Factors responses

The composition of PPG—PEG blends has been determined using gpc with coupled density and RI detectors. PEG and PPG have different response factors for the density and RI detectors which were exploited (173). An hplc system with CHROMPAC RP-18C2g column at 298°C and acetonitrile—water or methanol—water as the mobile phase has been used to gather information about the functionaUty of PPO (174). 

Antimicrobial Activity. The elfamycins antimicrobial specificity and lack of toxicity in animals can be explained in view of species-dependent specificity of elfamycin binding to EE-Tu. Inefficient cellular uptake or the presence of a nonresponding EE-Tu were cited as responsible factors for the natural resistance in Halohacterium cutiruhrum (67), Lactobaci//us brevis (68), and in actinomycetes (5,69). The low activity of elfamycins against S. aureus was also attributed to an elfamycin-resistant EE-Tu system (70). However, cross-resistance with other antibacterial agents has not been observed (71). 

The most widely used method of analysis for methyl chloride is gas chromatography. A capillary column medium that does a very good job in separating most chlorinated hydrocarbons is methyl siUcone or methyl (5% phenyl) siUcone. The detector of choice is a flame ionisation detector. Typical molar response factors for the chlorinated methanes are methyl chloride, 2.05 methylene chloride, 2.2 chloroform, 2.8 carbon tetrachloride, 3.1, where methane is defined as having a molar response factor of 2.00. Most two-carbon chlorinated hydrocarbons have a molar response factor of about 1.0 on the same basis. 

Purity. Gas chromatographic analysis is performed utilizing a wide-bore capillary column (DB-1, 60 m x 0.32 mm ID x 1.0 //m film) and a flame ionization detector in an instmment such as a Hewlett-Packard 5890 gas chromatograph. A caUbration standard is used to determine response factors for all significant impurities, and external standard calculation techniques are used to estimate the impurity concentrations. AHyl chloride purity is deterrnined by difference. 

This is too low. But it is possible to make it up by selecting the arrester at the primary with a lower switching if possible, or provide an arrester at the secondary. Moreover, the response factor, q, is considered very high, which may not be true in actual service and an arrester at the secondary may not be necessary in all probability. The design engineer can use a more realistic factor based on his past experience and the data available from similar installations. 

The response-factor approach is based on a method in which the response factors represent the transfer functions of the wall due to unit impulse excitations. The real excitation is approximated by a superposition of such impulses (mostly of triangular shape), and the real response is determined by the superposition of the impulse responses (see Figs. 11.33 and 11.34). ... 

The response factors are characteristic for the layer buildup of the selected wall and are calculated before (by a preprocessor program) or at the beginning ol the simulation. Numerical reasons limit the time step to approximately 10 to 60 min, depending on the thickness and material properties of the wall layers. The method allows the calculation of surface temperatures and heat fluxes bur not the determination of the temperature distribution within the wall. Due to the precalculation of these response factors, the computer time for the simulation might be significantly reduced. 

If energy is supplied to or extracted from a layer within the component, finite-difference models or problem-adapted one-dimensional response-factor- based models have to be used. 

Determine the response factors (r) for the detector relative to phenacetin ( = 1) as internal standard by carrying out three runs, using 1 /rL injection, and obtaining the average value of r. 

Correct the peak areas initially obtained by dividing by the appropriate response factor and normalise the corrected values. Compare this result with the known composition of the mixture. 

This result can be used to prepare a synthetic mixture to obtain relative response factors. 

Using the peak area method, prepare a standard solution in which the amounts of each component will approximate the amounts found in the sample being analyzed. From the standard solution, obtain the GC peak areas for each component. Assign to one of the major components a relative response factor (RF) of 1.0. This component is the reference. The response factors for the other components are obtained in the following manner. 

Where SA R is the specific area of the reference peak, and SA is the specific area of component x. AR is the GC peak area of the reference, Ax is the GC peak area of component x, WR is the weight of the reference, and Wx is the weight of component x. The weight percent of component x can be obtained from the sample chromatogram by using the relative response factors in the following equation ... 

S(A RFn) is the sum of the areas times the individual response factors for all the peaks in the chromatogram. The amount injected should be the same for both the standard and the unknown. 

