Organic phase content minimization

Peak type on chromatogram. The shape of the matrix peaks depends on the nature of the sample and also on the organic mobile phase content. For HPLC, since low-level detection is required, the interference of co-extract materials in the samples should be minimized. 

To a lOO-mL round-bottomed flask add 1-chlorobutane (25 mL,21.6 g,0.23 mole), sulfuryl chloride (8 mL, 13.5 g, 0.10 mole), 2,2 -azobis-(2-meth-ylpropionitrile) (0.1 g) and a boiling chip. Equip the flask with a condenser and gas trap as seen in Fig. 1. Heat the mixture to gentle reflux on the steam bath for 20 min. Remove the flask from the steam bath, allow it to cool somewhat and quickly, to minimize the escape of sulfur dioxide and hydrochloric acid, lift the condenser from the flask and add a second 0.1-g portion of the initiator. Heat the reaction mixture for an additional 10 min, remove the flask and condenser from the steam bath, and cool the flask in a beaker of water. Pour the contents of the flask through a funnel into about 50 mL of water in a small separatory funnel, shake the mixture, and separate the two phases. Wash the organic phase with two 20-mL portions of 5% sodium bicarbonate solution, once with a 20-mL portion of water, and then dry the organic layer over anhydrous calcium chloride (about 4 g) in a dry Erlenmeyer flask. The mixture can be analyzed by gas chromatography at this point or the unreacted 1-chlorobutane can be removed by fractional distillation (up to bp 85°C) and the pot residue analyzed by gas chromatography. 

To minimize the indane, 99, formation, dimerization was conducted in two-phase systems containing toluenesulfonic acid,354 sulfuric acid,355 356 electrophilic transition-metal complexes,357 the polymeric solid-state acid Nafion,358 359 metal oxide solid-state catalysts such as tungstophosphoric acid,360 various zeolites,361 362 mixed oxides,363 and montmorillonite clay in the presence of organic solvents.364 365 The major limitation of the cationic approach, however, is the unavoidable formation of internal isomer 100. Since isomer 100 is inert in radical polymerization, the lower the content of isomer 100, the higher activity of the 98 mixture. Even in the very best cases, its presence is never less than 5—15%. 

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