Sample preservation significance

An important consideration in sample preservation is the observance of holding time, which is defined by ASTM (ASTM, 1987) as follows The period of time during which a water sample can be stored after collection and preservation without significantly affecting the accuracy of analysis. ... 

This study enables us to draw a parallel between the behaviours of alumina and HY zeolite upon impregnation with oxomolybdate entities. In some conditions, when the buffer effect of the alumina is avoided, both supports see extraction of aluminium atoms and their inclusion in an Anderson-type heteropolyanion, AIMo6024H6. This entity is well dispersed on the alumina support whereas it appears as a bulk compound located in the macropores of the HY zeolite. However, it is still unknown whether the formation of this species is to be favoured. For promoted samples, a significant difference exists between both supports, since CoMo6024H6 can be preserved upon impregnation on a zeolite. Yet, the preparation of the catalysts has to be controlled the final calcination-rehydration steps tend to level the various synthesis and lead to the presence of AIMo6024H6. ... 

The effect of sample preservation on determination of F in healthy and pathological human thyroids has also been studied (Blazewicz et al., 2011). It was pointed out that the way of tissue preservation (either in formalin or by freezing) had no significant effect on the iodine determination result (a = 0.1) by ion chromatography combined with the pulsed amparometic detection method (IC-PAD). Sample decomposition is a critical step in iodides analysis as well. All reported methods have a digestion or ashing step prior to the final determination of... 

Nevertheless, the changes in the porosity are still less pronounced than those induced by ion exchange, especially in the case of silver. For ion-exchanged samples, a significant decrease in the specific adsorbent area and increase in the pore diameters compared either to the initial SiA120 sample or to the impregnated one and modified by direct incorporation is observed. This is probably due to the blockage of smaller pores, and thus only a part of metal ions are accessible to alkene molecules. Direct incorporation of Ag(l) or Cu(II) nitrate is accompanied by a small increase in the mean pore diameter. This procedure better preserves... 

The fifteen samples analyzed for amino acid composition were compared to a human type 1 collagen standard. There are no significant differences in amino acid composition among these samples, which range in age from stillbirth to adult. Analytical error is 10%. All samples show the typical composition of type 1 collagen (Table 1.1). Based on these results there is no reason to suspect differential preservation of specific amino acids in the small bones of infants in comparison to bones of adults and older children. 

None of the elemental data show any correlation with collagen yield. When compared to yield, the correlation coefficients are non-significant for C N (r = 0.4), %C (r = 0.4) and %N (r = 0.2). All samples with low elemental values are from layers of bone that showed poor histological preservation. While low values tend to come from bone with poor histological preservation, many samples from bone of equally poor preservation produced acceptable values. Lipid removal generally improved both the yield characteristics and elemental values. 

Sample preparation used to extract proteins from cells prior to analysis is an important step that can have an effect on the accuracy and reproducibility of the results. Proteins isolated from bacterial cells will have co-extracted contaminants such as lipids, polysaccharides, and nucleic acids. In addition various organic salts, buffers, detergents, surfactants, and preservatives may have been added to aid in protein extraction or to retain enzymatic or biological activity of the proteins. The presence of these extraneous materials can significantly impede or affect the reproducibility of analysis if they are not removed prior to analysis. 

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