Spectroscopic-grade solvent

It is however, pertinent to mention here that most pure pharmaceutical substances possess a characteristic value of E (1% 1-cm) at a specific wavelength in agiven spectroscopic-grade solvent (UVASOL(R)-Mcrck). This particular property is the basis for most assay methods included in pharmacopoeia that are absolutely free from interfering materials, besides being utilized for identifying substances. 

Making use of only spectroscopic grade solvents e.g., UVASOL(R) (Merck), and (Hi) Making use of cells that are absolutely transparent in the region 190-210 nm. 

Materials. Spectroscopic-grade solvents were used where fluorescence or contact angle measurements were to be made, appropriate purification steps were taken. The tetrahydrofuran was distilled from lithium aluminum hydride. For contact angle measurements, the following liquids and their surface tensions (dynes/cm.) at 20° were used water, 72.6 formamide, 58.2 ethylene glycol, 47.7 methylene iodide, 50.8 1-bromonaphthalene, 44.6 and n-hexadecane, 27.6. 

Solvents used for spectroscopy, especially nmr and uv, should be of high purity. Many suppliers provide spectroscopic grade solvents which are particularly suitable for uv spectroscopy because ultraviolet absorbing impurities have been removed. 

Table 2 Lower wavelength values for 50% transmittance of common spectroscopic grade solvents...

All solvents should be checked before use even if spectroscopic grade solvents are chosen. The storage of spectroscopic solvents needs particular care. Store in glass, in amber bottles, preferably under nitrogen for work of the highest quality. 

Chemical compounds that are routinely used in laboratory procedures are simply not required to have the level of purity that can be achieved through zone refinement. In most cases, the desired purity is readily achieved through other means. High-purity materials such as spectroscopic grade solvents at 99.999 percent purity are readily obtained through repeated fractional distillation and other processes, while reagent grade materials are acceptable at 99.9... 

Azobisi sobutylnitrile (AIBN), used as initiator, was purified by recrystallisation from ethanol. Chemical and/or spectroscopic grades solvents were used. 

Materials. The nearly monodisperse atactic PMMA, which was used for the electron beam lithography and fluorescence spectroscopy studies, was obtained from Pressure Chemical. It has a weight average molecular weight (Mw) of 188,100 and Mw/Mn< 1.08. Pyrenedodecanoic acid (PDA) used in the fluorescence studies was obtained from Molecular Probes and used as supplied. Spectroscopic grade benzene purchased from J.T. Baker was used as the spreading solvent in the PMMA and PMMA/PDA solutions. 

Ethyl alcohol, methyl alcohol and cyclohexane (UVASOL(R)-Grade) employed as solvents shall have an extinction, measured in a 1 cm cell at 240 nm with reference to water (spectroscopic grade), not exceeding 0.10. 

All chemicals and solvents used were of analytical and spectroscopic grades. Caffeine was obtained from Bilim Pharm, Ind, Turkey, Stock solutions of 100 gg luL of caffeine was prepared in distilled water. 

All chemicals and solvents used were analytical and spectroscopic grade. The sweeteners (aspartme, acesulfame-K), caffeine and sodium benzoate were obtained from Ulker Food Compai f, Turkey. Cola drinks were purchased from local markets. Stock solutions of 100 mL of Aspt, Ace-K, Caf and Na-Benz were prepared in 0.1 N H PO. 0.1 N H PO solution was prepared by diluting 9.09 mL orthophosphoiic acid (85%) to 1,000 mL. 

Materials. Olefins were Phillips pure grade, appearing to be better than the reported 99% purity by gas chromatographic analysis on an AgN03 column. Methylene blue was U.S.P. basic blue No. 9, and methanol was Baker spectrophotometric reagent. All other solvents were either chromatographic or spectroscopic grade. 

When the levels of impurities, including moisture, are unacceptable for particular reactions, and when large volumes of such solvents are likely to be required, it is frequently more economic to purify the commercial grades than to purchase the more expensive AnalaR grades. Solvents of the appropriate grade of purity should also be used in isolation (extraction) and purification (recrystallisation) processes, particularly in the latter stages immediately prior to spectroscopic and/or elemental analysis. 

