Pyrocatechol extraction

Alkyl pyrocatechol extractants provide greater group separation factors. Eu/Am separation factors of 70 have been reported for a non-equilibrium extraction in the system 4-(a,(z-dioctylethyl)-pyrocatechol/NaOH/DTPA (diethylenetriamine-N, N, N, N, N-pentaacetic acid) (or DTPP - diethylenetriamine-N, N, N, N", N"-pentameth-ylenephosphonic acid) (Karalova et al. 1982). The separation factors are based mainly on the difference in the rates of the metal-DTPA (or DTPP) complexation equilibria for Eu and Am. They are therefore highly dependent on the contact time. A principal limitation of the practical application of such a separation scheme is the relatively long contact times (> 10 min) required for extraction. However, the slow equilibration compares favorably with that for other lanthanide-actinide separation processes (e.g. TALSPEAK, section 7). 

That aqueous layer that was saved can be removed of most of its water by vacuum distillation, allowed to cool slightly then extracted with hot toluene. When the toluene cools, a few hundred more grams of catechol will crystallize out but will be contaminated with some heavy red bromo compounds. The crystals are filtered and vacuum distilled such that the pyrocatechol will distill over first, leaving the higher boiling bromo compounds behind. Yield is about 80% or 600g of catechol. 

Solvent extraction techniques are useful in the quantitative analysis of niobium. The fluoro complexes are amenable to extraction by a wide variety of ketones. Some of the water-insoluble complexes with organic precipitants are extractable by organic solvents and colorimetry is performed on the extract. An example is the extraction of the niobium—oxine complex with chloroform (41). The extraction of the niobium—pyrocatechol violet complex with tridodecylethylammonium bromide and the extraction of niobium—pyrocatechol—sparteine complex with chloroform are examples of extractions of water-soluble complexes. Colorimetry is performed on the extract (42,43). Colorimetry may also be performed directly on the water-soluble complex, eg, using ascorbic acid and 5-nitrosahcyhc acid (44,45). 

Korenaga et al. [26] have described an extraction procedure for the spectrophotometric determination of trace amounts of aluminium in seawater with pyrocatechol violet. The extraction of ion-associate between the alu-minium/pyrocatechol violet complex and the quaternary ammonium salt,... 

Several ions (e.g., manganese, iron (II), iron (III), cobalt, nickel, copper, zinc, cadmium, lead, and uranyl) react with pyrocatechol violet, and to some extent are extracted together with aluminium. The interferences from these ions and other metal ions generally present in seawater could be eliminated by extraction with diethyldithiocarbamate as masking agent. With this agent most of the metal ions except aluminium were extracted into chloroform, and other metal ions did not react in the amounts commonly found in seawater. Levels of aluminium between 6 and 6.3 pg/1 were found in Pacific Ocean and Japan Sea samples by this method. 

Aluminium Extraction of pyrocatechol violet complex with chloroform Spectrophotometry at 590 nm < 0.1 xg/l [26]... 

Five- to six-month-old tobacco plants (Nicotiana tabacum var. Samsun) grown in a glasshouse at 20°C were used for this study. Commercial synthetic substrates employed both for histochemical and biochemical assays were guaiacol, p-phenylenediamine-pyrocatechol (PPD-PC), 3-3 di-aminobenzidine (DAB), tetramethylbenzidine (TMB) and syringaldazine. Isopropylamine and monosodium salts of ferulic acid were also used as substrates as well as their / -fluorinated analogues substituted with a fluorine atom on the / -carbon (Fig. 1). Histochemical observations were done on hand-made transverse sections of fresh tobacco stems. Biochemical assays were performed separately on bark (inner cortical parenchyma, phloem and fibres) and xylem fractions. Technical data of incubation, enzyme extraction, spectrophotometric and electrophoretic assays were given elsewhere (5-7). Synthesis of fluorinated compounds was performed as previously described (4). 

A-Benzoylphenylhydroxylamine (BPHA) reacts with Nb20 in bioling acidic aqueous solutions to yield a monomeric seven-coordinated niobium compound [NbO(BPHA)3]. The hydroxylamine ligand could be displaced by tropolone or 8-quinolinol, and the ratedetermining step was shown to be associative (equation 38).427 Oxoniobium and tantalum(V) 8-quinolinolates have also been reported. The optimal conditions for the formation and extraction of the [Nb0(C6H402)3]3 ion formed in the niobium(V)-pyrocatechol system, have been investigated.428... 

In addition to the above method, based on the use of pyrocatechol violet, Tecator also describes a flow injection analysis for determining 0.5-0.5mg/l aluminium in soil extracts based on the measurement of the chromazurol-aluminium complex at 570 nm [4,5]. 

Pyrocatechol + zephiramine/chloroform A1 Interfering metal ions are extracted with sodium diethyldithiocarbamate and 8-hydroxyquinaldine 51)... 

Our studies have shown that in the presence of complex-forming agents actinides and lanthanides can be extracted from alkaline solution by using of ali-quat 336 and 4( c , oC -dioctylethyl)pyrocatechol. The latter reagent is more efficient, as it provides for quantitative extraction of trivalent actinides from very alkaline media and for appreciably better separation of actinides from rare earth elements. 

