Dichlorophenolindophenol Reagent

Dichlorophenolindophenol Reagent. Place 50 mg. of sodium 2,6-dichlorophenohndophenol (Eastman Organic Chemicals Dept., Rochester, N. Y.) in a beaker. Add 150 ml. of distilled water, warm gently untU dissolved, and then add 42 mg. of NaHCOj. Cool to constant volume, decant into a 200 ml. volumetric flask, and make up to volume with distilled water. 

Fill a buret with the standardized 2,6-dichlorophenolindophenol reagent. Pipet a convenient aliquot of the filtered homogenate, e. g., 10 ml., into a porcelain dish. 

The sodium salt of 2,6-dichlorophenolindophenol, N-(3,5-dichloro-4-hydroxyphenyl)-p-benzoquinone imine (Tiibnan reagent), is used especially in steroid chemistry for the conversion of a-hydroxy ketones into a-hydroxy acids and a-keto acids [976] (equation 20). 

Sulphite and sulphur dioxide can be determined from the changes in colour, produced by their reducing effect on iron(III) in the presence of 1,10-phenanthroline [61,62], TPTZ [63], or ferrozine [64] (for formulae see Ch. 26). Sulphite may also be determined indirectly with Hg(II) chloranilate [59] or thiocyanate [65]. Other reagents for sulphite include 2,6-dichlorophenolindophenol [7] and 5,5 -dithio-bis(2-nitrobenzoic acid) [66-68]. Reaction of SO2 with IOb in the presence of excess of chloride yields ICU", which forms an ion-pair with Pyronine G [69]. 

TWo methods have been investigated to determine sulHdes in solution (for HjS see Section 17.2). The first uses 2,6-dichlorophenolindophenol (DIP) as a reagent immobilized on XAD-2, XAD-4, or XAD-7 resin [94, 95]. The reflectance is measured in a flow cell in the 2-20 mM range. The response time (2-25 min) varies with the sulHde concentration. The phenanthroline... 

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