Sampling mass reduction

To demonstrate the effect in more detail a series of experiments was carried out similar to that of volume overload, but in this case, the sample mass was increased in small increments. The retention distance of the front and the back of each peak was measured at the nominal points of inflection (0.6065 of the peak height) and the curves relating the retention data produced to the mass of sample added are shown in Figure 7. In Figure 7 the change in retention time with sample load is more obvious the maximum effect was to reduce the retention time of anthracene and the minimum effect was to the overloaded solute itself, benzene. Despite the reduction in retention time, the band width of anthracene is still little effected by the overloaded benzene. There is, however, a significant increase in the width of the naphthalene peak which... 

Any mass reduction method must be in compliance with the fundamental sampling principle, that all parts of the lot (or subsample) have equal probability of ending up in the final sample (or subsample) for analysis. 

A salient example from the process sampling realm is therefore given here. In the routine PAT laboratory it was desired to perform a mass reduction as part of the process of transporting a powder material. A bypass stream was established and on this the device depicted in Fignre 3.5 is snpposed to deliver one 10% snb-sample, another 25% snbsample, with the remaining 65% ( reject ), fed back to the main stream. 

Petersen L, Dahl CK, Esbensen KH. Representative mass reduction in sampling—a critical survey of techniques and hardware. Chemom Intell Lab Syst 2004 74 95-114. 

Sampling in its strict sense is therefore a simple mass reduction. 

The influence of reactor temperature and duration of the pyrolysis process on the weight percentage of As in the pyrolysis residue and on the mass reduction of the wood sample is illustrated in Figure 3. Since the same trends are observed for the two other metals (Cr and Cu), the retainment of these metals in the pyrolysis residue is not presented here. 

The radioanalytical chemist finds several applications of the use of solvent extractions as mass-reduction steps prior to performing chromatographic procedures, particularly following non-isotopic carrying steps, or for samples whose dissolution included a substrate or container. For example, if iron hydroxide has been used as a co-precipitant, the subsequent removal of the iron can be accomplished by extraction from a hydrochloric acid solution into hexone (methyl isobutyl ketone). Nickel can be removed from a nitric acid solution by extraction into a chloroform solution of dimethylglyoxime. 

In Fig. 32.15, the effect of laterite-lignite mass on the reduction degree of laterite at an input power of 800 W and two times the stoichiometric addition of carbon is presented. By increasing the laterite s mass from lOg (I3.5g of mixture) to 365.5 g (493.5 g of mixture), a strong decrease of the reduction degree is observed, from about 70 to 25%. The effect on the reduction degree of sample mass should be correlated with the temperatures achieved for the respective samples under a given microwave radiation. Fig. 32.16. 

Logarithmic scale diagram of reduction degree as a function of sample mass for a laterlte-lignite mixture with two times the stoichiometric carbon addition at 800 W. (Reproduced from Ref. 19 with permission of Elsevier.)... 

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