Pyrocatechol Violet (formula 4.16) is a popular reagent for determining aluminium [11,31,33-36]. The value of 8 is 6.3-10 at 580 nm (pH 6.5-7.2) [35]. A relatively small increase in sensitivity is observed in ternary systems with CTA, CP, or poly(vinylbenzyltriphenylphosphonium) chloride [37-39]. The ternary complex with Zephiramine can be extracted into CHCI3 or 1,2-dichloroethane (e 9-10 at 590 nm) [40]. The extractive (xylene) method with the use of tridodecylethylammonium bromide is of very high sensitivity (e = 1.7-10 at 613 nm [41]. Aluminium was also determined by the FIA technique using Pyrocatechol Violet [42]. 

An extractable (toluene) ion-associate of the aluminium-pyrocatechol complex and Brilliant Green is the basis of a very sensitive method (e = 2.4-10 ) [75]. 

Gallium ions form coloured complexes with a number of triphenylmethane chelating reagents besides Eriochrome Cyanine R. Pyrocatechol Violet (PV) gives with Ga and diphenylguanidine a ternary complex, extractable into n-butanol-CHCh (1-fl) mixture (e=1.08-10 ) [32]. In another extractive spectrophotometric method with PV,... 

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]. 

The dithizone method is the most frequently applied extractive spectrophotometric method for determining lead. The convenient PAR or Pyrocatechol Violet methods (in the presence of a surfactant) can also be recommended, after extractive separation of lead as the iodide complex. 

Ion-associates of niobium anionic complexes with pyrocatechol [18], or oxalate [19], and quaternary ammonium ions have been used for separating Nb from other refractory metals (Ti, W, Mo, V). Niobium has been extracted from solutions containing Fe(III), Ti(IV), and V(IV) with the use of 4,5-dibromopyrocatechol [20]. The crown-ether dibenzo-18-crown-6 has also been used for the extraction of Nb [21]. Tantalum has been separated from V (in 6 M HCl) by extraction into triphenylphosphine oxide in toluene [22]. 

The Pyrocatechol Violet method has been used for determining tin in biological materials [5], foods [5,89], organic substances [2], rocks and ores [12], copper alloys [90], and steel [33]. Traces of tin in water and in lake sediments were determined with the aid of PV and CTA after preconcentration on polyurethane foam impregnated with dithiol [91]. Tin was also determined by the PV method in alloys after extractive isolation with the aid of tris(2-ethylhexyl)phosphate [92]. 

A chelating resin prepared by coupling Pyrocatechol Violet to Amberlite XAD-2 was applied to preconcentrate Zn (Ni and Pb) from well water [1]. 4M HNO3 was used to recover the metal ions. Solid-phase extraction of thiocyanate complexes with polyurethane foam makes a basis of quantitative separation of zinc traces from cadmium matrices [2]. PAR was used to determine Zn in aqueous extract. 

Niobium(v) forms a 1 2 complex with salicylhydroxamic acid in aqueous HCl which has a formation constant of ca. 2.5 x 10" P mol-. " The extraction of niobiumfv) with N-phenylacetylhydroxamic acid (A) in benzene and CHCI3 has been studied in the presence of pyrocatechol (B) or thiocyanate and a Nb A B complex of stoicheiometry 1 2 2 and a Nb I NCS one of stoicheio-metry 1 2 3 have been identified. " ... 

Cataryl . See 2,6-Dimethylnaphthalene CatecholXR, Catechol. See Pyrocatechol Catechu, black, extract. See Black catechu (Acacia catechu) extract Catechu, black, powder Catechu powder. See Black catechu... 

Propyl octanoate Propyl pelargonate Propyl valerate Pyrocatechol . Rosemary (Rosmarinus officinalis) extract L-Serine Sodium benzoate Sodium mono- and dimethyl naphthalene sulfonates Sorbic acid Thiamine HCI... 

Ternary complexes. Traces of proteins have been determined spectrophotometrically by formation of colored ternary ion-association complexes with pyrogallol red and molybdenum(VI) or pyrocatechol violet and molybdenmn(VI). Compounds containing the sulfydryl group were determined spectrophotometrically based on the extraction of their ternary ion-association complexes of rhodamine 6G and as-traphloxine cations with hexachloroantimonate(III) from buffered aqueous solutions into toluene. 

As already stated, the polyphenols are firmly bormd to the collagen in leathers which have been subjected to vegetable tanning. In the TFG of a leather sample we may therefore expect that this bond will be broken and that fragmentation of both the tannin and the collagen will occur. Fig. 10 ows the TFG of an animal in treated only with chromium salts (chrome-tanned leather). For comparison. Fig. 11 pves the TFG of a chrome leather that has been further tanned with mimosa extract the characteristic, prominent zones of resorcinol (3) and pyrocatechol (2) show up clearly. The typical products of thermolysis of vegetable tanned and unfinished leathers are compiled in Table 5. 

By employing DLS and electrochemical methods (using potassium hexacyanofer-rate K Fe (CN) and ferrocene used as electroactive probes), regions in [bmim] [PFg]-in-water microemulsion were located. On an average, the microemulsion droplet size was approximately 3 nm. The synthesized microemulsion proficiently solubilized a lipophilic dye, 4-(p-nitrophenylazo)-pyrocatechol (NAP) and also vitamin Kj with prospects in biological extractions, and also as solvent for enzymatic reactions. 

---