8-Hydroxyquinoline extraction reagent

Ashbrook, A. W. Commercial chelating solvent extraction reagents, II. w-Al-kenyl-8-hydroxyquinoline Purification and properties, Metallurgy Division, Mines Branch, Dept. Energy, Mines and Resources, Canada Report EMA 73-34 1973. 

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]. 

Colorimetric methods always include hafnium. Most methods employ a separation step such as solvent extraction. The three reagents used successfully are 8-hydroxyquinoline (88), alizarin red S (89), and catechol violet (90). 

Hydroxyquinoline, having both a phenolic hydroxyl group and a basic nitrogen atom, is amphoteric in aqueous solution it is completely extracted from aqueous solution by chloroform at pH < 5 and pH > 9 the distribution coefficient of the neutral compound between chloroform and water is 720 at 18 °C. The usefulness of this sensitive reagent has been extended by the use of masking agents (cyanide, EDTA, citrate, tartrate, etc.) and by control of pH. 

Acetic acid - 8-hydroxyquinoline reagent - dissolve 10 g 8-hydroxy-quinoline in a solution of 2.5 % (v/v) acetic acid and make up to 1 I. (The 8-hydroxyquinoline blocks the readsorption or precipitation of phosphate by active iron and aluminium during acetic acid extraction. Synonyms hydroxybenzopyridine oxine phenopyridine 8-quinolinol. Not carcinogenic, but may be harmful if swallowed, and causes irritation to eyes, respiratory tract and skin safety data sheet at http //www. jtbaker.com/msds/q7250. htm.)... 

Procedure (extraction). Transfer 2.5 g air-dry soil, 2 mm mesh size, into a 250 ml polypropylene screw-cap centrifuge bottle/tube and add 100 ml acetic acid - 8-hydroxyquinoline reagent. Cap the tube and shake overnight (17 h) on a reciprocating shaker, at approximately 275 strokes of 25 mm length per minute at a constant temperature (20°C). Centrifuge for 15 min at 2800 rpm and remove an aliquot for the determination of acid extractable inorganic phosphorus (a). 

Owing to steric hindrance (Section 10.2.2.3) the tris complex of aluminum with 2-methyl-8-hydroxyquinoline cannot form in aqueous solution so that this reagent can be used to solvent extract other metals from aluminum, which can then be solvent extracted in its turn and determined with unsubstituted 8-hydroxyquinoline.24 25 52... 

Hydroxyquinoline (oxine, 6), one of the earliest analytical reagents, also is one of the most widely studied N—O bidentates. Its early coordination chemistry was reviewed by Phillips.19 Its use as an in vivo agent in microbiological systems has been reviewed by Schulman and Dwyer.20 The extensive use of oxine and substituted forms, and closely related bidentates, for the analytical solvent extraction and colorimeteric determination of metal ions has been comprehensively reviewed.21 An unusual bridged bonding mode for oxine has been reported in which N monodentate and O... 

When Al is alloyed with Mg(as for use in some incendiary, tracer of photoflash compns), the tests and detns for such alloys include a)Granulation, using US Std sieves b) Moisture, by drying in a vacuum desiccator over HjSO for 24 hrs c)Grease wd ftus, by extraction with ether d)Aluminum, using 8 hydroxyquinoline reagent e)Mag-... 

Extraction techniques that involve a chemical reaction can be classified as nonselective extraction or concentration, when more than one analyte is extracted from the solution by using the organic collectors (e.g., 8-hydroxyquinoline and dithizone derivatives) and selective extraction or separation. The first step in such an extraction technique is the formation of the complex by adding the reagent(s) to the solution of analyte, and after the extraction of the complex in an organic solvent. The problem that can arise in a SIA system with these types of extraction is the precipitate that is formed, and this can contaminate the other sample and also can block the tubing. To avoid these problems, it is necessary either to dilute the sample in such a way that the precipitation equihbria will not be reached and that all the complex will remain dissolved in the solution, or by derivatization of the hgands to... 

A group of the methods for pre-concentration of traces includes the extraction of metals by the resins modified with organic reagents, e.g., 8-hydroxyquinoline, DDTK [58], Bromopyrogallol Red [59], Zincon [60], and crown ethers [61]. Reviews of the methods have been presented [62,63]. 

A large group of the methods is based on difunctional organic reagents that with metal ions form inner chelates, soluble in non-polar solvents. Such reagents are generally used in the extraction-spectrophotometric methods involving, e.g., dithizone, dithiocarbamates, 8-hydroxyquinoline, l-nitroso-2-naphthol, dioximes and PAN [l-(2-pyridylazo)-2-naphthol]. 