Solvents used for the preparation of solutions for spectroscopic examination (particularly infrared measurements) need to be rigorously purified or spectroscopic grades must be purchased (see Chapter 3). Even in this latter case, and particularly with the more hygroscopic solvents, the solvent may become contaminated with moisture during usage of the solvent from a previously opened bottle. It is therefore advisable to dry the solvent immediately before use by means of a molecular sieve. 

Rose bengal, dye content 92%, was purchased from Aldrich and was used as received. Solvents used for preparation of solutions for quantum yield measuranent were spectroscopic grade and were purchased from Aldrich. 

The checker reports that considerable loss of material occurred during the purification process and that only a 35% yield of compound melting at 114° was obtained. Use of spectroscopic grade n-hexane as a recrystallization solvent improved the yield. 

For use as solvent in a kinetic study (Olah ), Eastman spectroscopic grade nitromethane was washed three times with a solution containing 25 g. of NaHCOa and 25 g. of NaHSOs per liter, then with water, 5% sulfuric acid, water, aqueous NaHCOs, dried overnight with Drierite, then passed through a 2-ft. column of A in. type 4A Linde molecular sieves, and distilled at 58°/160 mm. from a small amount of sieve powder to yield solvent neutral to bromphenol blue in ethanol and dry to Karl Fischer reagent ( D 1.3790). 

All new compounds were fully characterized by spectroscopic data. UV-visible absorption spectra were measured with a Varian Cary 50 spectrophotometer. Spectroscopic measurements were done by using spectral grade solvents at 25 °C. Semi-empirical MO calculations were carried out with the AMI-COSMO method in the MOP AC package (MOPAC2000 ver. 1.0, Fujitsu Ltd, Tokyo, Japan, 1999). 

The poly(phenylene oxide) polymer was commercial resin obtained from Noryl Products Division, General Electric Company, Selkirk, NY. Solvents were spectroscopic grade. All other reagents were obtained from commercial sources and were used as received. 

Using deuterated solvents - these are expensive and should not be wasted. CDCI3 is 100 times more expensive than spectroscopic-grade CHCI3 and the others are at least 10-15 times more expensive than CDCI3. 

Polystyrene films were prepared by doubly dipping the substrate—a silicon wafer previously cleaned by pure solvents and etched by hydrogen fluoride—into solutions of 1 gL of pure polystyrene in carbon tetrachloride (spectroscopic grade) and allowing the solvent to evaporate. Thickness of the films thus obtained was estimated to be of the order of 100 A by elastic recoil diffiision analysis (ERDA) measurements [122]. 

The compound I was received from Professor S. Hunig of Wurzburg Univer-sitat. The compound I was recrystallized from cyclohexane five times. Commercially available 3-c.d. was recrystallized four times from aqueous solution. The solvents used were of spectroscopic grade. 

These polymers were dissolved in spectroscopic grade dioxane, and then filtered through a 0.45 pm membrane. The solutions were then spin-coated onto glass slides. The film thickness was controlled to 0.2-2.0 pm by adjusting the solution concentration and spin speed. The spin-coated films were then dried under vacuum for 24 h at 40-50 and stored in a desiccator until fiirther studies. Since the sulfonated and carboxylic substituted polyazophenols were water-soluble, deionized water was used as the solvent to dissolve these polymers (pH 11 water was used for the carboxylic substituted polyazophenol). The solutions were also filtered through a 0.45 pm membrane and the films were fabricated on glass substrates at temperature of 70 °C. The thickness of all spin-coated films was measured by using a Dektak IIA surface profilometer. 

Solvents. Reagent grade toluene and 95% ethanol were used for fractionation without further purification. Spectroscopic grade benzene was used as the solvent in sample-deposition solutions. Inasmuch as the OTMS reacts rapidly with moisture, all traces of water should be removed from the benzene prior to its use for this purpose. To this end, the benzene used for dissolution of samples C, CDS-B-4, D-1, D-2, and D-3 was first refluxed over calcium hydride and distilled to remove any residual water. A less stringent procedure was employed for samples A and B. 

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