Instrument factor

Precision When the analyte s concentration is well above the detection limit, the relative standard deviation for fluorescence is usually 0.5-2%. The limiting instrumental factor affecting precision is the stability of the excitation source. The precision for phosphorescence is often limited by reproducibility in preparing samples for analysis, with relative standard deviations of 5-10% being common. 

Labor factors are added to the instrument factors G = good, F = fair, P = poor. 

Instrumental factors. Heating rate. When a substance is heated at a fast rate, the temperature of decomposition will be higher than that obtained at a slower rate of heating. The effect is shown for a single-step reaction in Fig. 11.4. The curve AB represents the decomposition curve at a slow heating rate, whereas the curve CD is that due to the faster heating rate. If TA and Tc are the decomposition temperatures at the start of the reaction and the final temperatures on completion of the decomposition are TB and TD, the following features can be noted ... 

The second issue relates to the risk of perceptions about inappropriate relations between mentor and mentee (Wickman and Sjodin, 1997). Male-female mentoring relationships are perhaps exposed to greater scrutiny than same-gender pairs, and this may put extra pressure on both participants to emphasize career/instrumental factors at the expense of genuine and legitimate psychosocial benefits. 

A striking observation that lacks a satisfactory explanation is the existence of magic numbers, i.e. the fact that in a distribution of clusters some species with a certain number of carbon atoms are much more abundant than others. The exact clustering mechanisms are not completely understood, and, as noted by Rohifing et al.(IO), the origin of the observed distribution of clusters may depend upon instrumental factors. Accounting for this fact, however, there still seems to be a preference for clusters with certain numbers of atoms which cannot be explained solely as due to the experimental conditions. 

Other factors contribute to broadening. Instrumental factors are particularly difficult to remove from the breadth, and the effects of local strain can only be approximated. 

Where XA is the concentration of element A and dI /dXA is the absolute sensitivity factor of element A in matrix M. A calibration curve is established using known samples for each element in each matrix. Unknown concentrations may then be determined provided all instrumental factors and experimental conditions are held constant, which conditions may be difficult to fulfil. 

Factor Control Instrument Factor Labor Factor ... 

A and B are instrumental factors and g(T) the electric field correlation function which is related to the translational diffusion coefficient D by... 

Figure 4. Fluorescence spectra of Cu atoms isolated in solid Ar at 12 K (Cu/Ar 1/104) uncorrected for instrumental factors. The corresponding excitation wavelengths are indicated on the absorption spectrum shown at the upper left. (Reproduced from Ref. 34. Copyright 1982, American Chemical Society.)...

X-ray line broadening provides a quick but not always reliable estimate of the particle size. As Cohen [9] points out, the size thus determined is merely a ratio of two moments in the particle size distribution, equal to /. Both averages are weighted by the volume of the particles, and not by number or by surface area, as would be more meaningful for a surface phenomenon such as catalysis. Also, internal strain and instrumental factors contribute to broadening. 

Wendlandt has provided an extensive compilation of conditions and requirements that influence the shape of DTA thermograms [18]. These can be divided into instrumental factors (furnace atmosphere, furnace geometry, sample holder material and geometry, thermocouple details,... 

A common theme of industry guidelines is that every test result must be individually interpreted because of limitations and variations in conditions, and the complexity of the instrument. Factors such as sample size, container material, and heating rate can greatly affect results. Therefore, personnel with appropriate training and experience should be consulted both before testing and for interpretation of results. 

Fluorescence quantum yields are usually determined by integration of the fluorescence spectrum (and subsequent normalization using a standard of known fluorescence quantum yield in order to get rid of the instrumental factor k appearing in Eqs 3.17 or 3.18 see Chapter 6). In practice, attention should be paid to the method of integration. 

The analysis of a full tilt series of 2H NMR spectra not only allows the determination of the unique bond angle for a deuteriated methyl group, but also provides an internal check for the consistency of the spectral interpretation. In particular, simulations provide a means for the analysis of line-broadening effects, which arise from the sample mosaic spread as well as the intrinsic line width of the nuclear transition and instrumental factors. When line shapes are fitted to a full tilt series of spectra in a concerted manner and are also compared with the powder spectrum of an unoriented sample, the different contributions can be discerned. In that way an intrinsic line width of around 2 kHz is found for the spectra shown here, together with a mosaic spread between 8° and 10° for the three samples. 

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