Relative molar response

Another difficulty in the gas chromatographic separation of amino acids is the choice of detector and it may be necessary to split the gas stream and use two different detectors. The flame ionization detector, which is commonly used, is non-specific and will detect any non-amino acid components of the sample unless purification has been performed prior to derivatization. In addition the relative molar response of the flame ionization detector varies for each amino acid, necessitating the production of separate standard curves. As a consequence, although gas chromatography offers theoretical advantages, its practical application is mainly reserved for special circumstances when a nitrogen detector may be useful to increase the specificity. 

Compounds were quantified by comparing the computer calculated area for the brominated compound with the integrated response for a known amount of octachlo-ronaphthalene. Differences in ionization cross-section, which affect the sensitivity of the mass spectrometer to a given compound, were compensated for by determining the relative molar response (RMR) of authentic compounds to octachloronaphthalene. 

Relative molar response relative to the OCN 404 m/e ion. bAverage of 7 determinations. 

Compound Retention factor (k) Molar absorptivity ( 280)fe Relative molar response Corrected relative mass response ... 

Derivative Relative retention time Relative molar response... 

From the data in Table 11.1 the consistency of A is apparent. If we assume a constant A about equal to the DeBroglie A1 and with relative molar responses of similar compounds in the ECD at the same temperature, the activation energy for thermal electron attachment can be obtained from E x /irc - = RT(ln(Rlef/Rx)). This is only applicable to alkyl chlorides, bromides, or iodides. The activation energy of dissociative reactions for alkylfluorides is too large to be observed in the ECD. 

The activation energies for dissociative thermal electron reactions have been correlated with bond dissociation energies when available. Estimates of activation energies for dissociative reactions have been made by assuming a fixed value for A i and using relative molar responses or relative rate constants to calculate activation energy differences. Additional bond dissociation energies are obtained from these data. 

Amino acid Retention time (min-sec) Relative molar response serine = 1.00... 

With the aid of gradient elution, a reversed phase partition method and an internal standard, considerable progress has been made in the quantitative determination of each constituent of the main component phenols present in technical CNSL and in natural cashew-nut shell liquid provided that relative molar response (RMR) factors are used. A typical quantitative HPLC analysis of the technical material indicated cardanol (67.8%), cardol (18.2%), 2-methylcardol (3.3%), minor constituents (3.3%) and polymeric material (7.4%). 

TABLE 13.6 % COMPOSITION of the CONSTITUENTS of CARDANOL and CARDOLin TECHNICAL CNSL by HPLC ANALYSIS (RMR = relative molar response)... 

P. Mares, J. Skorepa, and M. Friedrich, Computerized quantitative analysis of methyl and ethyl esters of long chain fatty acids by gas-hquid chromatography using relative molar response, J. Chromatogr., 42 (1969) 435 41. 

The hierarchic interconnection of the characteristics of the measuring system is shown in Figure 8 and involves the sensitivity from which the selectivity and relative molar response are derived and the linearity of the measuring system, composed of three parallel criteria, namely, the linearity coefficient, the linear dynamic range, and the linearity error. 

The ratio of the magnitudes of the analytical properties of the analyte and standard (a/ast) in eqn [8], e.g., the thermal conductivity or ionization potential, is called the relative molar response (RMR,) and is used for normalization of the response magnitudes to a unit mass amount. 

Relative molar response in helium. Standard benzene == 100. 

Relative molar responses measured at 250°C in nitrogen detector gas using a Varian 3700 GC/CC-ECD. 

This method can also be used to determine the composition of additives, the only limitation being that toluene is not determined. After convenient dilution with n-heptane they are handled as gasoline and do not require previous calibration. For the calculations, the peak areas are corrected by factors which are theoretically deduced from the number of moles of methane or ethane produced per mole of each component and by the relative molar response of ethane as related to methane (1.88). 

Molex in Response of Response Factor Relative Molar Response Factor... 

The Relative Molar Response Is a constant that is caiculated by dwiding the slope of the refersnoed component by the oomponent that Is present In the reference standard. For example ... 

XI3 Calibration using Relative Molar Response Values... 

XI.3.5 Ratio the slopes of the referenced components (i) to the slopes of the reference components (r) present in the daily calibration standard. This gives the Relative Molar Response factor RAfRIi for component (i). The reference component must be present in the same instrumental sequence (except Hexanes +) as the referenced components. For instance, propane can be the reference component for the butanes and pentanes if propane is separated on the same column in the same sequence as the butanes and pentanes. Ethane can be the reference component for carbon dioxide if it elutes in the same sequence as carbon dioxide. The hexanes + peak can be referenced to propane or calculated as mentioned in the body of the standard. 

X1.3.6 For daily calibration a four component standard is used containing nitrogen, methane, ethane, and propane. The fewer components eliminates dew point problems, reactivity, is more accurate and can be blended at a higher pressure. The referenced components response factors are calculated from the current reference factor and the Relative Molar Response factor. Following is a description of the basic calculations, an example of deriving a Relative Molar Response factor (Fig. XI. 1), and a table showing how response factors are calculated (Table XI.2). 

Determine the response factors for propane, isobutane, and n-butane in the following manner. Calculate the relative molar response, RMR, for each of the normal paraffins starting with nCf as follows ... 

RMR, = relative molar response for the compound, nti = mole percent of Ae compound in the calibration mixture, and... 

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