Sample geometry, differences quantitation

Holzbecker and Ryan [825] determined these elements in seawater by neutron activation analysis after coprecipitation with lead phosphate. Lead phosphate gives no intense activities on irradiation, so it is a suitable matrix for trace metal determinations by neutron activation analysis. Precipitation of lead phosphate also brings down quantitatively the insoluble phosphates of silver (I), cadmium (II), chromium (III), copper (II), manganese (II), thorium (IV), uranium (VI), and zirconium (IV). Detection limits for each of these are given, and thorium and uranium determinations are described in detail. Gamma activity from 204Pb makes a useful internal standard to correct for geometry differences between samples, which for the lowest detection limits are counted close to the detector. 

A rapid, nondestructive method based on determination of the spatial distribution of ATP, as a potential bioindicator of microbial presence and activity on monuments, artworks, and other samples related to the cultural heritage, was developed [57], After cell lysis, ATP was detected using the bioluminescent firefly luciferin-luciferase system and the method was tested on different kinds of surfaces and matrices. Figure 3 reports the localization of biodeteriogen agents on a marble specimen. Sample geometry is a critical point especially when a quantitative analysis has to be performed however, the developed method showed that with opti-... 

The major problem with dta stems from the difficulty of obtaining a uniform temperature throughout the sample. For this reason, there is rarely quantitative agreement between the results of different workers. The peak shape and area on the thermogram are affected by non-uniformity of furnace temperature, rate of heating, sample geometry, particle size, and dilution with inert material. In many instances, the atmosphere above the sample also influences the reaction. 

Canonical ensemble density functional theory (CEDFT) has been employed for predicting hysteretic adsorption/desorption isotherms in nanopores of different geometries in the wide range of pore sizes (1 - 12 nm). It is shown that the CEDFT model qualitatively describes equilibrium and spinodal transitions and is in a reasonable quantitative agreement with experiments on well-characterized MCM-41 samples. A DFT-based method for calculating pore size distributions from the adsorption and desorption branches of nitrogen adsorption isotherms has been elaborated and tested against literature data on capillary condensation in MCM-41 samples with pores from 5 to 10 nm. 

---