Organic matrix content

For destructive measuring methods, a CRM would serve as a reference to check the recovery of a particular matrix removal procedure. This is especially important for open destructions at atmospheric pressure. Alternatively, isotope dilution methods may be used once isotopic equilibrium is established, loss of analyte does not affect the analysis result. Isotope dilution techniques are only available in a few specialised laboratories. Another type of problem is encountered in pressurised methods oxidising the matrix in a closed vessel or bomb. Due to the large amounts of gas (CO2, NO, SO2) evolving from samples with a high organic matrix content, an excessive pressure build-up occurs that prohibits the use... 

Combustion techniques are very useful for preparation of samples in which heteroatoms can be converted to ionic species suitable for determination by ion chromatography. Combustion is, therefore, used frequently for the analysis of biological samples, pharmaceutical preparations, polymerized substances, coal and other fuels, as well as foodstuffs and other samples with a very high organic matrix content. " Generally, conventional ion chromatographic methods for sohd samples are ... 

Figure 4.2 (a) A picture taken through the 4x objective in the trabecular bone of an iliac crest biopsy (b) same trabecula through the 15x objective with the area of analysis shaded (c) spatial distribution of the mineral component content (d) spatial distribution of the organic matrix content (e)... 

The presented results allow an understanding of the effect of inadequacy organic matrix of plant reference standai ds and dried milk on XRF result exactness. In the absence of similar RSMs calibrations, obtained with the help of plant RSMs, may be used for analysis of only non-fat milk powders. Correction on fat content will allow a spreading these calibrations on analysis of milk powders with any fat contents. 

From the beginning of 14C studies, bone was burdened with a marginal status as a sample type. It was missing from the list of sample materials which Libby initially recommended [10]. He and other researchers discouraged its use for the reason that the carbon content and specifically the organic carbon content, was low even in relatively recent bone and because it was a very porous structure potentially subject to chemical alteration and presumably to contamination. It was concluded that bone would systematically violate the third assumption of the 14C method as listed in Table 1. (It should be noted that "burned bone" was highly recommended. However, the sample material was the carbonized hair, skin, and other tissue rather than the bone matrix itself.)... 

The homy layer consists of about 10% extracellular components such as lipids, proteins, and mucopolysaccharides. Around 5% of the protein and lipids form the cell wall. The majority of the remainder is present in the highly organized cell contents, predominantly as keratin fibers, which are generally assigned an a-helical structure. They are embedded in a sulphur-rich amorphous matrix, enclosed by lipids that probably he perpendicular to the protein axis. Since the stratum comeum is able to take up considerably more water than the amount that corresponds to its volume, it is assumed that this absorbed fluid volume is mainly located in the region of these keratin structures. 

Widening interest in the quaHty of the environment has led to increased demand for information on a wide range of trace-metal contents of foodstuffs. Trace metals in foodstuffs are normally determined by spectroscopic techniques after complete destruction of the organic matrix. Destruction is achieved either by wet oxidation or by dry ashing additional treatment is normally required in order to obtain the metals of interest in a form suitable for analysis. Both methods of destruction are time consuming and tedious this is particularly true of the wet-oxidation procedure, which has the additional disadvantage of being potentially hazardous the methods require considerable analytical skill and experience. Both methods are prone to produce erroneous results either by the loss of an element of interest or by adventitious contamination from the component parts... 

On a relative basis, i.e. residues per 1000, there is virtually no one species like the other. In contrast, different shell samples from the same species and obtained from the same natural habitat yield identical amino acid patterns. It is of interest that (1) the structure of carbonates (aragonite-calcite-vaterite), (2) the content in trace elements, and (3) the stable isotope distribution are markedly effected by fluctuations in salinity, water temperature, Eh/pH conditions, and some anthropogenic factors. The same environmental parameters determine to a certain degree the chemical composition of the shell organic matrix. This feature suggests a cause-effect relationship between mineralogy and organic chemistry of a shell. In the final analysis, however, it is simply a reflection of the environmentally-controlled dynamics of the cell. 

Volume percentages of organic matter identifiable under the microscope only correlate well with total organic carbon contents if the unstructured groundmass is included in the volume calculation. From a relationship between TOC values, average densities of the rock matrix and the organic matter we deduce that in most samples the microscopic kerogen evaluation accounted for at least 80% of... 

Growing concern over environmental effects of acid rain has resulted in increased Interest in development of pre-combustion removal of sulfur from coal. Physical coal cleaning processes are effective for pyritic sulfur removal but do little to reduce the organic sulfur content of coal This paper reports the removal of organic sulfur from coal, employing ethyl or methyl alcohols as the solvent/ reactant. The process is based on the observation that, under supercritical conditions, reactions occur that selectively remove organic sulfur from the coal matrix. 

What properties of the matrix could affect availability (pH, organic matter content, etc.) ... 

This decrease in the organic sulfur content of the Lovilia/ROM coal was corroborated by a series of extraction experiments employing ASTM procedures and other analyses for sulfur and iron. The removal of organic sulfur from the other two coals could not be confirmed by this method. However, the different extraction procedures pointed to possible changes in the mineral components and in the organic matrix itself of the coals after the chemical desulfurization treatment. Such changes can affect the analytical values obtained by ASTM procedures. 

---