Hydroxyquinoline is a group reagent often applied to the precipitation or extraction of a large number of metals. The selectivity of metal reactions with oxine may be enhanced by masking agents such as EDTA, tartrate, oxalate, or cyanide. 

The extraction method using 8-hydroxyquinoline is not very sensitive, but it is highly selective. The really sensitive methods for spectrophotometric determination of aluminium are based on ternary systems, including triphenylmethane reagents (mainly Chrome Azurol S and Eriochrome Cyanine R) and some surfactants. 

Many other reagents have been used for determining iron, e.g., sulphosalieylic acid [106-109], ferron (7-iodo-8-hydroxyquinoline-5-sulphonic acid) (e = 4.0-10 at 610 nm) [110], Tiron [111,115], HTTA [116,117], pyrocatechol [118], phenylfluorone (in presence of Triton X-100 [119], morin (in the presence of a surfactant e = 6.3-10 ) [120-122], Alizarin S (extraction with Aliquat 336 in CHCI3] [123], Purpurin [124,125], salicylates[126,127], 2,2 -diquinoxalyl [128], sulphanilic acid in the presence of a surfactant [129], haematoxylin [130], and hydroxamic acid derivatives [13,14,131,132]. 

Other organic spectrophotometric reagents for Nb include 8-hydroxyquinoline-5-sulphonic acid [75], 5,7-dichloro-8-hydroxyquinoline (e =1.3-10 at 400 nm) [76], 5-chloro-7-iodo-8-hydroxyquinoline [77], Lumogallion [78], and thioglycolic acid [79], Nb has also been determined after extraction of its complex with 3-hydroxyflavone [80] and N-a-phenylstyrylacrylhydroxamic acids [81]. 

A number of other organic compounds is suitable for the diazotization and coupling reactions [62-69]. For example, the reaction with o-nitroaniline and N-(l-naphthyl)ethylenediamine leads to a method with e = 6.0-10 at 545 nm [68]. In some cases, 8-hydroxyquinoline is used for the coupling [70,71]. Many azo dyes formed by the use of various reagents are extractable [72-74]. In one of the methods [74], with hexanol as extractant, e = 5.2-10 at 610 nm. 

Other organic spectrophotometric reagents, recommended for determination of thorium are Bromopyrogallol Red [85], morin (e = 3.3-10 at 422 nm), quercetin [86,87], phenylfluorone [87], and 8-hydroxyquinoline [88], The anionic complex of 5,7-dibromo-oxine with Th forms an ion-associate with Rhodamine B which can be extracted into benzene (e = 8.8-10 at 552 nm) [89],... 

For the determination of metal cations, chelates are created with oxine (8-hydroxyquinoline), alizarine or benzoin, then extracted by organic solvents. In biochemistry, fluorescence has numerous applications for the quantification of proteins or nucleic acids by means of reagents which can affix with specificity to these compounds. This approach, sometimes very elaborate, in association with electrophoresis constitutes a more sensitive and less restricting method than detection by radioactive substrates. 

In addition to these reactions, metal ions and ligands may participate in many other equilibria reactions such as complex formation, protolysis, and hydrolysis reactions. In order to transfer metal ions quantitatively into the organic phase, the extraction conditions (pH, reagent concentrations, volume ratio of the liquid phases) must be optimized. Figure 146 represents the response of molybdenum as a function of pH in three different organic solvents with toluene-3,4-dithiol and 8-hydroxyquinoline as ligands. According to this plot the determination of molybdenum is most sensitive in MIBK... 

Selectivity of solvent extraction may be improved by using masking agents such as fluoride or cyanide ions in connection with 8-hydroxyquinoline. 8-Hydroxyquinoline reagent solution is prepared in an organic solvent (chloroform, butanol, ethylacetate, MIBK). 

As an analytical example of an addition of a reagent to the donor phase, extraction of metals from solutions containing a complex former as 8-hydroxyquinoline can be mentioned. 

A third technique which is somewhat less popular but still useful is application of surface adsorption reagents. Activated car n is generally used as the carrier after conversion of the metal ion(s) of interest to a suitable form. For example, iodide in ground water has been determined by this method after conversion to silver iodide [61]. Neutral 8-hydroxyquinoline complexes have been employed in which, again, the oxine complex is collected on activated carbon [62]. Use of activated carbon is particularly useful where PIXE is being employed as the analysis technique, since the resultant sample is ideal for direct presentation to the instrument [63]. Other preconcentration methods that have been employed in this area include electrodeposition [64], precipitation chromatography [65], liquid/liquid extraction, immobilized reagents [66], plus a variety of other techniques well known to the analytical chemist. 

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