Removing background color

Note The background color depends on the pH of the layer, it is, therefore, affected by the efficiency of removal of acidic mobile phase components before staining. 

Note Traces of ammonia left by the mobile phase should be completely removed from the chromatograms before the reagent is applied in order to avoid strong background coloration. The dipping solutions may also be applied as spray solutions. Secondary amines, amides, pyrimidines and purines do not react with the reagent [1]. In the case of benzodiazepines only those substances react which... 

The sensitivity that is achievable in staining is determined by (1) the amount of stain that binds to the proteins, (2) the intensity of the coloration, and (3) the difference in coloration between stained proteins and the residual, background coloration in the body of the gel (signal-to-noise ratio). With all of the common stains, unbound stain molecules can be washed out of the bodies of the gels without removing much stain from the proteins. 

Use a white background, not a gray or colored background. (Colored backgrounds may be used in posters to add visual appeal.) Remove horizontal and vertical gridlines unless they... 

For Coomassie dye staining, allow the slab to soak for about 30 minutes. Remove the dye solution by decanting and cover the gel with destaging solution. Replace the destaining solution with fresh solution about every 4-6 hours until background color is removed. The destaining procedure may require several days. Proteins will show up as dark blue bands on a nearly colorless background. 

The button image will be displayed in the Picture area, 16 pixels wide by 15 pixels high. You can add or remove pixels from the image. Click on any pixel in the Picture area to add a pixel of a selected color. Click a second time if you want to remove that color. Make the background color "Erase". This will provide a gray background identical to the rest of the button. 

In substance, ionically bonded plates had less background color than covalently bonded stationary phases and gave better resolution of racemic test material. In addition, preparation of impregnated plates was very simple and fast plates were cut into 5 X 10 cm sizes and placed in a large crystallizing dish, submerged with 30 ml tetrahydrofuran (THF) containing 1 g CS1. After 2 min, the plates were removed and washed with pure THF. 

Note This reagent sequence is a modiflcation of the reagent chlorine — potassium iodide — starch . Mobile phases containing ammonia must be removed completely before treatment with the reagent sequence, since otherwise the background will be colored too. Some secondary amines (e.g. diphenylamine) and some amides (e.g. 2,4-dinitrobenzamide) and methionine sulfoxide do not give reactions even in quantities of up to 1 to 2 (ig. 

At the end of this period the solution was removed from the condenser while still hot and titrated immediately with 0.002500 N sodium thiosulfate before any appreciable oxygen could be absorbed and oxidize iodide ion to triiodide ion. The disappearance of the yellow color of triiodide ion against a white background was used for the end point. These solutions usually had a slight brown tint at the end point, which was assumed to be organic matter distilled over from the soil. Accordingly, the blank was usually titrated first and its final color was used as a standard end point color for the other three solutions run with it. 

Phthalein test. Many phenols yield phthaleins, which give characteristic colorations in alkaline solution, when fused with phthalic anhydride and a little concentrated sulphuric acid. Place in a dry test tube 0.5 g of the compound and an equal bulk of pure phthalic anhydride, mix well together and add 1 drop of concentrated sulphuric acid. Stand the tube for 3-4 minutes in a small beaker of Silicone oil (or paraffin oil) previously heated to 160 °C. Remove from the bath, allow to cool, add 4 ml of 5 per cent sodium hydroxide solution and stir until the fused mass has dissolved. Dilute with an equal volume of water, filter and examine the colour of the filtrate against a white background if the solution exhibits a fluorescence, observe the colour against a black background. 

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