Color differentiation

Note The reagent can be employed on silica gel, kieselguhr, RP and, with lower sensitivity of detection, on cellulose layers. The color differentiation is probably greater on cellulose layers [1]. A dark blue background is produced on polyamide layers. 

Note The dipping solution can also be used as spray solution. Since the chromatogram zones slowly fade in the air it is recommended that the chromatograms be covered with a glass plate for long-term storage. Color differentiation is possible with purine derivatives [6, 8]. Diprophylline is not colored [6]. 

The reagent can, for instance, be employed on silica gel, kieselguhr. Si 50000, cellulose and NH2 layers the reaction is appreciably less sensitive on RP 18, CN and Diol phases, neither is there any color differentiation of the purine derivatives [8J. Cellulose and polyamide layers are not suitable, since the whole layer background is colored dark brown [8]. 

Note Tertiary amines and quaternary ammonium compounds yield stronger colors than primary amines [25]. The dipping solution can also be used as spray solution [44]. Other reagent compositions have also been reported in the literature (1, 3, 6, 12, 13, 15, 18, 21, 23, 41] In some cases the reagents have been made up in acetone [38, 39], methanol [14] or ethanol [37] and/or acidified with hydrochloric acid [3, 33, 37-40]. The concentrations of hexachloroplatinic(IV) acid have been in the range of 0.05 -0.4 those of potassium iodide between 0.5 and 24spray solution containing 2% potassium iodide and 0.23170 hexachloroplatinic(IV) acid hexahydrate in N-hydro-chloric acid is reported to yield the best coloration results with respect to detection sensitivity and color differentiation in the detection of morphine, codeine, quinine, methadone and cocaine [46]. Acidic reagent solutions have been recommended for benzodiazepines [10, 11]. Sulfones do not react [39]. 

The use of color-differentiation is favored whereas the use of color coding is controversial because of the limited number of colors, the prevalence of color blindness in the general population, and inappropriate reliance on color in lieu of reading the label. 

Note Anisaldehyde — sulfuric acid is a universal reagent for natural products, that makes color differentiation possible [6]. The background acquires a reddish... 

Many details of the anatomy and biochemistry of insect development from egg to adult are known. Growth and development are strictly regulated by hormones, and hormone concentration, relative and absolute, is vital for this to proceed correctly. The hormones control cuticle synthesis, molting, sexual maturation, color differentiation, reproduction, etc. 

The three different color-response mechanisms in the human eye are the scientific basis for the measurement of color that is standardized in the Cl E Standard Observer (1931). This system specifies color according to X, Y, Z tristimulus values and. v. , z chromaticity coordinates. Several alternative scales were subsequently developed to provide a better adaptation to the color differentiation ability of the human eye [9.26]. 

When testing for polyolefins with mercury(ll) oxide (see Section 6.2.1), in most cases, a yellow color develops more or less quickly. With blends of polyolefins, no significant color differentiation sufficient for identification occurs. However, if the polyethylene content of the blend is very high, no coloration, or only a slight coloration is seen because polyethylene does not react with mercury(ll) oxide. 

Several spray reagents permit a certain color differentiation between selected vitamin E derivatives. Thus P- and y-tocopherol can be distinguished using such spray reagents as phosphomolybdic... 

---