Phenol, determination spectrophotometry

M.C.B. Quaresma, R.J. CasseUa, M.F.B. Carvalho, R.E. SanteUi, Focussed microwave-assisted sample preparation total phenol determination in petroleum refinery effluents by flow injection spectrophotometry, Microchem. J. 78 (2004) 35 0. 

K.O. Lupetti, E.R.P. Rocha, O. FatibeUo-Filho, An improved flow system for phenols determination exploiting multicommutation and long pathlength spectrophotometry, Talanta 62 (2004) 463 67. 

Before the study of complexation, pKa values of acerands 4 and of the reference azophenol 13 were determined by spectrophotometry in 10% dioxane-water (Table 1). The table shows the increase of pKa values with decreasing crown ring size. This fact is explained by destabilization of the phenolate anion due to both the electrostatic repulsion between the phenoxide anion and the lone pair electrons of ethereal oxygen atoms and the blocking of the crown ring against solvation of the anion. 

Goldschmid O (1954) Determination of phenolic hydroxyl content of lignin preparations by ultraviolet spectrophotometry Anal Chem 26 1421-1423 Kuhn R, Roth H (1933) Mikro-Bestimmung von Acetyl, Benzoyl und C-Methylgruppen Ber Dtsch Chem Ges 66 1274-1277... 

The equilibrium is shifted completely to the right. Thanks to the presence of the phenolate group at the chain ends, the macromolecules could be counted by UV spectrophotometry (polytetramethylene oxide is transparent in the UV range). With the counter-ion B = BF termination was slow with B- = AlCl it was rapid. The active centres can be counted using the Saegusa and Matsumoto method and, together with a determination of the degree of polymerization and the concentration of macromolecules, the elementary constants can be determined (the dead-stop method). 

Goldschmid O (1954) Determination of phenolic hydroxyl content of lignin preparations by ultraviolet spectrophotometry. Anal Chem 26 1421-1423... 

After LLE into ethanolic KOH, the antioxidant BHT (32a) used in aircraft fuel was determined in the presence of Cu(n) ions, by UVV spectrophotometry at 368 nm. Linearity was observed in the 0 to 30 ppm range, RSD <2% . A UVV spectrophotometric method for determination of -cyclodextrin (126) is based on the formation of a complex with phenolphthalein (19, Section Vin.A.3). Both the intensity and hnear range are affected by the pH and the concentration of 19 in solution. The method was considered to be inadequate for precise determinations of 126 of purity higher than 98% see also application of a-cyclodextrin (85) for analysis of phenolics in Section IV.B.4 . Phenol in the presence of sodium nitroprusside, Na2[Fe(CN)5NO], and hydroxylamine, at pH 10.26-11.46, developed a blue coloration that could be applied for quantitative analysis (kmax 700 nm, e 1.68 x 10" LmoU cm , Sandell sensitivity 0.0052 p,g phenol cm ). Beer s law was found to be valid from 0.1 to 6.5 ppm". ... 

Zinc was determined in environmental samples [108] and in copper selenide [109] with the use of PAR. Zn was determined in brass (in the presence of Ni) by derivative spectrophotometry with the use of 2-(2-pyridylmethylene-amino)phenol [110]. The thiocyanate complex of Zn associated with Tetrazolium Violet has been applied for determining Zn in cadmium [1111. 

Zireonium has been determined in niobium by using Pyrocatechol Violet [71]. Hafnium has been determined in uranium alloys with the use of PAN [27]. 2-(2-Pyridylmethylenamino)phenol has been applied for determination of Zr in the presence of Cr (in bronzes) by derivative spectrophotometry [108]. 

Another option is to place the filtration unit inside the flow cell, as demonstrated in the spectrophotometric flow injection determination of hydrogen peroxide [297]. The analyte interacted with titanium(IV) and 2-((5-bromopyridyl)azo)-5-(N-propyl-N-sulfopropylamino) phenol (PAPS) yielding a red-purple complex. After ion pairing with CTAB, the complex was adsorbed and concentrated on a very small area of the membrane filter positioned inside the flow cell. The analyte was quantified directly in the membrane by solid-phase spectrophotometry (see 4.1.1.4). Thereafter, ethanol was injected in order to solubilise the complex and transport it to waste. 

UV/VIS spectrophotometry is a widely used spectroscopic technique. It has found use everywhere in the world for research, clinical analysis, industrial analysis, environmental analysis, and many other applications. Some typical applications of UV absorption spectroscopy include the determination of (1) the concentrations of phenol, nonionic surfactants, sulfate, sulfide, phosphates, fluoride, nitrate, a variety of metal ions, and other chemicals in drinking water in environmental testing (2) natural products, such as steroids or chlorophyll (3) dyesmff materials and (4) vitamins, proteins, DNA, and enzymes in biochemistry. 

