Chloro-oxine

Derivatives of 8-hydroxyquinoline are also used in spectrophotometric analysis. Chloro-oxine (5,7-dichloro-8-hydroxyquinoline) and bromo-oxine (5,7-dibromo-8-hydroxyquinoline, formula 4.43) react similarly to oxine. The absorption maxima of the complexes in chloroform solutions are shifted towards longer wavelengths and the sensitivity of the reactions is higher than in the case of oxine. 

The extraction of cadmium chelates with oxine, chloro-oxine, HTTA, dibenzoylmethane, anthranilic acid, and other chelating reagents has been investigated [14,15],... 

Spectrophotometric methods based on ion associates with basic dyes are very sensitive. The Co-thiocyanate complex was associated with Malachite Green (CCI4 -i- cyclohexane), (e = 8.6-10 ) [61], Turquoise Blue (triphenylmethane dye) (toluene -1- DMF) [62], and 6-nitrodimethyline-carbocyanine [63,64]. The anionic complex of Co with chloro-oxine [65] associated with Rhodamine 6G was extracted with benzene. The complex of Co with 2-nitroso-l-hydroxynaphthalene-4-sulphonic acid was extracted into CHCI3 as the associate with a basic azo dye (e = 1.66-10 at 566 nm) [66]. 

Manganese has been determined in the form of ion-associates the anionic chloro-oxine complex of manganese with Rhodamine 6G, extractable into benzene (e = 7.0-10 ) [46], and the cationic complex of Mn(II) with phen, associated with the acid dye Erythrosin, and extractable into ethyl acetate (e = 1.5-10 ) [47]. 

The dyes Rhodamine 6G [55] and Crystal Violet [56] form extractable ion-associates with the anionic complexes of nickel with chloro-oxine [551 and 4-chloro-2-nitroso-l-naphthol [56], (e = 7.7-10 - 8.2-10 ). The ion associate of Rose Bengal with the cationic nickel complex with 1,10-phenanthroline, extractable into nitrobenzene, is also the basis of a sensitive method (e > 1-10 ) [57]. Hydroxynaphthol Blue has been applied for determination of Ni in the presence of Cu by the derivative spectrophotometry method [58]. 

Other organic reagents used for determining tin include haematoxylin [71,74-76], chloro-oxine [77-79], and 2,2 -diquinoxalyl [80]. Micro-quantities of Sn(II) in the presence of Sn(IV) have been determined with the use of ferrozine [81]. Perron has been applied for extractive separation (CHCI3, tribenzylamine) and determination of Sn [82]. 

An even more serious problem can arise when dissolved species expected to predominate at high temperatures are undetectable at 25°C or are only present at concentrations which are too low for them to be adequately characterized thermodynamically. Examples are certain transition metal chloro-complexes (9,10) and mixed complexes of such metals with hydroxide and another ligand (11,12). Thus it seems that chloride complexing so alters the aqueous chemistry of copper and gold that supposedly inert gold components in autoclaves are reversibly oxidized by Cull (10) and it is likely that mixed oxine and hydroxy complexes of Fell contribute considerably to the gross under-estimation (by a factor of up to 10 ) of magnetite solubility in oxine (12,14). 

The interest in oxines has now moved from antimicrobial therapy to nuclear medicine and the chemotherapy of malaria. A few other applications have also been found 5,7-diiodo-oxinate enhances gastrointestinal uptake of zinc, an element whose deficiency may cause acrodermatis enteropathica1905 several halogenated oxines - 5-chloro-7-iodooxine (Entero-Vioform), 5,7-diiodooxine (Diodoquin) - have been used in the treatment of amoebic dysentry but this is now a discontinued therapy. 5-Methyloxine has proved an effective therapy in the treatment of cholera in humans191,1925. 

The analysis of brines perhaps deserves special mention as the high sodium chloride concentrations are extremely unfavourable for electrothermal atomisation and most troublesome in flame analysis. The preferred approach is probably solvent extraction with either oxine or APDC to remove the trace metals into a small volume of MIBK for flame atomisation or chloroform for electrothermal cells. Care must be taken to avoid interference from chloro-complexes in the extraction, and if this is suspected an ion-association extraction of these complexes might be preferable. 

Halogenated derivatives of oxine, Halogenation of oxine improves the performance against Gram-negative bacteria, and many such derivatives are in use. Halquinol (a mixture of 5-chloro- and 5,7-dichloro-oxine) and chlorquinaldol (5,7-dichloro-2-methyloxine), which are also issued as... 

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