UV absorbing layers

Unsaturated 5(477)-oxazolones have been studied as ultraviolet (UV)-absorbing layers," " as fungicides," " and as antibacterial agents." " " For example, 4-(3-phenoxybenzylidene)-2-substituted-5(4r/)-oxazolones 358 have been prepared and used as herbicides and fungicides." " ... 

Whereas the eadiest fluorescent-dye pigments would last only 20 days outdoors in a screen-ink film, fade resistance has been improved to such an extent that some modem daylight-fluorescent coated panels stiU have useful color after nine months or mote in Florida sunlight in a 45° exposure tack facing south. The fluorescent layer is usually coated with an acrylic film containing a uv absorber. Indoor-accelerated exposure equipment is, of course, invaluable in the development of such systems. Better dyes and resins very likely will make possible fat mote stable coatings in the future. 

Location of Separated Zones by Use of Visualization Reagents, UV Absorbance on Layers Containing a Fluorescent Indicator, and Densitometry... 

The same considerations will apply to other nonspecific methods of detection, such as fluorescence or UV absorbance determinations. Particularly with these methods, it must be appreciated that many of the cells used to form mono-layers secrete a variety of products such as lipids and proteins into both the donor and receiver compartments. These substances can result in a variable background in solutions and may interfere with solute quantitation. Even if a chromatographic method is used with fluorescence or UV detection, these products can still interfere with the separation unless specifically accounted for. 

A method for detecting compounds that have UV absorbance is the use of thin-layer plates that contain a fluorescence dye or indicator. Plates are developed and then placed under UV light. Compounds on the plate may show up as bright or dark spots depending on their interaction with the UV light and the fluorescence produced by the fluorescence indicator [9], It has been reported that flame ionization detection can also be used however, this is not a standard method [10]. 

System (8) has been described for quantitation of corticosteroids as common adulterants in local drugs [156]. The sample is extracted from its matrix by methanol, and the resulting supernatant layer subjected to the HPLC analysis. The column used was an ODS-Zorbax column (25 cm x 4.6 mm), and the mobile phase 7 2 11 acetonitrile-methanol-aqueous 1% phosphoric acid. An eluent flow rate of 0.8 mL/min was used, and the analyte detection was performed using the UV absorbance at 240 nm. The calibration graph was found to be linear in the ranges of 1-15 pg/mL for betamethasone, 0.5-20 pg/mL for prednisolone, and 1-30 pg/mL for cortisone acetate. 

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