Sample comminution

Formaldehyde Removal By Gas Elution. These experiments involve the continuous collection of formaldehyde removed by a controlled flow of gas over the wood samples. Variables studied include time, gas flow rate, sample comminution, gas type, humidity, and adhesive type. 

Spanjer, M.C., Scholten, J.M., Kastrup, S., Jorissen, U., Schatzki, T.F. Toyofuku, N. (2006) Sample comminution for mycotoxin analysis dry milling or slurry mixing Food Addit. 

Comminution of explosive materials represents a particularly high hazard and must, therefore, be left to qualified laboratory staff with special training in this area. Included in explosion hazard is the risk of dust explosions, always likely to be present in grinding operations involving high degrees of sample comminution. 

Mechanical treatment of samples, ranging from comminution by grinding to imposition of stresses along defined crystallographic directions in... 

Although SPME was applied initially for the analysis of relatively volatile environmental pollutants in waters, rapid developments have enabled SPME to be successfully applied for the analysis of pesticides in water, wine and more complex food samples such as honey, fruit juice and pears, vegetables and strawberries. With food samples, most analysts recognize the need for some sample pretreatment in order to minimize matrix effects. The matrix can affect the SPME efficiency, resulting in a reduced recovery of pesticides. The most common method is simply to dilute the sample or sample extract with water. Simpltcio and Boas comminuted pears in water prior to the determination of pesticides. Volante et al. extracted over 100 pesticides... 

Having comminuted the sample it may now be required to carry out a sieving analysis in order to obtain different size fractions for chemical analysis. Fritsch supply a range of devices for sieving analysers (Table 14.2). A practical scheme for sieving a soil sample is discussed below. 

Having as necessary, dried, homogenized or comminuted the samples, they must now be digested in a suitable reagent to extract elements in a suitable form for chemical analysis. In many organizations we have reached the point where the analyses pass from the hands of the person who took the sample to those of the analytical chemist. In the author s experience, however, it must be emphasized that to ensure best-quality results the whole procedure from, for example, statistically sampling a sediment to the final chemical analysis, should be handled by the same person. 

The CH is an intrinsic property of the material to be sampled, in which the individual units (particles, grains, etc.) are considered unalterable and indivisible (t/comminuted by the sampling process. The TOS calls all such units fragments. 

The grain size has a definite quantitative effect on the results. As the grain size is increased, resistance decreases. This is probably due to different intensities of the impulse action of the steel ball during comminution of the abradant samples which though of identical weight, differ in grain size. 

Bakon and Charkiewicz (1982) using the MAL tester carried out comparative tests with synthetic diamonds manufactured by De Beers (grades RDA, MDAS, SDA100, SDA, MDASE), in the USSR (grades ACO ACP, ACB, ACK) and in Poland (grades PDS, and MDS/MDS-k, MDS-s). Diamond samples were comminuted, and the following parameters were used vibration amplitude 5 0.1 mm, vibration frequency... 

Fig. 10.3. Steel capsule, in which diamond samples were being comminuted.

Before a food sample can be analyzed, consideration must be given to obtain a representative sample (66,67). The amount of sample material to be taken for analysis depends upon the inherent homogeneity of the material or the homogeneity achieved after comminution. 

Raw materials are the main means of carrying spoilage yeasts into the factory. Materials include liquid sugars, juice concentrates, comminutes and natural colors and flavours. Sample size is 250 ml (minimum). 

Comminution also may be used to examine the stability of dispersed phases such as oil droplets. Depending on the viscosity of the product one simply mixes it or breaks it up in a solvent (usually water but, for example, use fresh soybean oil for chocolate), a buffer or the appropriate dyes (below). For instance, we mix easily dispersible foods (cream cheese, ice cream mix or tablespreads) with dyes on slides in a ratio of about 1 1 before examination. Where the dye is a diachrome (that is, highly colored) or is fluorescent in the absence of the substrate (for example, Acridine Orange) some attempt must be made to remove excess, uncomplexed dye molecules which might confound the interpretation. This can be done by reduction of the dye concentration or by making the preparation thinner. The advantage of these simple techniques is that a battery of microchemical tests to identify protein, lipid and carbohydrate can be completed on multiple samples in a very short time period. 

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