Dragendorff

Most of the thiazoles studied absorb in the ultraviolet above 254 nm, and the best detection for these compounds is an ultraviolet lamp (with plates containing a fluorescent indicator). Other indicator systems also exist, among which 5% phosphomolybdic acid in ethanol, diazotized sulfanilic acid or Pauly s reagent (Dragendorff s reagent for arylthiazoles), sulfuric anisaldehyde, and vanillin sulfuric acid followed by Dragendorff s reagent develop alkylthiazoles. Iodine vapor is also a useful wide-spectrum indicator. 

Analyses in the pg range, e.g., in water and oil, can be carried out with thin-layer chromatography [244]. After separation on the thin-layer plates, then by Dragendorff reagent, colored spots are measured with the help of a spectral photometer at 525 nm. 

Fig. 22 Scheme for type B reagent sequence (cf. the reagent sequence ninhydrin — iron(lll) chloride — Dragendorff — potassium iodoplatinate [6]). 

Note The colors obtained are characteristic for the various substance classes (Table 1). Thus color tones obtained for phenothiazine derivatives are mainly reddish [1], If the j chromatogram zone contains more than 10 pg substance per spot there is only a colored 1 outer ring surrounding an uncolored center (Fig. 1) [1, 4]. The Forrest reagent does not interfere with subsequent detection with the Dragendorff reagent [1, 4], 1... 

FIGURE 11.4 Video scans of Fumaria officinalis chromatogram developed on alumina layer in eluent systems (a) 10% PrOH + CHjClj (b) first development with 10% PrOH + CH2CI2 on a distance of 18 cm and second development with MeOH on a distance of 10 cm. Plates scaimed after derivatization with Dragendorff s reagent. 

Lycopodium alkaloids Lycopodiaceae sp. SiOj CHClj-MeOH-NHj Dragendorff s reagent Identification 9... 

Macrocyclic lactam alkaloids Verbascum phoeniceum SiOj AcOEt + MeOH T + EtOH 254 nm r. Dragendorff s Identification 22... 

FIGURE 11.6 (a) Densitogram of PLC of Fumaria officinalis herb extract and (b) photocopy of isolated fractions (after spraying with Dragendorff s reagent). Numbers indicate isolated fractions. System silica/CHjClj + PrOH + AcOH (5 4 1). Plates double developed. 

FIGURE 11.23 Densitograms of Fumaria muralis herb extract chromatographed in system silica/PrOH + MeOH + AcOH + water + CHjClj (28 2 2 2 66). Plates double developed (a) plate scanned at 254 nm (b) plate scanned at 400 nm after spraying with Dragendorff s reagent. 

Figure 11.23a and Figure 11.23b show densitograms from the separation of Fumaria muralis extract scaimed in UV 254 mn (Figure 11.23a) and at 400 nm after spraying with Dragendorff s reagent (Figure 11.23b). It is seen that derivatization enables determination of alkaloid zones and their isolation from the nonalkaloid extract components.

Choline-containing phospholipids Potassium iodide-bismuth subnitrate (phosphatidylcholine and Dragendorff reagent... 

Dragendorff s reagent Dissolve 0.85 g of bismuth subnitrate in a mixture of 40 mL of water and 10 mL of glacial acetic acid (,Solution A). Dissolve 8 g of potassium iodide in 20 mL of water (Solution B). Transfer 5 mL of Solution A, 5 mL of Solution B, and 20 mL of glacial acetic acid to a 100 mL volumetric flask, dilute with water to volume, and mix. 

In the procedure with mobile phase 1 and 2, the visualization is accomplished by screening under uv light (254 and 366 nm) and in addition by spraying with Dragendorff s reagent, modified by Munier and Deboeuf, followed by 30 percent hydrogen peroxide. 

Beside the modified Dragendorff s reagent/hydrogen peroxide already mentioned, a variety of spraying reagents has been used for the visualization of bromocriptine. 

Reagents for detecting hydralazine were Dragendorff s reagent, alkaline dimethylaminobenzaldehyde, anisaldehyde, and Bratton-Marshall reagent. 

Dragendorff stain A. Potassium iodide 400 g l l in water. B. Bismuth subnitrate 17 g l-1 in 20% acetic acid. Mix A and B and water (1 4 15) immediately before use Choline containing Orange-red spots within a few minutes with gentle warming... 

Muscarine is detected by high-performance thin-layer chromatography (HPTLC), with a limit of detection of 50 ng (Stijve, 1981). Using Dragendorff reagent, muscarine appears as an orange spot. 

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