation technique that permits handling of microliter to submicroliter amounts of liquid samples, using the techniques of SPE, dialysis, and enzyme digestion. Various phases (reversed-phase, affinity, size-exclusion, etc.) are packed, embedded, or coated on the walls of pipette, permitting liquid samples to be transferred without undue pressure drop or plugging (Fig. 2.5). 

Safety While we list safety last, safety must always be at the top of the list of considerations. For example, you should not even consider a method requiring perchloric acid digestion for sample preparation unless your facility has the appropriate quality fume hood. In Table 21.10, we have listed some of the many safety issues you need to evaluate. 

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