Bromo-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. 

Various organic reagents are used for direct determination of calcium, such as murexide (ammonium purpurate) (e = 1.4-10 at 500 nm) [2,49], Metalphthalein [50], Calcein [51,52], Chrome Azurol S (in the presence of 1,10-phenanthroline) [53], Alizarin S [54], 8-hydroxyquinoline (extraction into CHCI3 in the presence of n-butylamine or butoxyethanol) [55], and Emodine (l,3,8-trihydroxy-6-methylanthraquinone) [56]. Calcium has been determined as a complex with Emodine, in the presence of Be and Mg, by the derivative spectrophotometry technique. The anionic complexes of calcium with bromo-oxine [57] or HTTA [58] have been extracted into benzene as ion associates with Rhodamine B. Calcium was also determined as a complex with o-cresolphthalein [59-63], or thymolphthalein [64]. 

Extractable ion-associates of Rhodamine B with anionic Mg complexes with bromo-oxine [56] and iodo-oxine (e = 2.7-10 at 545 nm, toluene) [57] have been used for determining magnesium. 

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