Analytical method sample size

A major advantage of static SIMS over many other analytical methods is that usually no sample preparation is required. A solid sample is loaded directly into the instrument with the condition that it be compatible with an ultrahigh vacuum (10" —10 torr) environment. Other than this, the only constraint is one of sample size, which naturally varies from system to system. Most SIMS instruments can handle samples up to 1-2 inches in diameter. 

On the basis of sample size, analytical methods are often classified as ... 

Mass loss determinations refer to the total change resulting from reactant decomposition and usually include contributions from a mixture of product compounds, some of which would normally be condensed under conditions used for accumulatory pressure measurements. Such information concerned with the overall process is, however, often usefully supplemented by evolved gas analyses (EGA) using appropriate analytical methods. Sestak [130] has made a detailed investigation of the effects of size and shape of reactant container on decomposition kinetics and has recommended that the sample be spread as a thin layer on the surfaces of a multiple plate holder. The catalytic activity of platinum as a reactant support may modify [131] the apparent kinetic behaviour. 

By utilizing the HPLC method, it is possible to determine the level of each individual toxin in sample solutions. This provides a "toxin profile" that can be very useful in PSP toxin research studies. The ability to examine relative changes in toxin concentration and profile has greatly facilitated studies relating to toxin production by dinoflagellates, metabolism of toxins in shellfish, and movement of toxins up the food chain. Since the HPLC method is easily automated and requires only very small sample sizes (< 1 g tissue), it has clear advantages over other analytical procedures for the toxins in many research situations. Two examples of the utilization of HPLC for the study of the PSP toxins follow. 

A comparison is made of the detector signal in the absorption versus scattering mode. Particle sizes are calculated for the standard latex samples and their mixtures using recently reported analytical. methods which account for imperfect resolution. 

The importance of particle size is directly proportional to the sub-sample size recommended by the analytical method. The larger the sub-sample size the larger the acceptable particle size. For sub-sample sizes of ig or greater a soil sieved through a imm screen is generally acceptable. Therefore if the sample is relatively coarse, e.g up to 2mm particles and the matrix CRM is an uniform sub-micron powder, it may be necessary to use a much larger sample from the material under test than for the CRM. 

The composition, properties and size (weight, volume) of the sample material to be analyzed are important aspects for analytical method development and for analyte enrichment vs depletion of sample matrix. 

As the sensitivity and selectivity of the above GC/MS methods are for many analytes around 1 pg injected into the GC system, cleanup by SiOa fractionation can be omitted when larger sample sizes (25-100 g) are possible. For difficult dry (e.g. hops, pharmaceutical herbs) or oily (e.g. rape seed, fat, liver) materials which start with smaller sample sizes (5-10 g) and tend to overload the chromatographic cleanup systems, however, cleanup is still an important requirement as the GC injection system is vulnerable when the ratio of co-extracted material to analyte is too high. 

The following is a general method for ground and surface water samples. Interferences in particular samples may require modification of this method. The analytical sample size is 200 mL, but the volume may be varied depending on the concentration of analytes in the sample. 

An example of adequate sample homogenization is given in Table 4. The experiment was conducted with two replicate treated soil samples. Each replicate was analyzed in duplicate. Three different sample aliquots (2, 5 and 10 g) were used from each replicate. Analyses of controls and fortified samples were also conducted concurrently with treated samples to evaluate method performance (i.e., extraction recoveries). These results show that residue values are the same regardless of sample size. Thus, thorough homogenization of soil samples coupled with mgged analytical methodology provides for satisfactory residue analysis. 

It was observed that the factors contributing to the variation of leachate data are solid waste characteristics, for example, the composition and size of the waste and degree of compaction, the moisture content and degree of rainwater infiltration, temperature, sampling, and analytical methods.47... 

Analytical method Minimum detectable (mg) Sample size (mg)... 

The structure of the catalysts was characterized by X-ray diffraction, IR-spectroscopy and transmission electron microscopy, their thermal stability was followed by thermal analytical method. The specific surface area and pore size distribution of the samples were determined by nitrogen adsorption isotherms. 

Yamamoto et al. [33] applied this technique to the determination of arsenic (III), arsenic (V), antimony (III), and antimony (V) in Hiroshima Bay Water. These workers used a HGA-A spectrometric method with hydrogen-nitrogen flame using sodium borohydride solution as a reductant. For the determination of arsenic (III) and antimony (III) most of the elements, other than silver (I), copper (II), tin (II), selenium (IV), and tellurium (IV), do not interfere in at least 30 000-fold excess with respect to arsenic (III) or antimony (III). This method was applied to the determination of these species in sea water and it was found that a sample size of only 100 ml is enough to determine them with a precision of 1.5-2.5%. Analytical results for surface sea water of Hiroshima Bay were 0.72 xg/l, 0.27 xg/l, and 0.22 xg/l, for arsenic (total), arsenic (III), and antimony (total), respectively, but antimony (III) was not detected. The effect of acidification on storage was also examined. 

Mass balance calculations were performed on till samples using Sn concentrations. Tin concentrations in till are sensitive to grain size partitioning and differing analytical methods, thus results from these calculations are qualitative. In the till, concentration gains relative to Sn in Zn, Au, Cd, Hg and Co were obvious after performing the calculations all of... 

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