Analysis of sugar composition in nectar can be used for detecting variation between flowers or nectaries from different taxonomic varieties, and consequently generate differences in type and frequency of visitation of pollinators. Alves et al. (2010) studied the total sugar concentration in soybean nectar Glycine max L. Merrill) var. Codetec 207 by spectrophotometry, using the general method for carbohydrates determination by phenol-sulphuric technique (Dubois et al., 1956). 

Another process consists of building the epoxycyclohexane unit into the bridge of a bisphenol molecule (Scheme 50) [30]. The condensation of phenol with 3-cyclohexene-l-carboxaldehyde may occur in the presense of both acid and alkaline catalysts. If oxalic acid was used as the catalyst, the yield of the bisphenol XLI reached 60%. Still higher yield was reached when excess phenol in the presence of HCl as catalyst was applied. The bisphenol XLI (melting temp. 318.5 °C) was obtained by crystallization from isopropanol. The -isomer contained small amounts of the -and o,o-isomer [31]. The structure of the product was confirmed by IR spectrophotometry and molecular weight determination. 

Antioxidant and antiozonant types most commonly used are aromatic amines or phenolics, though others are also employed, and can be determined using a variety of techniques such as UV-visible spectrophotometry, FTIR, near-infrared spectroscopy, TEC, GC (if the material can be volatilized), supercritical fluid chromatography, and HPLC. Identification of unknown antioxidants requires a separation technique like chromatography followed by mass spectrometry, NMR, ETIR, X-ray crystallography, etc. Standardized TEC methods are given in ASTM D3156 and... 

Ammonium ion is one of the inorganic species most frequently determined by UV-visible spectrophotometry. It is freed by the Kjeldahl method from organic matter and can be spectrophotometrically determined by reaction with phenol and hypochlorite in the presence of nitroprusside ion, with which it yields a blue compound (indophenol) with an absorbance maximum at 625 nm. Another alternative, especially avoiding the use of phenol, is by measuring the absorbance at 660 nm of an indophenol blue derivative generated by the reaction of ammonium ion with sodium salicylate in the presence of hypochlorite ion. These procedures are routinely used for the determination of ammonium ion with autoanalyzers. 

Other examples presented in the literature are those based on the use of copolymeric disk-based sorbent materials for the isolation and preconcentration of nitro-substituted phenol isomers and the concurrent removal of potentially interfering matrix components followed by onhne simultaneous determination of individual species by diode array spectrophotometry, via chemometric deconvolution of the overlapped spectra, without the need for chromatographic separation. In contrast to bead-extraction, no flow impedance is observed when using extraction disks while better enrichment factors are obtained because of the improved specific surface area. Compared with earlier methods for isolation/preconcentration of nitrosubstituted phenols based on liquid-liquid extraction, these systems should be regarded as environmentally friendly approaches because the use of harmful organic solvents is circumvented. 

R.A.S. Lapa, J.L.F.C. Lima, I.V.O.S. Pinto, Determination of phenolic compounds in waste waters hy sequential injection analysis and spectrophotometry, Int. J. Environ. Anal. Chem. 76 (2000) 69-76. 

Goddu, R.E, Determination of phenolic hydroxyl by near-infrared spectrophotometry. Anal. Chem., 30(12), 2009-2013, 1958. 

Most studies in TLC have been qualitative, and considerable experimentation may be necessary to obtain quantitative results, although excellent commercial layers and new equipment have aided the problem. Phenolic compounds have been analyzed by spectrophotometry off the plate at 725 nm (133) by means of Folin-Ciocalteu reagent, essentially sodium tungstate and molybdate with lithium sulfate (134). Chlorophenols have been quantified after reaction with dansyl chloride and separation (135). Channel TLC (linear relationships between spot lengths and concentration between 1 and 8 pg/spot) has been used (136). The phenols in cashew nut shell liquid have been quantified by off and on the plate methods with a flying-spot scanning procedure and densitometry (137) and the distribution of unsaturateds by TLC/MS (138). Catecholamines and their metabolites in urine have been quantified (12) and determined by on the plate fluorimetry (139). Hindered phenols have been analyzed by densitometry (140). Semiquantitative determinations of the coupling products of 4,4 -... 

Spectrophotometry utilizing the reagents 4-aminoantipyridine and MBTH is the classical technique for the nonspecific determination of phenolic compoimds. It is the basis for several official methods and was discussed earlier. 

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