Linear retention index

Figured.1.4 An FID chromatogram of concentrated extract of the same Concord grape essence shown Figure G1.1.3, drawn to display the data on a linear retention index scale. By simply comparing the index of a peak with the data listed in the flavornet, the odorants that have similar retention indices can be determined. Notice how large the methyl anthranilate peak is, but still no convincing peak for p-damascenone, even though both compounds have the same odor activity (intensity).

Donnelly JR, Sovocool GW (1992), Chemosphere 25 1299-1304. Gas chromatographic elution order and elution shift modelling for isomer specific analysis of halogenated dioxins" Donnelly JR, Munslow WD, Grange AH Pettit TL, Simmons RD, Sovocool GW (1991a), J. Chromat. 540 293-310. Correlation of structure with linear retention index for bromo- and bromochlorodibenzo-p-dioxins and bromodibenzofurans"... 

Standardization of retention times. This is the first step. Retention times of our odor zones have to be normalized by those of n-alkanes used as standards. To do that, the mixture of alkanes, which can be directly obtained from different chromatographic suppliers, is injected in exactly the same conditions in which the GC-O experiment was carried out. As nearly all the GC-O experiments use temperature gradients, the Retention Index or Linear Retention Index - not Kovats Index according to the lUPAC (lUPAC 1997) - will be determined with the formula... 

Vassilaros DL, Kong RC, Later DW, Lee ML (1982) Linear retention index system for polycyclic aromatic compounds. Critical evaluation and additional indices. J Chrom 252, 1-20. 

When a pure standard is not commercially available and its synthesis is not possible, identification may be carried by comparing retention indexes e.g. linear retention indexes, Kovats retention indexes) of compounds of interest with those of published in literature retention indexes are based on the values attributed, by definition, to a series of homologous compounds e.g. alkanes Cs = 800, C9 = 900) and its relation with its retention time. 

Linear retention index on a DB Wax column T.I. Tentatively identified. 

Fragmentation of these compounds are also similar. Therefore assignment of the individual component requires additional information, linear retention index or Kovat s index and confirmation with authentic standards. Manual interpretation of the mass spectrum is some time needed, when there is no fitted matching. Isotope abundance is very useful to postulate the identity of molecule or fragment. 

The library of Flavours and Fragrances of Natural and Synthetic Compounds, edited by Prof Mondello contains more than 3000 mass spectra in its second edition, linear retention index data, calculated Kovats RI and searchable chemical structures of compounds of interest for the flavours and fragrances industry as well as research applications (Wiley, ISBN 978-1-118-14583-8). 

Netherlands). The volatiles were then analyzed by GCMS, under the conditions reported by Elmore and colleagues [11], A series of ra-alkanes (C5-C25) in diethyl ether was analyzed, under the same conditions, to obtain linear retention index (LRI) values for the lamb aroma components. 

Means are from four replicate samples —, less than 0.2 ng in the headspace of 100 g of boiled pork. PDMS, polydimethylsiloxane DVB, divinylbenzene LRI, linear retention index. 

Compound Retention Time, min Adjusted Retention Time, min Kovats Retention Index 35 C Linear Retention Index... 

A 1.2 The Linear Retention Index is an extension of the Kovats concept to programmed temperature gas chromatography. The Linear Retention Index of a solute is dependent not only on the liquid phase but on other operating parameters as well. It is a useful indicator of relative retention of solutes on chromatographic systems operating under identical or nearly identical conditions. 

A 1.2.1 Based on the approximation that under programmed temperature conditions the actual retention times of members of a homologous series increase linearly with increasing carbon number, the Linear Retention Index is a number indicating (on a linear scale) the retention of a compound relative to the series of n-allmnes. 

A 1.2.2 The equation used to calculate the Linear Retention Index (Iprug) of a compound A is given by Eq A1.2 ... 

A 1.2.5 The usual application of the Linear Retention Index system is to linear programmed temperature analyses without isothermal plateaus (even at the beginning of the run). However, since the in ces are generally limited to analyses with essentially identical operating conditions anyway, some analysts have used the Linear Retention Index system to reduce data from procedures utilizing complex temperature profiles. Such indices are not theoretically defensible, but nevertheless are useful indicators of relative retention especially for standard test methods. 

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