It is crucial in quantitative GC to obtain a good separation of the components of interest. Although this is not critical when a mass spectrometer is used as the detector (because ions for identification can be mass selected), it is nevertheless good practice. If the GC effluent is split between the mass spectrometer and FID detector, either detector can be used for quantitation. Because the response for any individual compound will differ, it is necessary to obtain relative response factors for those compounds for which quantitation is needed. Care should be taken to prevent contamination of the sample with the reference standards. This is a major source of error in trace quantitative analysis. To prevent such contamination, a method blank should be run, following all steps in the method of preparation of a sample except the addition of the sample. To ensure that there is no contamination or carryover in the GC column or the ion source, the method blank should be run prior to each sample. 

The GC-MS conditions are given in Table 11. Response factors are specific for the commercial standard, the particular clean-up procedure, and the GC-MS system used [24]. 

It is seen that, individually, all the curves appear linear and any one of the five curves might be considered to give accurate quantitative results. However, the actual results that would be obtained from the analysis of a binary mixture containing 10% of one component and 90% of the other, employing detectors with each of the five response factors, is shown in Table 1. 

The refractive index detector, in general, is a choice of last resort and is used for those applications where, for one reason or another, all other detectors are inappropriate or impractical. However, the detector has one particular area of application for which it is unique and that is in the separation and analysis of polymers. In general, for those polymers that contain more than six monomer units, the refractive index is directly proportional to the concentration of the polymer and is practically independent of the molecular weight. Thus, a quantitative analysis of a polymer mixture can be obtained by the simple normalization of the peak areas in the chromatogram, there being no need for the use of individual response factors. Some typical specifications for the refractive index detector are as follows ... 

The use of an internal standard probably gives the most accurate quantitative results. However, the procedure depends upon finding an appropriate substance that will elute in a position on the chromatogram where it will not interfere or merge with any of the natural components of the mixture. If the sample contains numerous components, this may be difficult. Having identified a reference standard, the response factors for each component of interest in the mixture to be analyzed must be determined. A synthetic mixture is made up containing known concentrations of each of the components of interest and the standard. If there are (n) components, and the (r) component is present at concentration (Cr) and the standard at a concentration (Cst). 

Thus, the response factor (ar) for the component (r) is then given by... 

Thus, the concentration of any (or all) of the components present in the mixture can be determined providing they all adequately separated from one another. If the same type of mixture is being analyzed, the operating conditions are maintained constant and there is not an extreme change in the composition of the samples, the response factors usually need be determined only once a day. 

This reaction has been also described for low chlorinated dibenzodioxins. Assuming an identical MS response factor for monoBrDD and monobromohydroxy-biphenyl ether (monoBrDPE) a quantification study shows that monoBrDPE is much more stable towards photolysis compared to monoBrDD, because it accumulates in the mixture of the reaction products. For the dibrominated dibenzodioxins the same reaction (ether fission) is observed but to a minor extent. With triBrDD and higher brominated BrDD no diaryl-ether products are observed at all. 

It is generally necessary to multiply the response obtained from a detection method by a response factor to convert the response into a useful value. For instance, the response of a fluorescence detector would be multiplied by an appropriate factor (y to obtain the concentration of the particular toxin present, or by a different factor (f ) to calculate the toxicity. Since the specific toxicities of the various toxins - the ratios of toxicity to concentration - vary over a broad range, the f and f for a given toxin will generally be different, often greatly so. Furthermore, the f may vary for the different toxins, and the f may also vary. In an analysis, multiplication by the appropriate factor is straightforward because the various components of interest are resolved and the response for each can be multiplied by the appropriate response factor, f or f, for each toxin. Assays, however, present a dilemma. Because the components are not resolved and only one response is obtained, only one response factor can be used. The potential accuracy of an assay is therefore limited principally by the range of response factors to the... 

Davio et al. (43) report efforts to obtain monoclonal antibodies (mAbs) to STX. Because STX is a small molecule of approximately 300 daltons, well below the size necessary for immunogenicity, a carrier molecule must be conjugated to the hapten (STX). This technique must minimize alterations of the antigenic form. For the anti-STX antibodies tested to date, the ratios of immunoassay response factor to pharmacological potency for various STX derivatives differ substantially, the immunoassay being virtually unresponsive to some of the common natural derivatives (44). 

Figure 4 shows the cleavage pattern of RG-lyase toward the various RGO s. Again no bond-cleavage frequencies could be given since the response factors of the various products were not known. The RG-lyase cleaved the chain four units from the reducing end. When the... 

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