Effective carbon number

The effective carbon number neff is helpful in characterizing surfactants with an inner functional group. Surfactants with isomeric structures can be compared by means of the hydrophobicity index / [69], which indicates the influence of the effective length of the alkane chain on cM ... 

The chain lengths of different molecules were then compared with the chain lengths of hydrocarbons to calculate the carbon number which relates the elution volume of the compound to the elution volume of a real or imaginary n-hydrocarbon. The "effective" carbon number for benzene based on its elution volume was experimentally found to be 2.85 - i.e. it eluted near the elution volume for propane which has a carbon number of 3.0 while the calculations based on bond angles and radii of atoms indicated that benzene would have a carbon number of 3.55. Thus corrections to the calculations for carbon number were required. These were derived from the experimentally observed elution behavior of various molecules. 

ECN (effective carbon number), 689, 690, 708 Edible oils analysis, 636, 701 autoxidation, 614, 623, 661-2 peroxide value, 657, 658, 660-3 EDTA... 

Effective carbon number (ECN), flame ionization detection, 689, 690, 708 EHS (extremely hazardous substances), 744 Elastomers... 

This reaction is an almost quantitative counter of carbon atoms being burned. For hydrocarbons, this means that flame response is proportional to the number of carbon atoms, rather than weight or moles. Compounds with heterogroups on some of the carbon atoms lose some of their ability to form CH. This is usually corrected for by considering the effective carbon number, that number which would account for the compound s response. 

To improve the separation of the derivatives of fatty acids with the same effective carbon number, e.g., palmitoleic (C16 1), linoleic (18 2), andmyristic (C14 0), Baty et al. (33) reported the preparation of the anthrylmethyl esters derivatives of several fatty acids (with 9-hydroxy-methylanthracene and the catalyst 2-bromo-l-methylpyridinium iodide (BMPI)) with a view to analysis by HPLC and LC-MS (with gradient elution on a ZORBAK 5-/zm Cl8 column) (see Chemical Structure 1). The excess reagents were evaporated under nitrogen at 50°C, and the de-rivatized acids were taken up in 1 ml of mobile phase prior to chromatography. This method did not allow the resolution of the C16 1, 08 2, and C14 0 esters, although HPLC data obtained for the other acids correlated well with that obtained by capillary gas-liquid chromatography. 

Solid-probe mass spectrometric analysis (31) showed that the benzene-ether extracts consist mainly of organic acids. Therefore, these extracts were deriva-tized with dimethylsulfate-de to yield methyl-da-labeled derivatives. The derivatives were analyzed by GCMS and high resolution MS using techniques that have been described previously (31). Authentic samples of phenolic acids deriva-tized with dimethylsulfate-dg or diazomethane were also analyzed by GCMS for reference. The distribution of the organic acids as methyl esters was determined by measuring areas of GC fiame ionization detector peaks with a correction for the effective carbon number for each compound. 

Accurate g.l.c. analysis of mixtures of substances with a flame ionization detector (f.i.d.) depends upon a knowledge of the relative detector response of each compound. Variations in the f.i.d. responses of steroids in molar terms have now been put on a quantitative basis. There is a good linear relationship between molar f.i.d. response and the effective carbon number , which is the number of carbon atoms per molecule less half the number of oxygen atoms (over the ranges Ci8—C31, and Oo—O4). This behaviour parallels earlier conclusions for paraffin hydrocarbons, alcohols, and esters. G.l.c. data are reported for the trimethylsilyl ethers of 49 plant sterols on eight different columns. ... 

Empirical rules give contributions to effective carbon number ... 

Scanlon, J. T. and Willis, D. E., Calculation of FID relative response factors using the effective carbon number concept, J. Chromatogr. Set, 23, 333-340, 1985. 

Quantitations were made based on the "effective carbon number concept of Sternberg et al [6] with a FID. Response factors of the hydroperoxides were calculated as the corresponding alcohol s. Carbon balances are good, indicating that this increment method is suitable also for hydroperoxides. 

Allan and Teja [12] proposed a one-fluid approach for their model by obtaining the effective carbon number from n, j, = Sxj nj. They tested their method for 10 binary mixtures of various hydrocarbons including cyclic, aromatic, and paraffinic substances. They were able to estimate mixture viscosity with an overall AAD of 5.6%. 

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