Band intensity chromatography

Many other relations between -AH and Av (many of which are valid for separate classes of organic acids and bases) and a relation between -AH and the Vxh band intensity enhancement (AA 2) ave been proposed [34]. A more detailed and thorough analysis of the experimental spectral characteristics and enthalpies for various organic acid ase H-complexes was provided by logansen on the basis of several methods (chromatography, calorimetry and so on). The author suggested an universal proportionality relationship which was named the intensity rule [34] (equation 7), where AA / =... 

The infrared spectra of a set of 2-thiazolylthioureas are reported in Ref. 486. The ultraviolet spectra of l-aryl-3-(2-thiazolyl)thioureas are characterized by two bands of approximate equal intensity around 282 and 332 nm (492). For l-alkyl-3-(2-thiazolyl)thioureas these bands are shifted to 255 and 291 nm, respectively (492). The shape of the spectrum is modified further when l.l -dialkyl-3-(2-thiazolyl)thioureas are considered (491). Fragmentation patterns of various 2-thiazolylthioureas have been investigated (100, 493), some of which are shown in Scheme 158. Paper and thin-layer chromatography provide an effective tool for the analysis of these heterocyclic thioureas (494. 495). 

The checkers used a 40-cm. spinning-band column. The product, n2bD 1.4237, was shown to be 98.9% pure by gas-liquid chromatography on a 6-ft. 20% fluorosilicone column. The retention time was 3.75 minutes with a flow rate of helium of 100 ml. per minute, and a column temperature of 125° with the injection port at 170°. The 19 F n.m.r. spectrum (56.4 MHz) consists of four lines of equal intensity centered at +3396 Hz from trichlorofluoromethane (internal) and two sets of two overlapping quartets centered at +4369 Hz and +4461 Hz, respectively. The integrated intensities of the three sets of fluorine resonances are 3 1 1. 

Reagents used for the visualisation of amino acids on the dried chromatogram may be applied either by spraying or dipping. Those commonly used produce intensely coloured bands with approximately 20 nmol of each amino acid for paper chromatography and 5 nmol for thin-layer separations, although smaller amounts can be detected. 

In order to stop the reaction when the amount of monoole-finic product in the reaction mixture is highest, aliquots of the reaction mixture are removed at intervals and analyzed by infrared spectrometry or by gas chromatography. In the infrared spectrum the relative intensities of bands at 965 cm. (trans-CH=CH) and 702 cm. (m-CH=CH) are observed in successive aliquots. The reaction is stopped when the band at 965 cm.- attributable to the trans double bonds of the starting triene, has almost completely disappeared and the band at 702 cm.- (m-olefin) remains. 

For the investigation of a butadiene-styrene rubber, a set of three SEC columns in series was used 500 x 8 mm, d0 = 150 nm 500 x mm, d0 = 25 nm 800 x 8 mm, d0 = 4 nm, all three with dP = 10 pm. The flow rate was 1 ml/min. The injection amounted to 200 pi of a 2 % solution from which the carbon black had been removed. Although the additives of interest were separated from the polymer, they were still covered by an intense band from process oil. Hence, coupled-column chromatography with reversed-phase separation of SEC eluates became neccessary. 10 pi of the latter were injected into a C 8 column (250 x 2.2 mm dP = 10 pm) and analyzed at 0.5 ml/min flow rate through a water/acetonitrile gradient (rising from 20% B by 6%/ml). Here, UV detection was performed at 254 nm. The peaks of the additives could be clearly separated from the process oil band. The technique also proved useful for checking... 

A concentrated DCM solution of photolytically degraded PBO was spotted onto a silica thin-layer chromatography (TLC) plate and chromatographed using 20% ethyl acetate in DCM. The most intense coloured band (red/pink close to the origin) was scraped from the plate and eluted from the silica with methanol. 

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