Phenols, mobile

Direct separation of enantiomers may be performed on cellulose the use of microcrystalline cellulose is especially widely used. An other stationary phase is the microcrystalline triacetylcellulose, which is stable when using alcoholic and phenolic mobile phases however, it is unstable when glacial acetic acid and ketones are used. Optically active poly(meth)acrylate may be bound to the silica gel. and these stationary phases are widely used under the names of CHIRALPLATE or CHIR . Beta cyclodextrin can also be covalently bound to silica, and also reversed-phase plates may be used for chiral separation when the mobile phase consists of beta-cyclodextrin. 

Figure 7.16 Comparison between the calculated (dotted lines) and the experimental (solid lines) elution profiles of 4-tert-butyl phenol. Mobile phase, 65 35 (v/v) methanol/water linear velocity uq = 0.175 phase ratio, F = 0.749 column length, L = 25 cm Langmuir isotherm constants, a = 6.84, b = 0.0437 1/g. Concentration of 4-tert-butyl phenol, 75 g/1. The durations of the injection ramp, from left to right are 450,650,1000,1400, and 1900 seconds. Reproduced with permission from T. Ahmad, F. Gritti, B. Lin and G. Guiochon, Anal. Chem., 76 (2004) 977 (Fig. 5c). 2004 American Chemical Society.

Johns [116] could show that isocyanate spreads easily on a wood surface. 4% of isocyanate give panels the results which are comparable to those of boards bonded with 8% of a phenolic resin. The good mobility of MDI is based on several parameters [140] (1) MDI contains no water, and it cannot loose its mobility during adsorption on the wood surface (2) it has a low surface tension (ca. 50 dyn/cm) as compared to water (76 dyn/cm) (3) it has a low viscosity. 

Ion exchange, in which cation and/or anion resins are used to replace undesirable anionic species in liquid solutions with nonhazardous ions. For example, cation-exchange resins may contain nonhazardous, mobile, positive ions (e g., sodium, hydrogen) which are attached to immobile acid groups (e.g., sulfonic or carboxylic). Similarly, anion-exchange resins may include nonhazardous, mobile, negative ions (e.g., hydroxyl or chloride) attached to immobile basic ions (e.g., amine). These resins can be used to eliminate various species from wastewater, such as dissolved metals, sulfides, cyanides, amines, phenols, and halides. 

Dimethyl sulfoxide in the mobile phase acts as an intnnsic detector for certain phenols (e g dihydroxybenzenes) [194] on layers that have been treated with tin tungstate... 

This ether, CgHj. O. CHg, known as anisole, is a mobile oil of very fragrant odour. It is used to some extent in synthetic perfumery. It is prepared by the action of methyl iodide on sodium-phenol, according to the following equation —... 

Laboratory work involved making calibration curves which show the response of the system for various concentrations of pollutant, e.g., phenol. Typically, remote laser-induced fluorescence measurements from both the laboratory apparatus and the mobile unit are made on... 

A typical field test involves several steps (a) transporting the mobile unit to the site (b) instrument warmup (c) system check out, consisting of mobile unit measurements of distilled water and a 1-ppm stock phenol solution and (d) in situ measurements of the well water, repeated three times for statistical analysis. Signal levels recorded at a field site may be reported as equivalents of phenol (or other calibrant) using the calibration curves. Therefore, this method allows us to report the upper bounds of pollution levels. 

ESI-MS has emerged as a powerful technique for the characterization of biomolecules, and is the most versatile ionization technique in existence today. This highly sensitive and soft ionization technique allows mass spectrometric analysis of thermolabile, non-volatile, and polar compounds and produces intact ions from large and complex species in solution. In addition, it has the ability to introduce liquid samples to a mass detector with minimum manipulation. Volatile acids (such as formic acid and acetic acid) are often added to the mobile phase as well to protonate anthocyanins. A chromatogram with only the base peak for every mass spectrum provides more readily interpretable data because of fewer interference peaks. Cleaner mass spectra are achieved if anthocyanins are isolated from other phenolics by the use of C18 solid phase purification. - ... 

Pelander et al. [81] developed a computer program for optimization of the mobile phase composition in TLC. They used the desirability function technique combined with the PRISMA model to enhance the quahty of TLC separation. They apphed the statistical models for prediction of retardation and band broadening at different mobile phase compositions they obtained using the PRISMA method the optimum mobile phase mixtures and a good separation for cyanobacterial hepatotoxins on a normal phase TLC plate and for phenolic compound on reversed-phase layers. 

Males et al. [103] used aqueous mobile phase with formic acid for the separation of flavonoids and phenolic acids in the extract of Sambuci flos. In a cited paper, authors listed ten mobile phases with addition of acids used by other investigators for chromatography of polyphenolic material. For micropreparative separation and isolation of antraquinone derivatives (aloine and aloeemodine) from the hardened sap of aloe (Liliaceae family), Wawrzynowicz et al. used 0.5-mm silica precoated plates and isopropanol-methanol-acetic acid as the mobile phase [104]. The addition of small amounts of acid to the mobile phase suppressed the dissociation of acidic groups (phenolic, carboxylic) and thus prevented band diffusions. 

Figure 4.29 An example of the use of ternary solvents to control mobile phase strength and selectivity in reversed-phase liquid chromatography. A, methanol-water (50 50) B, tetrahydrofuran-water (32 68) C, methanol-tetrahydrofuran-water (35 10 55). Peak identification 1 - benzyl alcohol 2 phenol 3 3-phenylpropanol 4 2,4-dimethylphenol 5 benzene and 6 -diethylphthalate. (Reproduced with permission from ref. 522. Copyright Elsevier Scientific Publishing Co.)...

Figure 1.15 Fast analysis of a test mixture on a 10 cm x 4.6 mm I.D. column packed with 3 micrometer octa< ecylsilanized silica with a mobile phase flow rate of 3.4 mi. i.n (acetonitrile-water 7 3) and operating pressure of ca. 340 atmospheres. Peaks 1 uracil, 2 phenol, 3 - nitrobenzene, 4 - toluene, 5 -ethylbenzene, 6 - isopropylbenzene, and 7 - tert.-butylbenzene. (Reproduced with permission from ref. 222. Copyright Friedr. Vieweg 6 Sohn).

It has been observed that complete immobilisation of the stabiliser through a graft leads to deactivation. However, proper selection of the ratio of phenolic to graftable groups leads to a polymer-bound product which retains sufficient mobility to provide a high level of antioxidant activity. An n/m ratio of 5-10 provides an optimal balance of graftability and antioxidant activity [144]. 

Diglycidyl ether of bisphenol A (DGEBA, MW 340 Da) and 4,4 -dihydroxy-diphenylmethane (DHDPM, MW 200 Da) were analysed by SEC-MALS [784]. DGEBA and DHDPM are the basic oligomers of epoxy resins and phenol-formaldehyde condensates, respectively, which are widely used in the electronic and automotive industries. Excellent reproducibility ( 1 %) and good accuracy (better than 10%) were observed. SEC has also been used for the determination of mineral oil in extended elastomers [785] and in PS [178]. With heptane containing 0.05% isopropanol as the mobile phase, mineral oil is completely unretained and elutes before the solvent via SEC all other components in a PS extract are retained on silica and elute after the solvent peak. 

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