Visual detection limits

Detection and result The following hRf values (TLC, chloroform) were obtained carvacrol and thymol (red) 30—35, eugenol (salmon pink) 40 — 45 here the background was pale yellow colored. The visual detection limit was 200 — 500 ng per chromatogram zone. The colored zones faded after 1 to 2 hours. 

Detection and result The chromatogram was freed from mobile phase in a stream of warm air, immersed in the freshly prepared reagent mixture for 1 s and then dried in a stream of cold air. After a short time a-tocopherol yielded a red chromatogram zone on a colorless background at hRf 35—40. The visual detection limit on the HPTLC layer was 20 — 25 ng per chromatogram zone. 

Colored substance zones were obtained which could be analyzed quantitatively. The (visual) detection limits were hypericin 1 ng, rutin and chlorogenic acid 5 ng, hyperoside — quercetin 10 ng per mm chromatogram zone. The detection limits for densitometric analysis are between 20 and 50% of those for visual detection. 

The pink color of the cholesterol begins to fade after 5 min while the color of the bile acids deepens [2]. The visual detection limit in visible light is 1 pg for cholesterol and 2 pg per chromatogram zone for bile acids [2], Fluorimetric detection is more sensitive by a factor of 1000 ... 

Note Rhodamine 6G is a universal reagent which can also be incorporated in the TLC layers [4, 9] or added to the mobile phase [4], The spray reagent can also be made up in water [8], acetone [4, 6] or ammonia solution (c = 2.5 mol/1) [5]. The visual detection limit is most favorable when the water from the mobile phase or the detection reagent has not completely evaporated from the layer. This can be recognized by the fact that the background fluorescence has not turned from red to pink [4]. 

The visual detection limits for fluorimetric detection are substance-dependent and lie between 5 ng (adrenaline, noradrenaline) and 30 ng (homovanillic acid) substance per chromatogram zone. 

The visual detection limits are 0.3 to 1 pg substance per chromatogram zone. 

The visual detection limits for polyphenols and flavonoids are 0.2 to 1 pg substance per chromatogram zone [1]. The photometric detection limits are appreciably lower (see Procedure Tested ). 

Azinphos ethyl (h/ f 20-25), malathion (h/ f 40-45) and diazinone (h/ f 47-52) yielded white chromatogram zones on a blue background immediately. Before in situ quantitation the chromatogram was dried in the air until no film of moisture could be seen on the layer surface. It was then dried completely in a stream of warm air whereby the blue coloration of the background changed to brown (Fig. 1). The visual detection limits were 200 ng substance per chromatogram zone. 

Pesticide Optimum conditions Wavelength (nm) of maximum Visual detection limit (ug)... 

Colored substance zones were obtained which could be analyzed quantitatively. The (visual) detection limits were hypericin 1 ng, rutin and chlorogenic acid 5 ng. 

The color activity concept allows identification of key colorants in mixtures and their percentage contribution to total color after the concentration and visual detection limits of the single compounds under... 

Table II. Visual Detection Limits for Selected Pigments...

---